bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental study and finite element simulation of a glass fiber fabric shaping process
Authors: Boisse P. , Cherouat A. , Gelin J. C. , Sabhi H. 
Published: December 2004

AbstractA finite element simulation is proposed for the shaping of glass fiber fabric. The overall mechanical behavior of the fabric is obtained by combining the tensile behavior of a single thread and the current position of threads in the fabric. The constitutive model for a single thread in tension is based on a statistical approach and is identified using tensile tests. Shear and tensile tests have been carried out on fabric specimens to demonstrate that the behavior of the fabric mainly results from the contribution of each thread, the sliding between fiber threads having a small effect on the energy for the deformation mechanism of these fabrics. A numerical model for the shaping process is obtained based on a finite element approach using three‐ and four‐node membrane shell elements. The formulation accounts for the large displacements and large strains involved in the process as well as the mechanical behavior. A drawing simulation is presented in the case of an hemispherical punch. The comparison with experimental results obtained in this case shows good agreement.
The effect of isothermal aging on transverse crack development in carbon fiber reinforced cross‐ply laminates
Authors: Pederson C. L. , Gillespie J. W. , McCullough R. L. , Rothschilds R. J. , Stanek S. L. 
Published: December 2004

AbstractAn investigation into the effect of isothermal aging on the development of transverse cracks in cross‐ply laminates of two high temperature composite systems was performed. The composite materials investigated were BASF X5260/640–800 and DuPont Avimid K/IM6. Changes in the glass transition temperature, composite weight loss, crack density, and mode I intralaminar fracture toughness were monitored during isothermal aging in air at 177°C for up to 2232 h. The two laminate configurations used in this study include two variations of the generic cross‐ply configuration [02/90n]s, in whichnequals 1 and 2. The results of this investigation show that a layer of degraded material forms at the surface of the X5260/640–800 bismaleimide laminates and that the thickness of the degraded layer increases with aging time. After 744 h of aging, transverse cracks form in the surface plies and an increasing crack density evolves as aging time is increased; however, transverse cracks do not form in the inner 90° ply groups with aging during the time period investigated. The Avimid K/IM6 thermoplastic polyimide laminates, which show evidence of cracking prior to aging, do not exhibit any significant change in crack density with aging. The results of the aging experiments also show that the bismaleimide system exhibits a weight loss of 1.5% and an increase in glass transition temperature from 250°C to 300°C after 2232 h of aging at 177°C, while the thermoplastic polyimide system shows a weight loss of only 0.05% and an increase in glass transition temperature from 280 to 285°C after 2232 h. Changes in the resistance to crack formation are also seen in these materials during aging. The mode I intralaminar fracture toughness, a measure of resistance to transverse crack formation, shows a 50% decrease after aging for 2232 h for the bismaleimide system, while the behavior exhibited by the thermoplastic polyimide shows little evidence of a reduction.
Interfacial bonding and optical transmission for transparent fiberglass/poly(methyl methacrylate) composites
Authors: Weaver Kevin D. , Stoffer James O. , Day Delbert E. 
Published: December 2004

AbstractEvidence is presented relating the interfacial bonding strength and the optical transmission of transparent glass fiber reinforced PMMA composites. The temperature dependent (20° to 50°C) optical transmission of composites that contained uncoated 13 μm glass fibers and 13 μm glass fibers coated with divinyltetramethyl disilazane or 3‐(trimethoxysilyl)propyl methacrylate was found to decrease in the same order as the bond strength of the PMMA/glass fiber interface, namely, trimethoxy silane coated fiber, disilazane coated fiber, and uncoated fiber. SEM photographs showed similar fracture surfaces, clean fiber pull‐out, and no apparent bonding of the glass fiber to the PMMA for the composites containing uncoated and disilazane coated fiber, whereas, the composite containing trimethoxy silane coated fiber showed virtually no clean fiber pullout. Additional evidence for differences in the bonding strength is seen in the degradation (penetration of water and fiber whitening) on aging at 23°C in air or water for composites containing uncoated fiber (most degradation), disilazane coated fiber (slight degradation), and trimethoxy silane coated fiber (no degradation). The optical transmission between 20° and 30°C at 600 to 800 nm for the composite containing trimethoxy silane coated fiber decreased the least with increasing temperature (from ∼85% to 70%) while the composite containing uncoated fiber decreased the most (from ∼85% to 32%).
Fatigue behavior of quasi‐isotropic carbon fiber/PEEK laminates under tension‐tension loading
Authors: Ma C. C. M. , Lin S. H. , Tai N. H. , Wu S. H. , Wu J. F. 
Published: December 2004

AbstractFatigue behavior of carbon fiber reinforced poly(etheretherketone)(PEEK) laminates was investigated. The static tensile measurement, tension‐tension fatigue loading tests, and residual tensile strength measurement of the [0/45/90/‐45]2sAS‐4/PEEK laminates were performed at various levels of stress amplitudes. The influences of stress amplitude on the fatigue life and the residual tensile strength were investigated. The experimental results for fatigue life and residual tensile strength under different stress amplitudes are analyzed by the median rank method. TheS‐Ncurves at various survival probabilities are also presented by the pooled Weibull distribution function. Furthermore, a residual strength degradation model is used to predict the residual strength for the composites subjected to a number of fatigue cycles and to simulate the effects of the stress amplitude on the fatigue life. The agreement between experiment and theory is good.
Degradation behavior of mechanically fastened joints of glass‐reinforced crosslinked polyester immersed in hot water
Authors: Morii Tohru , Hamada Hiroyuki , Maekawa Zen‐Ichiro , Tanimoto Toshio , Hirano Takahiro , Haruna Kazushi 
Published: December 2004

AbstractThis study deals with the degradation of mechanically‐fastened GFRP joints immersed in hot water (80°C). The material used was randomly oriented E‐glass fiber continuous strand mat with a crosslinked polyester. Three kinds of joint geometries were adopted; thickness was 3 mm, hole diameter was 6 mm, the distance from hole center to top‐edge was 18 mm (3e), and specimen widths were 18 (3w), 30 (5w), and 42 mm (7w). Failure modes of original dry specimens were a function of joint geometry, The dominant failure mode of 3w3e joints was net‐tension, whereas 5w3e and 7w3e joints displayed bearing failure. As degradation progressed, the dominant failure mode gradually shifted from net‐tension to bearing failure. Strength reduction was marked in 5w3e and 7w3e joints, in which the dominant failure mode was bearing. Joint strength and failure mode were predicted from the combination of a macroscopic failure criterion and characteristic curves obtained from tensile testing of rectangular specimens with holes, bearing tests, and finite element analysis. Predictions agreed with experiment.
Effects of sizings on microscopic flow in resin transfer molding
Authors: Palmese G. R. , Karbhari V. M. 
Published: December 2004

AbstractSizings significantly affect the processing and final performance characteristics of resin transfer molded (RTM) parts. Manufacturers often use sizings to enhance compatability between the resin and reinforcement and to assist processing. In particular, such coatings can affect the microscopic flow characteristics of resins during the infusion stages of the RTM process. To understand the mechanisms by which sizings affect preform wet‐out and the extent of such effects, the influence of fiber sizings and fiber loadings on the flow of a vinyl‐ester resin system, through axially aligned carbon fibers, have been measured. The results and analysis of the experiments reported herein form the basis for a phenomenological model that describes the effect of sizings on micro‐flow in RTM. Furthermore, the work provides insight into the relationships among micro‐flow, macro‐flow, and preform infiltration. It is seen that sizings dramatically influence micro‐impregnation and, for the flow configuration studied, radial micro‐flow into fiber bundles was the rate limiting process for complete fiber bundle infusion.
Percolation conductivity of polymer composites filled with dispersed conductive filler
Authors: Mamunya E. P. , Davidenko V. V. , Lebedev E. V. 
Published: December 2004

AbstractThis paper deals with the conductivity of binary polymer composites filled with an electronically conductive material. A “dynamic cluster model” is offered to describe the conductivity of such polymer composites in the highly filled region, i.e. above the percolation threshold. The model is based on the following assumptions:

a modification of the basic statistical percolation equation, i.e. σ (φ−φc)t, where t = 1.6 to 1.9, should be applied for all systems in the highly filled region, although application is limited to the range φ = φc + Δφ, Δφ ⟹ 0 in the strict statistical percolation approach;
the most important modifications with respect to the basic equation of the statistical percolation theory are

(a) the use of a constant teff, including a constant part t1 (resembling “t” in the basic statistical percolation approach) and a variable part t2 (depending on the filler concentration φ of the specific mixture) and
(b) the definition of φc as the filler concentration where a perfect three‐dimensional network of the conductive phase has been established. This idea has been adopted from the bond‐percolation approach of Aharoni;

the resulting equation should include parameters of specific polymer composites.
The generalized equation σ = f(φ) is used to calculate the maximum possible conductivity of a certain mixture as well as the dependence of σ on the filler content.
Impact behavior of carbon fiber/ultra‐high modulus polyethylene fiber hybrid composites
Authors: Jang Jyongsik , Moon Sung‐In 
Published: December 2004

AbstractCarbon fiber (CF)/ultra‐high modulus polyethylene (UHMPE) fiber hybrid composites were fabricated using vinyl ester resin as a matrix. Interfacial adhesion of carbon fiber/vinyl ester composites and UHMPE fiber/vinyl ester composites as model composites was optimized using low temperature plasma treatment. Interlaminar shear strengths of carbon fiber/vinyl ester and UHMPE fiber/vinyl ester homocomposite were greatly increased by plasma and silane coupling agent treatment. From the result of the impact test, total absorbed energy of carbon fiber/UHMPE fiber hybrid composites was correlated with laminating sequences at optimized interfacial adhesion between the reinforcing fiber and matrix resin. UHMPE fiber layers of hybrid composites played an important role in absorbing energy. Elastic and plastic deformation of UHMPE fiber layers also played a key role in improving the impact properties of carbon fiber/UHMPE fiber hybrid composites.
Influence of cellulose as a filler in vulcanized rubber composites
Authors: Nunes R. C. R. , Mano E. B. 
Published: December 2004

AbstractComposites of elastomers and cellulose have been investigated. Copolymers of styrene‐butadiene rubber (SBR) and acrylonitrile‐butadiene rubber (NBR) as well as natural rubber (NR) were compounded with regenerated cellulose (Cellulose II). The technique for the incorporation of filler was based on the coprecipitation of the rubber latex‐cellulose xanthate mixture. Cellulose filler was used in the range of 0 to 30 phr. The best results were shown by the natural rubber‐regenerated cellulose systems. The different behavior of the systems is explained by experimental evidence. The reinforcement mechanism for NR compositions, which involves an induced crystallizing rubber (NR), seems to be different from the mechanism for SBR and NBR.
Effect of molecular weight distribution on fatigue crack propagation in poly(methyl methacrylate)
Authors: Kim S. L. , Janiszewski J. , Skibo M. D. , Manson J. A. , Hertzberg R. W. 
Published: December 2004

AbstractIt is well established that both molecular weight (M) and its distribution (MD) affect many polymer properties such as mechanical behavior. Thus studies have shown that fatigue life is enhanced by increases inM. Research here has shown that with notched specimens fatigue crack propagation (FCP) rates are dramatically decreased by increasingM, even when theMis high enough that the static fraeture energy has essentially reached its asymptotic limit. In this study, specimens of poly(methyl methacrylate) containing either high‐ or low‐Mtails were prepared and characterized. The earlier finding that FCP rates are inversely related to averageMwas confirmed, but specific effects ofMdistribution were observed. At constantMn, a low‐Mtail had little effect on FCP resistance, while a high‐Mtail improved FCP resistance of polymers whose averageMwas too low for effective entanglements. Thus with high‐Mtails, it was possible to test specimens whose averageM's were too low to permit machining. It is proposed that the effects noted are due to relative stabilization or destabilization of crazes ahead of the crack.
The temperature dependence of network forces in rubber‐like materials
Authors: Staverman A. J. 
Published: December 2004

AbstractIn the simplest model of rubber‐like materials only two kinds of forces are assumed: network forces with identical temperature dependence, and liquid forces which. are isotropic. For this simple model the relation between the temperature dependence of the network forces and that of the observed elastic force is calculated. When the elastic equation of the network is of the classical one term type, the well‐known equation of Flory, Ciferri and Hoeve is found without using assumptions about the physical meaning of the front factor in the elastic equation. When the elastic equation of the network is of the Mooney‐Rivlin type with two terms, the difference between the temperature dependence of the observed forces and of the network forces is found to depend on the ratio of the coefficients in the Mooney‐Rivlin equation and on the elongation. The effect of the internal pressure is to add a factor to this term. The conclusion is that detailed knowledge about the network forces is needed in order to establish the value of the correction term for thermal expansion in the equation for the temperature dependence of the elastic force in the material.
Entanglement and excluded volume effects in rubber elasticity
Authors: Gaylord Richard J. 
Published: December 2004

AbstractThe role of interchain excluded volume and entanglement in the elastic behavior of polymeric networks is theoretically examined. A three‐chain network model is used, with each chain confined within an infinite, rectangular cylinder. The cylinders and the network crosslinks, are assumed to deform affinely. When the cross sections of the cylinders are small, the network elastic free energy equation has the form

The λs represent the macroscopic deformation ratios. The constants A, B and C are functions of the number of each type of network chain (i.e., A contains the number of tie chains; C contains the number of loops and tie chains; B contains the number of dangling chain ends, unattached chains, loops and tie chains), their unperturbed dimensions and the sizes of the cylinders which confine them.
Fiber growth in tubular flow
Authors: McHugh A. J. , Ejike E. , Silebi C. A. 
Published: December 2004

AbstractData are presented for the seeded growth of polyethylene fibers from solutions undergoing laminar flow in tubular geometry. Radial growth rates are reported for solutions of high and low molecular weight fractions for the second stage fiber thickening process which occurs in the tube entrance region. Results are also shown for high molecular weight growth from fiberglass seeds which indicate an enhanced growth rate at elevated temperatures. A two‐stage growth pattern documented earlier for the high molecular weight fraction is shown to occur for the lower molecular weight material. The Discussion includes an analysis for the tapered fiber geometry in the second stage of growth and calculations for stress‐induced, diffusion‐limited growth in the first stage downstream from the tube entrance.
Polymerization of fibrin in shear flow fields
Authors: Clark H. G. , Puryear H. A. , Casper R. A. 
Published: December 2004

AbstractThe reaction of fibrinogen with thrombin to produce fibrin goes through a multistep sequence in which up to four peptides are cleaved off. When this reaction takes place at pH 6.3 in a shear flow field, the formation of fibrous product is retarded as compared with stagnant conditions. The retardation is greater at 50 s−1 than at 135 s−1. The morphology of the coagulated product appears to be different when produced at 50 s−1 than at either stagnant or 135 s−1, with the material at 50 s−1 having a sheetlike appearance in contrast to a fibrous appearance for the material at 135 s−1 and stagnant conditions: The explanation of the retardation may lie in the separation of thrombin from fibrinogen during the sheared reactions. Shear rate varies more in the vascular bed than does pH or ionic strength and probably is a more important factor in controlling physiological coagulation than these more frequently studied variables.
The classification of solvents for bis‐phenol‐a polycarbonate
Authors: Heiss Herbert L. 
Published: December 2004

AbstractA procedure is described which permits the classification of solvents according to their effect on polycarbonate (PC):Class I—dissolve amorphous or crystalline PCClass II—dissolve only amorphous PCClass III—convert amorphous PC to crystalline PCClass IV—none of the above.This classification is achieved by comparing solvents to CH2Cl2 with respect to the exotherm and rate of crystallization observed when the solvents are brought into contact with PC under controlled conditions.
Pressure dependence of diffusion coefficient for CO2 in glassy polymers
Authors: Toi Keio 
Published: December 2004

AbstractThe pressure dependence of the apparent diffusion and permeation coefficients were observed by using the permeation time‐lag method for CO2 in glassy poly(ethylene terephthalate) (PET), polystyrene (PS) and poly(vinyl chloride) (PVC) below 1 atm. The results show that the permeation coefficient is constant whereas the diffusion coefficient increases with pressure. According to the theoretical prediction of Paul, it can be concluded that the adsorbed CO2 in these glassy polymers is completely immobilized and does not participate directly in the diffusion. A computer was used in the numerical calculation to determine the true diffusion coefficient from the model of Paul, et al. A comparison of the curves calculated with these constants and experimental values gave excellent agreement for the three glassy polymers. But there is a large difference between the values of one of the parameters obtained by this time‐lag method and the sorption method. Relations between this difference and the magnitude of the parameters are discussed.
Selection of barrier materials from molecular structure
Authors: Lee W. M. 
Published: December 2004

AbstractA prediction technique for gas permeability from polymer structure has been developed on the basis of a specific free volume diffusion theory. In this theory, the free volume available per unit mass in a polymer structure controls the rate of gas diffusion and, hence, its rate of permeation. The smaller this specific free volume is, the more difficult the gas diffusion and, thus, the better its barrier to gases becomes. Specifically, the theory predicts a linear relationship between log (permeability) and (−1/specific volume). A number of existing polymers covering six orders of magnitude in CO2 permeability and O2 permeability were found to follow this correlation. The specific free volume in a polymer was obtained from group contribution calculations. As a result, the gas permeabilities become predictable from the specific volume in a polymer which, in turn, varies with its molecular structure. The advent of this specific free volume theory for gas permeation simplifies greatly the selection of barrier materials for packaging applications. For a given barrier application, a critical specific free volume is first defined from its gas barrier requirement. The polymer structures having specific free volumes smaller than the critical value are then identified. These are the polymers that would have the necessary barrier performance. By this theory, molecular structures, with string polar‐to‐polar interactions and hydrogen‐bonding forces are found to be good barriers to CO2 and O2.
Corona‐discharge treatment of polymeric films, II: Chemical studies
Authors: Carley James F. , Kitze P. Thomas 
Published: December 2004

AbstractPolymeric films, chiefly polyethylenes, were subjected to corona‐discharge treatment in a continuous treater at commercial rates in a program covering wide ranges of the main processing factors (2). Electron‐spin‐resonance measurements on freshly treated films found no free radicals. Reactions of the treated surfaces with a free‐radical compound, diphenyl picryl hydrazyl (DPPH) were studied, focusing mainly on the rate effects. The evidence indicates that corona treatment produces fairly stable peroxide structures of the forms RO2R and RO3R on polyethylene surfaces. RO3R reacts rapidly with DPPH alone, while RO2R undergoes a slower reaction after addition of the catalyst, triethylene diamine. DPPH is capable of detecting as few as 1013 peroxide groups per square centimeter. Activation energies were 12 kcal/mole for the uncatalyzed reaction and 16 kcal/mole for the amine‐catalyzed reaction. As with the physical effects reported earlier (2), the production of peroxides is most strongly dependent on the energy delivered to the film during treatment. This energy is proportional to the quotient of corona current and web speed, I/S, Regression analysis showed that air‐gap thickness, relative humidity, and number of electrodes used also were significant factors, while dielectric thickness and corona frequency were not. We found that‐γ, the polar component of surface energy of the treated film, which is nearly zero for untreated polyethylenes, is exponentially related to the concentrations of both RO2R and RO3R with a correlation coefficient for 92 specimens tested of 0.88. We believe this is the first strong evidence linking treatment factors, at commercial levels of treatment, to chemistry of the treated surface and linking both of those to changes in physical behavior of the surface.