Abstract:
A typical inventive embodiment describes a tubular shape and comprises a rigid outer layer, an elastomeric middle layer and a rigid inner layer. The elastomeric material is a strain-rate-sensitive polymer (e.g., polyurethane or polyurea) having a Young&#39;s modulus of approximately 700-1000 psi at 100% strain, and strong strain-rate-sensitivity in approximately the 10 3 /second-10 6 /second range. By the time that the projectile reaches the rigid inner layer, a projectile that impacts the three-layer system (commencing at the rigid outer layer) is structurally and kinetically diminished in its destructiveness by the rigid outer layer together with the elastomeric middle layer. Furthermore, the elastomeric middle layer becomes more rigid during a brief period in which it absorbs energy from the projectile, then again becomes elastic in a manner formative of a membrane covering the rigid inner layer. The elastomeric membrane tempers leakage if rupturing of the rigid inner layer has occurred.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. provisional application No. 60/564,584, filed 23 Apr. 2004, hereby incorporated herein by reference, entitled “Armor Including a Strain Rate Hardening Elastomer,” joint inventors Roshdy George S. Barsoum and Philip Dudt. 
   This application is a continuation-in-part of U.S. nonprovisional application no. 10/864,317, filed 10 Jun. 2004, hereby incorporated herein by reference, entitled “Armor Including a Strain Rate Hardening Elastomer,” joint inventors Roshdy George S. Barsoum and Philip Dudt, now U.S. Pat. No. 7,300,893 B2, issue date 27 Nov. 2007, which claims the benefit of the aforesaid U.S. provisional application No. 60/564,584, filed 23 Apr. 2004, entitled “Armor Including a Strain Rate Hardening Elastomer,” joint inventors Roshdy George S. Barsoum and Philip Dudt. 
   This application claims the benefit of PCT application (international application published under the Patent Cooperation Treaty) WO 2005/103363, filed 3 Nov. 2005, hereby incorporated herein by reference, entitled “Armor Including a Strain Rate Hardening Elastomer,” joint inventors Roshdy George S. Barsoum and Philip Dudt, which claims the benefit of the aforesaid U.S. nonprovisional application Ser. No. 10/864,317, filed 10 Jun. 2004, entitled “Armor Including a Strain Rate Hardening Elastomer,” joint inventors Roshdy George S. Barsoum and Philip Dudt, and which claims the benefit of the aforesaid U.S. provisional application No. 60/564,584, filed 23 Apr. 2004, entitled “Armor Including a Strain Rate Hardening Elastomer,” joint inventors Roshdy George S. Barsoum and Philip Dudt. 

   STATEMENT OF GOVERNMENT INTEREST 
   The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalties thereon or therefor. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to protective coverings (such as armor) that may be used for people and objects, more particularly to methods and devices for protecting entities from damage or injury caused by explosive or ballistic events. 
   Surface ships, submarines, small boats, buoys, tanks, oil rigs, pipelines and nuclear storage are examples of water-borne and fluid-containing objects that are vulnerable to leakage, inward or outward, that may be caused by explosive or ballistic attack. For instance, an explosive or ballistic event can puncture or otherwise rupture a marine vessel in at least one location, resulting in the rapid ingress of water and the concomitant sinking of the marine vessel, thus posing a great risk to the occupants of the marine vessel. A liquid container or gas container (made of any structural material) that is leaking due to an explosive or ballistic event can represent a chemical leak hazard or a fire hazard (e.g., when the container is a tank containing gasoline). 
   It is therefore desirable to protect water-borne and fluid-containing objects from harm caused by explosions and projectiles. More specifically, the protection of such objects is sought so as to mitigate structural damage (such as manifested by one or more ruptures) and the consequent ingress or egress of fluid material. 
   SUMMARY OF THE INVENTION 
   In view of the foregoing, it is an object of the present invention to provide a methodology for reducing or minimizing the damage ensuing from an explosive and/or ballistic event to a water-borne or fluid-containing object. 
   It is a further object of the present invention to reduce or minimize the fluid ingress or fluid egress that is associated with such ensuing damage. 
   The present invention provides diverse embodiments of a multilayered (plural-layered) combination of materials comprising at least one “highly strain-rate-sensitive” (synonymously referred to herein as “strongly strain-rate-sensitive” or “highly rate-sensitive” or “strongly rate-sensitive”) elastomeric material and at least one “rigid” (relatively more rigid) material. The rigid material, which is more rigid than the elastomeric material, can be any suitable structural material, including but not limited to a metal (wherein the term “metal” is broadly defined herein as any metallic material, e.g., an elemental metal or a metal alloy), a composite (e.g., a fiber-reinforced matrix composite), or a ceramic. The present invention&#39;s elastomer is typically a polymer such as a polyurethane or a polyurea, and is typically characterized by: a Young&#39;s modulus in the range of approximately 700 psi to approximately 1000 psi, at 100% strain; and, high (strong) strain-rate-sensitivity for strain rates in the range of approximately 10 3 /second to approximately 10 6 /second. Depending on the inventive embodiment, the inventive highly strain-rate-sensitive elastomer may also be characterized by high strain-rate-sensitivity outside of this 10 3 /sec-10 6 /sec range of strain-rates. The term “range” is intended herein to be “inclusive,” i.e., to include the delimiting (e.g., upper and lower) values of the range. The present invention&#39;s strain-rate-sensitive elastomer has the ability to practically immediately react to impact so as to rigidify while absorbing impact-related energy, and to then practically immediately return to its elastic (non-rigid) condition. As variously practiced, for instance, an inventive laminar configuration resists ballistic penetration in air, or resists rupture in a fluid medium, or averts or limits flooding following explosive damage to pipelines and ships. 
   The present invention&#39;s “high-strain-rate” (“highly rate-sensitive”) polymers exhibit greatly increased transient mechanical property changes under rapid loading, such as when exposed to explosively generated forces, and exhibit high elongations during and after load removal. A typical highly rate-sensitive polymer used in inventive practice is a substance from the polyurea family or the polyurethane family, or is a mixture of substances from the polyurea and polyurethane families. Among its benefits, during a dynamic event a highly rate-sensitive polymer&#39;s propensity toward transient high-rate dynamic mechanical strength elevations enables it to share loads with the metal substrate to which it is bonded, thereby improving resistance to rupture. When some inventive embodiments are practiced under certain conditions, a highly rate-sensitive polymer is capable not only of affording improved structural (e.g., ballistic) performance in terms of precluding or limiting rupturing, but also of acting as a membrane to avoid flooding or to control the rate thereof in the event that there is at least one rupture. 
   In accordance with typical embodiments of the present invention, a laminar composite structure comprises three adjacent layers, viz., (i) a structural first layer, (ii) a strain-rate-sensitive elastomeric second layer, and (iii) a structural third layer. The strain-rate-sensitive elastomeric second layer is situated between the structural first layer and the structural third layer. The strain-rate-sensitive elastomeric second layer is characterized by: a Young&#39;s modulus in the range of approximately 700-1000 psi at 100% strain; and, a strain-rate-sensitivity hardening in the range of approximately 10 3 /second-10 6 /second. The strain-rate-sensitive elastomeric second layer at least substantially consists of a polymer such as polyurethane and polyurea. The structural first layer and the structural third layer each at least substantially consist of a material such as metal, fiber-reinforced matrix composite and ceramic. 
   The laminar composite structure is characterized by resistance with respect to impact by a projectile that penetrates the structural first layer, wherein the projectile is mitigated upon traversing the structural first layer and the strain-rate-sensitive elastomeric second layer, and wherein the structural third layer is deformed but remains at least substantially intact upon impact by the projectile. The mitigation of the projectile includes blunting and/or breakage and/or slowing of the projectile. The deformation of the structural third layer includes denting and/or breakage of the structural third layer. 
   According to some inventive embodiments, the inventive laminar composite structure further comprises a fluid contained by the structural third layer, which has a tubular or other shape suitable for containment of fluid. The strain-rate-sensitive elastomeric second layer stiffens upon being traversed by the projectile. Moreover, the strain-rate-sensitive elastomeric second layer subsequently stretches so as to form a membrane that at least substantially covers the deformation (deformed portion) of the structural third layer. If the deformation of the structural third layer includes breakage, then the membrane reduces leakage of the fluid from the laminar composite structure. 
   The terms “tube,” “tubular” and “pipe” are synonymously used herein to broadly denote any elongate hollow body, without any limitation in terms of geometry of the elongate hollow body. Hence, a “tube” or “pipe” can describe any shape. A “tube” or “pipe” can be cylindrical or non-cylindrical, rectilinear or curvilinear or curved; its cross-sectional profile can be regular or irregular, uniform or non-uniform along its length. A “tube” or “pipe” is usually implemented to contain, conduct or convey a fluid (e.g., a liquid, a gas or a solid particulate), but is not necessarily so implemented according to this definition. 
   Other objects, advantages and features of the present invention will become apparent from the following detailed description of the present invention when considered in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the accompanying drawings, wherein: 
       FIG. 1  is an axially-longitudinally cross-sectional view of an embodiment of a cylindrical three-layer material system in accordance with the present invention. 
       FIG. 2  is a diametrically-transversely cross-sectional view of the inventive embodiment shown in  FIG. 1 . 
       FIG. 3  is a perspective view of the inventive embodiment shown in  FIG. 1 . 
       FIG. 4  is an axially-longitudinally cross-sectional view, partial and enlarged, of the inventive embodiment shown in  FIG. 1 , illustrating ballistic impact with respect to the inventive embodiment shown in  FIG. 1 . 
       FIG. 5  is an axially-longitudinally cross-sectional view of an embodiment of a cylindrical two-layer material system in accordance with the present invention. 
       FIG. 6  is a diametrically-transversely cross-sectional view of the inventive embodiment shown in  FIG. 5 . 
       FIG. 7  is the view of  FIG. 5 , illustrating external explosive impact with respect to the inventive embodiment shown in  FIG. 5 . 
       FIG. 8  is the view of  FIG. 5 , illustrating containment of a volatile or flammable liquid such as gasoline by the inventive embodiment shown in  FIG. 5 . 
       FIG. 9  is the view of  FIG. 5 , illustrating internal explosive impact with respect to the inventive embodiment shown in  FIG. 8 . 
       FIG. 10  is an axially-longitudinally cross-sectional view, similar to the view of  FIG. 1 , of an embodiment of a four-layer material system in accordance with the present invention. 
       FIG. 11  is a diametrically-transversely cross-sectional view of the inventive embodiment shown in  FIG. 10 . 
       FIG. 12  is a table listing three different commercially available polyurea formulations and some of their material properties. 
       FIG. 13  is a schematic of a method for associating a protective barrier with a cylindrical vessel or conduit in accordance with the present invention. 
       FIG. 14  is a schematic of another method (different from the method illustrated in  FIG. 13 ) for associating a protective barrier with a cylindrical vessel or conduit in accordance with the present invention. 
       FIG. 15  is a schematic of another method (different from the methods illustrated in  FIG. 13  and  FIG. 14 ) for associating a protective barrier with a cylindrical vessel or conduit in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIG. 1  through  FIG. 3 , a conventional pipe  11  having a cylindrical metal pipe wall  111  is covered with a cylindrical protective barrier  12  in accordance with the present invention. Protective barrier  12  includes an elastomeric layer  121  and a cylindrical metal sleeve  122 , the elastomeric layer  121  being situated intermediate the pipe wall  111  and the sleeve  122 . Elastomeric layer  121  is composed of a polymer (e.g., polyurea or polyurethane) characterized by high strain-rate sensitivity (strong strain-rate sensitivity). The present invention&#39;s combination  10 , which includes the pipe  11  and the present invention&#39;s protective barrier  12 , thus represents a laminar material system that includes three adjacent layers. In this multilayer system, a highly rate-sensitive elastomeric layer  121  is sandwiched between two “rigid” (i.e., more rigid than the elastomer of layer  121 ) layers, viz., pipe wall  111  and sleeve  122 . 
   Still referring to  FIG. 1  through  FIG. 3  and also referring to  FIG. 4 , inventive combination  10  represents a structure that affords effective resistance to penetration by kinetic rounds. This resistance to penetration, such as associated with ballistic attack, is important in protecting pipelines and a variety of other objects in which rupture can occur because of projectiles such as bullets or bomb fragments. The term “projectile” as used herein broadly refers to any body in motion that has been projected or impelled by force, typically continuing in motion by its own inertia, and typically a form of weaponry including but not limited to bullet, missile or bomb fragment. The structure shown in  FIG. 4  corresponds to the portion of inventive three-layer material system  13  that is in the path of bullet  38 , as shown in  FIG. 1 . 
   As illustrated in  FIG. 4 , metal sleeve  122  represents the strike face. A ballistic penetrator such as bullet  38  enters the metal sleeve  122  at location  44  and continues on bullet  38 &#39;s trajectory t. Bullet  38  thereby produces a hole  45  along trajectory t in the outer layer (viz., metal sleeve  122 ) and middle layer (viz., elastomer  121 ) of the inventive three-layer system  13 . The metal sleeve  122  acts in combination with the elastomeric layer  121  to blunt and/or fracture the bullet  38  through transient mechanical strength interactions. The elastomeric layer  121  also acts to slow down (reduce the speed of) bullet  38  by erosion and by absorption of heat energy. The portion of hole  45  that is contained in elastomeric layer  121  tends to “melt” back together in a narrowing manner. In a sense, the hole  45  portion in elastomeric layer  121  “heals” up so that elastomeric layer  121  layer reforms into a protective membrane, effectively constituting a seal against leakage. The blunted/broken bullet  38 ′ then strikes the wall  111  of pipe  11 . 
   As a result of being impacted by blunted/broken bullet  38 ′, it may be the case that pipe wall  11  is deformed (such as manifested by a dent  40 ) but not ruptured (e.g., broken, torn or penetrated) by blunted/broken bullet  38 ′. As portrayed in  FIG. 4 , since blunted/broken bullet  38 ′ has lost velocity and shape as compared with its former condition as bullet  38 , it may be that blunted/broken bullet  38 ′ can only form a dent  40  in pipe wall  111 . In such case, the interaction between bullet  38  and, sequentially, the sleeve  122  and the elastomer  121 , causes bullet  38  to fragment and blunt (thereby forming bullet  38 ′) and decelerate; the pipe wall  11  is only dented, rather than being penetrated, by bullet  38 ′. 
   On the other hand, pipe wall  111  may be ruptured, e.g., compromised in such a way that one or more openings large enough to permit leakage therethrough are created at one or more locations therein. If pipe wall  11  is ruptured, such as depicted by rupture  41  in  FIG. 4 , the elastomeric layer  121  will expand and seal (or partially seal), thus limiting any leakage in or out. If pipe  111  is a conduit for a liquid or gaseous fluid, leakage out of pipe  111  thus being of greater concern, the polymeric seal represented by elastomeric layer  111  would tend to limit this leakage. 
   With reference to  FIG. 5  and  FIG. 6 , cylindrical metal pipe wall  111  of pipe  11  is covered with a cylindrical protective barrier  12  that includes a highly rate-sensitive elastomeric layer  121  (such as shown in  FIG. 1  through  FIG. 3 ) but does not include a cylindrical metal sleeve  122 . The elastomeric layer  121  can be applied to pipe wall  111  using a conventional technique such as involving casting or spraying of an uncured polymeric substance. The present invention&#39;s combination  10 , which includes the pipe  11  and protective barrier  12  (which includes elastomeric layer  121 ), thus represents a laminar material system that includes two adjacent layers. In this two-layer material system, a highly rate-sensitive elastomeric layer  121  is placed on the outside surface of the innermost, “rigid” (i.e., more rigid than the elastomer of layer  121 ) layer, viz., pipe wall  111 . 
     FIG. 5  and  FIG. 6  portray an inventive combination  10  prior to an impacting event. Reference now being made to  FIG. 7  through  FIG. 9 , an external or internal explosion might take place with respect to an inventive combination  10  such as depicted in  FIG. 5  and  FIG. 6 . The elastomeric layer  121 , placed on the outside surface of pipe wall  111 , can serve to lend protection with respect to either an external explosive event  14   EX  (such as shown in  FIG. 7 ) or an internal explosive event  14   IN  (such as shown in  FIG. 8  and  FIG. 9 ). 
   As illustrated in  FIG. 7 , elastomeric layer  121  affords a degree of protection while facing an explosive pulse  14   EX , which can be conceived in this illustration to be either an underwater detonation/burst or a surface detonation/burst. The behavior of the inventive combination  10  would be similar whether submerged or non-submerged. The inventive combination  10  is characterized by a great elongation capacity after damaging loading has occurred. This elongation capacity is significantly greater than that which would characterize the pipe wall  111  in the absence of the elastomeric layer  121 . Upon occurrence of the external explosion  14   EX , elastomeric layer  121  becomes a residual membrane covering over the underlying deformation area  40  in pipe wall  111 , which includes denting and/or fracturing and/or rupturing such as represented by rupture  41  in pipe wall  111 . Thus, subsequent to the external explosion  14   EX , the elastomer  121  membrane itself remains intact or is only slightly ruptured (e.g., torn). If pipe  11  is submerged in water or other liquid, the elastomer  121  membrane either entirely prevents liquid from entering pipe  111  or substantially prevents liquid from entering pipe  111  (e.g., permitting the liquid to enter pipe  111  at a slow and manageable rate). 
   As illustrated in  FIG. 8  and  FIG. 9 , internal explosion  14   IN  occurs within a liquid-filled (e.g., gasoline-filled) pipe  11 , which can be conceived to be either in or out of water. Relative to internal explosion  14   IN , elastomeric layer  121  is situated on the opposite face of the pipe wall  111 . When ruptures  41  occur to the underlying wall  111  of the pipe  11 , elastomeric layer  121  provides a membrane over the damaged areas  40 , thereby reducing the potential for leakage out of the pipe  11 . Thus, subsequent to the internal explosion  14   IN , the elastomer  121  membrane itself remains intact or is only slightly ruptured (e.g., torn). If pipe  11  contains liquid or gaseous fluid  50 , the elastomer  121  membrane either entirely prevents the fluid from exiting pipe  111  or substantially prevents the fluid  50  from exiting pipe  111  (e.g., permitting fluid  50  to exit pipe  111  at a slow and manageable rate). 
   As usually practiced, the present invention&#39;s protective barrier  12  includes at least one elastomeric material layer (such as that which is applied through molding, casting, spraying or bonding) and at least one structural material layer (made of a metal or composite or other non-metal material). In the context of inventive practice, the terms “structural layer,” “structural material layer,” “rigid layer” and “stiff layer” are used synonymously herein to refer to a layer that is characterized by a degree of rigidity (or stiffness) so as to be more rigid (or stiff) than an elastomeric layer. Generally speaking, the “structural” character of a material, e.g., in terms of its load-bearing capability, directly relates to its rigidity (or stiffness); hence, an inventive “structural layer” is not only more rigid (or stiff) but is also more “structural” than is an inventive elastomeric layer. The present invention&#39;s structural material is typically a non-elastomeric material, but can be elastomeric (e.g., a fiber-reinforced elastomeric matrix composite material) in some inventive embodiments. The present invention&#39;s highly strain-rate-sensitive elastomeric layer has the quality of reacting instantaneously to impact (for instance, at strain rates in the 10 3 /sec-10 6 /sec range) so as to temporarily become significantly more rigid than it is in its normal (non-impacted) state, and of then returning to its normal elastic (e.g., viscoelastic) state shortly after absorbing energy associated with the impact. 
   The elastomeric material of which the present invention&#39;s elastomeric layer  121  is composed is typically characterized by a Young&#39;s modulus in the range between approximately 700 psi and approximately 1000 psi, at 100% strain. Moreover, the present invention&#39;s elastomeric material is typically characterized by strong strain-rate-sensitivity in the strain-rate range between approximately 1,000/second and approximately 1,000,000/second, especially or more typically in the strain-rate range between approximately 10,000/second and approximately 1,000,000/second. Some polyurethanes, some polyureas, and some other polymeric materials meet these criteria. Three commercially available polyureas meeting these criteria, and some of their characteristics, are set forth in  FIG. 12 . Plasite Protective Coatings, Inc. of Maple Shade, N.J., manufacturer of Semstone  403 , is now owned by Carboline Company of St. Louis Mo., a subsidiary of RPM of Medina, Ohio. Air Products and Chemicals, Inc. of Allentown, Pa., manufactures Versalink® P-1000 oligomeric diamine (polytetramethyleneeoxide-di-p-aminobenzoate). Polyshield HI-E™ is manufactured by Specialty Products Inc. (SPI) of Lakewood, Wash. These are but three examples among the many commercially available formulations, polymeric and otherwise, that may be strain-rate-sensitive elastomeric materials suitable for inventive practice. 
   Generally, elastomers meeting the above-said criteria (Young&#39;s modulus in the range of approximately 700-1000 psi at 100% strain; strain-rate-sensitivity hardening in the range of approximately 10 3 /second-10 6 /second) will also have the following characteristics in low rate-of-loading conditions: Young&#39;s modulus in the range between approximately 1200 psi and 1400 psi, at 300% strain; Young&#39;s modulus in the range between approximately 4000 psi and approximately 6000 psi, at 400% strain; elongation in the range between approximately 200% and approximately 800%, typically more than approximately 400%; tensile strength in the range between approximately 2000 psi and approximately 8000 psi; Poison&#39;s ratio in the range between approximately 0.45 and approximately 0.49 (as close to 0.5 as possible, which represents incompressibility of the elastomer). 
   Because of its high rate-sensitivity, a typical elastomer used in inventive practice is characterized by a Young&#39;s modulus that increases at high rate loading (e.g., rate loading in the range between approximately 5000/sec and approximately 6000/sec) from approximately 400 psi to: the range between approximately 20,000 psi and approximately 30,000 psi, under unconfined conditions; the range between approximately 500,000 psi and approximately 600,000 psi, under confined conditions. The terms “elastomer” and “elastomeric material,” as used herein, broadly refer to any material having elastic (e.g., viscoelastic) physical character, regardless of whether it includes at least one structural material (e.g., a plasticizer or an antioxidant) that is incorporated therein for at least one enhancement purpose. 
   The present invention can be practiced in multifarious laminar configurations in which the laminar configuration is inclusive of (i) one or practically any plural number of strain-rate sensitive elastomeric layers and (ii) one or practically any plural number of structural (stiff) layers. For instance, with reference to  FIG. 10  and  FIG. 11 , a an inventive combination  1000  includes all that inventive combination  1000  includes (i.e., structural pipe wall  111 , elastomeric layer  121   a , and structural sleeve  122 ) plus an additional elastomeric layer  121 , viz., elastomeric layer  122   b . This four-layer material system thus includes: a rigid, innermost layer (pipe wall  111 ); an elastomeric, second-innermost layer (elastomeric layer  121   a ); a rigid, second-outermost layer (sleeve  122 ); and, an elastomeric, outermost layer (elastomeric layer  121   b ). The cylindrical protective barrier  12  shown in  FIG. 11  and  FIG. 12  thus includes, in alternate arrangement, an elastomeric layer  121   a , a rigid layer  122 , and an elastomeric layer  121   b . The mechanism for protection from a projectile is similar to that for the inventive combination  100  shown in  FIG. 1  through  FIG. 3 , except that inventive combination  1000  provides an extra measure of protection; that is, elastomeric layer  122   b , placed on the sleeve  122  surface, serves to, further blunt and/or fragment and/or reduce the speed of a penetrator such as bullet  38  shown in  FIG. 4 . 
   In the light of the instant disclosure, the ordinarily skilled artisan will appreciate the various ways in which an inventive protective barrier  12  can be applied to an existing structure such as a conventional pipe  11 . For instance, again with reference to  FIG. 1  through  FIG. 3  and also with reference to  FIG. 13  through  FIG. 15 , there are various methods for associating the inventive protective barrier  12  shown in  FIG. 1  through  FIG. 3  with a pipe  11  (or other object) sought to be protected from ballistic or explosive impact. The end result of the distinguishable application methods shown in  FIG. 13  through  FIG. 15  is essentially the same, viz., an inventive combination  100  in which a rigid (e.g., metal) sleeve  122  is disposed around a rigid (e.g., metal) pipe wall  111  and in which strain-rate-sensitive elastomer  121  disposed between sleeve  122  and pipe wall  111 . 
     FIG. 13  illustrates a practical approach to coupling an inventive protective barrier  12  with a pipe  11 . The metal sleeve  122  is placed around pipe wall  111 , thus positioned so as to coaxially/concentrically encircle pipe wall  11  and leave an empty space  80  therebetween. The space  80  between sleeve  122  and pipe wall  111  is subsequently filled (e.g., via injection molding) with a highly rate-sensitive elastomer (in an uncured state), which is then permitted to cure for a suitable period, e.g., at least 24 hours, thereby forming elastomeric layer  121 . 
   According to the alternative approach illustrated in  FIG. 14 , highly rate-sensitive elastomer (in an uncured state) is sprayed or cast onto the outside surface of pipe wall  111  and is then permitted to cure for a suitable period, e.g., at least 24 hours. When the elastomeric material is completely cured, thereby forming elastomeric layer  121 , the sleeve  122  is placed around (positioned so as to circumscribe, but not too tightly) the elastomeric layer  121 , which coats/covers the outside surface of the pipe wall  111 . The approach shown in  FIG. 15  is similar to that shown in  FIG. 14 , except that the highly rate-sensitive elastomer (in an uncured state) is sprayed or cast onto the inside surface of sleeve  122 , rather than onto the outside surface of pipe wall  111 . The applied elastomer is permitted to cure upon the inside surface of sleeve  122  for a suitable period, e.g., at least 24 hours. When the elastomeric material is completely cured, thereby forming elastomeric layer  121 , the combination article that includes the elastomer  121  (on the inside of the combination article) and the sleeve  122  (on the outside of the combination article) is placed around (positioned so as to circumscribe, but not too tightly) the outside surface of the pipe wall  111 . 
   More generally, inventive practice can provide for the application of at least one elastomeric layer through molding, casting, spraying or bonding. Regardless of the inventive fabrication technique, inventive practice usually prefers the contiguous arrangement of the three layers. In the example shown in  FIG. 1  through  FIG. 3 , for instance, the three cylindrical layers—namely pipe wall  111 , elastomer  121  and sleeve  122 —are contiguously and circumscriptively configured. The metal sleeve  122  is the outermost layer of the inventive three-layer material system  13 . The metal sleeve  122  is the innermost layer of the inventive three-layer system  12 . The elastomeric layer  121  (which overlies the metal pipe wall  111  and underlies the metal sleeve  122 ) is the intermediate layer of the inventive three-layer system  13 . Thus, for instance, if the inventive combination  10  is made so as to dispose sleeve  122  around a completely cured elastomeric layer  121  (with which pipe wall  111  has been coated/covered), the elastomer  121  should fit inside the sleeve  122  so that the latter lightly hugs (without exerting undue pressure upon) the former. 
   The present invention, which is disclosed herein, is not to be limited by the embodiments described or illustrated herein, which are given by way of example and not of limitation. Other embodiments of the present invention will be apparent to those skilled in the art from a consideration of the instant disclosure or from practice of the present invention. Various omissions, modifications and changes to the principles disclosed herein may be made by one skilled in the art without departing from the true scope and spirit of the present invention, which is indicated by the following claims.