bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental verification of an optimal thermal design in a compression mold
Authors: Barone M. R. , Caulk D. A. , Panter M. R. 
Published: December 2004

AbstractA production sheet molding compound (SMC) mold for an automotive hood outer panel was instrumented with 64 thermocouples to measure cavity surface temperatures along two cross‐sections in each mold half and regulate the supply of steam to each heating line. The positions and temperatures of each heating line in the mold were optimized using an in‐house computer program to produce a minimum spatial variation in cavity surface temperature during steady cyclic molding. Provision was also made to heat the mold conventionally so that optimal and conventional heating could be directly compared in the same mold. While maintaining a 78 s overall molding cycle, the conventional heating system eventually produced a 10°C temperature variation on the cavity surface. This, in turn, led to serious resin undercure and severe difficulties in removing the part from the mold. When the optimal heating design was substituted in place of the conventional system, the surface temperature variation was reduced to less than 3°C and the problems experienced with conventional heating disappeared. For the most part, the measured temperatures in these experiments agreed with the results of the computer analysis to within 1°C.
Polyetheretherketone (PEEK): Processing‐structure and properties studies for a matrix in high performance composites
Authors: Seferis James C. 
Published: December 2004

AbstractThe processing, structure and properties of polyetheretherketone (PEEK) semicrystalline thermoplastic as matrix polymer for high performance composites has been investigated in this work. In processing PEEK samples with different crystallinities, a specially designed mold capable of cooling the polymer in excess of 115°C/s from its melt temperature was constructed. In addition, during processing studies, a reaction of PEEK in the presence of copper was discovered. Analysis of the samples in terms of their crystallinity values also provided a new method for measuring crystallinity of the matrix in the composite. Crystallization of low crystalline samples at room temperature in the presence of methylene chloride was also confirmed for the first time with polarized microscopy. However, at the same time, the excellent hygrothermal resistance of PEEK was also confirmed. Finally, dynamic mechanical and stress‐strain experiments with samples of different crystallinities elucidated the dependence of these properties to crystallinity. However, this study also elucidated that under normal processing conditions for high performance composites, PEEK properties may not be strongly affected by different levels of crystallinity.
Melt rheology of highly loaded ferrite‐filled polymer composites
Authors: Saini D. R. , Shenoy A. V. , Nadkarni V. M. 
Published: December 2004

AbstractThis paper presents new experimental data on the viscosity of ferrite‐filled polymers at high levels of loading. The choice of matrix and the choice of filler and filler loading has direct relevance to commercially important systems of magnetic plastics and rubbers. The effect of shear rate, concentration, and temperature on the rheological behavior of such highly loaded systems has been discussed in detail. The differences in the relative viscosities between the filled and unfilled systems for various matrices have been explained on the basis of polymer filler affinity and filler‐filler interaction.
Electrodeposition of a polymer interphase in carbon‐fiber composites
Authors: Subramanian R. V. , Crasto A. S. 
Published: December 2004

AbstractThe performance of an electrodeposited interphase of poly(butadiene‐co‐maleic anhydride) (BMA) in carbon‐fiber composites is investigated. Carbon fibers are electrocoated with BMA from an aqueous solution and the coated fibers are fabricated into composite bars for evaluation of mechanical properties. These composites show superior impact strength, but lower interlaminar shear strength, compared to composites made from commercially treated fibers. It is suggested that unsaturation in the butadiene segments of the interphase polymer leads to the formation of a crosslinked layer during electrodeposition and subsequent drying. Inadequate penetration of this interphase by bulky epoxy molecules leads to a weak interphase/matrix interface which is the locus of failure, generating the observed mechanical properties. These conclusions are supported by examination of the fracture surfaces by Scanning Electron Microscopy. Further evidence of lack of matrix penetration into the interphase comes from electron microprobe line scans for bromine performed on cross‐sections of single‐filament composites, the bromine being introduced into the matrix via a brominated epoxy resin. Appropriate control of the chemical structure and physical characteristics of the interphase polymer is thus indicated, for acieving simultaneous improvements in impact and interlaminar shear strengths.
Property modification of bulk molding compounds for use in injection molding
Authors: Pritchard M. , Gibson A. G. 
Published: December 2004

AbstractAlthough impact and flexural strength of injectionmolded bulk molding compounds increase initially with glass fiber content, these properties level out at a glass volume fraction between 0.1 and 0.2, limiting the achievable properties. Use of “special purpose” polyester resins gives no significant improvement in impact. The impact strength limitation is not worsened, however, by using the maximum processable level of filler, this being true for all fillers commonly used in polyester compounds. Replacement of a fraction of the glass by poly(ethylene terephthalate) fibers results in a substantial improvement in impact strength.
Spectroscopic studies of the gradient in the silane coupling agent/matrix interface in fiberglass‐reinforced epoxy
Authors: Hoh K.‐P. , Ishida H. , Koenig J. L. 
Published: December 2004

AbstractDifferential scanning calorimetry, Fourier transform infrared, and solid‐state carbon 13 nuclear magnetic resonance were used to study the silane coupling agent/epoxy resin interface. Penetration of epoxy into the hydrolyzed silane has been shown. The addition of a solvent can further increase the penetration of epoxy into the hydrolyzed silane by decreasing the viscosity of the epoxy. Bulk models of the gradient in the silane coupling agent/epoxy interface have shown that the concentration of silane and the degree of hydrolysis of the silane can determine the rigidity or mobility of the interphase region. When the silane is hydrolyzed, the possible formation of entanglements may increase the rigidity of the system and decrease the degree of phase separation through the formation of an interpenetrating network.
Mechanics of short fibers in filled styrene‐butadiene rubber (SBR) composites
Authors: Rueda L. Ibarra , Antón C. Chamorro , Rodriguez M. C. Tabernero 
Published: December 2004

AbstractDifferent short fibers (glass, carbon, cellulose, polyamide, and polyester with aspect, length/diameter, ratio of 600, 860, 500, 83, and 330 respectively) were added to styrene‐butadiene rubber (SBR) matrix filled with an inorganic semireinforcing mineral (sepiolite). In all cases, 18 parts by volume of fiber per 100 parts by mass of rubber were added. The fiber orientation attained (more than 60%) was evaluated by a ratio of directional mechanics on uncured samples. In glass and carbon fiber composites, because of decreases in fiber aspect ratio after mixing (10 and 35 respectively), no improvements in properties were obtained. The presence of fibers yields a large increase in green strength, stress at low strain, and tear strength. Logically, the elongation at break diminishes. The uncured and cured properties present a remarkable anisotropy. The adhesive employed (resorcinol‐formaldehyde) to increase fiber‐to‐matrix adhesion enhanced the composite properties, especially in the case of polyester fiber composites. Thus, for polyester fiber composites, green strength became 15.85 kg/cm2; stress at 25% strain, 10.2 MPa; tensile strength, 6.3 MPa; elongation at break, 36%; tear strength, 70 N; and swelling in longitudinal direction, 1.06.
Radiation‐curable carbon fiber prepreg composites
Authors: Saunders Chris B. , Dickson Lawrence W. , Singh Ajit , Carmichael Alistair A. , Lopata Vince J. 
Published: December 2004

AbstractRadiation processing is the utilization of ionizing radiation, usually photons or electron beams, to produce useful physical and chemical changes in a material. A potential application for electron beam processing for composite manufacturing is for curing carbon fiber prepregs. These prepregs, carbon fibers or fabrics preimpregnated with liquid polymer resin, are commonly used in the aircraft industry. Their use, however, can be time consuming and labor intensive. The advantages of radiation curing over thermal or chemical curing methods include improved rate control, reduced curing times, and curing at ambient temperature. There is no need for chemical initiators. A radiation‐curable prepreg has been designed to meet the mechanical and physical property specifications of a leading aircraft manufacturing company. The resin is a mixture of an expoxy diacrylate, polybutadiene diacrylate, and a multifunctional monomer. This resin was used to impregnate a plain weave carbon fabric, at a loading of 35 percent (by mass), using a solvent process. Preliminary characterization studies show that the cured polymer produced by irradiation in air to a dose of 40 kGy is amorphous with a maximum gel fraction of 85 percent. The softening point of the polymer varied from 228°C (30‐kGy sample) to 237°C (50‐kGy sample). The linear thermal expansion coefficient of the polymer was 1.7 × 10−4 m/m°C from 25°C to 150°C and was unaffected by varying the applied dose from 30 to 50 kGy.
Use of wood fibers in thermoplastic composites: VI. Isocyanate as a bonding agent for polyethylene–wood fiber composites
Authors: Raj R. G. , Kokta B. V. , Maldas D. , Daneault C. 
Published: December 2004

AbstractLinear low density (LLDPE) and high density (HDPE) polyethylenes were reinforced with wood fibers of aspen chemithermomechanical (CTMP) pulp. The different isocyantes: (i) polymethylene (polyphenyl isocyanate), (ii) tolene –2–4‐diisocyanate, (iii) 1–6 hexamethylene‐diisocyanate, and (iv) ethyl isocyanate used as bonding agents improved the tensile properties of the composites. HDPE performed better in comparison with LLDPE composites. Also, shorter fibers (mesh size 60) produced higher tensile strength and modulus in HDPE. The comparison of HDPE reinforced with aspen, mica, and glass fibers showed the effectiveness of wood fibers in terms of their cost and performance.
Analysis of coating on glass fiber reinforcements
Authors: Drumm Charlene A. , Ulicny John C. 
Published: December 2004

AbstractSeveral commercially available glass fiber reinforcements were analyzed to determine the amounts (“loadings”) and types of coatings applied by their manufactures. Loadings were determined by solvent extraction and pyrolysis and ranged from 0.54 to 4.22 weight percent with the heaviest amounts on random mats and the least amounts on rovings intended for filament winding and weaving. The major components of the solvent‐extracted coatings were identified by infrared (IR) and proton nuclear magnetic resonance (NMR) spectroscopies. All of the coatings analyzed could be sorted into three classes of coatings which matched the matrix types recommended by the glass manufacturers. In each case, the coating consisted primarily of a mixture of two separate materials, designated as the “unreacted resin” and the “lubricant”.
Synergism on electromagnetic inductance (EMI)‐shielding in metal‐ and ferroelectric‐particle filled polymers
Authors: Wenderoth K. , Petermann J. , Kruse K.‐D. , ter Haseborg J.‐L. , Krieger W. 
Published: December 2004

AbstractIn this paper the electromagnetic inductance (EMI)‐shielding of metal‐and ferroelectric‐particle filled polymers is described. The composite, containing only metallic fillers, has a shielding effectiveness comparable to conventional products. The addition of a few percent of ferroelectric material to this composite enhances the shielding behavior by several orders of magnitude—without increasing its electrical conductivity. In this three component composite the shielding effectiveness reaches a maximum close to the ferroelectric/paraelectric transition temperature. The synergetic effect, obtained by the addition of ferroelectrical particles, is related to the high dielectric losses of ferroelectric material close to its transition temperature.
Interfacial shear strength and failure modes of interphase‐modified graphite‐epoxy composites
Authors: Wimolkiatisak A. S. , Bell J. P. 
Published: December 2004

AbstractElectrocopolymerization of acrylonitrile/methyl acrylate/acrylic acid, acrylonitrile/methylacrylate, and glycidyl‐acrylate/acrylonitrile interlayers onto Hercules AS4 graphite fibers was used to improve simultaneously the effective interfacial shear strength, τe, and the fracture toughness of graphite‐epoxy composite materials. With a single‐fiber fracture test, τe for these coated fibers (embedded in a diglycidyl ether of bisphenol A ‐ 4,4′‐methylenedianiline matrix) was determined at various temperatures and under various hygrothermal treatments. At room temperature, the coated samples showed slightly improved shear strength over the uncoated sample. At elevated temperatures, a plot of τe vs. temperature for the uncoated sample showed two distinctive regions: an interface‐controlled plateau region at low temperatures, and a matrix‐controlled region at high (>80°C) temperatures. Only one region, which was controlled by the matrix and the interlayer, was observed for the GA/AN coated sample. The τe values determined were slightly higher than the shear strength of the bulk matrix, possibly because of stronger matrix properties at the interface. Optical micrographs of the coated sample tested at temperatures less than 100°C showed no matrix crack perpendicular to the fiber axis, indicating that the interlayer has effectively blunted the crack tip and restricted its propagation. The effect of moisture in the sample was to reduce τe for the coated sample. Upon dehydration, the strength was partially recovered. The treatments did not affect the uncoated sample, however. The fragmentation length data were fitted well by both Gaussian and Weibull distributions.
Accelerated characterization of a chopped fiber composite using a strain energy failure criterion
Authors: Yen Shing‐Chung , Morris Don H. 
Published: December 2004

AbstractThe creep and creep rupture response of a chopped fiber composite material (SMC‐R50) were investigated experimentally and analytically. The goal of this research was to use the short time laboratory data to predict long time creep and creep rupture behavior. The creep response data up to 200 min duration were obtained at various constant temperature and stress levels. The short time creep data were then modeled using a modified power law equation. The modified power law equation contains the parameters of the so‐called accelerated characterization procedure. Using this power law equation, the short time creep response at the elevated temperatures were able to successfully predict the long time creep response at a lower temperature and stress level. To predict the creep rupture behavior, the modified power law equation was then coupled with a strain energy based failure criterion. It was found that the same parameters that were used in the prediction of the long‐time creep response can also be used to predict the creep rupture. At a given temperature level, the strain energy density related to creep rupture was found to be a constant. Furthermore, this strain energy density was found to increase with an increase in temperature. With a limited amount of data, it was found that the strain energy based failure criterion coupled with the modified power law equation can be used to predict long time creep rupture behavior.
Three‐dimensional stress analysis of composite structures using isodyne techniques
Authors: Pindera J. T. 
Published: December 2004

AbstractIt is known that the stresses in lamination planes of composite structures are pronouncedly three‐dimensional, and that criticality of the lamination defects is often very high. It is also known that the classical methods of photoelastic stress analysis are often not reliable when stress states are three‐dimensional, with the exception of the gamma‐ray stress‐freezing method. The paper presents analytical and empirical evidence that the recently developed “isodyne” techniques allow reliable determination of the 3‐D stresses existing in components of real composite structures and in lamination planes.
Time‐dependent response of aramid‐epoxy‐aluminum sheet, ARALL, laminates
Authors: Pindera M.‐J. , Williams T. O. , Macheret Y. 
Published: December 2004

AbstractSelected results of an ongoing investigation aimed at characterizing the timedependent response of an aramid‐epoxy‐aluminum sheet laminate and its constitutents at 121°C are outlined in this paper. This laminate is a recently developed hybrid composite developed by the Aluminum Company of America, marketed under the ARALL‐4 tradename. The paper addresses the time‐dependent response of the above hybrid composite under creep loading. It is illustrated that ARALL‐4 laminates may exhibit substantial creep effects at stress levels below the proportional limit. The creep response is a nonlinear function of time and the applied stress level and is primarily due to the creep characteristics of the aluminum layers. An analytical model based on the assumptions of the classical lamination theory developed to model the time‐dependent response of these laminates under creep and thermal loading is shown to yield good correlation with the experimental data. It is also illustrated that the residual state of stress can influence the extent of creep. This offers the possibility of minimizing the creep effects by altering the state of residual stress with mechanical prestraining.
Rheological behavior and fiber orientation in slit flow of fiber reinforced thermoplastics
Authors: Mutel A. T. , Kamal M. R. 
Published: December 2004

AbstractThe flow behavior and fiber orientation in slit flow of a short fiber reinforced thermoplastic composite melt are investigated. A slit die with adjustable gap and interchangeable entrance geometries was designed and built. The slit die is fed by a single screw extruder. The bulk viscosity is calculated from the axial pressure profiles measured using three flush mounted pressure transducers. The effect of entrance geometry and gap dimensions on the fiber orientation and bulk flow behavior is specifically considered. A skin‐core composite fiber orientation is observed in the thickness direction. Fibers are oriented in the flow direction and parallel to the walls in the skin region irrespective of the entrance geometry. Different fiber orientation distributions in the core region can be realized by using different entrance geometries. However, the changes in the core fiber orientation are not fully reflected by the measured viscosities, due to highly oriented skin layer. Exit pressures obtained by extrapolation of linear pressure profiles are found to be all positive, but dependent on the die geometry and entrance conditions, even for the unfilled melts.
Viscoelastic characterization of high performance epoxy matrix composites
Authors: Woo E. M. , Seferis J. C. , Schaffnit R. S. 
Published: December 2004

AbstractDynamic mechanical analysis, stress relaxation, and creep experiments were performed to characterize the viscoelastic properties of a basic unmodified epoxy (Hercules 3501‐6) and a modified multiphase epoxy (Hercules 8551‐7), which are commonly used as matrices in high performance composites. The Arrhenius and WLF equations and a modified Standard Linear Solid (SLS) Model were used to quantify the viscoelastic behavior below, above, and at the glass transition temperatures, Tg. Both the modified and the unmodified epoxy systems exhibited a single relaxation peak above ambient temperature. The Tg of the modified epoxy at full cure was 170°C, which is 50°C lower than that of the basic epoxy. The glassy moduli of these two resin systems were found to be comparable, but the rubbery modulus of the modified epoxy was much lower than that of the basic epoxy system. However, the viscoelastic behavior of these two systems and their sensitivity to time‐temperature may be considered to be quite similar if they are compared with respect to their corresponding glass transition temperatures.
Effect of surfactant treatments on interfacial adhesion in single graphite/epoxy composites
Authors: Wu H. F. , Biresaw G. , Laemmle J. T. 
Published: December 2004

AbstractInterfacial adhesion between graphite fibers and epoxy matrices is one of the important parameters in controlling composite performance. Experiments were performed to verify the idea that polymerizable and nonpolymerizable nonionic surfactants can promote wetting and increase interfacial shear strength. Using a single‐fiber‐composite (SFC) technique with a Poisson/Weibull model of fiber strength and flaws, the effective interfacial shear strength (ISS) was determined. The effect of surfactant treatments on interfacial adhesion in single graphite/epoxy composites was also compared with the effects of treatment with deionized water, absolute alcohol, and acetone. The experimental results showed that the fibers treated with the nonpolymerizable surfactant gained 37% in interfacial shear strength relative to those untreated or those treated with deionized water, absolute alcohol, or acetone. The polymerizable surfactants showed a 10% increase in interfacial shear strength. The lognormal distribution provided the best fit for critical aspect ratios obtained from the SFC tests.
A nondestructive method to determine material properties in anisotropic plates
Authors: Fällström K.‐E. , Jonsson M. 
Published: December 2004

AbstractMaterial parameters in anisotropic rectangular plates are determined in a nondestructive way. Real‐time, TV‐holography is used to determine frequencies and shapes of the first five modes of vibration of plates with free‐free boundary conditions. According to rules given in the paper, finite element analysis is then used to determine two effective Young's moduli, the shear modulus, and the Poisson's ratio.
Deterrmining material properties in anisotropic plates using Rayleigh's method
Authors: Fällström K.‐E. 
Published: December 2004

AbstractMaterial parameters of anisotropic plates are determined. Rectangular anisotropic plates are tuned by changing the quotient between the length of the sides, so that the second and third modes of vibration, for free‐free boundary conditions, degenerate into the well‐known cross‐shaped and ring‐shaped modes, respectively. The first three modes of vibrations for these plates are determined by optical methods. The propagation of bending waves, generated by the impact of a ballistic pendulum on the plates, has also been optically studied. It is found that bending waves generated in the middle of the tuned plates will reach the boundaries of the plates simultaneously. This gives a relationship between main material parameters. Using this relation and Rayleigh's method for the first three modes of vibrations, the main material parameters for the plates, that is, the effective two Young's moduli, the shear modulus, and the Poisson's ratio, are determined.