bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tensile failure of notched fiber‐reinforced composite materials
Authors: Wetherhold Robert C. , Whitney James M. 
Published: May 2005

AbstractThe weibull brittle failure model is used to described the tensile strength degradation of a fiber‐reinforced composite material in the presence of a notch. This model uses the description of the state of stress near the notch and the Weibull shape parameter from a series of unnotched tensile tests. The Weibull‐model strengtyh degradation is evaluated using numerical integration of a reduced, one‐dimensional tensile volume. The numberical Weibull integral results are compared with the point stress failure theory. The comparison suggests that the two parameters of the point stress theory stem form the single Weibull shape parameter. The integral results are shown to be conservative when compared with data for two graphite. epoxy systems.
Moisture penetration into composites under external stress
Authors: Marom Gad , Broutman L. J. 
Published: May 2005

AbstractMoisture penetration at 95°C into glass fiber and graphite fiber‐reinforced epoxies is examined in stressed and unstressed materials. The study focuses on the effect of the angle between the stress and the fiber directions on the diffusivities. It is found that the consequence of applying external stresses to composites is an increase in their rate of moisture absorption, their maximum moisture content, and in the diffusion coefficients. As the angle between the loading and fiber directions in increased the rate and the maximum value of moisture absorption also increase. Their ratio, however, remains constant resulting in loading angle independence of the exposure of the composites to water produces a typical damage mechanism which enhances moisture take‐up.
Combining rules for predicting the thermoelastic properties of particulate filled polymers, polymers, polyblends, and foams
Authors: McGee Stuart , McGullough R. L. 
Published: May 2005

AbstractVarious models that have been proposed to predict the properties of particulate filled systems are reviewed and compared with experimental data. At filler volume fractions less than ∼0.2‐∼0.3, these models give essentially equivalent predictions that are within the scatter of experimental measurements. At higher volume fraction of inclusions, significantly different results are obtained from the various models. These predictions either overestimate or underestimate observed properties. New, theoretical combining rules are presented to predict the Young's modulus, Poisson's ratio shear modulus, bulk modulus, and coefficient of thermal expansion in terms of the properties of the matrix and inclusion and the volume fraction concentration of the inclusion. The predictions of these combining rules are in good agreement with experimental data that cover the feasible concentration range of inclusions for a variety of composite materials, ranging from particulate filled thermosetting resins to thermoplastic foams.
Fatigue crack propagation of sheet molding compounds in various evironments
Authors: Hoa S. V. , Ngo A. D. , Sankar T. S. 
Published: May 2005

AbstractThe effect of the absorption of water and isooctane on the rate of fatigue crack propagation of sheet molding compounds (SMC‐R30 and SMC‐R65) was investigated. A crack extension gage was used to measure the crack length. Results show that the absorption of water decreases the rate of fatigue crack propagation in the initial cycles but increases the rate of propagation in the final cycle. The absorption of isooctane into SMC‐R65 tends to decrease the rate of fatigue crack propagation. Microscopic observation shows considerable swelling of the polyester matrix due to the absorption of water and no significant apparent effect due to the absorption of isooctane.
Liquid absorption of a sheet molding compound
Authors: Hoa S. V. , Ouellette P. 
Published: May 2005

AbstractThe absorption of water, isooctane, methanol and ethanol into a sheet molding compound (SMC‐R30) at room temperature is studied. The absorption behaviors are shown to be Fickian, with constant diffusion coefficients. Desorption of methanol and ethanol soaked specimens causes considerable surface cracking.
Studies on polmer impreganted composites
Authors: Aminabhavi Tejraj M. , Patel Ramesh C. , Biradar Ningond S. 
Published: May 2005

AbstractEleven light weight polymeriozed composite materials derived from waste products were investigated. These waste materials after impregnation with a polymer were found to lhave better physico‐mechanical properties than ordinary cement concrete. Such impregnation, combined with fine sand and epoxy hardener, takes advantage of the optimum properties of the composites. The use of such polymerized composites for building constriction on a large scale can be undertaken, economizing on cement.
Analysis of the thickening reaction of a sheet molding compound resin through the use of dynamic mechanical testing
Authors: Gruskiewicz M. , Collister J. 
Published: May 2005

AbstractThe change in viscoelastic response of an unsaturated polyester during the course of thickening with magnesium oxide was evaluated, Rheological measurements were obtained to describe the effects of thickening as functions of time and magnesium oxide concentration. Previous researchers have made similar evaluations utilizing Brookfield viscosities. However, the test geometry asociated with a Brookfield T‐bar spindle is not well defined and data interpretation is consequently obscured. A Rheometrics Thermal Mechanical Spectrometer was used to obtain dynamic mechanical measurements ranging across three decades of frequency. Values of the elastic shear modulus, G′, the viscous shear modulus, G″, and the complex viscosity, η*, were calculated.
Fatigue behavior of thermosetting‐polyester‐matrix sheet‐molding compounds
Authors: Jeffery Mildred R. , Sourour Janine A. , Schultz J. M. 
Published: May 2005

AbstractTwo sheet molding compounds, one containing 65 weight percent E‐glass fiber and no filler (SMC‐65) and the other containing 50 weight percent glass and 15 weight percent CaCO3 filler were subjected to sinusoidal, load‐control, tension‐tension fatigue. The macroscopic behavior showed some notch sensitivity for both materials, but particularly for SMC‐65. The extent of failure damage over the specimen length decreased with decreasing load amplitude. Different failure mechanisms appear to operate under high‐ and low‐cycle fatigue conditions. Microscopic surface damage studies at stresses near the endurance limit showed several stages in the fatigue failure. For SMC‐65, these stages are, sequentially, matrix crack initiation and growth, matrix pulverization, fiber fracture, and fiber pullout. A similar, but less distinct pattern was observed for SMC‐50. Acoustic emission was also followed during fatigue cycling near the endurance limit. Distinct amplitude distribution peaks for each failure process were seen. It is suggested that matrix fracture, permanent deformation and Euler buckling are all important in high cycle fatigue failure.
The effect of water on the fracture surface energy of fiber‐reinforced composite materials
Authors: Thomson K. W. , Broutman L. J. 
Published: May 2005

AbstractThe effect of absorbed water on the fracture surface energy of both glass and graphite fiber unidirectional epoxy composites has been studied. The fracture energy parallel to the fiber direction was measured by the double torsion technique. Water was absorbed at 70°C while the sample was subject to an external tensile stress both parallel and perpendicular to the fiber direction. No degradation of fracture surface energy was measured for specimens stressed and immersed in water at 70°C for up to 1000 h. The fracture surface energy for the glass composite was greater than for the graphite composite, which was attributed to fiber pull‐out in the case of the glass composite.
Modulus development in oriented short‐glass‐fiber‐reinforced polymer composites
Authors: Curtis A. C. , Hope P. S. , Ward I. M. 
Published: May 2005

AbstractThe increase in modulus obtained in a short‐glass‐fiber‐reinforced polymer composite as a result of uniaxial deformation may be related to the observed increase in both fiber and matrix orientation. Quantitative measurements of both fiber and matrix orientation are presented for a series of samples of short‐glass‐fiber‐reinforced polyoxymethylene copolymer, processed to various substantial deformation ratios by solid‐phase hydrostatic extrusion. The polymer matrix becomes highly oriented at modest deformations, but the glass fibers orient in a slower pseudo‐affine manner and dominate the development of modulus in the composite. A simple “law‐of‐mixtures” model is used to demonstrate that perfect uniaxial orientation of the fibers is not achieved, but a better fit to measured modulus data is obtained by using an “aggregate” model applied to oriented fibers in an oriented matrix. The development of modulus with deformation ratio may be predicted very well if it is assumed that:the composite consists of a series‐coupled array of sub‐units, each containing continuous and fully oriented fibers in a fully oriented matrix; andorientation of the sub‐units develops with deformation in a pseudo‐affine manner.
Application of differential scanning calorimetry to cure optimization and quality control of a vinyl ester resin
Authors: Cummings L. C. 
Published: May 2005

AbstractTo optimize cure time for a given resin, the relationship between time, temperature, and degree of cure must be established. Using an epoxy‐based vinyl ester as an example, these relationships were determined with the use of differential scanning calorimetry (DSC). DSC curves can indicate the glass transition temperation (Tg) and the residual cure exotyherm (RCE) peak of a plastic of composite smaple. With increasing degree of cure, (Tg) increases, and the RCE peak area decreases. The data confirms a model showing that various timetemperature combinations can lead to the same degree of cure. Graphic representations of the relationships between time, temperature, and degree pf cure presented, which include degration regions (here, both Tg and shear strength are lowered). Graphs may be used for optimizing production cure conditions and for setting quality control criteria. This method should be applicable to most thermoset resins.
Effects of variation in composition and temperature on the amine cure of an epoxy resin model system
Authors: Byrne C. A. , Hagnauer G. L. , Schneider N. S. 
Published: May 2005

AbstractPrior liquid chromatographic studies have shown that the reactions in epoxy resin model system phenyl glycidyl ether,p‐chloroaniline, and Monuron include amine addition to epoxy, homopolymerization of the epoxy, and a chain‐transfer reaction involving the hydroxy groups of the addition products. The present work examines the effect of variation in concentration of the accelerator Monuron, the amine‐to‐epoxy ratio, and the temperature on the competitive reaction mechanisms. The fraction of phenyl glycidyl ether reacting by homopolymerization increases with accelerator concentration and decreases with increasing amine‐to‐epoxy ratio and increasing temperature. The estimated contribution from chain transfer is much smaller and appears to parallel the homopolymerization reaction, as might be expected.
Measurement of the thermal conductivity of polymer composites to high temperatures using the line source technique
Authors: Henderson J. B. , Verma Y. P. , Tant M. R. , Moore G. R. 
Published: May 2005

AbstractThe line source technique for determination of thermal conductivity has been modified to allow measurement to higher temperatures than previously attained. This required the addition of a high‐temperature tube furnace to the standard experimental equipment. The modified device was used to measure the temperature‐dependent thermal conductivities of a glass‐ and talc‐filled phenol‐formaldehyde(phenolic) resin and a glass‐ and fiberglass‐filled acrylonitrile‐butadiene (AB) copolymer. Thermal conductivities of the virgin material were measured from room temperature to the onset of thermal decomposition. The char material thermal conductivities were measured from room temperature to approximately 900°C. A least‐squares fit of the data yielded a linear‐curve fit for the virgin material and a third‐order fit for the char material.
A study of the kinetics of high‐temperature carbon‐silica reactions in an ablative polymer composite
Authors: Henderson J. B. , Tant M. R. 
Published: May 2005

AbstractThe kinetics of high‐temperature carbon‐silica reactions for a widely used glass‐filled phenolic resin have been studied. Weight‐loss and rate‐of‐weight‐loss data were obtained at four heating rates ranging from 5 to 50°C per minute using standard thermogravimetric techniques. Experimental data were obtained at temperatures between 30 and approximately 1700°C. The kinetic parameters were calculated from these data using a multiple heating rate technique. Close agreement was obtained between the fractional weight loss calculated using the kinetic parameters and the measured values.
Co‐injection molding of reinforced polymers
Authors: Akay G. 
Published: May 2005

AbstractCo‐injection molding of calcium carbonate filled polypropylene, short glass‐fiber‐filled polypropylene, or unfilled high‐density polythylene melts is studied using a mediumsize injection‐molding machine and a center‐gated disc mold. Injection molding is carried out under non‐isothermal conditions. Order of injection of the melts, injection speed, and mold temperature is changed in order to understand the mold filling in general and to investigate the type of skin/core structure and mechanical interlocking of the phases in the moldings. It is found that the order of injection is not significant in obtaining a skin/core structure but it is important in obtaining extensive phase interlocking, which is reduced if the flow rafe and the mold temperature are low. Presence of fillers appears to result in more mechanical interlocking of the phases.
The formation of coupling agent monolayers on the surface of mica
Authors: Favis B. D. , Blanchard L. P. , Leonard J. , Prudapos;homme R. E. 
Published: May 2005

AbstractThe interaction of very dilute solutions of a cationic vinylbenzyl silane (CVBS), a methacrylate functional silane (γ‐MPS), and an isopropyl‐tri‐(dioctylpyrophosphato) titanate (IDT) with a mica surface has been studied by carbon analysis. For all three coupling agents the dependence of adsorption with time of treatment follows a step‐like curve, where each step corresponds to a monolayer coverage on the mica. Under the operating conditions used it was noted that a particular monolayer is always completed before the next is started. The adsorption of γ‐MPS was found to be very sensitive to the time allowed for hydrolysis of the silane, while the adsorption of CVBS was relatively independent of the hydrolysis time when it is varied from 0 to 5400 s. The results indicate that γ‐MPS and CVBS near the mica surface form a dense structurally regular multilayer phase with the silane molecules oriented normal to the surface. IDT molecules occupy a surface area on mica which is characteristic of their branched nature.
Prediction of thermal and mechanical properties of glass‐epoxy composite laminates
Authors: Raghava R. S. 
Published: May 2005

AbstractThis paper provides an experimental test of the validity of laminate theory used for calculating thermoelastic properties of a unidirectional composite laminate. Theoretically calculated values of elastic moduli and coefficients of thermal expansion for unidirectional glass/epoxy laminates were compared with the measured values. Laminates (8″ × 8″ × 1/4″) as a function of ply orientation were made and their elastic moduli, thermal expansion coefficients, fiber volume, and void contents were measured.
Off‐axis tensile properties and fracture in a unidirectional graphite/polyimide composite (celion 6000/PMR 15)
Authors: Harper Jeffrey , Whittenberger J. Daniel , Hurwitz Frances I. 
Published: May 2005

AbstractTensile properties of unidirectional Celion 6000 graphite/PMR 15 polyimide composites prepared by hot molding and cold molding processes were measured at room temperature and 316°C, the upper use temperature of the polyimide resin, at both 45 and 90° to the fiber axis. The resulting fractures were characterized by scanning electron microscopy and materialographic techniques. Variation in tensile properties with processing history occurred in the elastic modulus and strain to failure for specimens loaded at 90° at 316°C, and in the fracture stress, and hence the in‐plane shear stress, for those loaded at 45° at room temperature. Significant plastic deformation was observed in the 45° orientation at 316°C for material produced by both processing methods. In general, fracture occurred by both failure within the matrix and at the fiber‐matrix interface; the degree of interfacial failure increased with temperature. Secondary cracking below the primary fracture surface also was observed.
Design concepts for the tallest free‐standing fiberglass stack
Authors: Plecnik Joseph M. , Whitman Warren E. , Baker Treven E. , Pham Mai 
Published: May 2005

AbstractThis paper presents design and materials considerations involved in the production of large, free standing glass reinforced plastic (GRP) industrial stacks. Because of large wind loads, such stacks must be designed with sophisticated structural analysis techniques, especially at load transfer points. This paper details such considerations for the world's tallest GRP stack.
Modification of epoxy‐reinforced glass‐cloth composites with a perfluorinated alkyl ether elastomer
Authors: Rosser Robert W. , Chen Timothy S. , Taylor Mark 
Published: May 2005

AbstractA perfluorinated alkyl ether diacyl fluoride prepolymer (molecular weight about 1500) was coreacted with Epon 828 epoxy resin and diamino diphenyl sulfone to obtain an elastomertoughened, glass‐cloth composite. Improvements in flexural toughness, impact resistance, and water resistance, without loss of strength, modulus of elasticity or a lowering of the glasstransition temperature, were realized over those of the unmodified composite. Factors concerning optimization of the process are discussed. Results suggest that a simultaneously interpenetrating polymer network may be formed which gives rise to a measured improvement in composite mechanical properties.
Kinematics of flow in sheet molding compounds
Authors: Barone M. R. , Caulk D. A. 
Published: May 2005

AbstractExperiments utilizing charges constructed of black and white sheet molding compound (SMC) reveal the basic kinematic mechanisms controlling the flow of the fiber‐filled compound in compression molding. The experimental results show that SMC deforms in uniform extension within individual charge layers, with slip occurring at the mold surface and, for slower closing speeds, also between the layers of SMC. When the mold closes rapidly, the charge extends uniformly through its thickness, with all slip concentrated at the mold surface.
Thermoelastic analysis of residual stresses in unidirectional, high‐performance composites
Authors: Nairn John A. 
Published: May 2005

AbstractWe present a thermoelastic analysis of the composite cylinder model for a undirectional composite including anisotropic fibers and an interphase region. We have found the magnitude of the residual thermal stresses on the micromechanics level induced by differential shrinkage between the anisotropic fibers and the matrix. For typical composites the largest residual stress is tension along the fiber direction, and a simple lower bound expression for this stress is given. Prediction of the magnitude of the thermal stresses requires knowledge of the thermal and physical properties of the matrix. The relevant properties for epoxy and thermoplastic matrices are discussed. The magnitude of the residual stresses can be reduced by tailoring the interphase region, but only if the interphase region serves to reduce the temperature for the onset of stress buildup. The volume fraction dependence of the longitudinal and transverse thermal expansion coefficients of the composite is compared to analogous expressions in the literature which do not include anisotropy of the fibers.
Tensile fatigue of glass fibers and composites with conventional and surface compressed fibers
Authors: Mandell J. F. , Mcgarry F. J. , Hsieh A. J.‐Y. , Li C. G. 
Published: May 2005

AbstractThe mechanism of tensile cyclic fatigue failure in conventional glass fiber dominated composites has been investigated using single fibers, strands, and composites. Surface damage to the fibers resulting from a fretting type of contact is identified as the dominant mechanism. Macrofibers of glass or glassceramic with residual surface compression have been developed to overcome the sensitivity both to cyclic and static fatigue. The macrofibers and their composites with several different matrices show greatly improved tensile fatigue resistance.
Processing of microcellular polyester composites
Authors: Youn Jae R. , Suh Nam P. 
Published: May 2005

AbstractA new method of producing microcellular polyester composites is developed. The microcellular foam which is produced by supersaturating the polyester resin with nitrogen is cured by dielectric heating. The lightweight composite contains about 10 μm size bubbles. By substituting the microcells for the particulate fillers of the conventional composites, the weight of the composite is reduced by 30 to 40 percent. A theoretical analysis based on classical nucleation theory is applied to predict the rate of nucleation. The diffusion controlled bubble growth is modeled and the theoretical prediction is in good agreement with experiment. The mechanical behavior of the microcellular composite has also been examined. Toughness is improved significantly whereas the flexural strength remains the same as that of a conventional sheet molding compound.
Crack length estimation procedure for short fiber composites: An experimental evaluation
Authors: Agarwal B. D. , Patro B. S. , Kumar Prashant 
Published: May 2005

AbstractValidity of the compliance matching procedure has been examined for short fiber composites experimentally by studying the behavior of damaged specimens. Comparison between the behavior of damaged and fresh specimens shows that the load—COD (crack mouth opening displacement) curve and fracture load of a damaged specimen are different from that of a fresh specimen having a machined crack of length equal to the estimated crack length in the damaged specimen. However, it has been clearly established that the secondary compliance of the damaged specimen can be used to accurately estimate the extent of damage to the specimen by earlier loading. Therefore, the use of the compliance matching procedure is justified for estimating instantaneous crack length in short fiber composites.
Interaction balances and properties of filled polymers
Authors: Richard C. , Hing Kuntharet , Schreiber H. P. 
Published: May 2005

AbstractThe dispersion behavior of calcium carbonate (CaCO3), of mica and of sized sand fractions in poly(vinyl chloride) (PVC) and polypropylene (PP) has been evaluated using fillers with various surface treatments. Mechanical properties of the compounds were also studied in order to question the role of interfacial forces in the context of dispersion and property parameters. Surface characteristics of polymers and fillers were obtained from inverse gas chromatography data. It has been shown that in the acidic PVC matrix, rapid dispersion of fillers is favored when strong acid‐base interactions exist at polymer filler contacts. Similarly, mechanical properties at large extension are improved by acid‐base interactions. In contrast, for polypropylene (PP), a van der Waals force material, fillers without pronounced acid or base surface characteristics tend to disperse more rapidly and produce mechanically stronger compounds. The importance of filler surface properties and thus, apparently, of acid‐base interfacial forces varies directly with increasing particle size of the dispersed phase.