METAL-THERMOPLASTIC-METAL LAMINATES AND A PROCESS FOR THE PREPARATION OF SUCH LAMINATES

Abstract: This invention relates to construction panels comprising metal-thermoplastic-metal laminates and a process for preparing same, said laminates possessing in combination critical service properties of high heat distortion temperature, low coefficient of linear thermal expansion, low inelastic ratio, and lightness in weight.

Description: METAL-THERMOPLASTIC-METAL LAMINATES AND A PROCESS FOR THE PREPARATION OF SUCH LAMINATES CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of Copending application Serial No. 972,537 filed December 22, 1978- BACKGROUND OF THE INVENTION Field of the Invention This invention relates to metal-thermoplastic- metal laminates comprisillg a metal layer laminated to each side of a thermoplastic ore layer selected from the group consisting of partly crystalline polyamides and polyesters These laminates have an improved combination of critical properties required for tUse in construction applications. Description of the Prior Art . Metal-thermoplastic-metal laminates and processes for their preparation are known. Seer for example, Bugel et al., U.S Patent 3,382,136; Zunich et al., U.S. Patent 3,352,742; and Pohl et al., Modern Plastics, 41 (7 March), 119-124 (1964) The laminates described in the above-noted references as well as other prior art laminates, however, resin general, limited in their applications, particu- larly when contemplated for use as construction panels where the combination of good dimensional stability under engineering loads at elevated temperatures (high heat-distortion temperatures), low thermal expansivity (low coefficient of linear thermal expans ion) and good recovery from flexural deflection (low inelastic ratio) are necessary properties of a light-weight laminate. SUMMARY OF THE INVENT ION A primary object of the present invention, therefore, is to provide a light-.seight metal-thermoplastic-metal laminate having an improved combination of service properties considered important and critical for demanding construction applications such as outer and inner building panels, appliance panels, and transportation vehicle body panels, for example, automobiles, boats, airplanes, and the like. A further object of the invention is to provide a light-weight construction panel laminate characterized by, among other properties, a combination of a high heat distortion temperature, a low coefficient of linear thermal expansion, and a low inelastic ratio (or high flexural elasticity). A still further object of the invention is to provide such a 32Laminate which, in addition to the critical properties deemed necessary for the cont struction applications, also has a wide range of additional desirable properties, for example, excellent deep-draw, simple-bend and stretch formability at elevated temperatures, very good ductility, very good energy absorption ability, (including resistance to denting), and very good-strength in flexure. Another object of the invention is to provide a laminate having a specially selected thermoplastic core layer composition. A further object is to provide a laminate which is particularly useful in applications requiring high flexural stiffness and a high heat distortion temperature. Still another object of the invention is to provide a laminate which is particularly adapted for use in automotive applications. An additional object of the present invention is to provide a process for the preparation of the aforementioned metal-thermoplastic-metal laminates. These and other objects will be apparent to those skilled in the art from the accompanying description and claims. The above objects are successfully accomplished by the present invention which is directed to metal-thermoplastic-metal laminates having in combination o an inelastic ratio less than about 93%; o a coefficient of linear thermal expansion less than about 63 x 10-6 C. 1; o a heat distortion temperature of at least about 1300C.; and o a maximum weight of no more than about 9.76 kg/m2; said laminate comprising: o a thermoplastic core layer selected from the group consisting of partly crystallie poly amides and pesters having a crystalline melting point greater than about 1300C.; and o a metal layer laminated on each side of the thermoplastic core layer, each metal layer having: a melting point greater than the crystalline melting point of the thermoplastic core layer; and a minimum thickness of about 0.00127 cm; wherein the thickness ratio of the sum of the metal layer-thicknesses to the thermoplastic core layer thickness is described by the region of numerical overlap of the parameter TR(YSm/TSc) as determined from the areas defined by the relationships of TR(YSm/TSc) to IRl, CLTEl, and (HDTl - HDTc)/(Tm@ HDTc), the lower boundary of said areas being defined by the equation of a straight line y = mx + b in which y is the y-axis parameters of IR,, CLTE and (HDT± - HDTC)/(Tm - HDTC), x is the x-axis parameter of TR(YSm/TSc), m is the slope of the straight line, and b is the intercept on the y-axis, with the proviso that: : o when y is IRQ, m is 108 and b is zero (0) for values of x from zero (0) to 0.65, and m is zero (0) and b is 70 for values of x greater than 0.65; o when y is CLTEl, m is -3.6 x 10 4 and b is 45 x 10-6 for values of x from zero (0) to 0.1, and m is zero (0) and b is 9 x 10 6 for values of x greater than 0.1; and o when y is (HDTl - HDTC)/(Tm - HDTC), m is 1 and b is zero (0) for values of x from zero (0) to 0.-05, m is 10 and b is -0.45 f-or values of x from 0.05 to 0.12, and m is zero (9) and b is 0.75 for values of x greater than 0.12; and the upper boundary of said areas being defined by the equation of a straight line as defined hereinabove, with the proviso that: o when y is IRQ, m is 280 and b is 30 for values of x from zero (0) to 0.25, and m is zero (0) and b is 100 for values of x greater than 0.25; o when y is CLTEl, m is -2.88 x 10 3 and b is 216 x 10-6 for values of x from zero (0) to 0.05, m is -1.29 x 10 4 and b is 78.5 x 10-6 for values of x from 0.05 to 0.26, and m is zero (0) and b is 45 x 10 6 for values of x greater than 0.26; and o when y is (HDTQ - HDTC)/(Tm - HDTc), m is c 112.5 and b is zero (0) for values of x from zero (0) to 0.004, m is 15.3 and b is 0.389 for values of x from 0.004 to 0.04, and m is zero (0) and b is 1 for values of x greater than 0.04; wherein: o IR is the inelastic ratio of the laminate as measured in flexure at 5 strain in the outer metal layers at the point of maximum deflection; o CLTE is the coefficient of linear thermal expansion of the laminate; 0 (HDTl - HDTc)/(Tm - HDTc) is a normalized heat distortion temperature variable wherein HDT is the heat distortion tempera ture of the laminate; HDTc is the heat distortion tempera ture of the thermoplastic core layer; T is the crystalline melting point mc of the thermoplastic core layer; o TR is the thickness ratio of the sum of the metal layer-thicknesses to the thermoplastic core layer thickness; o YSm is the thickness-weight-average tensl'- yield strength of the two metal layers at an offset of 5% elongation; and o TSc is the tensile strength of the thermo plastic core layer. Stated alternatively, the thickness ratio of the sum of the metal layer-thicknesses to the thermoplastic core layer thickness is described by the region of numerical overlap of the parameter TR(YSm/TSc) as determined from plots of IRg versus TR(YSm/TSC), CLTEg versus TR(YSm/TSC), and (HDTl - HDT@)/(T@ HDTc) versus TR(YSm/TSc) as shown, respectively, in FIGs. 1, 2 and 3 of the specification, in which IRl, CLTEl, (HDTl - HDTc)/(Tm@ - HDTc), TR, YSm, and TS are as defined hereinabove. c The provision of the process object is accomplished by a process which comprises: (a) disposing a metal layer on each side of a thermoplastic core layer selected from the group consisting of partly crystalline polyamides and polyesters, with the thick ness ratio of the sum of the metal layer thicknesses to the thermoplastic core layer thickness being determined as described' hereinabove; (b) laminating the thermoplastic core layer and the metal layers by subjecting the combination to elevated temperatures and a pressure sufficient to maintain face adhering contact; and Cc) cooling to ambient temperatures. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more readily understood by reference to the accompanying drawings in which: o FIG. 1 is a plot correlating inelastic ratio, IRg, with TR(YSm/TSC) for laminates both within and without the scope of the present invention; FIG. 2 is a plot correlating coefficient of linear thermal expansion CLTEg with TR(YSm/TSC) for laminates both within and without the scope of the present invention; and o FIG. 3 is a plot correlating a normalized heat distortion temperature (HDT) variable, g - HDTc)/CTm HDTc), with TR(YS.m/TSc) for laminates both within and without the scope of the present invention. DETAILED DESCRIPTION OF THE INVENTION 1. Critical Service Properties The metal-thermoplastic-metal laminates of the present invention are constructed of a thermoplastic core layer and two metal layers, one laminated on each side of the thermoplastic core layer. The laminates are characterized by a combination of critical service properties -- high heat distortion temperature, low coefficient of linear thermal expansion, low inelastic ratio (good elasticity in flexure), and lightness in weight -- as well as certain other desirable properties, which make them excellent for use as construction panels. The high heat distortion temperature of the laminates (HDTz) within the scope of this invention is a unique property and must be greater than about 130"C. (266 F.) to survive various conditions encountered in use. It is particularly important in applications requiring good dimensional stability under engineering loads and wherein the laminates may be subjected to elevated temperature conditions. For example, when the laminates are employed as construction panels for automotive applications, they are subjected to elevated temperature conditions extant in paint-curing ovens -at least about 135 C. (275 F.). In such an instance, a HDT of at least about 1350C. is necessary with about 16SC. (325 F.) being preferred in order to provide adequate dimensipnal stability at even higher t,empe,rature extant in many paint-curing ovens. It will be-appaFent of course that the laminates must be able to withstand exposure to such elevated temperature conditions extant in paint-curing ovens without buckling, warping, flattening out (if already formed into a shaped structure), and the like. Heat distortion temperature, also known as deflection temperature under flexural load, is measured according to a specific modification of ASTM D 648-72 test method for plastics. In this modification, the sheet specimen width, b, is about 2.22 cm (0.875 inch), the length is about 7.62 cm ±3 inches), the span between the supports is 5.08 cm (2 inches), and the maximum stress in the specimen is 1.82 x 106 N/m2 (264 psi) Surprisingly and unexpectedly, the heat distorsion temperature of the laminates (HDTg) within the scope of the present invention optimally can approach essentially that of the crystalline melting point of the thermoplastic core material (Tm ). As a result, the heat c distortion temperature of the laminates may exceed that of the thermoplastic core material by several hundred degrees. For example, a laminate (EXM1PLE 3) comprising two 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum layers and a 0.295 cm (0.116 inch, 116 mils) thick nylon 6,6 core layer interposed therebetween and laminated thereto had a heat distortion temperature of 228 C. (4420 F.) compared to C only 77 C. (171 F.) for the nylon 6,6 layer alone. Excellent dimensional stability under engineering stresses at elevated temperature is, therefore, a prime characteristic of the laminate, particularly when compared with the thermoplastic core materials alone. The crystalline melting points of thermoplastics (tic) is determined by differential scanning calorimetry (DSC) using a heating rate of 10 C. per minute. The values for crystalline melting point are taken as either the temperature at which the apparent melting rate was maximum, or the temperature at which essentially the last traces of melting are detected, the latter being preferred in instances wl;cre the difference between the two is substantial, for example, greater than 10 C. The marked increase in heat distortion temperature shown by the metal-thermoplastic-metal laminats over that of the thermoplastic core layer alone clearly illustrates the advantages of the present invention. Comparison of the heat distortion temperatures shown by laminates within the scope of the present invention with those shown by similar laminates having an amorphous thermoplastic core layer demonstrates that such laminates (those having an amorphous thermoplastic core layer) fail to show the same or similar marked increase shown by laminates of the present invention. For example, a laminate (EXANSLE 69) comprising two 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum layers and d 0.208 cm (0.082 inch, 82 mils) thick PARN 56/44 (nylon 56% 6, terephthalic acid-co-44% 6, isophthalic acid) layer having a degree of crystallinity of 35% (that is, partly crystalline) interposed therebetween and laminated thereto had a heat distortion temperature of 207 C. (405 F.) compared to only 1170 C. (243 F.) for the PARN 56/44 alone, O O an increase of 90 C. (162 F.). On the other hand, a similar laminate (EXAb,FLE 70) comprising two 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum layers and 0.178 cm (0.070 inch, 70 mils) thick amorphous PARN 56/44 as the thermoplastic core layer had a heat distortion temperature of only 1220 C. (252 F.) as compared to 1170 C. (2430 F.) for the PARN 56/44 alone, an increase of only 5 C. (9 F.). Low coefficient of linear thermal expansion in the plane of the laminate (CLTEg)[less than about 63 x 10 60 cm/cm/0C. (0C.1) (35 x 60F.)] is another critical property of the metal-thermoplastic-metal laminates of the present invention because in the construction applications contemplated, changes in part sizes due to temperature variations must be minimal in order to lessen the possibility of unsightly bulges and gaps between metal and concrete components and parts made with the laminates of this invention. The coefficient of linear thermal expansion is measured according to ASTM D696-70 test method for plastics It can also be determined by measuring the distance between two finely scribed parallel lines on the surface of the specimen with a calibrated traveling microscope or cathetometer. The specimen is contained in a rectangular hole in a heavy copper block which can be thermostatically controlled at various, widely separated temperatures. The rectangular hole in the copper block is only slightly larger than the cross-section of the specimen, and the scribed lines on the surface of the specimens are visible through a narrow slit machined into the copper block. While certain plastic materials are light weight and have high energy absorption capability 'high impact strength), making them desirable for use as construction panels, they suffer from the dsadv & tage that their coefficients of linear thermal expansion are 4 to 5 and even 10 times that of most metallic and vitreous construction materials, for example, aluminum, steel, and concrete. Their use for construction panels on metal or concrete structural frames often are precluded by the high differential thermal expansivity which leads to problems of fastening, and, in addition, by the unsightly gaps which would result between panels at low temperatures and/or the buckling of panels at high temperatures. The normal procedure for lowering the coefficient of linear thermal expansion of plastics is to incorporate glass fibers. Usually, 30 to 40 weight percent of glass is sufficient to reduce the coefficient of linear thermal expansion of a plastic to about that of aluminum (about 23.4 x 10 6 C -1). This, however, usually results in a strong but brittle material having very low elongation to break. That is, the composite cracks at very low impact regardless of whether the plastic per se is a strong but brittle resin, such as a thermoset polyester, o a tough polymer with high extensibility with high elongation to break, such as nylon 6,6. It will be noted, however, that the decreased multiaxial impact resistance of glass-filled plastics does not preclude the use of glass fibers in the thermoplastic core layer materials of the present invention in that lamination of suitable metal layers thereon as described hereinbelow tends to offset (at least in part) the undesirable properties of the glass-filled thermoplastics. Metals, of course, do not suffer the disadvantage of high coefficients of linear thermal expansion as do plastics. However, they generally are not lightweight, particularly at thicknesses sufficient for use as construction panels. Also, their elastic recovery from bending and denting generally is very poor. Thus, the metal-thermoplastic-metal laminates of the present invention provide the best of both worlds. That is to say, they are not only lightweight, but in addition, are characterized by a combination of high heat distortion temperatures, low inelastic ratios (good flexural elasticities), and low coefficients of linear thermal expansion. The coefficient of'linear thermal expansion must be less than about 63 x 10 6 C. -1. However, in certain applications requiring low thermal expansivity such as in the case of an automobile panel, the CLTEg preferably is less than about 54 x 106 C. 1 and more preferably less than 45 x 10-6 C. -1. The low CLTE values obtainable by the laminates of this invention (less than 63 x 10 C. -1), although somewhat greater than those of steel (about 15.3 x 10 6OC. 1) and aluminum (about 23.4 x 10 6 C. -1), are sufficiently low for demanding construction applications. An example of the low coefficient of linear thermal expansion exhibited by laminates of the present invention is as follows. A laminate (EXAMPLE 5) comprised of two 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum layers laminated on either side of a 0.180 cm (0.071 inch, 71 mils) thick nylon 6,6 layer had a coefficient of linear thermal expansion of 29.0 x 10-6 C. -1 compared to 23.6 x 10 6OC. 1 for the aluminum alone and the relatively high value of 110.2 x 10 6OC. 1 for the nylon 6,6 alone. Low inelastic ratio (IRg) (good flexural elasticity) (less than about 93%) is a critical property of the metal-thermoplastic-metal laminates. The inelastic ratio characterizes the elastic recovery of such laminate panels after being subjected to deflection sufficient to produce a substantial strain (for example, 5%) in the outer metal layers at the point of maximum deflection. It is measured according to a specific modification of ASTM D 790-71. The method may be described as follows: A sheet specimen with rectangular cross section of width b = 1.27 cm (0.5 inch), a thickness or depth d in cm (inches), and a length 1 = (L + s) where L is the span of the flexural test in cm (inches) and # > 1.27 cm (0.5 inch), is set horizontally into a three-point flexural test fixture (i.e., with the 1.27 cm (0.5 inch) width horizontal and the depth d vertical) and deflected vertically at a crosshead de flection rate D of 0.0212 cm/s (0.5 inch/ minute) to a deflection Do in cm (inches) such that the strain r in the central portion of the outer skin of the specimen is, except where noted otherwise, 5%, as computed in 2 percent by the formula r = 600dD0/L . The span L used is approximately 16 times the depth d, except for thicknesses or depths d < 0.172 cm '0.065 inches), whereupon the span used is 2.54 cm (] 00 inch). After bending the specimen to the specified deflection Doa the flexural loading is immediately removed at a crosshead deflection rate of 0.846 cm/s (20 inches minute). Then the specimen is immediately removed from the flexural test fixture, set on its edge on a flat surface and allowed to freely relax. Periodically, the specimen is placed in a fixture with the same span and configuration used in bending it, and its residual deflection Dr measured with a dial gauge. When the residual deflection Dr has reached its limiting, equilibrium value, Dr = DR, the inelastic ratio is computed according to the formula IR = 100 (DR/DO), in percent. The limiting, equilibrium value DR is attained usually within a period of one to two days, but always within one week. As noted hereinabove, the inelastic ratio (irk) is a critical and important characterization of the elastic recovery of laminate panels after they have been deflected sufficiently to produce substantial strain in their outer surfaces. If IRg is too high (low elasticity), both the degree of recovery of the laminates to their original shape after being strained substantially and the ability of the laminates to recover totally their original shape after being deflected in use to some lesser degree of strain will be inadequate under demanding use conditions. And, since one of the principal objects of the present invention is the provision of a metal-thermoplasticmetal laminate having an improved combination of service properties considered important for demanding construction applications, an important limitation of the present invention is the upper limit on iR. In general, materials having an inelastic ratio greater than 93% are too inelastic and/or too weak to be employed as construction panels under conditions demanding or requiring any elasticity (ormore specifically, elastic recovery) at all. The upper limit for the inelastic ratio of the laminates within the scope of the present invention as noted hereinabove, is therefore about 938. Moreover, laminates having inelastic ratios in the following ranges, determined at 5% strain in the outer metal layers at the point of maximum deflection as described hereinabove, are rated as follows: : INELASTIC RATIOS, IR RATING > 938 very poor 84-938 marginal 75-84% fair 30-75% good < 308 excellent Since both the degree of recovery of the laminate to its original shape after being strained substantially and the ability of the laminate to totally recover without experiencing any permanent dents and creases after being strained to a small degree increase as the inelastic ratio decreases, the lower the inelastic ratio becomes the more desirable the laminate becomes for demanding construction applications. Thus, laminates having inelastic ratios within the good and excellent ranges ( < 75%) are preferred. It will be recognized, of course, that while IR as employed herein is determined (except where noted otherwise) at a strain r of 5%, other strain values, either lower or higher, can be emploed. However, IR values determined at strain values other than 5% generally will differ from those determined at 5%. For example, an IR value determined at a strain less than 5% (such as 1.5%) will in general be lower than that determined at 5%. Conversely, an IR value determined at a strain greater than 5% (such as 8%) generally will be higher than that determined at 5%. It will be noted that the inelastic ratio for the laminates within the scope of the present invention, surprisingly, is always lower than that for the metal layer materials alone which have an inelastic ratio (irk) upper limit of about 95% (for very soft 1145-0 aluminum). As an example, a laminate (EXAMPLE 5) comprised of two 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum layers and a 0.180 cm (0.071 inch, 71 mils) thick layer of nylon 6,6 interposed therebetween and having good adhesion thereto had an inelastic ratio of only 27% compared to the very high inelastic ratio of 94% obtained for sheets of 1100-0 aluminum alone. Good elasticity (low and and consequently good dent recovery, is therefore a prime characteristic of the laminates of the present invention, particularly when compared to a conventional construction sheeting or panels made of metal alone. Lightness in weight of the laminate of the present invention is of particular interest because it results in a substantial weight savings in the total weight of a constructed object. For example, if the constructed object is an automobile, the weight savings should result in an increase in fuel economy for the particular automobile. It will be recognized, of course, that the total weight savings realized will depend upon the materials comprising the laminate, the total amount of the laminate employed, and the materials for which the laminate is being substituted. It will be apparent that when steel is employed as the laminate's metal layers, weight saving over steel itself [for example, 0.0813 cm (0.032 in., 32 mils) thich steel -- the most common type and thickness of automotive body panel material] will not be as great as when comparably dimensioned laminates having aluminum metal layers are employed. The weight reduction for laminates having steel layers is nevertheless substantial. For example, when a laminate (EXAMPLE 25) is prepared from two 0.00254 cm (0.001 inch, 1 mil) thick steel layers and 0.182 cm (0.0715 inch, 71.5 mils) nylon 6,6, its weight per unit area is only 38.5% (2.44 kg/m2, 0.500 lb./ft. ) of the 6.34 kg/m2 (1.3 lb./ft.2 weight of a 0.0813 cm (0.032 in.) thick steel sheet. For certain construction applications demanding very high strength and stiffness such as in portions of some automotive vehicle bodies and in some building surfaces, steel sheeting weighing as much as about 9.76 kg/m2 (2 1b. /ft.2) is used. Thus, the maximum weight of the laminates within the scope of the present invention, is about 9.76 kg/m2, with values substantially below this weight being preferred. Values less than 6.34 N/m2 (1.3 1b./ft.2), however, are most preferred, particularly for automobile applications. While each of the critical properties -high heat distortion temperature [greater than about 1300C.(2660F.), low coefficient of linear thermal expansion (less than about 63 x 10-6 C. -1), low inelastic ratio (less than about 93%), and lightness in weight (no more than about 9.76 kg/m2) -- is highly desirable, either taken alone is not sufficient. They must exist in combination. That is to say, in order to be broadly suitable for a wide variety and range of high performance construction applications, the metal-thermoplastic-metal laminates must have in combination a heat distortion temperature (HDT±) greater than about 1300C (266 F.), a coefficient of linear thermal expansion (CLTEl) less than about 63 x 10 6a -1, an inelastic ratio (irk) less than about 93%, and a maximum weight of no more than about 9.76 kg/m2. 2. Correlation of Critical Service Properties and Thickness Ratio The critical and important service properties of the laminates of this invention -- IRQ, CLTEl, and HDTQ -- are related to the ratio of the thicknesses of the component layers of the laminates via the product of the thickness ratio of the sum of the metal layer-,thicknesses to the thermoplastic core layer thickness times the ratio of the strengths of the component layers of the laminate, or in mathematical symbols, via the following dimensionless parameter: : TR(YSm/TSc) wherein TR is the thickness ratio of the sum of the metal layer-thicknesses to the thermo plastic core thickness; YS- is the thickness-weight-average tensile m yield strength of the two metal layers - that is, the sum of the products of the thickness of each metal layer times its tensile yield strnegth at an offset of 5% elongation divided by the sum of the metal layers thicknesses, or in mathematical symbols, (tiySi + tiiysii)/Tm wherein ti, tii, ysi, and ysii are as defined herein below; and Tm is the sum of the metal layers thicknesses or (ti + tii);' and TS c is the tensile strength of the thermoplastic core material. The tensile yield strength at an offset of 5% elongation for the metal layers (ys) is determined substantially in accordance with ASTM D638-72, entitled, "Standard Method of Test for Tensile Properties of Plastics". Type I specimens are employed and the speed of testing is 5.0 mm per minute. The metal test specimens herein were pre o conditioned at 23 C. at 50% relative humidity for at least 18 hours and testing was conducted at 230 C. and 50% relative humidity. The value for ys is that of the metal after being subjected to the thermal conditions of lamination. In many cases this value for ys will not be substantially different from that of the metal before lamination since for many metals no significant change in ys occurs under typical lamination thermal conditions. In those cases where the value for ys must be determined on the metal after having been subjected to the thermal conditions of lamination, the @al @@ @d @e separated from the core of the laminate for such a determination; for example, the thermoplastic core cc :d be dissolved and the metal layers isolated for such determination. It is recognized that some metal layers may experience break before a strain of 5% offset. For, such metals the maximum tensile strength for the material is tobe used as the value for ys. The tensile strength of the thermoplastic core material (TSc) is also determined substantially in accordance with ASTM D638-72. Type I test specimens are employed and the speed of testing is 5.0 mm per minute. Specimens were pre-conditioned at 23 C. for at least 18 hours. All nonlaminated polyamide specimens were kept dry, as molded in sealed cans with anhydrous magnesium perchlorate or anhydrous calcium sulfate desiccants during the preconditioning period and all other specimens were pre-conditioned at 50% relative humidity. The tensile strength of the thermoplastic materials is taken as the tensile stress at yield or in the absence of a yield point, the tensile stress at fail (break. The value of TS is of the rorp thermal conditions C after subjection to lamination/ which in general will be the same as the thermoplastic material before lamination. In instances where the thermoplastic is such that significant changes in TSc would likely occur during lamination, the value of TSc can be determined, for example, by subjecting a representative sample of the thermoplastic material alone to the lamination thermal conditions and taking a measurement on the resultant material. The thickness ratio (TR) is described by the region of numerical overlap of the parameter TR(YSm/TSC) as determined from the areas defined by the relationships of TR(YSm/TSc) to IRl (FIG. 1), CLTEl (FIG. 2), and (HDTl - HDTc)/(Tmc - HDTc) (FIG. 3). The lower boundary of such areas is defined by the equation for a straight line y = jrnx + b in which y is the y-axis (vertical-axis) parameters of IRg, CLTEg, and (HDTQ - HDTc)/(Tmc - HDTc), x is the x-axis (horizontal-axis) parameter of TR(YSm/TSc), m is the slope of the straight line, and b is the intercept on the y-axis. When y is IRl, m is 108 and b is zero (0) for values of x from zero (0) to 0.65, and m is zero iO) and b is 70 for values of x greater than 0.65. then y is CLTEl, m is -3.6 x 10-4 4 and b is 45 x 1O-6 for values of x from zero (0) to 0.1, and m is zero (0) and b is 9 x 10-6 for values of x greater than b.1. When y is (HDT - HDTc) /(Tmc - HDTC), m is 1 and b is zero (0) for values of x from zero (0) to 0.05, m is 10 and b is -0.45 for values of x from 0.05 to 0.12, and m is zero (O) and b is 0.75 for values of x greater than 0.12. The upper boundary of the areas defined by the relationships of TR(YSm/TSc) to IRQ (FIG. 1), CLTEl (FIG. 2), and (HDTl - HDTc)/(Tmc - HDTc) (FIG. 3) is also defined by the equation for a straight line defined hereinabove for.the lower boundary of such areas. When y is IRQ, m is 280 and b is 30 for values of x from zero (0) to 0.25, and m is zero (O) and b is 100 for values of x greater than 0.25. When y is CLTEl, m is -2.88 x 10-3 3 and b is 216 x 10-6 for values of x from zero (0) to 0.05, m is -1.29 x 10-4 and b is 78.5 x 10-6 for values of x from 0.05 to 0.26, and m is zero (0) and b is 45 x 10-6 for values of'x greater than 0.26. When y is (HDTz - HDTC)/(Tm - HDTc), m is 112.5 and b is zero (0) for values of x from zero (0) to 0.004, m is 15.3 and b is 0.389 for values of x from 0.004 to 0.04, and m is zero (0) and b is 1 for values of x greater than 0.04. Referring to FIG. 1, it is readily seen that all of the data falls within a band defined at its outer limits by curves 1 and 2, which are, respectively, the upper and lower boundaries of the area defined by the relationship of TR(YSm/TSc) to IRl. Thus, where it is desirable to have a laminate possessing a specified inelastic ratio, IRg (less than the maximum value of 93% noted hereinabove), the thickness ratio of the laminate is readily determined by drawing a horizontal line rom the desired IRg value to the point of intersection at curve 1 (and curve 2, where possible), which @@lue(s) can be read from the TR(YSm/TSC) axis. The point of intersection at curve 1 Cat IRg greater than about 30%) will establish a minimum value for the dimensionless parameter. TR itself can then be readily determined by substituting easily determined and/or known values of YS and TS for chosen metal c and thermoplastic core layers in the dimensionless parameter. If the same horizontal line drawn to intersect curve 1 also intersects curve 2, then an upper limit for TR(YSm/TSc) as well as TR alone can also be determined in the same manner as described for the lower limits. In such an instance, a range of values for TR(YSm/TSC) and hence TR will be established. On the other band, where the horizontal line drawn to intersect curve 1 does not also intersect curve 2, then, consistent with the thickness and weight limitations discussed hereinabove, there is no upper limit for TR(YSm/TSc). Referring to FIG. 2, it is readily seen that all of the data also falls within a band defined at its outer limits by curves 3 and 4, the upper and lower boundaries, respectively, of the area defined by the relationship of TR(YSm/TSc) to CLTE In a manner similar to that described for FIG. 1, once a desired CLTEg (less than 63 x 10-6 C.-1) is specified, the value (or values) for TR(YSm/TSc) and hence TR itself can be readily determined. Referring to FIG. 3, again it is readily seen that all of the data falls within a band defined at its outer limits by curves 5 and 6, which are the upper and lower boundaries, respectively, of the area defined by the relationship of TR(YSm/TSc) to (HDTl HDTC)/tTm - HDTC). Once a desired value for .HDT [greater ±han the minimum value of about 130 C. (266 F.)] is specified, known values of HDTc and Tm for chosen thermoplastics can be substituted in theC normalized HDT variable, (HDTl - HDTc)/(Tmc - HDTc) to obtain a value between zero (0.0) and 1.0. Once that value is determined, the TR(YSm/TSc) value (or value can be determined as described for FIGs. 1 and 2 by drawing a horizontal line from the desired (HDTQ - HDTc )/(Tm - HDTc) value to the point of intersection at curve 9 (and curve 6, where possible). Thus the optimum and preferred TR range for any given laminate having a specified balance of IR±, CLTEl, and HDT can be readily ascertained by correlating the TR(YSm/TScJ values obtained from FIGs. 1, 2 and 3 and determining the region of numerical overlap of such values. In general, since the combination of low IRg', low CLTEl, and high HDT is preferred, a TR(YSm/TSc) within the range between about 0.08 and 0.6 is preferred, although as indicated by FIGs. 1, 2 and 3, other values are also suitable. It will be noted, however, that regardless of the TR value, the minimum thickness of each metal layer must be at least about 0.00127 cm (0.0005 inch (0.5 mils) and the maximum weight of the laminate must be no more than about 9.76 kg/m2 (2 lb./ft. 2) More- over, as a practical matter, TR must be greater than zero (0) (thermoplastic alone) and less than absolute infinity (metal alone) in that the metal-thermoplasticmetal laminates within the scope of the present invention cannot be comprised of either metal or thermoplastic alone. Once TR is determined, if a thickness is chosen for either the metal layers or the thermoplastic core layer, the thickness for the remaining component layer is readily determined. It will be noted, however, that in the specific instance wherein the metal layers have different compositions (that is, ysi and ysii, as defined hereinbelow, are not equal, the relative thicknesses of the metal layers must be specified in order to determine the value of YSm which in turn is required in order to calculate TR from the TR(YSm/TSc) relationship as illustrated hereinbelow. Of course, once TR is determined and since T (from t. + t.. where t. and t.. are the m 1 11 1 11 thicknesses of the respective metal layers arbitrarily labeled as "i" and "ii") is known,the required thermoplastic core layer thickness is readily determined. The manner by which FIGs. 1, 2, and 3 described hereinabove are employed to establish values for TR(YSm/TSC) and hence TR alone is to choose values for the properties -- IR CLTE and HDTl -- commensurate with the intended end use. For example, if the end-use application would require an IRg of 33%, then a value for TR(YSm/TSC) renging from about 0.010 to about 0.31 would be indicated by FIG. 1. If the end-use application would also require a CLTEg of 24.3 x 10-6 C. -1, then a TR(YSm/TSC) value ranging from about 0.057 to approximately infinity (or simply a value of at least about 0.057 would be indicated by FIG. 2. And, if a HDTl of 218 C. would be required for the contemplated end use, choosing nylon 6 (HDTC = 65 C.; Tm = 2200C.) as the thermoplastic core layer for iliustrative purposes, the normalized variable (HDTl - HDTc)/(Tm@ - HDTc) can be readily solved [(218 C c 65 C.)/(220 C. 650C.)] to give a value of 0.99. This normalized HDT variable value would require, according to FIG. 3, a TR(YSm/TSc) value ranging from about 0.039 to approximately infinity (or again, simply a value of at least about 0.039). The optimum TR(YSm/TSc) values for a laminate having an IRQ of 33%, a CLTEl of 24.3 x 10 6 C.-1, a HDTl of 218 C., and nylon 6 as the thermoplastic core layer would be the region of numerical overlap, namely, between 0.057 and 0.31. The optimum values for TR itself can be readily determined once the metal layers -- for example, aluminum and more particularly the specific composition (type) and thickness of aluminum -- are specified. Since TR(YSm/TSc) = 0.057 to 0.31 then TR = 0.057 (TSc/YSm) to 0.31 (TSc/YSm) If, for illustrative purposes, 1100-0 aluminum [ti = tii = 0.0127 cm(0.000127 m, 0.005 inch 5 mils)]; ysi = Ysii = 58.25 x 10 NIm (8.45 x @@@ lb./in. ) at an offset of 5% elongation; ; YSm = (tiysi + tiiysii)/Tm = [(0.000127 m x 58.25 x 106 N/m2) + (0.000127 m x 58.25 x 106 N/m2)]/ 0 00054 - @@ @@ - 106 N/m2 @@ @@@@@@ @@ the @@t@l 0.000254 = 58.25 x 106 N/m2 is chosen as the metal layers and nylon 6 [TSC = 75.14 x 106 N/m2 (10.9 x 103 1b./in.2)] as noted hereinabove, is chosen as the thermoplastic core layer, then 2 TR = 0.057(75.14 x 106 N/m2 = 0.057 x 1.29 = 58.25 x 106 N/m2 0.074 and 6 2 TR = 0.31 (75.14 x 106 N/m2) = 0.31 x 1.29 = 0.40 58.25 x 106 N/m2 Thus TR should range between about 0.074 and 0.40 for the above-specified balance of IRl, CLTEl, and EIDTQ values for a laminate comprised of equally thick sheets of 1100-0 aluminum as the metal layers and nylon 6 as the thermoplastic core layer. An experimental laminate possessing the above-specified combination of properties with TR having the value of 0.151 is described in EXAMPLE 67. In similar manner, if an end-use application for a laminate comprised of equally thick sheets of 1100-0 aluminum (YSm = 58.25 x 10 N/m2) as the metal layers and poly(ethylene terephthalate) (HDTc = 890C.; Tm = 2520 C.; TSc = 77.21 x 106 N/m2) as the thermoplastic core layer would require an IRg w- 50 .l, a CLTF of 29.5 x 10 6 C -1 and a HDT of 240 C., the region of overlap for TR(YSm/TSc) values as determined from FIGs. 1, 2 and 3 would indicate an optimum range between about 0.042 and 0.285, and hence a TR range between about 0.056 and 0.38. An experirental example of such a laminate with a TR value of 0t165 is EXAMPLE 71. it will be noted that since the laminates of this invention have two metal layers, one on each side of the thermoplastic core layer, the metal layers can have either the same or different compositions as long as the combination of critical service properties are met Metal layers having different thicknesses also may be employed so long as such thicknesses come within the limits established by the metal layers' minimum thickness requirement and the maximum weight requirement of the resultant laminate, and the combination of critical and important service properties are met. When metal layers having different compositions and/or thicknesses are employed, it is preferred that certain important characteristics of the metal layers be substantially balanced in order to avoid problems such as warping, buckling, and the like when such laminates are exposed to variations in temperature. The important characteristics of the metal layers should be balanced unsofar as practicable such that: (a) CLTE. = CLTE; (b) tiEi = tiiEii@@; and (c) tiysi = tiiysii; wherein CLTEi and CLTEii, ti and tii, Ei and Eii, and ys and Ysii are, respectively, the coefficients of linear thermal expansion, thicknesses, elastic moduli, and tensile yield strengths of the respective metal layers arbitrarily labeled as "i" and "ii". However, as a practical matter, generally it is preferred that both metal layers be of the same composition and thickness. As an example wherein metal layers having different compositions (and different thicknesses) are employed -- 0.00508 cm (0.0000508 m, 0.002 inch, 2 mils) thick 304 stainless steel - annealed and 0.0152 cm (0.000152 m, 0.006 inch, 6 mils) 0.0152 centimeter) thick 6061-0 aluminum, arbitrarily labeled as t. and tii, respectively, for example -and wherein, for illustrative purposes, nylon 6,6 is employed as the thermoplastic core layer, if the end use application would require an IRz of 45%, then a value for TR(YSm/TSC) ranging from about 0.051 to about 0.42 would be indicated by FIG. 1. If the end use application would also require a CLTE of 32.8 x 10-6 0C. -1, then aTR(YSm/TSc) value ranging from about 0.034 to approximately infinity (or simply a value of at least about 0.034) would be indicated by FIG. 2. And, if a HDT± of 250 C. (or higher) would be required for the contemplated end use, using nylon 6.6 (HDTC = 770 C.; Tm = 263 C.), as noted hereinabove, as the thermoflastic core layer, the normalized HDT variable can be readily solved [(250 C. - 77 C.)/ (2630 C. - 770 C.)] to give a value of 0.93. This normalized HDT variable value would require, according to FIG. 3, a value ranging from about 0.035 to approximately infinity (or again, simply a value of at least about 0.035). The optimum values for TR(YSm/TSc) for a laminate having an IR of 45%, a CLTE 6f 32.8 x 10 C.-1, and an HDT&alpha; of 250 C. (482 F.) would be between 0.051 and 0.42, the region of numerical overlap for FIGs. 1, 2 and 3. The optimum values for TR itself can be readily determined since, as noted hereinabove, 304 stainless steel-annealed (ti = 0.0000508 m; ys = 369.52 x 106 N/m2 (53.6 x 103 lb./in.2) at an offset of 5% elongation and 6061-0 aluminum (tii = 0.000152 m; ysii = 112.37 x 106 N/m2 (16.3 x 103 1b./in.2) at an offset of 5% elongation) are employed as the metal layers. Since TR(YSm/TSc) = 0.051 to 0.42 then TR = 0.051 (TSC/YSm) to 0.042 (TSC/YSm) The strength values (YSm and TSC) are. as follows: YSm = (tiysi + tiiysii)/Tm 6 = [(0.0000508 x 369.52 x 106) + (0.000152 x 112.37 x 106)]/0.0002028 = (18771.62 + 17080.24/0.0002028 = 35811.86/ 0.0002028 = 176.78 x 106 N/m2 TSc = 83.42 x 106 N/m2 Therefore, TR = 0.051(83.42 x 106 N/m2 = 0.051 x 0.47 = 176.78 x 10 N/m 0.024 and TR = 0.42 (83.42 x 106 N/m2g = 0.42 x 0.47 = 176.78 x 1Ot N/m 0.20 Thus, TR should range between about 0.024 and about 0.20 for the above-specified balance of IRl, CLTEl, and HDTl values for a laminate comprised of a 0.00508 cm thick sheet of 304 stainless steelannealed and a 0.0152 cm thick sheet of 6061-0 aluminum as the metal layers and nylon 6,6 as the thermoplastic core layer. An experimental example of such a laminate having a-TR value of 0.0768, with IRg measured with steel on the tension side and with CLTE measured on the steel side is described in EXAMPLE 55. It will be noted that if IRg and CLTE were in turn measured from the aluminum side for the above-described laminate, TR(YSm/TSc) and TR would vary slightly from the above-indicated values due to the lack of an absolute balance between ' \ CLTEi and CLTEii, tiEi and tiiEii, and tiysi and tiiysii. For example, IRg as measured with the 6061-0 aluminum on the tension side had a value of 43 O and CLTEg as measured from the aluminum side had a value of35.5 x 10 6 C. 1. HDTQ, however, remained unchanged in this instance. These values would require a range of TR(YSm/TSc) values between about 0.045 and about 0.405, as indicated by FIG. ), a value of at least about 0.026 as indicated by FIG. 2, and a value of at least about 0.035 as indicated by FIG. 3, with the range between 0.045 and 0.405 (FIG. 1) defining the region of numerical overlap. The value for TR alone would therefore be between about 0.021 and about 0.19, which range correlates quite well with the TR value of 0.0768 for the laminate described in EXAMPLE 55. 3. Other Important Properties In addition to the above critical construction application properties, most of the laminates-within the scope of the present invention also have excellent flexural stiffness, high flexural modulus, excellent formability at elevated temperatures, very good ductility, and high energy absorption ability. Excellent fleural stiffness and high effective flexural modulus (a measure of unit flexural stiffness) are highly desirable properties which the laminates preferably should possess. The desirability resides in the fact that the laminates must be sufficiently stiff so as to minimize the need for structural framing and/or to minimize flexural deflection of the laminate panels from wind, marine hydraulic, and other loads. The ability of the laminates to resist wind and hydraulic pressures is particularly significant when they are used, for example as automotive vehicle body panels, boat body panels, and as outer panels in building construction. Flexural stiffness m is measured according to G specific version of ASTM D 790-71. The specific version can be described as follows: A sheet specimen with a rectangular cross-section of width b = 1.27 cm (0.5 inch),.a thickness or depth d in cm (inches), and a length # = (L + where L is the span of the flexural test in cm (inches) and e > 1.27 cm (0.5 inch), is set hori zontally into a three-point flexural test fix ture Li.e., with the 1.27 cm (0.5 inch width horizontal and the depth d vertical) and deflec ted vertically at a cross-head rate D of 0.00212 cm/s (0.05 inch/minute). The applied load P in N (lb.) is recorded, as the deflection D in cm (inches) increases at the specified constant rate. For thicknesses or depths d ' < 0.165 cm (0.065 inches), the span L is 2.54 cm (1.00 inch). Otherwise, the span is approximately 16 times the thickness or depth of the sheet specimen. The effective flexural modulus Eb in N/m2 (psi) is computed from the formula EB = L3me/4bd3, where me in N/m (lb./in.) is the experimental slope of the initial, linear portion of the load versus deflection curve. The flexural strength S in N/m2 (psi) is com puted from the formula S = 3PL/2bd2; unless otherwise specified, this strength is computed as the stress at which the strain in outer skin of the central portion of the specimen is r = 600dD/L2 = 5%. The flexural stiffness ni is computed as m = 4bd3EB/L3 for the specific case of b = 2.54 cm (1.00 inch) and L = 2.54 cm (1.00 inch). A flexural stiffness of about 52.53 x 103 N/m (300 lb./in.) is the lowest value that can be utilized for sheeting or panels in construction and building applications, even where framing is maximized and requirements on flexural deflection of the panels is minimal. This flexural stiffness is characteristic of 0.0508 cm (0.020 inch, 20 mils) thick sheets of relatively weak and inelastic 5052-0 aluminum weighing 2 2 1.37 kg/m (0.280 lb./ft. ). This lowest useful flexural stiffness of about 52.53 x 10 N/m, as well as even higher values of at least about 131.85 x 103 N/m (753 lb./in.), is readily achieved with the laminates of the present invention. For example, as shown in the following table, a laminate (EXAMPLE 23) comprised of two 0.0127 cm (0.005 inch, 5 mils) thick layers of 5052-0 aluminum laminated on each side of a 0.0711 cm (0.028 inch, 28 mils) thick layer of nylon 6,6 had a flexural stiffness of 161.44 x 103 N/m (922 1b./in.) [an effective flexural modulus of 28.95 x 109 N/m2 (4.2 x 106 psi)] and a weight of 1.49 kg/m2 (00306 lb./ft.2) compared to a stiffness of 38.00 x 103 N/m (217 1b./in.) for a 0.133 cm (0.0523 inch, 52.3 mils) thick sheet of nylon 6,6 alone weighing 1.51 kg/m2 (0.310 1b./ft.2). Thus, the laminate gives much higher stiffness than an aluminum sheet of only slightly less weight per unit area and even higher stiffness relative to that of a much thicker sheet of nylon 6,6 alone having equivalent weight per unit area. FLEXURAL EFFECTIVE STIFF- FLEXURAL NESSb WEIGHTc MODULUS DENSITY m, W, EB D, SHEETINGa 103 N/m kg/m2 109 N/m2 kg/m2-cm 0.0508[0.0508, 5052-0 A1] 52.53 1.37 64.11d 26.88e 0.0965[0.0127, 5052-0 Al/nylon 6,6/5052-0 Al] 161.44 61.49 28.95 -0.133[0/nylon 6,6/0] 38.00 1.51 2.62d 11.37 0.152[0.0152, 6061-T6 A1/nylon 6,6/6061-T6 Al] 606.72 2°21 27.64 - FLEXURAL EFFECTIVE STIFF- WEIGHTc FLEXURAL NESSb lvEIGHTC MODULUS DENSITY m, @, @B D, SHEETINGa 103 N/m kg/m2 109 N/m2 kg/m2-cm 0.0813[0.0813, Autobody Steel] 443.00 6.34 133.05d 78.14e 0.0813[0.0813, 6061-T6 A1] 226.93 2.20 68.18 27.07e 0.102[0.102, 6061-T6 A1] 434.25 2.75 66.80d 27.07e 0.194[0/nylon d 6,6/0] 117.84 2.20 2.62@ 11.37 a Sheet thickness d (cm) [metal layers i and ii thickness (cm) metal layer i type/thermoplastic core layer type/ metal layer ii type]. b result computed from EB using m = 4 d EB. c Result computed from component thickness(es) and den sity(ies). d result obtained for same type of sheeting of different thickness, d. @ Taken from Lynch, Handbook of Materials of Science, Vol. II, CRC Press, Cleveland, 1975. As shown in the above table, a laminate (EX AMPLE 38) comprised of two 0.0152 cm (0.006 inch, 6 mils) thick 6061-T6 aluminum layers laminated to each side of a 0.122 cm (0.048 inch, 48 mils) thick nylon 6,6 layer had a flexural stiffness of 606.72 x 103 N/m (3465 lb./in.)[an effective flexural modulus of 27.64 x 10 NAm2 (4.01 x 106 psi)] and a weight, of 2.21 kg/m2 (0.453 lb./ft.2), compared to: : (a) a flexural stiffness of 443.00 x 103 N/m (2530 lb./in.) and a weight df 6.34 kg/m2 (1.3 lb./ft. 2) for 0.0813 cm (0.032 inch, 32 mils) thick automobile body steel; (b) a flexural stiffness of 226.93 x 103 N/m (1296 lb./in.) and a weight of 2.20 kg/m2 (0.451 lb./ft.2) for 0.0813 cm (0.032 inch, 32 mils) thick 6061-T6 aluminum alone; (c) a flexural stiffness of 434.25 x 103 N/m (2480 1b./in.) and a weight of 2.75 kg/m2 (0.564 1b./ft.2) for 0.102 cm (0.040 inch, 40 mils) thick 6061-T6 aluminum alone; and (d) a flexural stiffness of 117084 x 103 N/m (673 lbO/in.) and a weight of 2.20 kg/m2 (0.451 lb./ft.2) for 0.194 cm (0.0762 inch, 76.2 mils) thick sheet of nylon 6,6 alone. Thus, the lamiante is 37% stiffer in flexure and 65% lower in weight per unit area than the 0.0813 cm thick steel. The laminate is more than 2.5 times stiffer in flexure than the 606l-T6 aluminum alone at equivalent weight per unit area and 37% stiffer than the 6061-T6 aluminum alone having a weight per unit area more than 20% higher than that-of the laminate. And the laminate is more than five times stiffer than nylon 6,6 alone having substantially the same weight per unit area. It will be noted that in applications demanding relatively high flexural stiffness such as in automotive vehicle body panels and the like, a flexural stiffness of at least about 262.65 x 103 N/m (1500 lb./in.) is preferred, with values of at least about 437.75 x 103 N/m t2500 lb./in.) or higher being even more preferred. Excellent formability is a necessary property for the laminates if they are to be formed into shaped structures subsequent to preparation; that is, subjected to post-forming operations. The excellent formability and very good ductility of the metal-thermoplastic-metal laminates prepared from ductile metal layers and a ductile thermoplastic core layer ensure that such laminates can be formed into a variety of shapes -- from slightly curved to deep drawn -- without failure or rupture. The terms "ductile" and "ductility" as employed herein to describe the metal and thermoplastic core layer components and the laminates within the scope of the present invention refer to such materials having a tensile elongation at break or fail of at least 10% as measured by ASTN D 638-72 test method for plastics. The forming (or, more accurately, post-forming) of the laminate can be readily accomplished by procedures Known to those skilled in the art One such procedure suitable for use herein involves subjecting the laminate to forming pressures at elevated temperatures, that is, a temperature which is sufficiently high to soften the thermoplastic core layer and permit the forming operation. to be carried out without concurrent delamination, weakening of the metal layers and/or the thermoplastic core layer, and the like. For most of the laminates of the present invention the forming operation at or near ambient temperatures is to be avoided since most of the laminates within the scope of the invention would not be expected to be cold formable at such temperatures. Herein laminates are not considered to be cold formable if at or near ambient temperature performance in a deep draw test is poor and/or the degree of bending sustainable is low and/or performance in tne Olsen Cup Test is poor, such tests being further discussed hereinafter. Moreover, an additional advantage in carrying out the forming operation at elevated temp era- tures is that such temperatures would usually effectively destroy the ambient-temperature memory of the laminate, and thus its tendency to recover to its straightened andlor flattened configuration upon removal of the forming pressure. This loss of memory (or reset) is retained up to sub stantially the original forming temperatures and for some laminates even higher. As a result, at elevated temperatures laminates of the present invention prepared, for example, from ductile metal layers and a ductile thermoplastic core layer are formable into permanently shaped structures. An important measure of the formability of the laminates within the scope of the present invention may be gained in a deep-drawing test, typical conditions for which are shown in the table below. In this test, a flat, circular sheet of laminate is forced into a female die by a male punch, to form a cup. A successful deep-draw with a high draw ratio (ratio of blank diameter to punch diameter) is desirable. Draw ratios comparable to those of drawing quality steel of equivalent stiffness are preferred. Values which are 50 percent lower than such steel are acceptable for many applications but values much lower than this would usually be considered poor. For example, as shown in the following table, a very good draw ratio between about 2.00 and about 2.31 is obtained with aluminum/nylon 6,6/aluminum or aluminum/polyester-polyether block copolymer-modified PET/aluminum laminates when the tests are conducted at temperatures between about 80 C. (176 F.) and 200 C. (392 F.). ThiS ratio is comparable .o the value of about 2.4 for drawing quality steel and, in many instances, better than the value of about 2.1 for drawing quality aluminum. Laminates which have a core of nylon 6,6 and metal layers of ductile low carbon steel have been found to perform well in the deep-draw test at ambient conditions. It will be noted, however, that the draw ratios shown in the table below are not limiting values, and therefore even higher draw ratios for such laminates are contemplated. RUN 1 2 3 4 5 EXAMPLE 5/82 5/82 5/82 42 58 BLANK DIAMETER, cm 7.19 7.62 7.26 6.86 6,65 BLANK TEMPERA TURE, C. 180 150 150 130 150 DIE TEMPERA TURE, C. 140 140 140 130 150 BANK HOLDER PREµSURE, 103 0 689.40/ 689.40 689.40 1861.38 1378.80 BLANK HOLDER TEMPERATURE, C. 140 150 150 130 150 PUNCH DIAME TER, cm 3.3a 3.3a 3.3a 3.3a 3.3b PUNCH TEMP ERATURE, C. 25 25 25 25 25 LUBRICANT Hydro- Hydro- Carbo- Hydro- Hydro Carbon Carbon Wax Carbon Carbon Grease Grease 20M Grease Grease DR4W SPEED, cm/s 0.51 0.51 2.33 0.51 0.51 DRAW RATIO 2.18 2.31 2.20 2.08 2.02 a Polished Punch. b Smooth Punch. Another important measure of the formability of the laminates is the degree to which they can be bent without fracture. The degree of bending sustainable by most laminates of the present invention without fracture is extremely poor at ambient temperatures and would in many cases be unsuitable for any applications requiring simple bending around even fairly large radii. Bending would be in general considered poor if the laminate would not sustain a 900 bend around a radius two times the thickness of the laminate. At elevated temperatures many of the laminates can readily be bent, without fracture, around radii sufficiently small for many applications. It should be pointed out, however, that certain laminates within the present invention have been found to have good bending capability at ambient temperature, for example, laminates which had a nylon 6,6 core and ductile low carbon steel metal layers. It would be expected that other laminates within the present invention may also perform well in bending tests at ambient conditions. Still another test of formability is a ball punch deflection test. Such as the Olsen Cup Test which involves only stretch (now draw) and wherein a sheet of laminate sample is securely clamped in a-ring die and stret,ch-formed to failure (first appearance OI a t'racture) wltn a /hemispherical punch under conditions typically as shown in the table below. One measure of performance is the forming ratio [ratio of punch penetration depth (deflection) to punch diameterj, with a high ratio being desirable. Using this test at low punch deflection rates (about 1 27 cm min) and ambient tempera- tures, very good worming ratios or between about 0.300 and about 0.400 have been obtained for laminates within the scope of the present invention, for example, laminates which had a nylon 6,6 core and ductile low carbon steel metal layers and other laminates as shown in the table below. These values are comparable to (and in many instances better than) the values obtained for aluminum and steel. Ratios even lower tan 0.300, for example as low as 0.150, are acceptable for some applications but values much lower than this would be considered poor performance in this test. PUNCH METAL THERMOPLASTIC DIAMETER DEFLECTION FORMING EXAMPLE TYPE THICKNESS,a cm TYPE THICKNESS,cm cm cm RATIO 12 5052-0 Aluminum 0.00762 Nylon 6,6 0.173 5.08 1.524b 0 300 14 " 0.0127 " 0.160 5.08 1.778 0.350 20 " 0.0127 " 0.168 5.08 1.727c 0.340 42 6061-0 Aluminum 0.0152 " 0.160 5.08 1.981c 0.390 -- Autobody Steeld 0.0838 -- -- 5.08 1.956c 0.385 -- 6061-T4 Aluminum 0.132 -- -- 5.08 1.549c 0.305 -- " 0.0813 -- -- 5.08 1.346c 0.265 -- 6061-0 Aluminum 0.0152 -- -- 5.08 1.321c 0.260 -- 5052-0 Aluminum 0.0127 -- -- 5.08 1.229c,e 0.242 -- " 0.00762 -- -- 5.08 0.993c,e 0.195 -- 1100-0 Aluminum 0.0102 -- -- 5.08 1.821c 0.358 -- " 0.0127 -- -- 5.08 1.603c,e 0.316 a Thickness for each metal layer. b Slight localized necking observed. c Sample deflected to fracture. d Sample taken from a 1977 Chevrolet Monte Carlo Hood. e Average of two runs. f Nose of punch was polished hard steel testing was with no lubrication between punch and specimen Since successful de±p- drswing and bending of most laminates within--the scope of :LNiS invention require the use of elevated temperatures, it is decidedly advantageous to carry'out the forming operation at elevated temperatures for most of the laminates, particularly for most laminates which are to be subjected to elevated temperature conditions subsequent to being, formed into the desired shape. And, as noted hereinabove, laminate temperatures between about 800 C. (176 .) and about 2000 C. '(392? F ) generally are suitable for carrying out post-forming operations. It will be apparent, of course, that the laminates within the scope of the present invention, when considered with respect to the combination of critical properties which they possess as well as the excellent formability in most cases indicated by the high-draw ratio, bending, and stretching characteristics obtained in drawing, bending and stretching tests, provide clear advantages over known laminates and other construction panel materials for use as construction panels then compared with metals per se, the combination of critical and important service properties -- high heat distortion temperature, low coefficient of Iin'ea:: : thermal expansion, low inelastic ratio, lightness in weight and excellent formability in most cases -- makes the lai- nates even more desirable for use as construction panels. Very good ductility at ambient temperatures is exhibited by the laminates of the present invention when both the metal layers and the therinoplastic core layer are in ductile states0 It will be recognized that while it is possible to use non-ductile forms of suitable metals in which higher flexural strength and higher effective flexural-modulus laminates are obtained, the formability discussed hereinabove is substantially reduced. However, where shaped structures are not required or desired, and substantially flat structures are suitable, non-ductile forms of suitable metals may be employed. One measure of the ductility of the laminates may be obtained via the aforemenLloned Olsen Cup Test. Other measures of ductility inol--ze tensile elongation which is measured according to ASTM D 638-72 test method for plastics, and multi axial impact strength which is measured via te Gardener Impact Strength (G1S) Test. In the Gardner Impact Strength Test, a sheet of test specimen at least 5008 cm by 5.08 cm (2 inches by 2 inches) in area is placed on the flat horizontal surface of a heavy steel test anvil The specimen is centered over a vertical cylindrical hole [3.18 cm (1.25 inch) inside diameter] in the test anvil. A light-weight polished steel punch with a 1.59 cm (0.625 inch) diameter bemispherical tip is placed on the top center of the specimen A 1082 kg (4 lbo) hammer is dropped from a selected height onto the punch, thereby subjecting the specimen to an impact energy in N-m tin.-lbO) determined by the product of the weight of the hammer and its initial height in cm (inches). Each laminate specimen is impacted only one time, and the formation of any crack on either side of the specimen is considered a failure for the particular impact. The test usually requires a fairly large number of test specimens (usually at least 12 to 16 for each test), and the maximum height at which more than half of the specimens pass without failure is used to calculate the GIS to within + 0.226 N-m (2 in.-1b.). From these measurements, it was determined that ductile laminates within the scope of the present invention having 20 to 30 percent less weight (mass)/m2 than 000813 cm (0.032 inch) thick automobile body steel show no failure at impact energies up to at least 18008 N-m (160 inO-lbO) and exhibit significantly smaller dents at these impacts than do the 0*0813 cm thick steel panels. Similar results are also obtained when compared with aluminum panels. Thus, the metal-thermoplastic-metal laminates also possess high energy absorption ability in that they are capable of absorbing high impact forces with little, if any, denting, and, as an additional feature, any dents which do occur can be readily hammered out without damage. Excellent weathering resistance is another valuable property exhibited by the laminates of the present invention. It will be apparent, of course, that the metal layers, if unprotected steel and the like, will corrode upon long and continuous exposure to the weathering elements. However, the adhesion between the metal layers and the thermoplastic core layer is highly resistant tn weather. For example, little or no loss in adhesion occurs with aluminum-nylon-aluminum laminates after one month in boiling water. Further, aluminum-nylon-aluminum laminates show no loss in peel strength after 13 months in water, or after 11 months in saturated aqueous calcium chloride or sodium chloride solutions, all at ambient temperatures. The adhesive peel strength of the layers of the laminates of the invention are not narrowly critical and can vary over wide limits. There is no particular upper limit on the peel strength since in the construction applications contemplated, the stronger the adhe simon, generally the more suitable is the laminate, particularly in post-forming operations. A lower limit on peel strength of the metal layer-thermoplastic core layer adhesion, however, is much more important and generally should be greater than about 1.75 x 103 N/m (10 pounds/linear inch) as measured by ASTM D 903-49 (Reapproved 1972). It will be apparent that, in addition to each of the properties ennumerated and discussed hereinabove, the metal-thermoplastic-metal laminates possess 'smooth metal surfaces. Since among the metals listed hereinbelow as being suitable, certain of the surfaces -- for example, steels, iron, and the like corrode upon continued exposure to weathering clements, it is highly advantageous to be able to easily apply a protective surface coasting to such corrosion-prone metal surface and cure such protective coating so as to enhance the strength and hardness of the coating.and securely adhere it to the metal surface. Thus, the laminates -- shaped, as well as substantially fat -- are readily protected by applying con @entional metal protective coatings to at least one of .h- metal so races and curing the same at elevated temperatures. As an example, since the most common of such protective coatings is paint, the metal surfaces are easily primed and painted. The paint may be cured at elevated temperatures, without the laminate undergoing distortion. For example, with respect to automobiles, curlng of the paint often is carried out at temperat1res 25 high as about 163 C. (3250 F.). The painted laminate is thereafter cooled to ambient temperatures. It will be recognized, however, that the actual temperature employed to cure the protective coating may vary according to the protective coating. But regardless of the actual temperature employed, whether lower or higher, It is contemplated that the protective coating will be cured at an appropriate temperature easily determined b those skilled in the art. 4. Component Materials of the Laminates Materials useful within the scope of the present invention must of necessity possess those properties and characteristics which will yield the laminate having an improved combination of service properties considered important and critical for demanding construction applications. Such critical combination of properties, as noted hereinabove, includes, among others, a heat distortion temperature of at least about 1300 C. (2660 F.), a coefficient of linear thermal expansion less than about 63 x 10 C. 1, an inelastic ratio less than about 93%, and a weight less than about 9.76 kg/m2 (2 lb./ft. 2) The thermoplastic core layer materials are selected from the group consisting of paitly crystalline oclyamides and polyesters. These thermoplastics possess the necessary properties to meet the requirements demanded of thermoplastics useful within the scope of the present invention. Included among the property requirements are: (a) the the@@oplastic core layer materia must be partly crystalline; and (b) the thermoplastic core layer material must have a crystalline melting point greater than 1300 C. (2660 F.). The term "partly crystalline polyamides and polyesters" is employed herein to describe polyamideand polyester-based thermoplastic compositions, at least 407c by weight of which is organic thermoplastic polymer(s), with at least 50% by weight of the organic thermoplastic polymer(s) being polyamide or polyester polymer chains or chain segments having a degree of crystallinity (DC) greater than about 15%. This at least 50% by weight is referred to herein as the partly crystallinepolyamide or polyester portion. The degree of crystallinity is specified by the following formula: DC = (dpc - d0c)/(d100c - d0c) wherein: o dpc is the density of the partly crystalline polyamide or polyester portions of the thermo plastic composition at 23 C., exclusive of substantial volume fraction(s) of other non crystallizable organic-polymer-modifier or inorganic-filler phases which the thermo plastic core composition may contain; o d is the density of the amorphous fractlo Oc (DC = 0%) of-the partly crystalline polyamide' or polyester portion of the thermoplastic compositlon at 23 C.; and d100c is the density of the crystalline fraction (DC = 100%) of the partly crystalline polyamide or polyester portion of the thermoplastic compo- sition at 23 C. The value of d100c may be calculated from the crystal type and crystal lattice parameters obtained from wide- . angle X-ray diffraction measurements. The value of doc may be obtained via density measurements on quenched samples exhibiting no apparent degree of crystallinity by X-ray diffraction of differential scanning calorimetric measurements. Alternatively, the value of d@ Sned by . ained by extrapolating the dependence of den s ty of partly crystalline samples of the organic poly cr with known finite values of apparent degree of crys zallnit) (DC ) to the value of density d at which DCa is zerc. Values of DC for the partly crystalline or a ganic polymer samples may be determined either via wideangle X-ray diffraction, as that percent the X-ratiation diffracted at wide angles by the polymer crystallites is of the total X-radiation both diffracted and scattered at wide angles by both the polymer crystallites and the amorphous portions of the polymer, or by differential scanning calorimetric measurements of the latent eat of melting, whereupon the apparent degree of crystallinity DCa is that percentage the measured heat of melting is of an estimated fixed value for the perfect polymer crystal In addition to the property requirements (a) and (b) listed hereinabove, the thermoplastic core layer preferably should be ductile, particularly in those laminates which are to be subjected to post-forming operations and have a void level less than about 15% in that higher void levels tend to adversely affect the multiaxial impaet resistance and formability of the laminates fabricated therefrom, Materials which meet the above requirements of the thermoplastic core layer, as noted hereinabove, are selected from the group consisting of partly crystalline polyamides and polyesters having crystalline melting points greater than 1300 C. (2660 F.). Illustrative of suitable partly crystalline polyamides are various nylons, for example, nylon 6 or poly(C-caprolactam) or poly(imino-l-oxohexamethylene), nylon 11 or poly(ll-aminoundecanoic acid) or poly(imino-l-oxoundecamethylene), nylon 12 or poly(lauryl lactam) or poly(12-aminododecanoic aCi-l) or poly(imino-l-oxododecamethylene), nylon 6,6 or poly (hexamethylene adipamide) or poly (iminoadipolyimino- hexamethylene), nylon 6,9 or poly(hexamethylene azelaamide) or poly(hexamethylene nonandiamide) or poly(iminohexamethy leneiminoazelaoyl), nylon 6,10 or poly(hexamethylene sebacamide) or poly(hexamethylene decanediamide) or poly (iminohexamethyleneiminosebacoyl), nylon 6,12 or poly (hexamethylene dodecanoamide) or poly(iminohexamethyleneiminododecanedioyl), and nylon 4 or poly(6-butyro- lactam) or poly(imino-l-oxotetramethylene), nylon 7 or poly(7-aminoheptanoic acid) or poly(7-aminooenanthylic acid) or poly(imino-l-oxoheptamethylene), nylon 8 or poly(8-aminocaprylic acid) or poly(8-aminooctanoic acid) or poly(imino-l-oxooctamethylene), nylon 10,6 or poly (decamethylene adipamide) or poly(iminoadipoyliminodecamethylene) and numerous partially aromatic nylons (PARNs). PARNs result when an aromatic residue or unit is substituted in whole or in part for a aliphatic residue or unit in an aliphatic nylon polymer. For example, substitution of all of the adipic acid [HOOC-(CH2)4 COOH] residues in nylon 6,6 by those from mixtures of about 50-70t terephthalic acid (TA, or p-HOOC-C6H5-COOH)/- 50-308 isophthalic acid(IA, or m-HOOC-C6H5-COOH) gives suitable, PARNs which are high-melting; partly crystalline nylons 6,TA-co-6,IA or poly(hexamethylene tere-co-iso-. phthalamides) or poly (iminohexamethyleneiminoterephthaloyl co-isophthaloyls). Other suitable PARNs are partly crystalline nylons 6,6-co-6,-TA, nylons 6,6-co-6,tA, nylons 6,6-co-6,TA-co-6,IA, and other similar PARNs, including partly crystalline PARNs wherein some or all of the diamine residues have aromatic character and those containing lactam residues, such as nylons 6-co-6,6-co-6,TA. Various other types of copolyamides also are suitable.- Examples are partly crystalline copolyamides of nylons 6-cO-ll; nylons 6-co-12/ nylons 6-co-6,6; nylons 6-co-6,9; nylons 6-co-6,12; nylons ll-co-12; nylons ll-co @@; nylons 11-co-6,9; nylons 11-co-6,12; nylons 6-co-6 6,10; nylons 6,6-co-6,9-co-6,10; nylons 6,9-co-6, TA c-6,IA and many other similar partly crystalline conoç- amides. Various block copolymers with partly crystalline polyamide hard blocks or chain segments also are suitable. Examples of such materials are nylon 6-blockpoly(tetramethylene oxide), nylon 6-block-poly(polypropylene oxide) nylon 6-block-poly(±-caprolactone), nylon 6block-poly(butadiene), nylon 6-block-poly(dimethylsiloxane), nylon 6,6-block-poly(tetramethylene oxide), nylon 6,6-block-poly(propylene oxide), nylon 6,6-block-poly (butadiene), nylon 6,6-block-poly(dimethylsiloxane), and many other similar block copolymers with partly crystalline polyamide blocks or chain segments, including those with partly crystalline copolyamide blocks or chain segments, such as (nylon 6,6-co-6)-block-poly- (tetramethylene oxide), (nylons 6,TA-co-6,IA)-blockpoly(tetramethylene oxide). These block copolymers with partly crystalline chain segments and soft or rubbery or elastomeric blocks or chain segments can exhibit lownotch sensitivity and high toughness and resistance to impact, even at low temperatures. Other suitable types of block copolymers are those with more than one type of crystallizable hard blocks, such as nylon 6,6-blockpoly(ethylene terephthalate), nylon '6,6-block-poly(tetra- methylene terephthalate), and block copolymers where both types of blocks or chain - segments are hard, but only the polyamide or copolyamide'blocks or chain segments are crystallizable, such as nylon 6,6-block-poly (oxy-l,4-,-phenylenesulfonyl-l,4-phenyleneoxy-l,4-pheny- leneisopropylidene-l,4-phenylene), Numerous graft copolymers with partly crystalline polyamide or copolyamide bocks or chain segments also are suitable. Examples of such materials are poly (ethylene-co-propylene)-graft-nylon 6, poly(ethyleneco-propylene)-graft-nylon 6,6, poly(ethylene-co-propylene)graft-nylon 6,6, poly (ethylene-co-propylene) -graft- (nylon 6,TA-co-6,IA), poly(butyl acrylate)-graft-nylon 6,6, poly (butyl acrylate)-graft- (nylon 6,TA-co-6,IA), polyisobutylene-graft-(nylon 6,TA-co-6,IA) e As in the case of certain block copolymers, soft, rubbery or elastomeric polymers grafted with partly crystalline polyamides or copolyamides can have low notch sensitivity and high toughness and resistance to impact even at low temperatures. Also suitable as the thermoplastic core layer in the laminates of this invention are blends or mixtures of the above partly crystalline polyamides, and polyamide and copolyamide block and graft copolymers. Examples are blends of nylon 6 with nylon 6-block-poly (tetramethylene oxide), nylon 6,6 with nylon 6-blockpoly(propylene oxide), nylon 6,6 with poly(ethyleneco-propylene)-graft-nylon 6,6, nylon 6,6 with poly(butyl acrylate)-graft-nylon 6,6 and many other similar blends. Such materials also can exhibit low-notch sensitivity and high toughness and resistance to impact, even at low temperatures. Illustrative of suitable polyesters are partly crystalline poly(alkylene terephthalates) having -alky line groups or residues with two to about ten carbon atoms, such as poly(ethylene terepht-halate), poly(butylene terephthalate) or poly(tetramethylene terephthalate), polytdecamethylene terephthalate, poly(l,4-cyclohexyldi methylol terephthalate) and many similar partly crystalline poly (alkylene terephthalates). Partly crystalline poly(alkylene tereplithalateco-isophthalates) having alkylene groups with two to about eight carbon atoms and a terephthalate residue/isophthalate residue ratio greater than about 2.5 also are suitable. Examples are partly crystalline poly(ethylene 70-100% terephthalate-co-30-0% isophthalates), polybutylene 70-100% terephthalate-co-30-0% isophthalates), poly(l,4-cyclohexyldimethylol 70-100% terephthalate-co SG-Q% isophthalates), and numerous other partly crvstal- line alkylene glycol-terephthalate copolyesters, such as partly crystalline poly(ethylene-co-butylene terephthal- @tes), poly (ethylene-co-neopentylene terephthalates), poly (butylene-co-cyclohexyldimethylol terephthalates), @@ly (ethylene-co-cyclohexyldimethylol terephthalates), an@ poly (ethylene-co-cyclohexyldimethylol terephthalateco-isophthalates). Partly crystalline. copolyesters of alkylene glycols with other aromatic dicarboxylic acids are also suitable . Examples are partly crystalline poly (ethylene terephthalate-co-2,2'-biphenyldicarboxylates), poly (butylene terephthalate-co-4,4'-biphenyldicarboxylates) poly(butylene terephthalate-co-phenylindanedicarboxylates), poly (butylene terephthalate-co-t-butylisophthalates), and poly(butylene terephthalate-co-2,6-naphthalenedicar- boxylates). Partly crystalline copolyesters containing some aliphatic dicarboxylic acid residues, and which have high crystalline melting points [i.e., above 1300 C. (2660 F.)] are also suitable. Examples are high melting, partly crystalline poly(ethylene terephthalate-co-adipates), poly(l,4-cyclohexyldimethyfol terephthalate-co-adipates), and poly(butylene terephthalate-co-adipates) Numerous partly crystalline aromatic polyesters and copolyesters are also suitable0 Examples are poly[bi- (4-hydroxy-phenyl)-l,2-ethane isophthalate], poly[bis(4- hydroxyphenyl)methane isophthalatel, polylp-hydroxyben- zoyl-co-ethylene terephthalates], polylpthydroxybenzoyl- co-ethylene terephthalate-co-isophthalates], poly [bis (4 hydroxyphenyl)-l,2-ethaie isophthalate-co-azelaoates], and poluy [bis (4-hydroxyphenyl)-1,2-ethane terephthalateco-azelaoates]. Just as block copolymers with partly crystalline polyamide chain segments are suitable as the thermoplastic core layer in the laminates of the present invention, so too are block copolymers with high-melting, partly crystalline polyester of co-polyester blocks or chain segments. A few examples of such block copolymers are poly (ethylene terephthalate)-block-poly-(tetramethylene oxide), poly (butylene terephthalate)-block-poly-(tetramethylene oxide), poly(butylene terephthalate-co-isophtha late)-block-poly(tetramethylene oxides), poly(ethylene terephthalate)-block poly (E -caprolactone), and poly (tetra- methylene terephthalate-co-isophthalate)-block-poly(buta dienes) These types of block copolymers also can have low-notch ens sensitivity and high toughness and resistance to impact, even at low temperatures Graft copolymers with high-melting, partly crystalline polyester of copolyester blocks or chain segments also are suitable as the thermoplastic core layer. A few examples are high-melting, partly crystalline polyisobutylene-graft-poly(ethylene terephthalate), polyisobutylene-graft-poly(butylene terephthalate), poly(ethylene-co-propylene)-graft-poly(butylene terephthalate-co-isophthalaltes), and poly(butadiene)-block poly(butylene terephthalate). These types of graft copolymers also can have low notch sensitivity and high toughness and impact strength, even at low temperatures. The thermoplastic materials can be modified with fillers, reinforcing agents, plasticizers, stabilizers, flame retardants, and other polymer modifiers, as are well-known in the art, in order to alter their properties and thereby enlarge the scope of applicability. One such modification comprises reinforcing the thermoplastic materials with mineral and/or organic fillers and fibers which may have been treated with adhesion promoters or coupling agents capable of increasing the adhesion of the fillers and fibers to the thermoplastic matrix molecules. A large number or organosilane compounds (discussed hereinbelow) have been found to be especially capable of performing the task of improving the adhesion between thermoplastics and mineral fillers and glass fibers, thereby creating a synergistic effect when compared to non-treated fillers and fibers. Preferred mineral fillers include small-particle-size quartz, wollastonite, feldspar, calcined kaolinite clay, and the like. The concentration of such mineral fillers, when employed, can vary from very small amounts, such as one or two percent by weight, up to about 508 by weight, or even higher, with concentrations between about 20% and about 45% by weight being preferred. Fibers suitable for use as modifying agents include glass fibers and other high modulus, high performance fibers, such as graphite, boron, steel, aromaticpolyamide fibers, potassium titanate wiskers and the like. It will be noted that while such high modulus high Perfor- mance fibers -- glass fibers, for example -- improve the strength and flexural modulus of the thermoplastics such as herein employed, they result in a decreased multiaxial impact resistance. In spite of this apparent drawback, however, concentrations of fibers up to about 10% by weight or even higher (for example, about 45% by weight) may be advantageously employed for certain property enhancement, where desired. Metals which are useful within the pre@ent invention are fairly wide in scope. Such metals, however, must meet certain requirements. These requirements are: (a) the metal must have a melting point greater than the crystalline melting point of the thermoplastic core layer, that is, greater than at least 1300 C. (2660 F.); (b) each metal layer must have a minimum thick nes of at least about 0.00127 cm (0.0005 inch, 0.5 mil). In addition to requirements (a) and (b), the @etais prefferably should have n tensile yield strength at an effset of 0.2% elongation greater than 1.82 x 106 N/m2 (264 1b. lin 1) at temperatures greater than the crystalline melting point of the thermoplastic core layer, a modulus of elasticity in tension greater than about 34.47 x 109 N/m2 (5 x 106 psi) at ambient temperatures, and the metals preferably should ce ductile, particularly when the resultant laminates are to be subjected to post-forming operations. The tensile yield strength at an offset of 0.2% elongation and he modulus of elasticity in tension are determined in accordance with ASTM D638-72 discussed hereinbefore. Metals which meet the above requirements, that @s, those which @@sult in laminates possessing in combitation the critically important heat distortion tempera-. ture of at least about 130 C. (266 F.), coefficient f linear thermal expansion less than about 63 x 10-6 C.-1, nelastic ratio less than about 93%, and weight less than about 9.76 kg/m2 t2 lb /ft. 2), may be either ferrous or on ferrous Exemplary of the ferrous metals are steels, particalarly low-carben @teels, staipless steels, galvan- ized iron, and the like. Non-ferrous metals are exemplified by aluminum, magnesium, zinc, tin, nickel, titanium, copper, cobalt, beryllium, and high melting [that is, greater than 1300 C. (266 F.) alloys of each of these metals, such as various brasses and bronzes. The thermoplastic core layer and the metal .layers are uniformly and securely laminated together to forp thc laminates If desired, a suitable adhesion agent from among those listed hereinbelow may be employed to facilitate the formation of laminates possessing the critically important properties discussed in detail hereinbove. It will be noted that while the employment of an adhesion agent in the laminates is not essential, in general it is preferred to employ an adhesion agent to ensure strong jmetal-thermoplastic adhesion. tor example, a peel strength of at least about 1.75 x 103 N/m generally is adequate. It will be apparent, however, that even stronger metal-thermoplastic adhesion is preferred. Adhesion agents, when employed, which are suitable for anchoring the metal layers to the thermoplastic core layer to provide adequate adhesion of the metal layers to the thermoplastic core layer are not narrowly critical. All that is necessary is that such adhesion agents are compatible with the laminate component layers and provide adhesion between the facing metal and thermoplastic core layers' surfaces adequate for the contemplated end use. Such adhesion agents include, for example, organosilane adhesion promoters or coupling agents. Illustrative of classes of suitable organosilane adhesion agnets are amino-functional alkyltrialkoxysilanes, epoxy-functional alkyltrialkoxysilanes, glycidoxy-functional alkyltrialkoxysilanes, and mixtures thereof. These classes of organosilanes are exemplified, respectively, by gamma-aminopropyltriethoxysilane and N beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane, beta-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, gammaglycidoxypropyltrimethoxysilane, and gamma-methacryloxypropyltrimethoxysilane. These compounds are commercially available from Union Carbide Corporation, New York, New York 10017 as A-llOO silane, 0-li20 silane, A-186 silane, A-187 silane, and A-174 silane, respectively. Gamrna-Glycidoxypropyltrinethoxysilane and N-beta- (aminoethyl)-gamma-propyltrimethoxysilane also are commercially available from Dow Corning Corporation, Midland, Michigan 48640 as Z6040 silane and Z6020 silane, respectively. Such silane coupling agents may be employed as alcoholic solutions, aqueous alcoholic solutions, or simply aqueous solutions. The conc:entraLion of the silane solution typically is between about 0.01% and about 1.5% by weight. Other suitable adhesion agents may also be em ployed. Exemplary of such other suitable adhesion agents are adhesives such as nitrile rubber-phenolic resins, epoxies, acrylonitrile-butadiene rubbers, urethane modi ied acrylics, polyester-co-polyamides, polyester hot melts, polyester hot melts crosslinked with polyisocyan- 3tes, polyisobutylene modified styrene-butadiene rubbers, urethanes, ethylene-acrylic acid copolymers, ethylenevinyl acetate copolymers, and the like. Of the suitable adhesion agents listed hereinabove, the organosilane adhesion promoters or coupling agents are preferred in that the resultant metal-thermoplastic adhesion is both stronger and more resistant to deterioration and failure. Various techniques employing the adhesion agents noted hereinabove so as to ensure the required adhesion between the facing metal -layer-thermoplastic core layer surfaces are suitable. One such technique gives exceptional results when the metal layers are aluminum and the thermoplastic core layer is a nylon, a nylon copoly ier a nylon terpolymer, poly(ethylene terephthalate), or modification thereof, An exemplary method employing this technique to fabricate the laminates so as to ensure strong metal-thermoplastic adhesion may be described as follows, with aluminum and nylon 6,6 being used as the metal layers and the thermoplastic core layer, respectively, or convenience. The aluminum-metal layers are first subjected to a degreasing operation to remove any grease and dirt from their surfaces (although such degreasing is unnecessary, and therefore may be omitted, when the metal is already free of such contaminants). For example, washing the surface or complete submersion thereof in toluene or some other suitable solvent is convenient. If desired, the cleaned aluminum layers then may be soaked in a hot dichromate-sulfuric acid (chromic acid) solution or a dilute solution of aqueous alkali metal hydroxide -- for example, sodium hydroxide or-potassium hydroxide -- to etch the surface, although said etching is not an absolute necessity. Excess etching agent, whether hot chromic acid or dilute aqueous alkali metal hydroxide, is removed from t etched surface by thorough rinsing of such surface in water. Following the pre-treatment (when necessary), the aluminum-metal layer surfaces are treated with an organosilane adhesion promoter to provide the preferred adhesion agent. Alternatively, the nylon 6,6 layer similarly may be treated with an organosilane adhesion promoter. But in any event, the organosilane adhesion promoter (or in general the adhesion agent) is interposed between the facing surfaces of the aluminum layers and the nylon ,6 layer regardless of whether it is placed on the surfaces of the aluminum layers or the surfaces of the nylon 6,6 layer. As noted hereinabove, however, the impcs-tion of an organosilane adhesion promoter between the facing surfaces of the metal layers and the thermoplastic core layer, while convenient, is not a absolute necessity. Other adhesion agents tor no adhesion agent a; alp so can be employed, although the organosilane adhesion promoters are preferred for use as adhesion agents. As an example, laminates comprised of aluminum, as the metal layers laminated to a thermoplastic core layer of a mincral-reinforced nylon 6-co-6,6 (VYDYNEs R-240), and of aluminum laminated to a block-copolymer (HYTRELs 0 4056)-modified poly(ethylene terephthalate), can be prepared without utilizing any adhesion agent at all. Such laminates possess all the critical and important properties necessary for use as construction panels, even though the long-term stability of the metal-thermoplastic bond may suffer adversely. It will be appreciated, however, that (when employed) the particular pre-treatment and adhesion agent, and procedure employed to provide the desired laminate will vary depending upon both the particular metal layers and thermoplastic core layer employed and their condition. The elevated temperatures and pressures employed in the preparation of the laminates are not narrowly critical. Suitable temperatures necessary for the formation of strong and secure metal-thermoplastic adhesion can vary, for example, between about 1000 C. (2120 F.) and about 350" C. (6620 F.). In a similar manner, suitable pressures are those sufficient to maintain contact between the facing surfaces of the two metal layers and the thermoplastic core layer in order to pe- vide metal-thermoplastic adhesion having a peel strength of at least about 1.75 x 103 N/m (10 lb./linear inch), -. It will of course be appreciated that thepar- ticular conditions of temperature, press-ure and the like will vary depending upon the particular materials making up the laminates. A variety of methods of actually fabricating the laminates of the present invention may be employed including compression molding, extrusion lamination, and the like. One preferred method of fabrication of the laminates is to extrude a sheet of the thermoplastic material being employed and laminate the molten thermoplastic layer between the two metal layers, so as to betain excellent adhesion as noted hereinabove. It is also possible to cast some the-rinoplastics, such as nylon 6 and its block copolymers, by polymerizing e-caprolac- kam by anionic polymerization in situ between the metal layers using acyllactams and the like such as acetylcap- rolactam, adipoyl-bis-caprolactam, therephthaloyl-bis caprolactam, isophthaloyl-bis-caprolactam, and the like as initiators. It is also contemplated that the metal layers can be preformed to the desired shapes by stan- dard metal-shaping techniques and held in a mold while the thermoplastic core layer is injection molded, com pression molded, or cast polymerized between them. 5. Experimental Examples The following Examples illustrate the present invention. They are not to be construed as limitive upon the overall scope thereof. EXAMPLE 1 A general description of the procedures em ployed to prepare the metal-thermoplastic-metal laminates of this invention is given below. The procedure can be conveniently described as a step-wise procedure consis ting of the following operations in the order given: (a) metal pre-treatment; (1) metal degreasing; (2) metal cleaning/etching; (b) thermoplastic pre-treatment; (c) application of the adhesion agent (if employed); (d) fabricating the laminate. It will be noted, however, that steps (a) and/or (b) mav be unnecessary and therefore may be omitted where the metal layers and/or the thermoplastic core ay@r materials are free from contaminating agents such - @,@@@ , and the like, for example, contempor ly or newly extruded materials. fa) Metal Pre-treatment (1) etal Degreasing -- The metal surface is cl@aned (when necessary) of processing oils by vapor degreasing in a suitable solvent, such as trichloroethylene. Alternatively, the surface is wiped clean with a clean cloth (a Webril Litho Pad is convenient) while immersed in a suitable solvent, such as, for example, trichloroethylene, l,l,l-trichloroethane, toluene, acetone, and the like. The metal surface is thereafter rinsed with fresh solvent, either the same or different -- for example, an acetone rinse following an initial cleaning with toluene -- without wiping and the excess solvent allowed to evaporate. (2) Metal Cleaning/Etching -- Following the degreasing [Step (a) (1)] (when employed) the metal preferably is cleaned/etched prior to the application of the adhesion agent (when employed) in order to provide the highest metal-thermoplastic-adhesion strength, although in many cases the cleaning/etching is not necessary. The metal surface can be etched by either chemical or non-chemical means. Non-chemical etching (or mechanical abrasion) includes brushing with a wire brush, grit blasting with alumina or steel grit, wet sanding, and the like. Either of these etching treatments is followed by degreasing as described in Step (a) Cl) The chemical etching media may be either alkaline, acid or some combination thereof. Suitable alkaline etching media include aqueous solutions of sodium hydroxide, sodium netasilicate, proprietary metal cleaners available commercially, such as, for example Apex 764 M cleaner (available froc Apex Alkali products Company, Philadelphia, Pennsylvania), and the like Suitable acid et@ning media include dichromate-sulfuric acid (chromic acid) solutions, aqueous hydrochloric acid solutions, phosphoric acid solutions, and the like. The particular medium employed may vary depending on the metal being used in that different metals sometimes require different treatments. In certain instances metals are suitably cleaned with several o the treat dents Exemplary treatments for specific metals include the following: (1) Aluminum a) sodium hydroxide solution, 2-5% at 25 C.; b) sodium metasilicate solution - 50.0 grams/liter at 700 CO; c) Apex 764 M cleaner - 50ç0 grams/liter at 700 C.; and d) sodium dichromate solution - 30.0 grams sodium dichromate (Na2Cr20702H20), 150 milliliters concentrated sulfuric acid (sp. gr. 1.84), and 1 liter water at 600 C. (2) Low Carbon Steel a) phosphoric acid, 2% at 250. Co (3) Stainless Steel a) Apex 764 M cleaner - 5000 grams/liter at 700 C.; b) wipe with 1:1 hydrochloric acid-water, abrade lightly with a wire brush, then Apex 764 M cleaner - 50X0 grams/liter at 700 CO; and c) abrade lightly with a wire brush, then Apex 764 M cleaner - 50.0 grams/liter at 70* C. The metal surface is etched by immersing the metal in the etching medium for an appropriate time period0 Typical treatment times are: sodium hydroxide solution, 2-5 minutes; Apex 764 Wi cleaner and sodium metasilicate solutions, 2 minutes; dichromate-sulfuric acid (chromic acid) and phosphoric acid solutions, 5 minutes. Following the cleaning/etching treatment, the metal is thoroughly rinsed with water. hen an alkaline medium treatment is employed, in general, the metal is washed with hot, running water while wiping with a clean cloth (a Webrils Litho Pad is convenient), followed by a hot water rinse without wiping. The metal is thereafter blown dry with a jet of clean air or nitrogen. When an acid medium treatment is employed, in general, the metal is washed successively with tap water and demineralized water. If a silane adhesion promoter is to be applied as in Step (c), it usually is applied directly to the wet metal although it also can be applied to the dry metal, if desired. If silane is not to be used, the metal is first blown dry as described above and then oven dried at a suitably convenient temperature. (b) Thermoplastic Pre-Treatment In order to obtain good metal-thermoplastic adhesion during Step (d) hereinbelow, any processing aid present, for example, a mold release agent as in the case of a cast thermoplastic sheet, must be removed. If the thermoplastic is not to be used above its melting point in subsequent operations [Step (d)J, its surface is prepared by thoroughly wiping with a suitable solventmoistened clean cloth, abrading lightly, again wiping the surface, and finally drying. On the other hand, if Step (d) involves melting the thermoplastic, the sanding or abrading step is not necessary unless it is to remove foreign material from the surface of the thermoplastic. (c) Application of the Adhesion Agent The application method for the adhesion agent (when employed) depends on the particular system being used. been adhesion agents referred to as adhesion promoters as for example, the organosilane coupling agents are employed, they are applied as dilute solutions (usually about 0.01% to about 100% by weight) to the surface in question. The amount of such agent applied to the surface in question is generally quite small, and only a small amount is retained on the surface -- a monomolecular layer being ideal for good metal-thermoplastic adhesion. The gd- hesion promoters may be applied to the metal surface and/or the thermoplastic surface by immersing the surface in question into the solution or by spraying the solution onto the surface. In either case, the material is allowed to drain briefly and thereafter dried either by air drying or forced air drying with a jet of air or nitrogen without touching the silanetreated surface. An alternative method involves incorporating the adhesion promoter into the thermoplastic However, an application to themetal surface is the preferred method in that following the application, the metal can be readily baked at elevated temperatures, usually about 1300 C. for between about 5 minutes and about 30 minutes, to assure complete dryness of the metal surface prior to use in Step (d). When adhesion agents such as an epoxy or a nitrile-rubber/phenolic-system is employed, they are usually applied by conventional coating techniques, for example, metering bar, roll coater, and the like. Such adhesion agents are applied in an amount such that the thickness is measured in thousandths of a centimeter (cm). They may be applied to the metal and/or the thermoplastic surface. (d) Fabricating the Laminate Procedure (1) - Adhesion Promoter Adhesion Agent Laminate' -- The-laminates containing the organosilane adhesion promoters are fabricated by placing a layer or sheet of metal on each side of a layer of thermoplastic, with the silane-treated side of the metal layers in contact with the thermoplastic core layer. For com@enience and to avoid polymer flash getting pin two hot press platens during the actual laminating phase, a "throw-away" back-up sheet is placed between the treated metal layers and the press platens, Thin gage aluminum foil is useful for this purpose. Additional back-up sheets, for example-, polished metal sheets to ensure surface smoothness of the finished laminate, can also be used. The assembly is placed in a press and heated above the melting point of the polymer under sufficient pressure to maintain contact between the metal and thermoplastic and to cause the thermoplastic to flow to the thickness desired. The laminates total thickness, in addition to the total thickness of the metal layers, is controlled by using suitable spacers between the platens or, preferably, a TEPLON9R coated metal mold frame of designated thickness around the perimetcr of the laminate assembly0 Contact at the desired temperature is maintained for a time sufficient to ensure good metal and thermoplastic adhesion, usually a few seconds up to about 30 minutes. The metalthermoplastic-metal laminate is then cooled under pressure to below the melting point of the thermoplastic. The pressure is then released and the laminate removed from the press. Certain laminates, for example, those containing poly(ethylene terephthalate)-based thermoplastics, are slowcooled under pressure in the press to about 80-1400 C below the crystalline melting point of the thermoplastic, and/or after being removed from the press, the laminate is post-annealed for about 1 hour, also at about 80-140 C. below the crystalline melting point of the thermoplastic. Procedure (2) - Adhesive Adhesion Agent Laminate -- The laminates containing adhesive adhesion agents are fabricated by disposing a metal layer on each side of a thermoplastic core layer in such a manner that the adhesive adhesion agent is interposed between the facing surfaces of the metal layers and the thermoplastic core layer. The assembly is placed in a press and heated under pressure to cure the adhesive and obtain metal-thermoplastic adhesion. Generally, the assembly is not heated above the melting point of the thermoplastic. As a result, the total thickness of the fabricated laminate is determined by the sum of the total thickness of the metal layers and the thickness of the thermoplastic core layer used to prepare it. Procedure (3) - Non-Adhesion Agent Laminate - The laminates containing neither adhesion promoter nor adhesive adhesion agents are fabricated by disposing a metal layer on each side of the thermoplastic core layer in a suitable riold The assembly is placed in a press and heated above the melting point of the polymer to effect lamination as described in Procedure (1) above. Procedure (4) - Continuous Extrusion Procedure -- The thermoplastic is extruded, in the melt between two layers of metal. Contact under pressure is maintained by pressing means such as suitably spaced, heated and/or chilled rolls and/or platens. Alternatively, the extruded thermoplastic melt may be allowed to solidify before contact with the metal alyers and then laminating as described in either of Procedures (1), (2) or (3), depending upon whether ar, adhesion agent is employed. Pressing means, such as suitably spaced, heated and/or chilled rolls and/or platens are used to effect the necessary con tact between the metal and thermoplastic. EXhNSLE 2 A metal-thermoplastic-metal laminate was prepared using 0.00508 cm (00002 inch, 2 mils) thick 1100-0 aluminum as the -metal layers and nylon 6,6 having a degree of crystallinlty of 338 as the thermoplastic core layer. The aluminum surface was degreased by immersion in trichloroethylene as described in EXAMPLE 1 above and then, cleaned/etched by immersion in a 5% aqueous solution of sodium hydroxide at ambient temperatures for a period of 5 minutes. The aluminum was removed from the alkaline solution and rinsed with hot, running water while wiping with a clean cloth (a Webril Litho Pad is convenient) followed by a hot water rinse without wiping and thereafter blown dry with a jet of clean nitrogen. A 0°48 aqueous solution of A-1100 silane was applied to the cleaned/etched aluminum surface and the sheets hung vertically to drain and air dry. They were then heated in an oven at 1300 C. for thirty minutes. The treated aluminum layers and the nylon 6,6 were assembled in a 0s178 cm (0*070 inch) thick TEFLON#- coated stainless steel mold frame with the treated surfaces of the aluminum layers facing the nylon 6,6. The assembly was placed in a platen press heated to 2850 C. Pressure was applied and maintained for 10 minutes after the nylon 6,6 had flowed to fill the mold cavity. The laminate was then cooled under pressure to 2000 C., afterwhich the pressure was released and the laminate. removed from the press. The laminate's properties are- tabulated in TABLE 1. EXAMPLES 3 - 9 Metal-thermoplastic-metal laminates using 1100-0 aluminum as the metal layers and nylon 6,6 as the thermoplastic core layer were prepared according to the procedure described in EXAMPLE 2 above. The properties of the laminates, including the component layers' thicknesses, are tabulated in TABLE 1. EXAMPLE 10 A 0.185 cm (0.073 inch, 73 mils)thick metalthermoplastic-metal laminate was prepared using 0.00254 cm (0.001 inch, 1 mil) thick 5052-0 aluminum sheets as the metal layers and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer. The aluminum surface was degreased by immersion in toluene followed by an acetone rinse as described in EXAMPLE 1 nd then cleaned/etched by immersion in a 50.0 grams/liter solution of sodium metasilicate at 70 C. for a period of 2 minutes. The aluminum was removed from the solution and rinsed with hot, running water while wiping with z clean cloth (a Webrils Litho Pad is convenient) followed by a hot water rinse without wiping and thereafter blown dry with a jet of clean nitrogen. A solution containing 2.5 milliliters of A-1100 silane in 1,000 milliliters of distilled water was applied to the cleaned/etched aluminum surface and the sheets hung vertically and allowed to drain and air dry. The treated aluminum layers and the nylon 6,6 were assembled in a 0.180 cm (0.071 inch) thick TEFLONS coated stainless steel mold frame and laminated as described in EXAMPLE 2 above. The laminate's properties are tabulated in TABLE 1. EXAWLES '11 - 14 Metal-thermoplastic-metal laminates using 5052-0 aluminum as the metal layers and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer were fabricated according to the procedure described in EXAMPLE 10 above. The laminates' properties are tabulated in TABLE 1. EXAMPLE 15 A metal-thermoplastic-metal laminate was fabricated using 000762 cm (0.003 inch, 3 mils) thick 5052-0 aluminum as the metal layers and nylon 6,6 having a degree of crystallinity of 3% as the thermoplastic core layer. The aluminum surface was degreased by immersion in X,l,l-trichloroethane as described in EXAMPLE 1 above and then cleaned/etched by immersion in a sodium dichromat dih rate, 150 milliliters concentrated sulfuric acid (sp. gr. 1.84), and 1 liter water at 600 C. for a period of 5 minutes. -The aluminum was removed from the chromic acid solution and rinsed thoroughly with running water followed by a demineralized water rinse. A 0o4% aqueous solution of A-1100 silane in distilled water (pH adjusted to 4.0 with formic acid) was applied to the cleaned/etched surface of the wet aluminum, The aluminum sheets were blown dry with a jet of clean nitrogen and heated in an oven at 1300 C. for 2 minutes. The treated aluminum layers and the nylon 6,6 were assembled in a 0.133 cm (0.0525 inch) thick TEFLONS coated stainless steel mold frame with the treated surfaces of the aluminum layers facing the nylon 6,6. The assembly was placed in a platen press heated to 2850 C. A pressure of 453.5 kg (0.5 ton) or less ram force was applied for 3 minutes and thereafter increased to 13605 kg (15 tons) for 1 minute. The laminate was then cooled under pressure to 138 C., afterwhich the pressure was released and the laminate removed from the press. The laminates properties are tabulated in TABLE 1. EXAMPLES 16 - 24 Metal-thermop.lastic-metal laminates using 50520 aluminum as the metal layers' and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer were fabricated according to the procedure described in EXAMPLE 15 above. The laminates' properties are tabulated in TABLE 1. EXAMPLE 25 A 0.187 cm (0.0735 inch, 73.5 mils) thick metal thermoplastic-metal laminate was prepared using 0.00254 ca (0.owl inch, 1 mil) thick 304 stainless steel (annealed) sheets as the metal layers and nylon 6,6 having a degree of crystallinity of 33 as the thermoplastic core layer. The stainless steel surface was degreased by immersion in toluene as described in EXAMPLE 1 above and then cleaned/etched by immersion in a 50.0 grams/ liter solution of Apex 764 M (a product Qf Apex Alkali Products Company, Philadelphia, Pennsylvania) gt 70" C. for a period of 2 minutes. The stainless steel was removed from the cleaning/etching solution and rinsed with hot, running water while wiping with a clean cloth (a Wcbrils Litho Pad is convenient) followed by a hot water rinse without wiping and thereafter blown dry with a jet of clean nitrogen. A solution containing 2.5 ailliliters' ot A-1100 silane in 1,000 milliliters of distilled water was applied to the cleaned/etched stainless steel surface and the sheets hung vertically and allowed to drain and air dry. They were then heated in an oven at 90" C. for 10 minutes. The treated stainless steel layers and the nylon 6,6 were assembled in a 0.182 cm (0.0715 inch) thick TEFLON -coated stainless steel mold frame with the treated surfaces of the stainless steel layers facing the nylon 6,6. The assembly was placed in a platen press, heated to 2850 C. Pressure was applied and maintained for 10 minutes after the nylon 6,6 had flowed to fill the mold cavity. The laminate was then cooled under .pressure to 1750 C., afterwhich the pressure was released and the laminate removed from the press. The laminate's properties are tabulated in TABLE 1 EXAMPLES 26 - 37 Metal-thermoplastic-metal laminates using 304 stainless steel (annealed) as the metal layers and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer were fabricated according to the procedure described in EXAMPLE 25 above. The laminates' properties are tabulated in TABLE 1. EXAMPLE 38 A metal-thermoplastic-metal laminate was prepared using 000152 cm (0.006 inch, 6 mils) thick 6()ol-T6 aluminum as the metal layers and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer according to the procedure described in EXAMPLE Z above, except that following the degreasing step, the aluminum was sanded with wet 400-grit sandpaper and cleaned/etched in a 2.5% aqueous sodium hydroxide solution A 0.122 cm (0.048 inch) thick TEFLON -coated stainless steel mold frame also was employed. The laminate's properties are tabulated in TABLE i. EXAMPLES 39 - '41 Metal-thermoplastic-metal laminates were prepared using 6061-T6 aluminum as the metal layers and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer. The aluminum surface was degreased by immersion in trichloroethylene as described in EXAMPLE 1 above and then cleaned/etched by immersion in a 10% aqueous hydrochloric acid solution at ambient temperatures for a period of 10 minutes. The aluminum was removed from the cleaning/etching solution and rinsed thoroughly with running water followed by a demineralized water rinse, buffed with steel wool, and air dried. The aluminum sheets were immersed in a 0.4t aqueous solution of A-1100 silane in distilled water and hung vertically to drain and air dry. They were then heated in an oven at 1300 C. for 30 minutes. The laminates were assembled and fabricated as described in EXAMPLE 2 above. The properties of the laminates, including the component layers' thicknesses, are tabulated in TABLE 1. EXAMPLES 42 - -44 Metal-thermoplastic-metal laminates using 6061-0 aluminum as the metal layers and nylon 6,6 having a degree cf cAystallinity of 33% as the thermoplastic core layer were prepared according to the procedure described in EXAMPLE 38 above The properties of the laminates, including the component layers' thicknesses, are tabulated in TABLE 1. EXAMPLES 45 - 48 These Examples illustrate the preparation of metal-thermoplastic-metal laminates without subjecting the metal layers to either degreasing or cleaning/- etching. Laminates were prepared using Lithoplate aluminum (Lith-Kem-Ko, wipe-on offset, brush grain) as the metal layers and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer0 The aluminum sheets were immersed in a ,solution contain X 4 milliliters of A-1100 silane in 1000 milliliters of 95% ethanol and hung vertically to drain and air dry0 They were then heated in an oven at 1300 C. for 30 minutes. The laminates were assembled and fabricated as described in EXAMPLE 2 above. The properties of the laminates, including the component layers' thicknesses are tabulated in TABLE 1. EXA'!PLE 49 - 54 Metal-thermoplastic-metal laminates were prepared using C 1010 low carbon steel - annealed as the metal layers and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer according to the procedure described in EXAMPLE 2 above, except that the cleaning/etching was effected by immers,ion in a 2% aqueous solution of phosphoric acid at ambient temperatures for a period of 0.25 minute (15 seconds). The laminates' properties, including the component layer thicknesses, are tabulated in TABLE 1. EXAMPLES 55 - 56 These Examples illustrate the preparation of metal-thermoplastic-metal laminates having metal layers of different composition and thicknesses on each side of the thermoplastic core layer. EXAMPLE 55 -- A 0.284 cm (0.112 inch, 112 mils) thick laminate was prepared using 0.00508 cm (0.002 inch, 2 mils) thick 304 stainless steel (annealed) and O . 0152 cm (0.006 inch, 6 mils) thick 6061-0 aluminum as the metal layers and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer. The metal layers were degreased by immersion in l,l,l-tri- chloroethane as described in EXAMPLE 1 above and thereafter cleaned/etched by immersion in 50.0 grams/liter aqueous solution of Apex 764 M at 700 C. for a period of 2 minutes. The metal layers were removed from the cleaning/etchirig solution and rinsed thorqughly with running water followed by a demineralized water rinse. A 0.3% aqueous, solution of A-1100 silane in distilled water (pH adjusted to 4.0 with formic acid) was applied to the cleaned/etched surfaces of the wet metals. The metal sheets were blown dry with a jet of clean nitrogen and heated in an oven at 1300 C , for 2 minutes. The treated metal layers and the nylon 6,6 were assembled in a 0.264 cm (0.104 inch) thick TEFL0N coated stainless steel mold frame with the treated surfaces of the metal layers facing- the nylon 6,6, The assembly was placed in a platen press heated to 285 C. A pressure of 907 kg (1 ton) or less ram force was applied for 3 minutes and thereafter increased to 13605 kg (15 tons) for 1 minute. The laminate was then cooled' under pressure to 38 C., afterwhich the pressure was released, then the laminate removed from the press. The laminate's properties are tabulated in TABLE 1. EXAMPLE ,56 -- A 0.279 cm (0.110 inch, 110 mils) thick metal-thermoplastic-metal laminate was prepared using 0.00508 cm (0.002 inch, 2 mils) thick 304 stainless steel (annealed) and 0.0127 cm (0.005 inch, 5 mils) thick 3003 H25 aluminum as the metal layers and nylon 6,6 having a degree of crystallinity of 33% as the thermoplastic core layer according to the procedure described in EXAMPLE 55. The laminate's properties are tabulated in TABLE 1. EXAMPLE 57 A metal-thermoplastic-metal laminate was prepared using 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum as the metal layers and ZYTEL ST-801 (a high impact nylon 6,6) as the thermoplastic core layer according to the procedure described in EXAMPLE 10, except that the aluminum was cleaned/etched in a 50.0 gram/liter aqueous solution of Apex 764 N and a 0.173 cm (0.068 inch) thick TEFLON -coated stainless steel mold frame was employed. The laminate's properties are tabulated in TABLE 1. EXAMPLE 58 This Example illustrates the preparation of a metal-thermoplastic-metal laminate without the use of an adhesion agent. A 0.190 cm (0.075 inch, 75 mils) thick laminate was prepared using 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum as the metal layers and VYDYNEe R-240 (a Monsanto mineral reinforced nylon 6-co-6,6) as the thermoplastic core layer. The aluminum surface was degreased by immersion in 1,1,1-trichloroethane as described in EXAMPLE 1 above and then cleaned/etched by immersion in a sodium dichromate (chromic acid) solution containing 30.0 grams sodium dichromate dihydrate, 150 milliliters concentrated sulfuric acid (sp. gr. 1.84), and 1 liter water at 600 C. for a period of 5 minutes. The aluminum was removed from the cleaning/etching solution, rinsed thoroughly with running water followed by a demineralized water rinse, blown dry with a jet of clean nitrogen, and heated in an oven at 130 C. for 2 minutes. The dry cleaned/etched aluminum layers, and the VYDYNE R-240 were assembled in a 0.165 cm (0.065 c) thick TEFLON#-coated stainless steel mold frame @@ the cleaned/ethched surfaces of the aluminum layers acig the VYDYNE# R-240. The assembly was placed in a platen press heated to 285 C. A pressure of 1814 kg (2 tons) or less ram force was applied for three minutes and thereafter increased to 22675 kg (25 tons) for I minute. The laminate was then cooled under pressure to 1380 C, afterwhich the pressure was released and the laminate was removed from the press ,The laminate's iJerties are tabulated in TABLE 1 EXAMPLE 59 The procedure of EXAMPLE 58 was repeated except that 0.0152 cm (0.u06 inch, 6 mils) thick C061-0 aluminum was used as the metal layers and a 0.160 cm (0.065 inch) thick TEFLON & coated stainless steel mold frame was employed. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 60 The procedure of EXAMPLE 60 above was repeated, except that 000152 cm (0.006 inch, 6 mils) thick 6061-T6 aluminum was used as the metal layers and a 0.122 cm U.u48 inch) thick TEFLON#-coated stainless steel mold frame was employed The properties of the laminate are tabulated in TABLE 1. EXAMPLE 61 Ine procedure of Example 58 above was repeated, except that 0.0127 cm (0.005 inch, 5 mils) thick 5052-0 aluminum was used as the metal layers and 0.165 cm (0.065 inch) thick TEFLON#-coated stainless steel mold frame was employed. The properties of the laminate are tabulated in TABLE i. EXAMPLE 62 The procedure described in EXAMPLE 61. above was repeated except that 0.152 cm (0.060 inch) thick TEFLON#- coated stainless steel mold frame was employed. The laminate's properties are tabulated in TABLE 1. EXAMPLE 63 A metal-thermoplastic-metal -laminate was prepared using 0.0127 cm (0.005 inch, 5 mils) thick 5052-0 aluminum as the metal layers and a mineral reinforced nylon 6-co-6,o '(available commercially from Monsanto Company, St. Louis, Missouri 63166 as VYDYNE# R-220) as the thermoplastic core layer. The aluminum surface was degreased by immersion ,n trichlorcethylene as described in EXAMPLE 1 above and then cleaned/etched by immersion in a 5% aqueous sodium hydroxide solution at ambient temperatures for a period of 5 minutes. The aluminum was removed from the alkaline sol@tion and rinsed thoroughly with running water followed by a demineralized water rinse. A 0.4% aqueous solution of A-1100 silane in distilled water was applied to ne cleaned/etched surface of the wet aluminum Th aluminum sheets were blown dry with a jet of clean nitrogen and heated in an oven at 1300 C. for 15 minutes. The treated aluminum layers and the VYDYNEe R-220 were assembled in a 0.168 cm (0.066 inch) thick TEFLON coated stainless steel mold frame with the treated surfaces of the aluminum facing the VYDYNE# R-220. The assembly was placed in a platen press heated to 2850 C. A minimal pressure of ram force was applied for 3 minutes and thereafter increased to 22675 kg (25 tons) for 1 minute. The laminate was then cooled under pressure to 2000 C., afterwhich the pressure 'a released and the- laminate removed from the press. The properties of the laminate are tabulated in TABUS 1. EXAMPLE 64 A metal-thermoplastic-metal laminate was prepared using 0.00508 cm (0.002 inch, 2 mils) thick C 1010 low carbon steel (annealed) as the metal layers and VYDYNE# R-240 as the thermopiastic core layer. The steel surface was degreased by immersion in l,i,l-trichloroethane as described in EXAMPLE 1 above and then cleaned/etched by immersion in a 2% aqueous solution of phosphoric acid at ambient temperatures for a period of 5 minutes. The steel was removed from the phosphoric acid solution and rinsed thoroughly with running water followed by a demineralized water rinse A 0.2% aqueous solution of A-1100 silane in distillea water (pH adjusted to 4.0 with formic acid) was applie@ to the cleaned/etched surface of the wet steel. The steel sheets were blown dry with a jet of clean nitrogen and heated in an oven at 130 C. for 2 minutes. The treated stee@ @ayers, and the VYDYNE# R-240 were assembled in a 0.124 cm (0.049 inch) thick TEFLON#- coated stainless steel mold frame with the treated sur-faces of the steel facing the VYDYNE R-240. The assembly was placed in a platen press heated to 2850 C. A pressure of 907 kg (1 ton) or less ram force was applied for 3 minutes and thereafter increased to 13605 kg (15 tons) for 1 minute The laminate was then cooled under pressure to 660 C., afterwhich the pressure was released and the laminate removed fro the press. The properties of the laminate are tabulated in TABLE, 1. EXAMPLE 65 A 0.127 cm (0.050 inch, 50 mils) thick metalthermoplastic-metal laminate was prepared using 0.00762 cm (0.003 inch, 3 mils) thick 304 stainless steel (annealed) as the metal layer, and VYDYNE# R-24 0 as the thermoplastic core layer according to the procedure described in EXAMPLE 64 above except that the cleaning etching was effected by immersion in a 50.0 gram/liter aqueous solution of Apex 764 M at 700 C. for a period f 2 minutes, a 0.112 cm (0.044 inch) thick TEFLON#-coated stainless steel mold frame was employed, and the fabricated laminate was cooled to 380 C. before releasing the pressure. The laminate's properties are tabulated in' TABLE 1. EXAMPLE 66 A 0.185 cm (0.073 inch, 73 mils) thick metal thermoplastic-metal laminate was prepared using 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum as' the metal layers and nylon 6,6 containing 10% by weight fiberglass as the thermoplastic core layer according tq the, procedure described in EXAMPLE 25 above, except th-:-- the degreasing in toluene was followed by an acetone rz @e, the dry A-1100 silane-treated aluminum sheets were heat' in an oven at 130 C. for 5 minutes, and a 0.160 cm (0.063 inch) thick TEFLON#-coated stainless steal mol@ frame was employed. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 67 A 0 z 0.193 cm (0.075 inch, 76 mils) thick metal- thermoplastic-metal laminate was prepared Vsing 0.0127 cm (0.005 inch, K mils) thick 1100-0 aluminum as the metal layers and nylon 6 as the thermoplastic core layer according to the procedure described in EXAMPLE 66 above, except that a 0.168 cm (0.Q66 inch thick TEFLON#-coated stainless steel mold frame was employed. The properties of the laminate gre tabulated in TABLE 1. EXAMPLE 68 The procedure describe in EXAMPLE 67 was repeated except that nylon 6 containing lot by weight fiberglass was employed as the thermoplastic core layer and a 0.157 cm, (0.062 inch) thick TEFLON#-coated stain less steel mold frame was employed. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 69 A 0.234 cm (0.0,92 inch, 92 mils) thick metal thermoplastic-metal laminate was prepared using 0.0127 cm (0.005 inch, 5 mils) thick 1}00-0 aluminum as the metal layers and nylon 56% b? TA-co-44% 6. IA (PARN 56/- 44) having a degree of crystallinity of 45* as tbe thermoplastic core layer according to the procedure described in EXAMPLE 15 above except as follows. The treated aluminum layers and the PARN 56/44 were assembled in a 0.208 cm (0.082 inch) thick TEFLON#- coated stainless steel mold frame with the treated surfaces of the aluminum layers facing the PARN 56/44. The assembly was placed in a platen press heated to 299 C. A pressure of 1814 kg (2 tons) or less ram force was applied for 3 minutes and thereafter increased to 13605 kg (15 tons) for 1 minute. The laminate was then-cooled under pressure to 66 C,, afterwhich the pressure was released. The laminate was removed from the press and annealed at 1700 C. for one hour. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 70 This Example illustrates the use cf an amer- phous thermoplastic as the thermoplastic core layer for comparison purposes. The procedure described in EXAMPLE 69 was repeated except as follows. The treated aluminum layers, and the PARN 56/44 were assembled in a 0.178 cm (0.070 inch) thick TEFLON#- coated stainless steel mold frame with the treated sur- faces of the aluminum layers facing the PARN 56/44. The assembly was placed in a platen press heated to 3100 C. A pressure of 1814 kg (2 tons) or less ram force was applied for 3 minutes and thereafter increased to,13605 kg (15 tons) for 1 minute. The laminate was then im- mersed immediately in an lce-water mixture. The prop erties of the laminate are tabulated in TABLE 1. EXAMPLE 71 A 0.179 cm (0.0705 inch, 70.5 mils) thick metal- thermoplastic-metal laminate was prepared using 0.0127 cm'(0.005 inch, 5 mils". thi+R 1100-0 aluminum as the metal layers and poly(athylene terephthalate)(?ET) having a degree of crystallinity of 38% as the thermoplastic core layer according to the procedure described in EXAMPLE 15 above except as follows. The treated aluminum layers and the PET were assembled in a 0.154 cm (0.0605 inch) thick TEFLON#- coated stainless steel mold frame with the treated surfaces of the aluminum layers facing the PET. The assembly was placed in a platen press heated to 240 . A pressure of 1814 kg (2 tons) or less ram force was applied for 3 minutes and thereafter increased to 13605 kg (15 tons) for 1 minute. The laminate was then cooled under pressure to 55 C. afterwhich the pressure was released. The laminate was. removed from the press an annealed at 1500 C, for 1 hour. The properties of :3 laminate are tabulated in TABLE 1. EXAMPLE 72 The procedure described in EXAMpLE 71 above was repeated excap@ that a 0.254 cm (0.100 inch) thick TEFLON#-coated stainless stee@ mold frame was employed, The properties ot the laminate are tabulated in TABLE 1, EXAMPLE 73 A metal thermoplastic-metal laminate was prepared using 0.0140 cm (0.0055 inch, 5.5 mils) thick Lithoplate aluminum as the metal layers and poly (ethylene, terephthalate) (PET) having a degree of crystallipity of 38% as the thermoplastic core layers The aluminum was degreased by immersion in methylene chloride as described in EXAMPLE 1 above and allowed to air dry. A Z5020 silane solution was prepared by agi tating a mixture of 11.1 grams of Z6O2O silane in a solution of 3 drops of glacial acetic acid in 3.6 grams of water at ambient temperatures to form a clears single- phase solution, which was diluted with 2254.0 grans of ethanol. The degreased aluminum was wetted thoroughly with the above-prepared That silane solution, blown dry with a jet of clean nitrogen and heated in an oven at 100 C. for 10 minutes. The treated aluminum layers and the PET were assembled in a 0.279 cm (0.110 inch) thick TEFLON#- coated stainless steel mold frame with the treated surfaces of the aluminum facing the PET. The assembly was'placed in a platen press heated to 2820 C. A mini- mal pressure of ram force was applied for 3 minutes and thereafter increased to 22675 kg (25 tons) for 1 minute. The laminate was then cooled under pressure to 660 C., afterwhich the pressure was released and the laminate removed from the press. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 74 This Example illustrates the use of an amor phous- thermoplastic core layer for comparison purposes The procedure described in EXAMPLE 71 above was repeated except as follows. A 0.193 cm (0.076 inch, 76 mils) thick metalthermoplastic-metal laminate using 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum as the metal layers and PET as the thermoplastic core layer were fabricated according to the procedures described in EXAMPLE 70 above, except that the platen press temperature was 2850 C. The properties of the laminate are tabulated in TABLE 1. EXAMPLES 75 - 81 These Examples illustrate the preparation of metal-thermoplastic-metal laminates without etching the metal layers or employing an adhesion agent. Laminates were prepared using 1100-0 aluminum as the metal layers and a melt blend of PET having a degree of crystallinity of 38% and 11. 7t poly (butylene tere-co-isophthalate)-block-polyh (butylene glycol) (HYTRE@# 4056, available commercially from E. I. du Pont de Nemours 4 CO., Wilmington, Delaware 19898) as the thermoplastic core layer. The aluminum surface was degreased by immersion in trichloroethylene as described in EXAMPLE 1 above, hung vertically, and allowed to air dry without dripping. The degreasing was repeated with methanol. The degreased aluminum layers and the PET/11.7% HYTREL 4056 blend were assembled in a TEFLON2)-coated stainless steel mold frame with the degreased surfaces (either' metal layer surface) of the aluminum layers facing the PET/11.7% HYTRELs 4056 blend. The assembly was placed in a platen press heated to 2790 C. A minimal pressure of ram force was applied for 3 minutes and thereafter increased to 22675 kg (25 tons) for 1 minute. The laminate was then cooled under pressure to 1000 C., afterwhich the pressure was released and the laminate removed from the press. The properties of the laminates, including the component layers' thicknesses, are tabulated in TABLE 1. EXAMPLE 82 A metal-thermoplastic-metal laminate was prepared using 0.0127 cm (O,q05 inch, 5 mils) thick 1100-0 aluminum as the metal layers and PET/11.7% HYTREL# 4056 as the thermoplastic core layer. The aluminum was degreased in 1,1,1-trichlorocthane as described in EXAMPLE 1 above and then cleaned/etched by immersion in a 5 aqueous solution of sodium hydroxide at ambient temper- tures for a period of S minutes. The aluminum was removed from the alkaline solution and rinsed thoroughly with running water followed by a demineralized water rinse. A solution of 0.9985 gram of A-11O0 silane in 3.126 gram of water and 243.0 grams of ethanol (pH adjusted to 4.0 with formic acid) was sprayed onto the cleaned/etched surface of the wet aluminum. The aluminum sheets were blown dry with a jet of clean nitrogen and then heated in an oven at 1300 C. for 15 minUtes. The treated aluminum layers and the PET/11,7% HYTREL 4056 were assembled in a 4.150 cm (0.059 inch) thick TEFLON#-coated stainless steel mold frame with the treated surfaces of the a-1,wninum zero facing the PET/11.7% HYTREL# 4056. The assembly was placed in a press heated to 2790 C. A pressure okg 2721 kg (3 tons) or less ram force was applied for 3 minutes and thereafter increased to 22675 kg (25 tons) for 1 minute. The laminate was then cooled under pressure to 52 C., afterwhich the pressure was released. The laminate was removed from the press and annealed by melting to 1500 C. for 20 minutes. The laminate's properties are. tabulated in TABLE 1. EXAMPLE 83 The procedure described in EXAMPLE 82 above was repeated except that a 0.165 cm (0.065 inch) thick TEFLON#-coated stainless steel mold frame was employed, The laminate's properties are tabulated in TABLE 1. EXAMPLE 84 A metal-thermoplastic-metal laminate was fabri cated using 0.0127 cm (0,005 inch, 5 mil$) thick 5052-0 aluminum as the metal layers and PET/11.7% HYTRELB 4056 as the thermoplastic core layer. The aluminum surface was degreased in l,l,l-trichloroethane as described in EXAMPLE 1 above and then cleaned/etched by immersion in a sodium dichromate (chromic acid) solution containing 30.0 grams sodium dichromate dihydrate, 150 milliliters concentrated sulfuric acid (sp. gr. 1.84) and 1 liter water at 600 C. for a period of 5 minutes. The aluminum was removed from the chromic acid solution.and rinsed thoroughly with running water followed by a demineralized water rinse. A 0.4% aqueous solution of Z6040 silane in distilled water (pH adjusted to 4.0 with formic acid) was applied te the cleaned/etched surface of the wet aluminum. The aluminum sheets were blown dry with a jet of clean nitrogen and heated in an oven at 130 C. for 2 minutes. The treated aluminum layers and the PET/11.7% HYTRELs 4056 were assembled in a 0.203 cm (0.080 inch) thick TEFLON#-coated stainless steel mold frame with the treated surfaces of the aluminum layer facing the thermoplastic core layer. The assembly was placed in a platen press heated to 2790 C. A pressure of 1814 kg (2 tons) or less ram force was applied for 3 minutes and thereafter increased to 22675 kg (25 tons) for 1 minute. The laminate was then cooled under pressure to 138 C., afterwhich the pressure was released and the laminate removed from the press. The laminate's properties are tabulated in TABLE 1. EXAMPLES 85 - 87 Metal-thermoplastic-metal lamiantes using 50520 aluminum as the metal layers and PET/11.7% HYTREL 4056 as the thermoplastic core layer were prepared according to the procedure described in EXAMPLE 84 above. The properties of the laminates including the component layers' thicknesses, are tabulated in TABLE 1. EXAMPLES 88 - 91 Metal-thermoplastic-metal lamiantes were prepared using 6061-0 aluminum as the metal layers and a melt blend of PET/11.7% HYTREL# 4056 as the thermoplas tic core layer, The aluminum @ urface was degreased by immersion in trichloroethylene followed by an acetone rinse as described in EXAMPLE i above and then cleaned/etched by immersion in o 2.5% aqueous sodium hydroxide solution at ambient temperatures for a period of 5 minutes. The aluminum was removed from the alkaline solution and rinsed thoroughly with running water followed by a demineralized water rinse. The wet aluminum- was immersed in a mixture of 50 milliliters of A-llOO silane solution (prepared by mixing 0.83 gram of A-llOO silane with 208.0 grams of water) and 50 milliliters of A-174 silane solution (prepared by agitating a mixture of 10.0 grams of A-174 silane, 2.5 grams or water, and 0.04 gram of glacial acetic acid at ambient temperatures to form a clear, single-phase solution, and diluting ijith 2449.0 grams of water and 10 milliliters of ethanol), blown dry with a jet of clean nitrogen and heated in an oven at 130 C. for 2 minutes. The treated aluminum layers and the PET/11.7% HYTREL 4056 were assembled in a TEFLON -coated stainless steel mold frame with the treated surfaces of the aluminum facing the PET/11.7% HYTREL 4056. The assembly was placed in a platen press heated to 279 C. A minimal pressure of ram force was applied for 3 minutes and thereafter increased to 22675 kg (25 tons) for an additional 3 minutes. The laminate was then cooled under 'pressure to 660 C., afterwhich the pressure was released and the laminate removed from the press, The properties of the laminates, including the component layers' thicknesses, are tabulated in TABLE 1. EXAMPLES 92 - 94 The procedure described in EXAMPLES 88-91 above was repeated, except that 6061-T6 aluminum was used as the metal layers flnd ethanol was omitted from the A-174 silane solution. The properties of the laminates, including the component layers' thicknesses, are tabulated in TABLE 1 EXAMPLE 95 The procedure described in EXAMPLE 73 above was repeated except that a melt blend of PET/11.7% HYTREL 4056 was employed as the thermoplastic core la/er. The properties of the laminate are tabulated i in TABLE 1. EXAMPLE 96 A 0.127 cm (0.050 inch, 50 mils) thick metal thermoplastic-metal laminate using 0.00508 cm (0.002 inch, 2 mils) thick C 1010 low carbon steel-annealed as the metal layers and PET/11.7% HYTREL# 4056 as the thermoplas tic core layer was prepared according to the procedure described in EXAMPLE D above except that the steel layers were immersed in the phosphoric acid solution for 2 : @- utes, a 0.117 cm (0.046 inch) thick TEFLON#-coated s less steel mold frame was employed, and the fabricated laminate was' cooled to 38 C. before being removed from the press. The laminate's properties are tabulated in TABLE 1. EXAMPLE 97 The procedure described in EXAMPLE 96 above was repeated except that a 0.208 cm (0.082 inch) thick TEFLON -coated stainless steel mold frame was emplc, The laminate's properties are tabulated in TABLE 1. EXAMPLE 98 A metal-thermoplastic-metal laminate was prepared using 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum as.the metal layers and a melt blend of PET having a degree of crystallinity of 38% and 11.1% poly (ethylene terephthalate)-block-45% poly (outylene ox@de) (PETBCP), with the poly (butylene oxide) blocks haviii;j a molecular weight of 1000, as the thermoplastic core @a@ The aluminum was degreased by immersion in methyle@ chloride as described in EXAMPLE 1 above and allow to air dry. The aluminum was immersed in an equivolume solution (50 milliliters each) of A-1100 silane solu tion (prepared by mixing 10.6 milliliters of A-llOO silane and 31.3 milliliters of water with 2095 milliliters of ethanol) and A-174 silane solution (prepared by agitating a Trixture of 9,6 milliliters of A-174 silane, 2.5 milliliters Of water and 2 drops of glacial acetic acid at ambient temperatures or 30 minutes to form a clear, single-phase solution and diluting with 3120 milliliters of ethanol), blqwn dry with a jet of clean nitrogen and heated in an oven at 1300 C. for 2 minutes. The treated aluminum layers and the PET/ll. 78 PETBCP were assembled in a 0.282 cm (0.111 inch) thick TEFLON#-coated stainless steel mold frame and laminated as described in EXAMPLES 88-91 above. The laminate's properties are tabulated in TABLE 1. EXAMPLES 99 -'10 2 Metal-thermoplastic-metal laminates using 6061-0 aluminum as the metal layers and a melt blend of PET/11.7% PETBCP as the thermoplastic core layer were prepared according to the procedure described in EXAMPLES 88-91 except that the acetone rinse was omitted in the de reasing step. The properties of the laminates, including the component layers' thicknesses, are tabulated in TABLE 1. EXAMPLE 103 A metal- thermoplastic-metal laminate was prepared using 0.0152 cm (0.006 inch, 6 mils) thick 6061-T6 aluminum as the metal layers and a melt blend of PET/11.7% PETBCP as the thermoplastic core layer was prepared as described in EXAMPLES 99-102 except that following the degreasing, the aluminum was wet sanded with 400-grit .wet sandpaper prior to being etched in the 2.5% aqueous sodium hydroxide solution0 The properties of the laminate are tabulated in TABLE 1. EXAMPLE 104 A metal-thermoplastic-metal laminate using 0.0127 cm (0.005 inch, 5 mils) thick aluminum as the metal layers and partly crystalline poly(ethylene terephthalate)-block-5% poly (butylene oxide) (PET-b-5% PBO), with the PBO block having a molecular weight of 1000, as the thermoplastic core layer was prepared according to the procedure described in EXAMPLE 15 above. The laminate's properties are tabulated in TABLE. 1. EXAMPLE 105 This Example illustrates the preparation of a metal-thermoplastic-metal laminate without etching the metal or using an adhesion agent. A laminate was prepared using 0.017 cm (0.005 inch, 5 mils) thick 1100-0 aluminum as the metal layers and partly crystalline poly(ethylene terephthalate) block-24% poly(butylene oxide) (PET-b-24% PBO), with the PBO blocks having a molecular weight of 1000 as the thermoplastic core layer. The aluminum was degreased by immersion in methylene chloride as described in EXAMPLE 1 above and allowed to air dry. The degreased aluminum layers and the PET-b-24% PBO were assembled in a 0.292 cm (0.115 inch) thick TEFLONcoated stainless steel mold frame with the degreased surfaces (either surface) facing the PET-b-24% PBO. The assembly was placed in a platen press heated to 2820 C. A minimal pressure of ram force was applied for 3 minutes and -thereafter increased to 22675 kg (25 tons) for an additional 3 minutes. The laminate was then cooled under pressure to 660 C., afterwhich the pressure was released and the laminate removed from the press. The properties of the laminate are tabulated in TABLE 1. EXAMPLES 106 - 109 Metal-thermoplastic-metal laminates using 11000 aluminum as the metal layers and a melt blend of poly (ethylene terephthalate) (PET) having a degree of crystallinity of 38% and 23.5% HYTREL 4056 as the thermoplastic core layer were prepared according to the procedure described in EXAMPLES 88-91 except that methylene chloride was employed as the degreasing solvent and the cieaning/- etching of the aluminum surface was effected by immersion in a 5% aqueous sodium hydroxide solution at ambient temperatures for a period of 10 minutes. The properties of the laminates are tabulated in TABLE 1 EXAMPLE 110 The procedure described in EXAMPLE 73 above was repeated except that a melt blend of PET having a degree of crystallinity of 38% and 23.5% HYTREL# 4056 was employed as the thermoplastic core iairer, The laminate's properties are tabulated in TABLE 1. EXAMPLE 111 The procedure described in EXAMPLE 70 above was repeated, except that a melt blend of PET having a degree of crystallinity of 38% and 10% poly (oxycarbonyl- oxy-1,4-phenyleneisopropylidene-1,4-phenylene (also known as poly[2,2-bis(4'-phenylene)propane carbonate] or simply polycarbonate or PC, available commercially as MERLON# M100 from Mobay Chemical Corp., Pittsburgh, Pennsylvania 15205) was employed as the thermoplastic core layer anda 0.183 cm (0.072 inch) thick TEFLON#-coated stainless steel mold frame was employed. The laminate's properties are tabulated in TABLE 1. EXAMPLE 112 A 0.190 cm (0.075 inchy, 75 mils) thick metalthermoplastic-metal laminate using 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum as the metal layers d polyCethylene 80% terephthalate-co-20% isophthalate) (PET/- I 80/20) haring a degree of crystallinity of 32% as the thermoplastic core layer, and a 0.4 aqueous solution of A-1100 silane in distilled water (pH adjusted to 4.0 with formic acid) as the adhesion agent was prepared according to the procedure described in EXAMPLE 84 above except as follows.' The treated aluminum layers and the PET/I 80/20 were assembled in a 0.165 cm (0.065 inch) thick TEFLON# coated stainless steel mold frame with the treated sur- faces of the aluminum layers facing the tET/I 80/20. The assembly was placed in a platen press heated to 2400 C. A pressure of 1814 kg (2 tons) or less ram. force was applied for 3 minutes and thereafter increase to 13605 kg (15 tons) for 1 minute. The laminate Fas then slow-cooled under pressure to 540 C., afterwhich the pressure was reieased and the laminate removed from the press. The laminates? properties are tabulated it TABLE 1. EXAMPLE 113 The procedure described in EXAMPLE 70 above was ,repeated except that amorphous PET/I 80/20 having a degree of crystallinity of only 5% was used as the thermoplastic core layer, a 0.170 cm (0.067 inch) thick TEFLON#-coated stainless steel mold frame was employed and the platen press was heated to 285 C. The property ties of the laminate are tabulated in TABLE 1 for com, parison purposes. EXAMPLE 114 The procedure described in EXAMPLE 13 above was repeated except that the amorphous PET 80/20 had a degree of crystallinity of only 3.3% and a 0.142 cm (0.056 inch) thick TEFLON# @@ated stainless steel mol@ frame was employed.. The properties of the laminate are tabulated in TABLE 1 for comparison purposes. EXAMPLE 115 A metal-the. @@plastis-metal laminate was pre- pared using 0.0127 cm (0.005 inch, 5 mils) thick 1100 ,aluminum as the metal layers and a partly crystalline melt blend of poly(ethylene 80% terephthalate-co-20% iso- phthalate),(PET/I 80/20) and 11.7% HYTREL 4056 as the thermoplastic core layer. The aluminum surface was @@ greased by immersion in methylene chloride as described in EXAMPLE 1 above and allowed to air dry. The degreased aluminum was immersed in a 0.4% solution of 26020 silene in ethanol (prepared as described in EXAMPLE 75 abovej, blown dry with a jet of clean nitrogen and heated in an oven at 100 C. for 10 minutes. The treated alami@@m layer@ and the PET/@ of @0/- 11.7% HYTREL# 4056 were asser@led in a 0.25@ or (0.@@@ inch) thick TEFLON#-coated sta@n@@. sb@@l @old @@@ with the treated surfaces of the aluminum facing, tilt PET/I 80/20/11.7% HYTREL# 4056. The assembly was p in a platen press heated to 249 C. A minimal pressurs of ram force was applied for 3 minutes and thereafter increased to 22675 kg (25 tons) for an additional 3 minutes. The laminate was then cooled under pressure to 66 U., afterwhich the pressure was released and the laminate removed from the press. The laminate was annealed by melting to 1500 C. for 20 minutes. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 116 The procedure descrived in EXAMPLE 115 above was repeated except that 0.0140 cm (0.0055 inch, 5.5 mils) thick Lithoplate aluminum was employed as the metal layers and a 0.279 cm (0.110 inch) thick TEFLON coated stainless steel mold frame was employed. The laminate's properties are tabulated in TABLE 1. EXAMPLE 117 The procedure described in EXAM--PLE 112 was em- ployed except that poly(butylene terephthalate) (PBT) was employed as the thermoplastic core layer and a .165 cm (0.065 inch) thick TEFLON#-coated stainless s mold frame was employed. The properties cr the 1 laminate are tabulated in TABLE 1. EXAMPLE 118 The procedure described in EXAMPLE 117 using a 0.282 cm (0.111 inch) thick TEFLON#-coated stainless steel mold frame was employed. The laminate's proper- ties are tabulated in TABLE 1. EXAMPLE 119 The procedure described in EXAMPLE 73 above was employed except that partly crystalline poly(butylene terephthalate) (PBT, available commercially as VALOX 310 fro General Electric Company Pittsfield, Massachusetts 01201) was employed as 'the thermoplastic core layer and the press platens were heated to 25 The laminate's properties are tabulated in TABLE 1. EXAMPLE 120 The procedure dessribed in EXAMPLE 115 above was repeated except that a partly crystalline melt blend of PBT and 11.7% HYTREL# 4056 (PBT/11.7% @@ HYTREL# 4056) was employed as the thermoplastic core layer The laminate's properties are tabulated in TABLE 1. EXAMPLE 121 The procedure described in EXAMPLE 120 above was repeated except that 0.0140 cm (0.0055 inch, 5.5 mils) thick Lithoplate aluminum was employed as the metal layers. The laminate's properties are tabulated in TABLE 1. EXAMPLE 122 The procedure described in EXAMPLE 119 was repeated except that 0.0127 cm (0.005 inch 5 mils) thick 1100-0 aluminum was employed as the metal layers, a partly crystalline melt blend of PBT and 23.5% HYTRELs 4056 (PBT/23.5% HYTREL# 4056) was employed as the thermo@. plastic core layer, and a 0.274 cm (0.108 inch) thick TEFLON#-coated stainless steel mold frame was employe@ The laminate's properties are tabulated in TABLE 1. EXAMPLE 123 The procedure described in EXAMPLE 122 above was employed except that Don cm (0.005 inch, 5.5 mils) thick Lithoplate aluminum was employed as the metal layers and a 0.277 cm (0 109 inch) thick TEFLON coated stainless steel mold frame was employed. The laminates properties are tabulated in TABLE 1. EXAMPLE 124 A 0.211 cm (0.83 inch, 83 mils) thick laminate using 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum as the metal layers and HYTREL 7246 as he thermo- plastic core layer was prepared according to the procedure described in EXAMPLE 15 above except that the initial applied pressure was 1814 kg (2 tons') or less ram force and the fabricated laminate was @ooled to 54 C. before being removed from the press. The pro- perties of the laminate are tabulated in TABLE 1 EXAMPLE 125 The procedure described in EXAMPLES 106 109 was employed except that a partly crystalline poly(but@ lene terephthalate-co-isophthalate)-block-poly (butylene oxide) (HYTREL 7246) was employed as the thermoplastic core layer and a 0.282 cm (0.111 inch) thick TEFLON coated stainless steel mold frame was employed. The laminate's properties are tabulated in TABLE 1. EXAMPLE 126 A metal-thermoplastic-metal laminate was prepared according to the procedure described in EXAMPLE 73 above except that HYTREL 7246 was employed as the thermoplastic core layer. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 127 A metal-thermoplastic-metal laminate was prepared according to the procedure described in EXAMPLE 73 above except that a partly crystalline poly(butylene tèrephthalate-co-isophthalate)-blocli-poly(butylene oxide) (HYTREL() # 6346) was employed as the thermoplastic core layer. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 128 A metal-thermoplástic-metal laminate was prepared according to the procedure described in EXAMPLE 119 above except that a partly crystalline poly(butylene terephthalate-co-isophthalate)-block-poly(but)tlene oxide) (HYTREL 5555) was employed as the thermoplastic core layer and a 0.264 cm (0.104 incn) thick TEFLON#-coated stainless steel mold frame was employed. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 129 Th'e procedure described in EXAMPLE 119 was employed except that a partly crystalline poly(butylene terephthalate-co-isophthalate)-block-poly(butylene oxide) (HYTREL 4055) was employed as the thermoplastic core layer. The properties of the laminate are tabulated in TABLE 1. EXAMPLES 130 - 1 33 These Examples illustrate the fabrication of metal-thermoplastic-metal laminates by polymerization of monomeric material between the metal layers. The properties of the laminates are tabulated in TABLE 1. The laminates were prepared using 0.0127 cm (0.005 inch, Smils) thick aluminum as the metal layers. The aluminum surface was degreased by immersion in toluene followed by an acetone rinse as described in EXAMPLE 2 above and then cleaned/etched by immersion in 5% aqueous sodium hydroxide at ambient temperatures for a period of 2 minutes. The aluminum was removed from the alkaline solution and rinsed for 10 minutes with running water followed by a demineralized water rinse. A 0.4% solution of A-1100 silane in ethanol was sprayed onto the cleaned/etched surface of the wet aluminum. The aluminum sheets were blown dry with a jet of clean nitrogen and heated in an oven at 1800 C. for 30 minutes EXAMPLE 130 - - A laminate was prepared by in situ polymerization of a nylon 6 block copolymer between Lithoplate aluminum layers. A solution was prepared containing 60.0 grams of VORANOLs 2120 (polyoxypropylene glycol with hydroxyl number of 56.8), 14.4 grams of isophthaloyl-biscaprolactam, 1.5 grams of FLECTOLe H (polymerized 1,2dihydro-2,2,4-trimethylquinoline), and 109.0 grams of @-caprolactam. The solution was dried by distilling 25 milliliters of caprolactam under reduced pressure. A separate catalyst solution was prepared by adding 7 milliliters of 3 molar ethylmagnesium bromide in diethyl ether to 175.0 grams of dry molten c-caprolactam at 1000 C. The solution was evacuated to remove ether and ethane p,d, held at 1000 C. under nitrogen until just prior to use. A mold was prepared by placing the two aluminum sheets between heated platens in a closed press such that the treated surfaces would face the polymerized thermoplastic. The aluminum sheets were separated by 0.318 cm (0.125 inch) thick TEFLON# spacers. With the mold and reactive solutions at 130 C., the solutions were pump cast into the mold using Zenith gear pumps. The stream volute ratio of monomer solution to catalyst solution was 1.12:1. The streams were mixed by means of a Kenics static mixer. After 5 minutes in the mold the laminate was removed and allowed to cool. The nylon 6 block copolymer contained 20% by weight polyoxypropylene blocks. EXAMPLE 131 -- A laminate was made similar to EXAMPLE 130 above except that 1100-0 aluminum was employed as the metal layers. EXAMPLE 132 -- A nylon 6 laminate was prepared by polymerizing E-caprolactam between 1100-0 aluminum. The mold was prepared as described in EXAMPLE 130 above. A solution was prepared containing 350.0 grams of molten ±-capro- lactam, 1.5 grams of FLECTOL H, and 3.4 grams of PEI- 1000 (polyethylenimine, 30% aqueous solution). The solu tidn was dried by distilling 50 milliliters of caprolactam at reduced pressure. The solution was catalyzed by the addition of 6.2 milliliters of 3 molar ethylmagnesium bromide in diethyl ether, followed by thorough degassing under vacuum. The solution temperature was adjusted to 1300 C. and 1.7 milliliters of acetylcaprolactam was mixed in to serve as an initiator. The solution was then poured into the mold heated at 1800 C. The casting was allowed to cure 10 minutes before removal from the mold. EXAMPLE 133 -- A 40% calcined kaolinite clay reinforced nylon 6 laminate was prepared by reacting a caprolactam slurry between 1100-0 aluminum sheets. The mold was prepared as described in EXAMPLE 130 above. A mixture of 230.0 grams of ±-caprolactam, 1.5 grams of FLECTOLX H and 2.0 grams of FEi-1000 were heated under nitrogen to 1300 C. To this stirred solution was added 12!00 grams of Alsilate W calcined kaolin, keeping the slurry temperature above 100 C. To the resultant slurry was added 1.2 milliliters of A-1100 silane. The mixture was evacuated and dried by distilling 50 milliliters of caprolactam. The vacuum was released to nitrogen and the slurry cooled to 1000 C. To this mixture was added 3.2 milli liters of 3 molar ethylmagnesium bromide in diethyl ether followed by thorough degassing under vacuum. The vacuum was released through nitrogen and 1 milliliter of acetyl caprolactam added to the catalyzed slurry followed by stirring for 30 seconds. The slurry was poured into the mold, heated at 1800 C. and allowed to cure for 10 minutes before removing from the mold. EXAMPLE 1'34 This Example illustrates the fabrication of a metal-thermoplastic-metal laminate using an adhesive ad-' hesion agent. The laminate was prepared using 0.0127 cm (0.005 inch, 5 mils) thick 1100-0 aluminum as the metal layers. The aluminum surface was degreased by immersion in toluene as described in EXAMPLE 1 above followed by an acetone rinse and then cleaned/etched in a 50.0 grams/liter aqueous solution of Apex 764 M at 700 C. for a period of 2 minutes. The aluminum was removed from the cleaning/etching solution and rinsed with hot running water while wiping with a clean cloth (a Webril(µ) Litho Pad is convenient) followed by a hot water rinse without wiping and thereafter blown dry with ,a jet of clean nitrogen. The aluminum was then heated in an oven at 1300 C. for 10 minutes. An epoxy adhesive consisting of 67:33 weight mixture of EPON 871:EPON -828 (aliphatic. epoxy resin, weight per' epoxide, 390-470 and unmodified bisphenol A epoxy resin, weight per epoxide, 185-192, respectively, ava'ilable commercially from Shell Chemical Company, Houston, Texas 77002) with EPON- curing agent V-25 [a polyamide, equivalent weight (amount to react with 1 mole of epoxide) of about 163] was applied to the cleaned/etched surface of the aluminum as 0.00508 cm (0.002 inch, 2 mils) thick films. The treated aluminum layers and a sheet of nylon 6,6 were assembled, with the adhesivetreated aluminum surfaces facing the nylon 6,6 and laminated under pressure at 2850 C. for 10 minutes, cooled under pressure to 200 C., and removed from the press. The properties of the laminate are tabulated in TABLE 1. EXAMPLE 135 The properties of the metal-thermoplasticmetal laminates prepared as described in EXAMPLES 2-134 are tabulated in TABLE 1, with EXAWLES 70, z 74, 113 and 114, which are comprised of amorphous thermoplastic core layers, being included for comparison purposes. The ' properties of the component metal layers and thermoplastic core layers are tabulated in TABLES 2 and 3, respectively. Specimens for all the tests were preconditioned at 23 C. (730 F.) for at least 18 hours. Except for the coefficient of linear thermal expansion and heat distortion temperature measurements, all tests were done at 23 C. and 50t relative humidity. All non-laminated polyamide specimens were kept dry, asmolded in sealed cans with anhydrous magnesium perchlorate or anhydrous calciuri sulfate desiccants during the preconditioning period at 23 C. All other specimens were preconditioned at 50% relative humidity, It is to be understood that the values for the thickness of the thermoplastic reported in TABLE 1 represent an approximate average of the values for the various laminate specimens employed in the physical tests performed on the laminate, it being understood that minor variations in thickness may exist among such specimens obtained from the experimental laminate samples prepared. Unless otherwise indicated, the reported tensile properties for the metals are for the metal before being subjected to the thermal conditions of lamination and these values would not be expected to substantially change after being subjected to the thermal conditions of lamination in the corresponding Examples herein. TABLE 1. CONT'D METAL THBRMOPLASTIC EXAMPLE TYPE THICKNESSa,cm TYPE THICKNESS,cm TR 2 1100-0 Aluminum 0.00508 Nylon 6,6 0.178 0.0571 3 " 0.0127 " 0.295 0.0861 4 " 0.0127 " 0.216 0.118 5 " 0.0127 " 0.180 0.141 6 " 0.0254 " 0.114 0.446 7 " 0.0254 " 0.279 0.182 8 " 0.0254 " 0.173 0.294 9 " 0.0254 " 0.0940 0.541 10 5052-0 Aluminum 0.00254 " 0.180 0.0282 11 " 0.0762 " 0.178 0.0856 12 " 0.0762 " 0.173 0.0881 13 " 0.0127 " 0.165 0.154 14 " 0.0127 " 0.160 0.159 15 " 0.00762 " 0.133 0.115 16 " 0.00254 " 0.284 0.0179 17 " 0.00762 " 0.282 0.0540 18 " 0.0127 " 0.175 0.145 19 " 0.0127 " 0.175 0.145 20 " 0.0127 " 0.168 0.151 21 " 0.0127 " 0.168 0.151 22 " 0.0127 " 0.127 0.200 23 " 0.0127 " 0.0711 0.357 24 " 0.0127 " 0.0483 0.526 25 304 Stainless Steel-annealed 0.00254 " 0.182 0.0279 26 " 0.000254 " 0.531 0.000957 27 " 0.00254 " 1.112 0.00457 28 " 0.00127 " 0.528 0.00481 TABLE 1. CONT'D METAL THBRMOPLASTIC EXAMPLE TYPE THICKNESSa,cm TYPE THICKNESS,cm TR 29 304 Stainless Steel-anhnealed 0.00127 Nylon 6,6 0.290 0.00876 30 " 0.00127 " 0.279 0.00910 31 " 0.00127 " 0.493 0.0103 32 " 0.00127 " 0.174 0.0146 33 " 0.00254 " 0.292 0.0174 34 " 0.00508 " 0.173 0.0587 35 " 0.00762 " 0.163 0.0935 36 " 0.00762 " 0.107 0.142 37 " 0.00762 " 0.0533 0.286 38 6061-T6 Aluminum 0.0152 " 0.122 0.249 39 " 0.0152 " 0.109 0.279 40 " 0.0152 " 0.180 0.169 41 " 0.0152 " 0.251 0.121 42 6061-0 Aluminum 0.0152 " 0.160 0.190 43 " 0.0152 " 0.112 0.271 44 " 0.0152 " 0.168 0.181 45 Lithoplate Aluminum 0.0140 " 0.259 0.108 46 " 0.0140 " 0.161 0.174 47 " 0.0140 " 0.147 0.190 48 " 0.0140 " 0.0978 0.286 49 C 1010 Low Carbon Steel-annealed 0.00762 " 0.180 0.0847 50 " 0.00508 " 0.297 0.0364 51 " 0.00762 " 0.277 0.0550 52 " 0.00508 " 0.173 0.0587 53 " 0.00508 " 0.119 0.0854 54 " 0.00762 " 0.119 0.128 TABLE 1. CONT'D METAL THBRMOPLASTIC EXAMPLE TYPE THICKNESSa,cm TYPE THICKNESS,cm TR 55 (304 Stainless Steel-annealed 0.00508) Nylon 6,6 0.264 0.0768 ( ) (6061-0 Aluminum 0.0152) 56 (304 Stainless " Steel-annealed 0.00508) " ( ) 0.260 0.0734 (3003-H25 Aluminum 0.0140) 57 1100-0 Aluminum 0.0127 ZYTEL# ST-801 0.173 0.147 58 " 0.0127 VYDYNE# R-240 0.165 0.154 59 6061-0 Aluminum 0.0152 " 0.160 0.190 60 61-T6 Aluminum 0.0152 " 0.122 0.249 61 5052-0Aluminum 0.0127 " 0.165 0.154 62 " 0.0127 " 0.152 0.167 63 " 0.0127 VYDYNE# R-220 0.168 0.151 64 C 1010 Low Carbon Steel-annealed 0.00508 VYDYNE# R-240 0.124 0.0819 65 304 Stainless Steel-annealed 0.00762 " 0.112 0.136 66 1100-0 Aluminum 0.0127 Nylon 6,6/10% 0.160 0.159 67 " 0.0127 Nylon 6 0.168 0.151 68 " 0.0127 Nylon 6,6/10% 0.157 0.162 fiberglass 69 " 0.0127 PARN 56/44 (@tystalline) 0.208 0.122 TABLE l. CONT'D METAL THERMOPLASTIC EXAMPLE TYPE THICKNESSa,cm TYPE THICKNESS,cm TR 70 1100-0 Aluminum 0.0127 PARN 56/44 (amorphous) 0.178 0.143 71 " 0.0127 PET 0.154 0.165 72 " 0.0127 PET 0.254 0.100 73 Lithoplate Aluminum 0.0140 PET 0.279 0.100 74 1100-0 Aluminum 0.127 PET (amorphous) 0.168 0.151 75 " 0.0127 PET/11.7% HYTREL# 4056 0.216 0.118 76 " 0.0127 " 0.165 0.154 77 " 0.0254 " 0.183 0.278 78 " 0.0508 " 0.152 0.668 79 " 0.0127 " 0.264 0.0962 80 " 0.0127 " 0.249 0.102 81 " 0.0127 " 0.312 0.0871 82 " 0.0127 " 0.150 0.169 83 " 0.0127 " 0.165 0.154 84 5052-0 Aluminum 0.0127 PET/11.7% HYTREL# 4056 0.203 0.125 85 " 0.0762 " 0.175 0.0870 86 " 0.0127 " 0.165 0.154 87 " 0.0127 " 0.165 0.154 88 6061-0 Aluminum 0.0152 " 0.160 0.90 89 " 0.0152 " 0.160 0.190 90 " 0.0152 " 0.160 0.0.190 91 " 0.0152 " 0.0914 0.333 92 6061-T6 Aluminum 0.0152 " 0.249 0.122 93 " 0.0152 " 0.163 0.187 94 " 0.0152 " 0.0914 0,333 95 Lithoplate Aluminum 0.0140 " 0.290 0.0966 TABLE 1. CONT'O METAL TUERMOPLASTIC EXAMPLE TYPE TMICKNESSa,cm TYPE THICKNESS, cm TR 96 C 1010 Low Carbon 0.00508 PET/11.7% HYTREL# Stcel-anncaled 4056 0.117 0.0868 97 " 0.00508 " 0.208 0.0488 98 1100-0 Aluminum 0.0127 PET/11.1% PETBCP 0.282 0.0901 99 6061-0 Aluminum 0.0152 " 0.249 0.122 100 " 0.0152 " 0.163 0.187 101 " 0.0152 " 0.165 0.184 102 " 0.0152 " 0.0914 0.333 103 6061-T6 Aluminum 0.0152 " 0.163 0.187 104 1100-0 Aluminum 0.0127 PET-b-5% PBO-1000 0.168 0.151 105 " 0.0127 PET-b-24% PBO-1000 0.292 0.870 106 " 0.0127 PET-23.5% HYTREL# 0.236 0.108 4056 107 " 0.0127 " 0.282 0.0901 108 " 0.0127 " 0.282 0.0901 109 " 0.0127 " 0.165 0.154 110 Lithoplate Aluminum 0.0140 " 0.282 0.0993 111 1100-1 Aluminum 0.127 PET/10% PC 0.183 0.139 112 " 0.0127 PET/I 80/20 0.165 0.154 113 " 0.0127. PET/I 80/20 0.170 0.149 (amorphous) 114 " 0.0127 " 0.142 0.179 115 " 0.0127 PET/I 80/20 11.7% 0.282 0.0901 HYTREL# 4056 116 Lithoplate Aluminum 0.140 " 0.282 0.0993 117 1100-0 Aluminum 0.0127 PBT 0.165 0.154 118 " 0.0127 " 0,282 0.0901 119 Lithoplate Aluminum 0.0140 " 0.282 0.0995 TABLE 1. CONT'D METAL THERMOPLASTIC EXAMPLE TYPE THICKESSa,cm TYPE THICKNESS,cm TR 120 1100-0 Aluminum 0.0127 PET/11.7% HYTREL# 0.279 0.0909 4056 121 Lithoplate Aluminum 0.0140 " 0.279 0.100 122 1100-0 Aluminum 0.0127 PBT/23.5% HYTREL# 0.274 0.0927 4025 123 Lithoplate Aluminum 0.0140 " 0.277 0.101 124 1100-1 Aluminum 0.0127 HYTREL# 7246 0.185 0.137 125 " 0.0127 " 0.282 0.0901 126 Lithoplate Aluminum 0.0140 " 0.282 0.0993 127 " 0.0140 HYTREL# 6346 0.282 0.0993 128 " 0.0140 HYTREL# 5555 0.264 0.106 129 " 0.0140 HYTREL# 4055 0.282 0.0993 130 " 0.0127 Hylon 6-b-20% 0.318 0.0799 POP 131 1100-1 Aluminum 0.0127 0.318 0.0799 132 " 0.0127 " 0.318 0.0799 133 " 0.0127 Nylon 6/40% 0.318 0.0799 calcined clay 134 " 0.0127 Nylon 6,6 0.180 0.141 a Thickness for each metal layer b Measured at 1.82 x 106 N/m2, except where noted otherwise. c Determined, except where noted otherwise, at a strain, r. of 5% in the outer metal layers at the point of maximum deflection. d Measured according to ASTM D 256-73 test method for plastics, e Steel side. f Steel on tension side. g Aluminum side. h Aluminum on tesnion side. TABLE 1. CONT'D EFFECTIVE FLEXURAL CLTE# MDT#b IR#C STIFFNESS STRENGTH MODULUS EXAMPLE 10-6 C. -1 C. % 103 N/m 106 N/m 109 N/m2 2 46.3 136 11.5 137.19 5.52 3 35.8 228 19.0 127.54 11.44 4 > 250 128.23 11.44 5 29.0 > 250 27.0 1034.84 114.44 19.17 6 7 28.6 > 250 39.5 131.68 17.72 8 26.8 > 250 68.0 126.16 26.96 9 25.0 > 246 92.5 120.64 21.51 10 45.5 168 17.0 231.66 129.61 5.86 11 34.9 > 246 49.0 159.94 12.34 12 157.18 10.27 13 30.6 > 250 809.66 177.18 18.89 14 27.5 72.0 746.63 179,93 18.89 15 30.2 > 246 53.5 273.51 183.38 13.44 16 55.8 166 11.0 133.05 5.45 17 34.6 > 250 30.0 144.77 9.65 18 832.25 173.73 16.61 19 908.24 175.80 18.13 20 774.82 178.55 17.37 21 780.95 183.38 17.51 22 26.3 > 246 79.0 358.60 201.30 16.34 23 25.6 87.0 161.44 202.68 28.95 24 24.7 85.0 191.65 40.33 25 33.1 > 250 33.0 511.64 174.42 12.68 26 134 3659.59 117.89 3.84 27 178 41148.50 131.68 4.76 28 178 TABLE 1. CONT'D EFFECTIVE FLEXURAL CLTE# HDT#b IR#c STIFFNESS STRENGTH NODULUS EXAMPLE 10-6 C.-1 C. % 103 N/m 106 N/m 109 N/m2 29 150 30 153 31 49.0 > 250 19.0 5743.28 143.40 7.51 32 > 250 33 38.9 > 250 24.0 1346.17 147.53 8.27 34 26.8 59.0 690.07 210.96 18.20 35 22.3 70.0 751.88 222.68 21.58 36 21.6 82.0 309.05 253.01 27.51 37 17.8 85.0 131.85 297.13 65.91 38 81.0 606.72 260.59 27.64 39 307.47 29.78 40 75.0 196.48 22.61 41 33.5 191.65 17.65 42 62.0 160.63 18.27 43 137.19 30.89 44 139.95 24.68 45 164.77 15.24 46 169.59 23.65 47 162.01 25.58 48 166.15 31.44 49 16.2 > 250 66.5 211.65 21.58 50 159.94 15.58 51 175.80 18.68 52 17.8 > 250 47.0 159.94 22.54 53 493.43 156.49 36.61 54 762.21 183.38 50.40 TABLE 1. CONT'D EFFECTIVE FLEXURAL CLTEl HDTlb IRlC STIFFNESS STRENGTH MODULUS EXAMPLE 10-6 C.-1 C. % 103 N/m 106 N/m 109 N/m2 55 (32.8e > 250f 45.0f) (158.56f 16.41f) ( ) ( ) (35.5g > 250h 43.0h) (166.15h 17.58h) 56 (23.2e > 250f 45.0f (159.94f 16.34f) ( ) ( ) (34.7g > 250h 43.0h) (166.83h 17.17h) 57 30.2 > 250 47.0 598.32 84.11 12.41 58 24.8 239 27.0 682.54 159.25 15.93 59 26.3 239 54.0 183.38 19.72 60 61 62 28.3 240 78.0 216.47 21.79 63 34.2 240 184.07 19.58 64 18.2 > 237 66.5 317.98 211.65 21.03 65 19.3 > 240 78.0 408.86 278.52 32.19 66 26.6 238 26.0 147.53 14.27 67 24.3 218 33.0 122.71 12.82 68 25.0 217 27.0 135.81 12.41 69 40.0 207 20.0 commat; r=1.5% 83.42 10.07 TABLE 1. CONT'D EFFECTIVE FLEXURAL CLTE# HDT#b IR#c STIFFNESS STRENGTH MODULUS EXAMPLE 10-6 C.-1 C. % 103 N/m 106 N/m 109 N/m2 70 29.0 122 24.5 91.69 9.03 71 29.5 240 30.1 126.85 14.75 72 37.4 110.30 13.86 73 28.4 152.36 15.72 74 29.0 79 36.0 90.31 13.99 75 28.8 238 39.0 97.89 11.72 76 77 28.1 238 80.5 114.44 18.61 78 24.8 244 93.5 97.89 25.51 79 244 101.34 11.79 80 246 104.10 11.86 81 104.10 11.86 82 25.2 54.0 598.14 115.82 15.72 83 26.8 815.44 94.45 19.03 84 26.8 243 74.0 149.60 14.82 85 126.16 10.62 86 239 87 88 73.0 127.54 15.79 89 240 90 91 90.0 138.57 19.44 92 29.2 75.0 173.04 17.72 93 203.37 27.30 94 79.0 &commat; r=3% 230.95 35.37 95 119.96 12.00 TABLE 1. CONT'D EFFECTIVE FLEXURAL CLTE# HDT#b IR#c STIFFNESS STRENGTH MODULUS EXAMPLE 10-6 C.-1 C. % 103 N/m 106 N/m 109 N/m2 96 19.3 > 240 78.0 291.54 174.42 22.96 97 18.7 239 53.0 144.77 12.13 98 249 111.68 12.20 99 28.1 52.5 126.16 15.17 100 117.20 27.16 101 246 102 109.61 31.99 103 168.21 39.50 104 27.9 243 30.0 113.06 10.27 105 228 34.47 7.86 106 27.5 238 38.5 79.28 12.75 107 103.41 13.03 108 242 84.80 9.10 109 77.21 19.17 110 30.4 239 83.42 13.72 111 23.9 219 23.0 119.96 13.72 112 28.8 117 27.0 119.96 13.72 113 27.4 80 43.0 85.49 9.51 114 74 42.0 101.34 12.68 115 81.35 12.89 116 95.83 13.99 117 25.7 > 207 36.0 commat; r=4% 96.52 16.75 118 101.34 12.86 119 225 145,46 15.03 TABLE 1. CONT'D EFFECTIVE FLEXURAL CLTE# HDT#b IR#c STIFFNESS STRENGTH MODULUS EXAMPLE 10-6 C.-1 C. % 103 N/m 106 N/m 109 N/m2 120 54.46 7.58 121 103.41 122 71.01 11.72 123 87.55 12.62 124 28.1 185 83 616.70 54.12 10.62 125 212 51.70 10.55 126 214 62.74 9.10 127 194 57.22 9.31 128 49.64 7.01 129 27.58 3.72 130 26.6 127.54 13.79 131 25.6 72.39 5.45 132 25.6 117.20 8.00 133 30.4 130.30 11.10 134 39.8 234 495.01 120.92 9.17 TABLE 1. CONT'D TENSILE STRENGTH, 106 N/m2 ELONGATION, % MODULUS GIS IZOD, NOTCHEDd EXAMPLE YIELD FAIL YIELD FAIL 109 N/m2 N-m N-m/m 2 3 4 5 6 91.00 82.04 17.7 25.5 2.79 7 8 9 10 11 101.34 93.76 19.0 27.0 12 97.89 95.83 13.0 15.2 13 113.06 106.86 17.0 21.5 14 110.30 103.41 17.0 22.0 15 16 17 18 103.41 97.89 17.0 23.5 19 108.93 99.96 18.0 23.5 20 108.93 102.72 17.0 23.0 21 108.24 108.24 14.5 19.0 22 23 24 25 26 27 28 TABLE 1. CONT'D TENSILE STRENGTH, 106 N/m2 ELONGATION, % MODULUS GIS IZOD, NOTCHEDd EXAMPLE YIELD FAIL YIELD FAIL 109 N/m2 N-m N-m/m 29 30 31 32 33 34 35 36 37 38 39 134.43 123.40 3.24 40 110.30 104.79 2.83 41 42 43 98.59 21.69 15.5 21.0 3.10 44 100.65 93.28 13.0 18.5 3.24 45 46 47 48 49 116.51 108.24 13.0 19.0 3.79 50 51 52 104.79 104.10 16.0 18.0 3.45 53 54 TABLE 1. CONT'D TENSILE STRENGTH, 106 N/m2 ELONGATION, % MODULUS GIS IZOD, NOTCHEDd EXAMPLE YIELD FAIL YIELD FAIL 109 N/m2 N-m N-m/m 55 56 57 58 9.04 59 9.04 60 9.04 61 > 18.08 62 113.75 10.0 8.27 > 18.08 63 104.10 2.7 11.10 < 0.68 64 65 66 67 68 69 TABLE 1. CONT'D TENSILE STRENGTH, 106 N/m2 ELONGATION, % MODULUS GIS IZOD, NOTCHEDd EXAMPLE YIELD FAIL YIELD FAIL 109 N/m2 N-m N-m/m 70 71 1.36 37.37 72 48.04 73 74 75 76 > 18.08 77 78 79 > 18.08 53.91 80 > 18.08 49.11 81 > 18.08 54.98 82 63.42 58.60 4.3 11.7 2.34 > 18.08 87.01 83 74.75 84 85 72.39 65.49 6.25 14.0 26.20 > 18.08 86 78.59 73.77 8.9 17.8 2.55 > 18.08 87 > 18.08 88 89 70.32 64.1 2.41 90 > 18.08 91 92 84.11 77.90 3.9 7.9 9.65 6.33 82.21 93 95.83 89.62 4.1 7.7 11.72 9.94 109.68 94 108.93 104.10 7.4 3.1 17.24 6.78 168.68 95 > 18.08 59.79 TABLE 1. CONT'D TENSILE STRENGTH,10 N/m2 ELONGATION, % MODULUS GIS IZOD, NOTCHEDd EXAMPLE YIELD FAIL YIELD FAIL 109 N/m2 N-m N-m/m 96 97 98 > 18.08 47.51 99 72.39 65.49 4.7 12.0 2.83 > 18.08 68.86 100 71.01 68.94 5.9 12.0 2.83 > 18.08 101 102 74.46 71.70 10.0 15.0 2.96 14.92 103 90.31 86.86 5.0 11.0 0.76 8.59 104 70.46 105 > 18.08 81.14 106 107 11.30 79.00 108 > 18.08 73.66 109 > 18.08 109.43 110 > 13.56 59.25 111 112 113 114 115 5.20 48.58 2.71 52.31 116 117 118 11.75 44.31 119 11.75 53.38 TABLE 1. CONT'D TENSILE STRENGTH,10 N/m2 ELONGATION, % MODUEUS GIS IZOD, NOTCHEDd EXAMPLE YIELD FAIL YIELD FAIL 109 N/m2 N-m N-m/m 120 > 18.08 80.07 121 > 18.08 104.09 122 > 18.08 77.40 123 > 18.08 112.63 124 125 > 18.08 110.50 126 > 18.08 100.89 127 > 18.08 358.71 128 16.27 768.67 129 2.16 560.49 130 131 218.86 132 133 134 TABLE 2. PROPERTIES OF METALS NETAL DENSITYa CLTEm a IRmb TYPE THICKNESS,cm kg/m2-cm 10-6 C. -1 % 1145-0 Aluminum 0.102 27.07 23.8 95.0 " 0.0127 27.07 23.8 1100-0 Aluminum 0.104 27.07 23.6 94.0 " 0.102 27.07 23.6 " 0.0508 27.07 23.6 " 0.0254 27.07 23.6 " 0.0127 27.07 23.6 3003-H14 Aluminum 0.0635 27.46 23.2 88.0 3003-H25 Aluminum 0.0140 27.46 23.2 3003-H19 Aluminum 0.0127 27.46 23.2 5052-0 Aluminum 0.0813 26.88 23.8 87.5 " 0.102 26.88 23.8 " 0.0127 26.88 23.8 " 0.00762 26.88 23.8 6061-0 Aluminum 0.163 27.07 23.4 91.0 " 0.0635 27.07 23.4 " 0.0152 27.07 23.4 6061-T6 Aluminum 0.0813 27.07 23.4 80.0 " 0.127 27.07 23.4 83.0 " 0.470 27.07 23.4 " 0.102 27.07 23.4 " 0.0152 27.07 23.4 304 Stainless Steel-annealed 0.122 80.26 15.5c 88.0 " 0.00762 80.26 17.3 C 1008 Low Carbon Steel 0.109 92.8 C 1010 Low Carbon Steel - annealed 0.00762 @.34 15.1 TABLE 2. CONT'D TENSILE STRENGTH, 106 N/m2 FDEXURAL NODULUS AT OFFSET, % ELONGATION, % MODULUS STIFFNESS METAL 106 N/m2 0.2 5.0 10.0 FAIL FAIL 109 N/m2 103 N/m 1145-0 Aluminum 39.71 278.06 " 68.94 38.12 46.95 74.46 74.46 ,13.0 1100=0 Aluminum 68.94 42.74 299.25 " 68.94 39.43 256.35 " 68.94 32.04d " 68.94 79.97 30.0 " 68.94 33.85 58.25 64.87 71.01 30.1 3003-H14 Aluminum 68.94 3003-H25 Aluminum 68.94 152.36h152.36h 152.36h 7.6h 3003-H19 Aluminum 68.94 237.84 2.3 3003-0 Aluminum 70.32 64.11 213.45 " 70.32 416.91e " 70.32 97.21 153.05 179.93 194.41 19.5 " 70.32 103.41 153.74 184.07 198.55 19.2 6061-0 Aluminum 68.94 41.23 1097.88 " 68.94 65.49 " 68.94 54.46 112.37 -- 128.23 18.0 6061-T6 Aluminum 68.94 68.18 226.93 " 68.94 65.42 " 68.94 42.90f " 68.94 434.25f " 68.94 250.94 282.65 -- 293.00 304 Stainless Steel-annealed 193.03 112.37 " 259.21 369.52 443.97 574.96 24.0 C 1008 Low Carbon Steel 162.01 1308.70 C 1010 Low Carbon 326.78 349.53 372.28 376.03 23.0 Steel- 199.93-206.82 annealed TABLE 2. CONT'D FLEXURAL STRENGTH, 10@ N/m2 AT STRAIN, r. % METAL 0.5 1.0 3.0 5.0 MAXIMUN 1145-0 Aluminum 67.77 77.90 99.27 106.17 106.17 " 1100-0 Aluminum 74.46 87.55 118.58 128.92 128.92 " 70.32 70.28 99.96 104.79 104.79 " " " 3003-H14 Aluminum 3003-H25 Aluminum 3003-H19 Aluminum 5052-0 Aluminum 255.77 320.57 379.17 317.81 380.55 " " " 6061-0 Aluminum 101.34 130.30 173.73 201.99 " " 6061-T6 Aluminum 324.71 488.10 548.07 537.73 554.28 " 310.23 535.66 587.37 598.40 598.40 " " " 304 Stainless Steel-annealed 441.91 556.35 703.19 765.23 779.02 " C 1008 Low Carbon Steel 483.27 503.26 @598.40 623.91 C 1010 Low Carbon Steel-annealed TABLE 2. CONT'D METAL DENSITYa CLTEma IRmb TYPE THICKNESS,cm kg/m2-cm 10-6 C -1 % Low Carbon Steel Paint Test Panel 0.0965 91.0 1977 Oldsmobile Delta 88 Hood -Aluminum 0.109 84.0 1977 Oldsmobile Delta 88 Hood -Steel 0.0864 92.7 1977 Chevrolet Monte Carlo Hood -Steel 0.0838 92.5 1977 Chevrolet Monte Carlo Hood -Steel 0.0813 -78.14 a Taken from: Lynch, Handbook of Materials of Science, Vol. II, CRC Press, Cieveland, 1975, except where noted otherwise. b Determined, except where noted otherwise, at a strain, r, of 5% in the outer layers at the point of maximum deflection. c Observed. d Calculated from the average of 42.74 and 39.43 moduli, 41.08. for 0.104 cm and 0.102 cm thick 1100-0 aluminum, respectively. e Calculated from 64.11 modulus for 0.102 cm thick 5052-0 aluminum. f Calculated from the average of 68.18 and 65.42 moduli, 66.80, for 0.0813 cm and 0.127 cm thick 6061-T6 aluminum, respectively. g Calculated from 133.05 modulus for 0.0838 cm thick steel from 1977 Chevrolet Monte Carlo Hood. h Values are for the metal before subjection to the thermal conditions of lamination. Values for the metal after subjection to such conditions are: Tensile strength (106 N/m2) = 111 &commat; 0.2% offset, 130 &commat; 0.5% offset, 134 &commat; fail. Tensile elongation &commat; fail = 9.8% TABLE 2. CONT'D TENSILE STRENGTH, 106 N/m2 FLEXURAL MODULUS AT OFFSET, % ELONGATION, % MODULUS STIFFNESS METAL 106 N/m2 0.2 5.0 10.0 FAIL FAIL 109 N/m2 103 N/m Low Carbon Steel Paint Test Panel 173.73 1977 Oldsmobile Delta 88 Hood - Aluminum 62.67 506.04 1977 Oldsmobile Delta 88 Hood - Steel 167.52 668.88 1977 Chevrolet Monte Carlo Hood 133.05 485.73 1977 Chevrolet Monte Carlo Hood - Steel 443.00g TABLE 2. CONT'D FLEXURAL STRENGTH, 106 N/m2 AT STRAIN, r. % METAL 0.5 1.0 3.0 5.0 MAXIMUM Low Carbon Steel Paint Test Panel 606.67 686.64 744.55 744.55 751.45 1977 Oldsmobile Delta 88 Hood - Aluminum 283.34 388.82 483.27 520.50 523.25 1977 Oldsmobile Delta 88 Hood - Steel 477.75 513.60 581.16 588.06 1977 Chevrolet Monte Carlo Hood - Steel 330,91 383.31 463.28 467.41 477.06 1977 Chevrolet Monte Carlo Hood. - Steel TABLE 3. PROPERTIES OF THERMOPLASTICS. FLEXURAL THERMOPLASTIC DENSITYa CLTEc HDTcb IRcc MODULUS STIFFNESS STRENGTH TYPE THICKNESS,cm kg/m2-cm 10-6 C. -1 C. % 109 N/m2 103 N/m 106 N/m2 Nylon 6,6 0.138 11.37c 110.2 1.3 2.62 699.52 110.99 " 0.132 77 ZYTE# ST-801 0.130 10.79e 130.9 62 1.2 1.45 323.06 72.39 VYDYNE# R-240 0.146 13.88e 87.5 109 5.6 4.96 1504.28 142.71 VYDYNE# R-220 0.128 14.59e 83.5 99 Nyion 6,6/10% fiberglass 0.138 81.2 113 3.0 3.61 142.71 Nylon 6 0.135 11.2y 133.6 65 0.8 2.55 104.79 Nylon 6/10% fiberglass 0.133 68.0 100 2.4 3.93 146.84 PARN 56/44 (crystalline) 0.145 12.15f 57.6 117 0.4 3.03 119.27 " 0.080 57.6 117 1.5 4.14 95.14 (&commat; r=2%) PARN 56/44 (amorphous) 0.128 11.73f 63.9 117 0.38 2.41 120.65 PET (crystalline) 0.136 13.75f 92.7 89 0.81 2.83 118.58 PET (amorphous)# 0.333 13.32 83.2 68 0.78 2.21 83.42 PET/11.7% HYTREL 4056 0.211 112.0 " 0.351 82 4.6 1.86 64.11 PET/23.5% HYTREL# 4056 0.318 93.1 82 1.86 67.63 PET/1@ 1% PETBCP 0.318 91.8 68 5.9 2.00 73.08 PET-b-5% PBO-1000 0.353 116.3 75 1.6 2.69 97.2@ PET (crystalline)/ 10% Poiycarbonate 0.343 83.7 @@ 1.2 @.65 115.@@ TABLE 3. CONT'D TENSILE MODULUS STRENGTH, 10 N/m2 ELONGATION, % Tm , C. Tg g, C. THERMOPLASTIC 109 N/M2 YIELD FAIL YLELD FAIL c c Nylon 6,6 2.96 83.42 63.42 18.0 36.0 263 " ZYTEL# ST-801 1.79 51.64 7.1 > 50.0 265 VYDYNE# R-240 5.03 95.83 92.83 3.9 12.0 246 VYDYNE# R-220 6.55 85.14 1.8 241 Nylon 6,6/10% fiberglass 3.79 91.00 3.7 260 Nylon 6 2.69 75.14 4.6 > 50.0 220 Nylon 6/10% fiberglass 3.93 94.45 3.3 218 PARN 56/44 (crystalline) 78.74 2.2 301 " 301 PARN 56/44 (amorphous) 2.55 88.00 5.6 > 50.0 PET (crystalline) 3.03 77.21 4.8 257 PET (amorphous) 2.21 54.95 3.9 50.0 PET/11.7% HYTREL# 4056 " 2.34 58.60 5.6 > 50.0 257 PET/23.5% HYTREL# 4056 1.79 45.50 5.0 > 50.0 257 PET/11.1% PETBCP 3.09 73.42 260 PET-b-5% PBO-1000 2.83 68.94 41.23 5.0 30.0 256 PET (crystalline)/ 10% Polycarbonate 2.85 74.46 4.5 > 50.0 242 TABLE 3. CONT'D FLEXURAL THBRMOPLASTIC DENSITy2 CLTEc HDTcb IRcc MODULUS STIFFNESS STRENGTH TYPE THICKNESS,cm kg/m2-cm 10-6 c. -1 c. % 109 N/m2 103 N/m 106 N/m2 PET/I 80/20 (crystalline) 0.361 13.71 82.3 75 1.1 2.76 114.44 PET/I 80/20 (amorphous) 0.366 13.40 78.5 75 4.5 2.17 91.00 PBT 0.345 13.08e 140.6 52 0.66 2.21 79.97 HYTREL# 7246 0.343 12.48e 166.0 53 0.40 5.31 132.73 22.75 a Literature values, as noted. b Measured at 1.82 X 106 N/m2 except where noted otherwise. c Determined, except where noted otherwise, at a strain, r, of 5% in the outer layers at the point of maximum deflection. d Value for commercial product. Taken from: International Plastics Selector, Cordura Publi. cations, Inc., La Jolla, CA, 1977. e Taken from product brochure for commercial product. f Experimental value. g Taken from: Brandrup and Immergut, Eds., Polymer Handbook, 2nd ed., John wiley @ Sons, New York, 1975. TABLE 3. CONT'D TENSILE MODULUS STRENGTH, 10 N/m2 ELONGATION, % Tm , C. Tg g, C. THERMOPLASTIC 109 N/M2 YIELD FAIL YIELD FAIL c c PET/I 80/20 (crystalline) 2.83 76.52 4.5 18.5 202 PET/I 80/20 (amorphous) 3.03 63.49 3.45 > 50.0 PBT 2.14 55.84 12.0 > 50.0 230 HYTREL# 7246 0.55 27.58 22.0 > 50.0 216 Thus, it is apparent that there has been provided, in accordance with the present invention metalthermoplastic-metal laminates and a process for preparing same that fully satisfies the objects and advantages set forth hereinabove. While the invention has been described with respect to various specific examples and embodiments thereof, it is understood that the invention is not limited thereto and that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the invention.

Claims: WHAT IS CLAIMED IS: 1. A metal-thermoplastic-metal laminate having in combination: an inelastic ratio less than about 93%; a coefficient of linear thermal expansion less than about 63 x 10-6 C -1 a heat distortion temperature of at least about 13.0 C .; C.; and a maximum weight of no more than about 9.76 kg/m2; said laminate comprising: a thermoplastic core layer selected from the group consisting of partly crystalline polyamides and polyesters having a crystalline melting point greater than about 130 c.; and a metal layer laminated on each side of the thermo plastic core layer, each mental layer having: a melting point greater than the crystalline melting point of the thermoplastic core layer; and a minimum thickness of about 0.00127 cm; wherein the thickness ratio of the.sum of the metal layerthicknesses to the thermoplastic core layer thickness is described by the region of numerical overlap of the parameter TR(YSm/TSC) as determined from the areas defined by the relationships of TR(YSm/ TSc) to IRt, CLTE#, and (HDT# - HDTc) / (Tmc - HDT), the lower boundary of said areas being defined by the equation of a straight line y = mx + b in which y is the y-axis parameters of IRt, CLTE and (HDT# - HETc) (Tm - HDT ) x is the x-axis parameter of c TR(YSm/TSc), m is the slope of the straight line, and b is the intercept on the y-axis, with the proviso that: : when y is IRt, m is 108 and b is zero (0) for values of x from zero (0) to 0.65, and m is zero (0) and b is 70 for values of x greater than 0.65; when y is CLTE m is -3.6 x 10-4 4 and b is 45 x 10-6 for values of x from zero (0) to 0.1, and m is zero (O) ard b is 9 x 10-6 for values of x greater than 0.1; and when y is (HDT# - HDTc) / (Tm - HDTc), m is l and b is zero (0) for values of x from zero (0) to 0.05, m is 10 and b is -0.45 for values of x from 0.05 to C.12, and m is zero (0) and b is 0.75 for values of x greater than 0.12; and the upper boundary of said areas being defined by the equation of a straight line as defined hereinabove, with the proviso that: when y is IR±, m is 280 and b is 30 for values of x from zero (0) to 0.25, and m is zero (0) and b is 100 for values of x greater than 0.25 when y is CLTE#. m is -2.88 x 10-3 3 and b is 216 x 10-6 for values of x from zero (0) to 0.05, m is -1. 29 x 10-4 and b is 78.5 x 10-6 for values of X from 0.05 to 0.26, and m is zero (0) and b is 45 X 10 6 for values of x greater than 0.26; and when y is (HAT# - HDTc)/(Tmc - HDTc), m is 112.5 b is zero (0) for values of x from zero (0) to 0.004, m is 15.3 and b is 0.389 for values of X from 0.004 to 0.04, and m is zero (0) and b is 1 for values of x greater than 0.04; wherein: : IRt is the inelastic ratio of the laminate as measured in flexure at 5% strain in the outer metal layers at the point of maximum deflection; CLTE# is the coefficient of linear thermal expan sion of the laminate; (HDT# - HDTc) / (Tmc - HDTc) is a normalized heat distortion temperature variable wherein HDT is the heat distortion temperature of the laminate; H@@@'s the heat dj @@@@@@ temperature, the thermoplastic corc layer; Tmc is the crystalline melting point of the thermoplastic copse layer; TR is the thickness ratio of the sum of the metal layer-thicknesses to the thermoplastic core layer thickness; ; YSm is the thickness-weight-average tensile yield strength of the two metal layers at an offset of 5% elongation; and TSc is the tensile strength of the thermoplastic core z core layer. 2. The laminate of Claim 1 wherein the partly crystalline polyamides and polyesters are selected from the group consisting of thermoplas"tic compositions which have a partly crystalline polyamide or polyester portion having a degree of crystallinity of at least about 20%. 3. The laminate of Claim 1 wherein the thermoplastic core layer is a partly crystalline polyamide. 4. The laminate of Claim 3 wherein the partly crystalline polyamlde is selected from the group consisting o nylon 6,6; nylon 6; and nylon 6-C0-6,6. 5. The laminate of Claim '4 wherein the partly crystalline polyamide is nylon 6,6. 6. The laminate of Claim 3 wherein the partly crystalline polyamide is a partially aromatic nylon. 7. The laminate of Claim 6 wherein the partially aromatic nylon is a nylon 6, terephthalic acid-co-6, isophthalic acid. 8. The laminate of Clai 1 wherein the thermo- plastic core layer is 2 partly crystalline polyester. 9. The laminate of Claim 8 wherein the partly crystalline polyester is a poly(alkylene terephthalate)., 10. The laminate of Claim 9 wherein the poly (alkylene terephchalate) has an alkylene group containing from 2 to 10 carbon atoms. 11. The laminate of Claim 10 wherein the poly (alkylene terephthalate) is selected from the g'roup consisting of poly(ethylene terephthalate) and poly(butylene terephthalate) 12. The laminate of Claim 10 whc'x'ein the poly(alkylene terephthalate) is a bloc copolymer-modified poly(alkylene terephthalate). 13. The laminate of Claim 12 wherein the block copolymer-modified poly(alkylene terephthalate) is a poly (ethylene terephthalate) / poly (butylene tere-co-isophthalate). block-poly(butylene glycol) blend. 14. The laminate of Claims 1, 2, 3, 4, 5, 6. 7, 8, 9, 10, 11, 12 or 13 wherein the thermoplastic core layer material contains an added modifying agent. 15. The laminate of Claim 14 wherein the added modifying agent is high modulus, high performance fibers. 16. The laminate of Claim 15 wherein the high modulus, high performance fibers are glass fibers. 17. The laminate of Claim 16 wherein the glass fibers are present in concentrations of between abouL 't% and about 45% by weight. 18. The laminate of Claim 14 wherein the added modifying agent is a mineral filler. 19. The laminate of Claim 18 wherein the mineral filler is present in concentrations of between about 1% and about 50% by weight. 20. The laminate of Claim 19 wherein the mineral filler is calcined kaolinite clay. 21. The laminate of Claim 1 wherein the metal layers laminated on each side of the thermoplastic rrg layer have the same composition. 22. The laminate of Claim 21 wherein the metal layers are selected from the group consisting of aluminum, low carbon steel and stainless steel. 23. The laminate of Claim 22 wherein the metal layers are aluminum. 24. The laminate of Claim 1 wherein the metal layers have different compositions. 25. The laminate of Claim 1 wherein the metal layers laminated on each side of the thermoplastic core layer are of equal thickness. 26. The laminate of Claim 1 wherein both the metal layers and the thermoplastic core layer are ductile. 27. The laminate of Claim 1 which is a substantially flat structure. 28. The laminate of Claim 1 which is a non-flat shaped ,structure. 29. The laminate of Claim 1 wherein the thermoplastic core layer and the metal layers are uniformly laminated together via an adhesion agent interposed between the facing surfaces thereof. 30. The laminate of Claim 29 wherein the adhesion agent is an organosilane adhesion promoter. 31. The laminate of Claim 30 wherein the organosilane adhesion promoter is an amino-functional alkyltrialkoxysilane. 32. The laminate of Claim 31 wherein the aminofunctional alkyl-trialkoxysilane is selected from the group consisting of g,amma-aminopropyltrietboxysilane and N-beta (aminoethyl) -gamma-aminopropyltrimethoxysilane. 33. The laminate of Claim 30 wherein the organosilane adhesion promoter is a glycidoxy-functional alkyltrialkoxysilane. 34. The laminate of Claim 33 wherein the glycidoxy-functional alkyltrialkoxysilane is gamma glycidoxypropyltrimethoxysilane. 35. The laminate of Claim 30 wherein the organosilane adhesion promoter is a methacryloxy-functional alkyltrialkoxysilane. 36. The laminate of Claim 35 wherein the 'methacryloxy-functional alkyltrialkoxysilane is - methacryloxypropyltrimethoxysilane. 37. The laminate of Claim 30 wherein the organosilane adhesion promoter is a mixture of an amino-functional alkyltrialkoxysilane and a methacryloxy-functional alkyltrialkoxysilane. 38. The laminate of Claim 37 wherein the amino- functional alkyltrialkoxysilane and the methacryloxy functional alkyltrialkoxysilane of the mixture are gamma,- aminopropyl tri e thoxys ilane and gamma-me thacryloxypr'opyitr,i methoxysilane, respectively. 39. The laminate of Claim 29 wherein the adhesion agent is an adhesive. 43. The laminate of Claim 39 wherein the adhesive is an epoxy resin. 41. The laminate of Claim 1 suitable for use as an automobile body panel wherein: (a) the heat distortion temperature is at least o about 135 C.; (b) the coefficient of linear thermal expansion is less than about 45 x 10 0C.1; (c) the inelastic ratio is less than about 75%; and (d) the maximum 'weight is less than about 6.34 kg/m2 surface area; said laminate further having a flexural stiffness of at least about 262.65 x 103 N/m. 42. A process for the preparation of a metalthermoplastic-metal laminate having in combination: an inelastic ratio less than about 93%; a coefficient of linear thermal expansion less than about 63 x 10-6 C. -1; a heat discorcion cemperature of at least about 130 C.; and a maximum weight of no more than about 9.76 kg/m2; which process comprises: : disposing a metal layer on each side of a thermoplastic core layer selected from the group consisting of partly crystalline polyamides and polyesters having a crystalllne melting point greater than about 1300C., each metal layer having a melting point greater than the crystalline melting point of the thermoplastic core layer and a minimum thickness of about 0.00127 cm; ; wherein the thickness ratio of the sum of the metal layer-thick nesses to the thermoplastic core layer thickness is described by the region of numerical overlap of the parameter TR(YSm/TSc) as determined from the areas defined by the relationships of TR(YSm/TSc) to IR#, CLTE#, and (HDT# - HDTc)/ (Tmc - HDTc), the lower boundary of sails areas being defined by the equation of a straight line y = mx + b in which y is the y-axis parameters of IR#, CLTE#, and (HDT# - HDTc)/ (Tmc - HDTc), x is the x-axis parameter of TR(YSm TSc), m is the slope of the straight line, and b is the intercept on the y-axis, with the proviso that: : when y is IRQ, m is 108 and b is zero (0) for values of x from zero (0) to 0.65, and m is zero (0) and b is 70 for values of x greater than 0.65; when y is ClTE#, m is -3.6 x 10-4 4 and b is 45 x 10-6 for values of x from zero (0) to 0.1, and mis zero (0) and b is 9 x 10-6 for values of x greater than 0.1; and when y is (HDT# - HDTc)/(Tmc - HDTc), m is 1 and b is zero (0) for values or x from zero (0) to 0.05, m is 10 and b is -0.45 for values of x from 0.05 to 0.12, and m is zero (0) and b is 0.75 for values of x greater than 0.12; and the upper boundary of said areas being defined by the equation of a straight line as defined hereinabove, with the proviso that: : when y is IR#, m is 280 and b is 30 for values of x from zero (0) to 0.25, and m is zero (0) and b is 100 for values of x greater than 0.25; when y is CLTE#, m is -2.88 x 10-3 and b is 216 x 10-6 for values of x from zero (O) to 0.05, m is -1.29 x 10-4 and b is 78.5 x 10-6 for values of x from 0.005 to 0 26 and' ra is zero (0) and b is 45 x 10-6 for values of x greater than 0.26; and when y is (HDT# - HDTc) (Tmc - HDTc), m is 112.5 and b is zero (0) for values of x from zero (0) to 0.004, m is 15.3 and b is 0.389 for values of x from 0.004 to 0.04, and m is zero (0) and b is 1 for values of x greater than 0.04; wherein: : IR# is the inelastic ratio of the laminate as measured in flexure at 5% strain in the outer metal layers at the point of maximum deflection; CLTEt is the coefficient of linear thermal expansion of the laminate; (HDTi - HDTc)/(Tmc - HDTc) is a normalized heat distortion temperature variable wherein HDTQ is the heat distortion temperature of the laminate; HDTc is the heat distortion temperature of the thermoplastic; Tmc is the crystalline melting point of the thermoplastic core layer; TR is the thickness ratio of the sum of the metal layer-thicknesses to the thermoplastic core layer thickness; YSm is the thickness-weight-average tensile yield strength of the two metal layers at an offset of 5% elongation; and TS is the tensile strength of the thermoplastic core layer; laminating the thermoplastic core layer and the metal layers by subjecting the combination to elevated temperatures and a pressure sufficient to maintain face-adhering contact; and cooling to ambient temperatures. 43. The process of Claim 42 wherein the elevated temperatures are between about 100 C. and 350 C. 44. The process of Claim 42 wherein an adhesion agent is interposed between the facing surfaces of the metal layers and the thermoplastic core layer. 45. The process of Claim 44 wherein the adhesion agent is an organosilane adhesion promoter. 46. The process of Claim 45 wherein the organosilane adhesion promoter is an amino-functional alkyltrialkoxysilane. 47-. The process of Claim 46 wherein the aminofunctional alkyltrialkoxysilane is selected from the group consisting of garmna-aminopropyltriethoxysilane and N-beta (aminoethyl) -gamma-aminopropyltrimethoxysilane. 48. The process of Claim 45 wherein the organosilane adhesion promoter is a glycidoxy-functional alkyltrialkoxysilane. 49. The process of Claim 48 wherein the glycidoxy-functional alkyltrialkoxysilane is gammaglycidoxypropyltrimethoxysilane. 50. The process of Claim 45 wherein the organosilane adhesion promoter is a methacryloxy-functional alkyltrialkoxysilane. 51. The process of Claim 50 wherein the methacryloxy-functional alkyltrialkoxysilane is gamma methacryloxypropyl trime thoxys i lane. 52. The process of Claim 45 wherein the organosilane adhesion promoter is a mixture of an amino-functional alkyltrialkoxysilane and a methacryloxy-functional alkyltrialkoxysilane. 53. The process of Claim 52 wherein the aminofunctional alkyltrialkoxysilane and the methacryloxy- functional alkyltrialkoxysilane are gamma-aminopropyl triethoxysilane and gamma-methacryloxypropyltrimethoxysilane, respectively. 54. The process of Claim 44 wherein the adhesion agent is an adhesive. 55. The process of Claim 54 wherein the adhesive is an epoxy resin. 56. The process of Claim 42 which further comprises: (a) applying a weather resistant protective coating to at least one of the metal sur faces of the metal-thermoplastic-metal laminate; (b) curing the protective coating at elevated temperatures; and thereafter (c) cooling to ambient temperatures. 57. A process for the preparation of a metal thermoplastic-metal laminate which comprises: (a) orienting two metal layers to provide a spatial separation therebetween; and (b) casting a thermoplastic core layer between the two metal layers by in situ polymeri zation therebetween of monomeric material at polymerization conditions. 58. The process of Claim 57 wherein the monomeric material is E-caprolactam and the thermoplastic core layer is nylon 6. 59. The process of Claim 57 wherein the monomeric material is -caprolactam, an acyl-bis-caprolactam, and polyoxypropylene glycol and the thermoplastic core layer is a nylon 6/polyoxypropylene block copolymer 60. The process of Claim 59 wherein the acyl bis-caprolactam is isophthaloyl-bis-caprolactam. .61. The process of Claim 57 wherein the mono meric material is E-caprolactam admixed with calcined kaolinite clay and the thermoplastic core layer is a calcined kaolinite clay reinforced nylon 6. 62. The process of Claim 61 wherein the calcined clay reinforced nylon 6 is a 20% to 45% calcined kaolinite clay reinforced nylon 6.

Inventors: ERICKSON, FLOYD BUREN, GABBERT, JAMES DELVIN, HEDRICK, ROSS MELVIN, WOODBREY, JAMES CALVIN
Applicants: MONSANTO COMPANY
Application year: 1979
Main classification: B32B15
IPC codes: B32B15