bluuebunny/crossref_metadata_2025_split huggingface dataset:
Forced torsional properties of PMR composites with varying nadic ester concentrations and processing histories
Authors: Hurwitz Frances I. 
Published: May 2005

AbstractPMR polyimide resin was prepared from 4,4′‐methylenedianiline (MDA), the dimethyl ester of 3,3′,4,4′‐ benzophenonetetracarboxylic acid (BTDE) and the monomethyl ester of 5‐norbornene‐2,3‐dicarboxylic acid (NE). The NE group serves as a chain terminator and crosslinking site. PMR/Celion 6000 composites were fabricated from resins having varying NE concentrations using two molding processes, and the laminates characterized in forced torsion. Glass transition temperatures (Tg) of 360–390°C were observed in the crosslinked resins, as compared with the literature value of 284°C reported for the uncrosslinked systemTgdidnotdecrease with decreasing NE concentrations over the range from 2.0 to 1.25 moles. Stoichiometry, within the range studied, showed little influence on shear properties; however, a 25% variation in matrix shear modulus with processing was observed. TheG12values determined in forced torsion were in excellent agreement with those reported from tensile tests of ±45° laminates. A branching and possible secondary crosslink mechanism is proposed based on dynamic mechanical behavior and infrared spectra of the composites.
The effect of glass fibers on the rheological behavior of polypropylene melts between rotating parallel plates
Authors: Mutel A. T. , Kamal M. R. 
Published: May 2005

AbstractThe Rheometrics mechanical spectrometer has been employed in the parallel plate mode to study the rheological behavior of pure polypropylene resin and melts filled with 10, 20, 30, and 40 percent by weight glass fibers. Steady‐state shear data show that, for loadings above 20 percent fiber, increasing fiber loading leads to an increase in viscosity of the melt. The effect of increasing fiber content becomes smaller at higher shear rates. For the same loading range, fiber addition increases the first normal stress difference, and the effect of fiber loading becomes smaller with increasing shear rate. At 10 percent loading, the viscosity of the filled polymer melt is lower than that of the pure resin melt. These results require further confirmation.Strain sweeps employing dynamic measurements in conjunction with the parallel plate mode of the Mechanical Spectrometer were carried out. In general, it was found the dynamic properties are strain dependent. Steady shear data employing the cone‐and‐plate mode were not repeatable.
Rheology of mica‐reinforced polyethylene melts
Authors: Fisa B. , Utracki L. A. 
Published: May 2005

AbstractSeven samples of HDPE containing 0, 2, 5, 10, 25, 40 and 60 weight percent of mica were prepared on a roll mill at 200°C. The samples were tested at T = 150, 170, 190 and 210°C for a wide range of rate of deformation from 10−2 to 2 × 104 s−1. Both capillary and rotational rheometers were used. The samples were found to be thermally stable. The results indicate that η, G′, and G″ increase with mica content for the whole range of deformation rates. The relaxation time spectrum for the sample containing 60 weight percent of mica showed a particulate contribution. The zero shear viscosity was discussed in terms of suspension theories.
Particle flow and sintering processes in extrusion
Authors: Swanson C. L. , Fanta G. F. , Bagley E. B. 
Published: May 2005

AbstractThe flow mechanism of particulate polymers during processing is reviewed. The extrusion of starch‐g‐poly(methyl acrylate) polymers is a good example of this type of processing, since graft copolymers retain their granular appearance and do not melt, even at high temperature, due to the rigid starch matrix. The formation of a continuous plastic by extrusion is accomplished by the sintering of heat‐deformed granules in the high‐pressure zone of the extruder die. Photomicrographs confirm this mode of formation. Plots of flow rate through the extruder die versus pressure in the die are presented. Tensile strengths and percent elongation of extruded specimens are not greatly affected by variations in flow rate. The equilibrium moisture content (about 5 percent) of starch‐g‐poly(methyl acrylate) plasticizes the starch component and thus reduces the operating pressure in the die. Tensile strengths, however, are unaffected by the presence of equilibrium moisture. Final traces of residual acid (resulting from initiator solution) are difficult to remove from starch‐g‐poly(methyl acrylate), and prolonged heating of the graft copolymer in the presence of this acid results in polymer degradation.
Thermoplastic vs. thermosetting structural composites
Authors: Muzzy John D. , Kays Ancil O. 
Published: May 2005

AbstractHigh performance composites are normally fabricated from continuous fiber and fabric reinforcements embedded in a thermosetting resin. Currently, thermoplastics are receiving considerable attention as matrix materials in structural composites. These thermoplastic composites can be fabricated by novel techniques which are less cumbersome and potentially faster than curing in an autoclave. In this paper, fabrication techniques and physical properties of thermosetting composites will be compared. Applications where thermoplastic composites are particularly well suited will be presented.
Stress‐rupture lifetime of a poly(ethylene terephthalate)/glass composite under an alkaline solution environment
Authors: Schultz J. M. , Lhymn Chang 
Published: May 2005

AbstractStress corrosion testing of injection molded, short‐fiber (E‐glass) reinforced poly(ethylene terephthalate) (PET), in a 10 weight percent NaOH solution, indicated that a PET‐matrix degradation mechanism was operating. This is in direct contrast to the fiber degradation observed in acidic (10 weight percent HCl solution) stress corrosion tests on this material. Stress‐rupture lifetime in the alkaline solution was shorter than that in the acidic solution, suggesting that the alkaline attack on the PET matrix is more aggressive than the acidic attack on the E‐glass fibers. In both environments, fiber/matrix interface deterioration was also observed. Alkaline lifetime versus toughness behavior has been analyzed by established statistical methodology, using the empirical lifetime expression and the Weibull distribution function.
Fatigue crack propagation in composites with spherical fillers‐II effect of the size of the filler
Authors: Gadkaree K. P. , Salee G. 
Published: May 2005

AbstractA study of the effect of spherical glass beads of mean diameters of 46 microns, 89 microns, and 133 microns, on fatigue crack propagation rates, was carried out at ten and thirty weight‐percent beads. The resin was a low‐molecular‐weight [Mn= 8200, (MwMn) = 2.04] Bisphenol A‐terephthalate/isophthalate thermoplastic copolyester. Fatigue crack‐grwoth rates were measured using compliance method. The relationship between logarithm of stress intensity factor change and logarithm of crack‐growth rate is linear for 46 micron beads. For the 89 micron beads, the relationship is still approximately linear. The incorporation of 133 micron beads, however, results in large fluctuations in crack‐growth rates with changes in stress intensity factor range. A mechanism is proposed to explain this behavior. A relationship between interparticle distance and fatigue crack‐growth resistance is also observed.
Polyfunctional epoxies: Part I. rubber‐toughened brominated and nonbrominated formulations for graphite composites
Authors: Nir Z. , Gilwee W. J. , Kourtides D. A. , Parker J. A. 
Published: May 2005

AbstractA new trifunctional epoxy resin, Tris‐(hydroxyphenyl)methane triglycidyl ether, was compared to a state‐of‐the‐art resin, 4,4′‐diaminodiphenyl methane (TGDDM), in graphite composites. Rubber‐toughened brominated and nonbrominated formulations were compared for their mechanical performance, environmental stability, thermochemical behavior, and flame retardancy. It was found that the new resin performs almost the same way as the TGDDM does, but has some improved properties. The fracture toughness of the various formulations was studied carefully and the overall performance of the new resin is discussed.
The matrix phase microstructure of a glass poly(ethylene terephthalate) injection‐molding compound
Authors: Lhymn Chang , Schultz J. M. 
Published: May 2005

AbstractMicroscopic observations of thermoplastic poly(ethylene terephthalate) reinforced with short E‐glass fibers revealed a unique matrix microstructure influenced by the orientation of densely packed glass fibers. The observed platelets tend to surround a fiber in a cylindrical sheath pattern. This observation of the crystalline platelet morphology is possible by the combination of ion‐etching and the shadowing effect of protruding fibers.
Three‐phase carbon microballoon syntactic foam composites
Authors: Kenig S. , Raiter I. , Narkis M. 
Published: May 2005

AbstractThis paper describes three‐phase syntactic foams consisting of microballoons, resin, and air voids. The microballoons comprise carbon and silica spheres in various proportions, always at a close‐packed structure (0.6 volume fraction). Compressive, electric, and dielectric properties are demonstrated as functions of parameters like resin content, temperature, and various carbon/glass proportions. The good combination of mechanical, thermal, and electrical properties may qualify these foams for applications including attenuation of electromagnetic radiation.
Composite‐material mechanics: Properties of planar‐random fiber composites
Authors: Bert Charles W. , Kline Ronald A. 
Published: May 2005

AbstractThis paper is primarily a literature review of over ten dozen papers on the methodology for predicting elastic stiffnesses, tensile strength, thermal expansion, and thermal conductivity of planar‐random fiber composites from the reinforcement geometry and appropriate properties of the constituent materials. Particular attention is devoted to the effects of fiber volume fraction, fiber curvature, fiber length, and fiber orientation, since variations in these properties can be introduced during the manufacturing process.
Cellulose‐Reinforced nylon‐reaction injection molded composites
Authors: Zadorecki Pawel , Abbås Kent B. 
Published: May 2005

AbstractThe properties of cellulose‐reinforced nylon‐6 block copolymers were studied. Composites were prepared by Reaction Injection Molding (RIM) of a nylon system in which one of the reactants contained cellulose fibers. Incorporation of cellulose fibers into the liquid reactant of the nylon‐RIM system resulted in increased viscosity, depending on the amount and the aspect ratio of cellulose fibers. After proper drying, cellulose did not disturb the polymerization of the nylon‐RIM system. The cellulose fibers increased the stiffness of the nylon‐6 block copolymer. The stiffening effect depended on the aspect ratio and surface treatment. The tensile strength of cellulose‐nylon composites was slightly decreased. Elongation at break and impact strength were reduced compared to glass fiber‐reinforced nylon. Dynamic mechanical measurements (DMA) showed that the cellulose improved the elastic modulus of the nylon, especially at elevated temperatures. Scanning Electron Microscopy (SEM) on fractured surfaces showed improved adhesion between fiber and matrix when a surface treated cellulose was used.
Characterization of the aramid: Epoxy and carbon: Epoxy interphases
Authors: Garton Andrew , Daly John H. 
Published: May 2005

AbstractThe matrix/reinforcement interphase in aramid fiber/epoxy and carbon fiber/epoxy composites were modeled by coating an internal reflection spectroscopy (IRS) element with a thin layer of an aramid or of carbonized poly(acrylonitrile) (PAN). The coated element was then used as a substrate on which the curing of an epoxy resin took place. Infrared (IR) spectroscopy was used to demonstrate that the simulated reinforcement surfaces modified the crosslinking chemistry in the first 200–400 nm of epoxy matrix adjacent to the surfaces, producing an interphase of matrix material with properties different from those of the bulk of the epoxy matrix. This hypothesis was confirmed by the fabrication and testing of a series of unidirectional aramid fiber/epoxy and carbon fiber/epoxy composites.
Dispersive mixing in roll‐mills
Authors: Manas‐Zloczower I. , Nir A. , Tadmor Z. 
Published: May 2005

AbstractA theoretical model of the dispersive mixing process in roll‐mills is proposed. The model is based on the assumption that intensive mixing is dominated by agglomerate rupture in the narrow nip high shear flow field between the rolls. The dynamics of agglomerate size distribution and its dependencies on a number of variables and parameters are presented.
Composites containing glass spheres and fibers. I. Young's and flexural moduli
Authors: Dai S‐R. , Piggott M. R. 
Published: May 2005

AbstractExperiments on sphere‐filled aligned fiber reinforced polyester resins show that the Young's and flexural moduli of the composites are increased by the presence of the spheres. The increase is particularly marked for composites made with flexible resins, and has potential for improving the properties of aligned fiber laminates. The moduli in the absence of fibers do not fit well with existing theory, and agreement with finite element analysis is only observed in the case of the rigid polyester. When fibers are present synergistic effects are observed.
Fiber orientation development in molding of polymer composites
Authors: Kenig S. 
Published: May 2005

AbstractThe hydrodynamics and heat transfer that take place during molding of short fiber polymer composites have been analyzed. Consequently, the fiber orientation development has been qualitatively modeled and the flow mechanisms that contribute to fiber orientation have been identified: 1. Spreading radial flow in the vicinity of the cavity gate, originates transverse orientation of fiber with respect to the flow direction. 2. The fountain flow in the advancing front contributes to orientation of fibers in the surface layer in the flow direction. 3. Converging type flow, as the melt front flattens, causes some alignment in the flow direction. 4. Shear flow, which in the nonisothermal case, contributes to fiber orientation in the flow direction, at some distance from the wall. As a result of these mechanisms a layered structure is formed, having distinct fiber orientations. The experimentally observed fiber distributions in injection molding of thermoplastics, transfer, and compression molding of thermosets, agree with the qualitative predictions. The suggested orientation mechanisms may guide the mold and product designers as to the effect of gate location, mold dimensions, and processing variables on the final properties of the article.
Experimental study and calculations of short glass fiber orientation in a center gated molded disc
Authors: Vincent M. , Agassant J. F. 
Published: May 2005

AbstractShort glass fiber orientation in a center gated molded disc of polyamide is studied using optical microscopy techniques. The very different orientation between the core and the surface of the molding is quantified with an orientation function. The influence of the molding conditions is investigated. A numerical scheme is used for modeling the mold filling with a viscous melted polymer. A computation method is introduced to describe the fiber movement during the flow. The theoretical results are in good agreement with the experimental ones. In particular, the very different orientation between the skin and the core of the disc is well predicted.
Effects of moisture on interface modified graphite epoxy composites
Authors: Benatar Avraham , Gutowski Timothy G. 
Published: May 2005

AbstractGraphite epoxy composites which are exposed to high humidity environments suffer a loss in their shear and transverse properties. In addition to the effect of moisture on the matrix, thermodynamic theories suggest that the interface may suffer irreversible damage. In this study, we investigated if fiber surface treatments could improve fiber matrix adhesion as well as the wet composite properties. Plasma polymerization was used to generate very thin coatings with the polar component of the surface energy varying from 1.8 to 5.3 (dyne/cm)1/2. These coatings were characterized by ESCA and SEM, and a micro‐Wilhelmy technique was used to determine the dispersive and polar components of the surface energy. The uniaxial composites made with the treated fibers were tested wet and dry in short beam shear. It was found, as is well known, that the dry shear properties could be improved by up to 40 percent. Two effective treatments were oxygen etching and polymerization with methylmethacrylate monomer. However, all the wet samples failed at the same stress regardless of the surface treatment used. These results strongly suggest that the shear and transverse properties of the wet composites are dominated by the epoxy and cannot be improved by interface treatments.
Composite lamination—analysis and modeling
Authors: Appelt B. K. , Gotro J. T. , Schmitt G. P. , Ellis E. T. , Wiley J. P. 
Published: May 2005

AbstractMultilayer printed circuits are a prime example of complex polymer composites. One of the critical steps in manufacturing of the circuit boards is the lamination process, which is frequently simulated by the aborted flows test (AFT). In order to obtain a composite free of voids and good interlaminar adhesion, it is imperative for the resin to flow into metal interfaces as well as intermix in the resin interfaces. On an empirical basis, the AFT is used as a process monitor for making prepreg, the glass fiber reinforced dielectric which supports the circuitry. Under a given set of conditions (temperature profile, pressure, layup), AFT measures advancement and reactivity of prepreg. By using a given batch of prepreg, the optimum laminating conditions can be identified, which are mainly a function of the temperature profile. Here, a calorimetric and rheological study of prepreg cure kinetics during lamination is presented. The flow process is being modeled by calculating the viscosity from combining a temperature dependent viscosity term with a kinetically controlled molecular weight term.
Dynamic mechanical behavior and structure of ternary blends of polypropylene/EPDM rubber/polyethylene
Authors: Kolařík J. , Velek J. , Agrawal G. L. , Fortelný I. 
Published: May 2005

AbstractThe dynamic mechanical behavior of ternary blends of isotactic polypropylene (80–0 percent)/EPDM rubber (20 percent)/high‐density polyethylene (0–80 percent) was investigated in the temperature range from −196 to 100°C by means of a free‐oscillating torsional pendulum. The structure of the blends was examined by a scanning electron microscope on etched surfaces cut by a fractured glass edge in liquid nitrogen. Dynamic mechanical response spectra and microphotographs of the systems studied show that the minor thermoplastic forms the core of EPDM rubber inclusions. At 20 percent rubber in the blends, the inclusions can accommodate from 20 to 30 percent polyethylene or polypropylene. Addition of either thermoplastic not exceeding this limit has almost the same effect on the stiffness, damping, and yield stress of the blends as the addition of the same amount of rubber. Ternary blends with equal or slightly different polypropylene and polyethylene fractions have the structure of interpenetrating phases in which EPDM rubber forms the interface layer.
Determination of the orientation of short glass fibers in sheet molding compound (SMC)
Authors: Kau Hua‐tie 
Published: May 2005

AbstractA computer based semiautomatic procedure has been developed to measure the fiber orientation on the surface of Sheet Molding Compound (SMC) plaques. The principal orientation direction and the Hermans' orientation descriptor were used to summarize the fiber orientation distribution. The results show that only slight orientation was produced in the SMC plaque with a centrally placed charge occupying 40 percent of the area of the mold. Plaque to plaque, top surface to bottom surface, and region to region variability in the fiber orientation were observed. With a flow length of less than 3 fiber lengths in these plaques, the Hermans' orientation descriptor was in the range of 0.1 to 0.5. The descriptor varied appreciably with increasing sampling area and consistently displayed a sharp transition across the boundary of the original charge area, indicating distinct flow behaviors inside and outside the charge area. Likewise, the principal orientation direction varied with increasing sample area, albeit with some degree of coordination between the top and the bottom surfaces. Finally, the orientation of fibers in the four quadrants of the same plaque differed significantly. Based on the descriptor for each quadrant, the flow could be radial from the center of the plaque, rotational with the top and bottom surfaces in similar angular displacements, or twisted with the two surfaces moving in opposite directions, all indicating local nonuniformity of the flow.
A model for resin flow during composite processing part 2: Numerical analysis for unidirectional graphite/epoxy laminates
Authors: Dave R. , Kardos J. L. , Duduković M. P. 
Published: May 2005

AbstractIn this paper numerical results are presented for resin flow during processing of unidirectional graphite/epoxy laminates. Resin pressure and velocity profiles, as well as resin loss, specific permeability, and resulting thickness changes, were computed to examine the effects of one and two‐dimensional flow, initial laminate thickness, and various cure cycles. Input data to the model are also discussed in detail. Analysis of the input data on the stress‐strain behavior of graphite fiber beds showed that the bed consolidation behavior can be divided into three regions. “Free‐bleeding” (O psig and negligible bleeder resistance to flow at the boundaries) during two‐dimensional resin flow leads to rapid decay in resin pressure. Comparison of the predicted results for the resin mass loss and the average final thickness per ply with experimentally determined values shows good agreement.
The effect of pressure on the curing behavior of unsaturated polyester resins
Authors: Lee Dai‐soo , Han Chang Dae 
Published: May 2005

AbstractThe effect of pressure on the curing behavior of unsaturated polyester resin was investigated, both experimentally and theoretically. The resin used was a general‐purpose unsaturated polyester resin and the initiator used was t‐butyl perbenzoate. A series of isothermal runs with differential scanning calorimetry (DSC) were made at various levels of cure pressure. It was found that the rate of cure was retarded under pressure, and that the ultimate degree of cure went through a maximum at a certain pressure as the cure pressure was increased from atmospheric pressure to 6.21 MPa (900 psi). It was interpreted that pressure has two competing effects on the curing behavior of unsaturated polyester resin; one is a free volume effect that hinders the curing reaction and the other is a thermodynamic effect that favors it. Therefore, when the pressure is higher than a certain level, the free volume effect becomes predominant over the thermodynamic effect, the ultimate degree of cure diminishing as the cure pressure is increased beyond that level. Theoretical interpretation of the experimental results is given, using a mechanistic kinetic model developed in our previous publication.
Ternary blends in the toughening of epoxy resins
Authors: Levita G. , Marchetti A. , Lazzeri A. , Frosini V. 
Published: May 2005

AbstractThe fracture properties of two types of ternary blends (amine terminated rubber/Bisphenol‐A/DGEBA resin) have been studied. In the first type, B, setting was obtained by using piperidine as the hardener. In the second type, C, the rubber was used as both the hardener and the toughener. Both types showed an increased fracture resistance over the binary rubber/resin formulations. The drawback of the too high reaction rate shown by type B blends can be eliminated by using type C blends which can be easily B‐staged.