bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interlaminar stresses in tapered laminates
Authors: Hoa S. V. , Daoust J. , Du B. L. , Vu‐Khanh T. 
Published: May 2005

AbstractTapered laminates of unidirectional layers of glass/epoxy and graphite/epoxy are investigated. These laminates have a thickness variation along their length. This was accomplished by having layers dropped off near the midlength of the laminate. Stress and strain variations were obtained using three‐dimensional finite element models. Calculated values using the finite element method compare well with experimental results for the point of first delamination. This agreement allows the determination of a suitable finite element mesh for subsequent models of other tapered laminates with fiber orientations other than unidirectional.
Simulation of flow in compounding machinery: Internal mixers and modular corotating intermeshing twin‐screw extruders
Authors: White James L. , Kim Jin‐Kuk , Szydlowski Witold , Min Kyonsuka 
Published: May 2005

AbstractHydrodynamic lubrication theory has been applied to analyze flow in internal mixers and twin‐screw extruders. Fluid motions in mixing regions are interpreted as being due to coupling of drag flow and pressure gradients. Pressure fields and mean flow patterns have been computed. Distributive and dispersive mixing are interpreted in terms of computed fluid fluxes in the processing machinery.
Short fiber reinforced thermoplastics. II. Interrelation between fiber orientation and rheological properties of glass fiber‐reinforced Noryl
Authors: Vaxman A. , Narkis M. , Siegmann A. , Kenig S. 
Published: May 2005

AbstractMechanical properties of short fiber reinforced thermoplastics depend on the fiber orientation distribution produced during the melt flow processing step. An experimental investigation of fiber orientation during shear flow through a circular die is presented. A quantitative determination of the glass fiber orientation distribution was done by analyzing photomicrographs of polished extrudate sections. Planar and axial fiber orientation distributions as affected by shear rate and total shear are discussed. The reliability of a classical metallographic technique for fiber orientation determination was evaluated. Orientation effects are expressed by a single orientation parameter which is used to account for the average fiber orientation contribution to the relative viscosity. The influence of shear rate, total shear, fiber concentration, and temperature on fiber orientation has been investigated. It is concluded that an orientation parameter should be used to account for fiber concentration effects on the relative viscosity. Calculated values, considering the orientation parameter, show good agreement with the experimental relative viscosity results.
Effects of sorbed caprolactam on the crystallinity, morphology, and deformation behavior of polyetheretherketone and poly(phenylene sulfide)
Authors: Wilfong Debra L. 
Published: May 2005

AbstractStudies on the high temperature sorption of caprolactam by polymer resins and their composites have been conducted. The systems investigated were glass fiber reinforced (GFR) poly(phenylene sulfide) (PPS), polyetheretherketone (PEEK) neat resin, GFR PEEK and carbon fiber reinforced (CFR) PEEK. To measure changes of caprolactam sorption, melting behavior, mechanical properties, and fracture surface morphology were determined. Absorption of caprolactam by the PEEK composites was 30 to 40 percent less than by the neat resin. This is attributed to the fibers, which acted to constrain the matrix and thus limit its swellability. Reductions in melt temperature, percent crystallinity, ultimate tensile strength, and modulus were observed following exposure to the chemical environment. The loss of strength and stiffness was a consequence of the degradation of the matrix/fiber interface by the sorbed caprolactam.
Graphite/polyimide composites with improved toughness
Authors: Delvigs Peter 
Published: May 2005

AbstractStudies were performed to determine the toughness characteristics of composites prepared from modified addition‐type polyimides, using Celion 6000 graphite fiber as the reinforcement. The polyimides were prepared from aromatic diamines containing flexibilizing ether connecting groups. The composite flexural and short beam shear strengths were determined at room temperature and elevated temperatures. Composite toughness was evaluated using 10° off axis tensile tests and double cantilever beam fracture tests at room temperature. The effects of the flexibilized resin structure on composite mechanical properties, toughness characteristics, and thermo‐oxidative stability are discussed.
A study of glass fiber–epoxy composite interfaces
Authors: Liao Y.‐T. 
Published: May 2005

AbstractFourier transform infrared spectroscopy was utilized to characterize the interfacial bonding in glass‐fiber‐reinforced composites. The pH of the treating solution significantly affects the interfacial chemical bonding. The natural pH of the solution gives the maximum interfacial bonding. The decrease of the interfacial bonding is due to the side reactions that occur when NaOH or HCl is added to the solution. The temperature of the curing process has little effect on the amount of the interfacial chemical bonding. We attribute this to the reaction rate constant of the interfacial reaction being much larger than that of the epoxy polymerization. From the hygrothermal behavior, we have found the amount of silane needed for hygrothermal condition is different from that for dry condition.
The response of fibrous composites to impact loading
Authors: Jang B. Z. , Chen L. C. , Hwang L. R. , Hawkes J. E. , Zee R. H. 
Published: May 2005

AbstractThe response of advanced composites to low‐velocity projectile loading was investigated. The impact failure mechanisms of composites containing various fibers with different strength and ductility were studied by a combination of static indentation testing, instrumented falling dart impact testing, acoustic emission monitoring, and scanning electron microscopy (SEM). The composites containing fibers with both high strength and high ductility (eg., polyethylene (PE) fibers) demonstrate a superior impact resistance as compared to those containing fibers with high strength (eg., graphite fibers) or high ductility (eg., nylon fibers) but not both. Upon impact loading, the composites containing PE fibers usually exhibited a great degree of plastic deformation and some level of delamination. These mechanisms acted to dissipate a significant amount of strain energy prior to the penetration phase of the impact process. No through penetration was observed in all the samples containing more than three layers of PE fabric except when loaded at relatively high rates and low temperatures. Although certain levels of delamination also took place in other composite systems, very little plastic deformation occurred, allowing ready penetration of the projectile. The stacking sequences in the hybrid laminates studied were found to play a critical role in triggering or inhibiting the processes of plastic deformation and delamination and, therefore, controlling their energy absorption capability. The penetration resistance of composites appeared to be dictated by the fiber toughness. The later property must be measured in a simulated high‐rate condition.
The resin‐fiber interface in polyurethane and polyurethane‐unsaturated polyester hybrid
Authors: Damani S. G. , Lee L. James 
Published: May 2005

AbstractA polyurethane (PU) is compared with the polyurethane‐unsaturated polyester (PU‐UPE) hybrid to examine the changes of the resin‐fiber interphase in the presence of a sizing compatible component, UPE, in the matrix resin. The formation of resin‐fiber interphase is critical in structural reaction injection molding (SRIM) and resin transfer molding (RTM) because resin solidification (i.e., gelation and vitrification) occurs in seconds (SRIM) or minutes (RTM). Kinetic (DSC, FTIR spectroscopy), mechanical (single fiber test, fracture surface analysis), and microscopic (birefringence, SEM) studies were used to analyze the interface. Kinetic results indicate poor chemical compatibility of the sizing with PU and increased chemical interactions of the sizing with the PU‐UPE resin. Mechanical and microscopic analyses also point in favor of improved interphasial behavior with the PU‐UPE resin.
Review of cure of polymers and composites by microwave energy
Authors: Mijović Jovan , Wijaya Jony 
Published: May 2005

AbstractThe fundamental concepts of microwaves and their application as an alternative energy source for cure of polymers and composites are discussed. The mechanisms of interaction between electromagnetic waves and organic materials are described, and studies reported in the literature on microwave cure of polymers and their composites are discussed. Information is presented about materials, microwave applicators, modes of microwave energy application, and means of monitoring reactions. It is concluded that microwaves as the source of energy offer advantages over thermal cure but that a fundamental study of cure in the microwave field is necessary to fully assess their effect on the physical/mechanical properties of cured polymers.
Multi‐Nuclear NMR spectroscopic and proton NMR imaging studies on the effect of water on the silane coupling agent/matrix resin interface in glass fiber‐reinforced composites
Authors: Hoh Ka‐Pi , Ishida Hatsuo , Koenig Jack L. 
Published: May 2005

AbstractMulti‐nuclear NMR spectroscopy and proton NMR imaging are used to investigate the absorption of water as well as the effect of water on the relaxation of the silane coupling agent/epoxy resin interface. For samples in which leaching occurred, proton NMR imaging is used to complement weight measurements by showing the amount and location of the water in the sample.13C and29Si solidstate NMR spectroscopy show that the water can interact with the silane coupling agent and affect the relaxation of the sample. Water can leach out the low molecular weight oligomers and/or further hydrolyze the silane coupling agent.
Effects of environmental exposure on fiber/epoxy interfacial shear strength
Authors: Gaur Umesh , Miller Bernard 
Published: May 2005

AbstractThe TRI microbond technique for direct determination of fiber/resin interfacial shear strength in composites has been used for investigation the influence of environmental conditions on adhesive bonding in certain systems. The small dimensions involved in the method facilitate uniform exposure and short exposure times. We have observed significant changes in both average shear strength and in shear strength distributions on exposing aramid/epoxy and glass/epoxy microbond assemblies to steam or hot water. Shear strength dropped to a plateau value in both cases, the reduction being more drastic with the glass fiber. Vacuum drying restored shear strength completely in aramid/epoxy microassemblies, even when the surface of the aramid fiber had been chemically modified, but there was only partial regeneration of bond strength with the glass/epoxy system.
Solvent stress cracking and failure mechanisms in polyetherimide composites
Authors: Hsieh Alex J. , Schneider Nathaniel S. , Mandell John F. 
Published: May 2005

AbstractSolvent stress cracking studies have been carried out in o‐xylene and other solvents on polyetherimide (PEI) based materials including neat resin, woven fabric composites, and adhesively bonded systems. The results show crack growth in solvents at very lowGIlevels as compared with tests in air. The composite and adhesively bonded systems have sufficiently high residual thermal stresses to drive an array of intersecting matrix/adhesive cracks even without mechanical loading. The matrix/adhesive residual stress driven crack patterns in these systems are shown to retard main delamination crack growth relative to that in the neat resin, and to raise the applied thresholdG1level for main crack growth by about a factor of ten, as predicted by an approximate model.
Interfacial phenomena in cellulose/polyethylene composites
Authors: Bataille P. , Allard P. , Cousin P. , Sapieha S. 
Published: May 2005

AbstractA systematic study of the mechanical properties of linear low density polyethylene (LLDPE) and high density polyethylene (HDPE) filled with cellulose was conducted. When benzoyl peroxide (BPO) was used and when the components were mixed at 160°, the yield strength of the LLDPE/cellulose composite increased by 70% whereas that of HDPE increased by only 15%. If BPO is replaced by dicumyl peroxide (DCP) the yield strength attains a plateau value at a lower concetration. Yield strength for the cellulose/LLDPE system, where the cellulose had been pretreated with silane, showed a relatively small improvement as compared to the effect of the peroxides addition. The presence of gel in the compound is also discussed.
A model for composite laminate bend‐forming under arbitrary curvature distribution and extensive interlaminar sliding
Authors: Talbott Margaret F. , Miller Alan K. 
Published: May 2005

AbstractWhile thermoplastic matrix composites are of increasing interest for a variety of applications, methods of forming these materials are still under development. One way of hastening their development and utilization is to develop models which predict the material response to processing. One such model is under development and will predict the response of a consolidated laminate which is being formed to a singly‐curved shape. The model accounts for the unique features of thermoplastic composites, namely the continuous inextensible fibers and the need for extensive relative ply sliding. At this stage in model development, it treats a laminate as a series of alternating layers of elastically hard and elastically soft material. The hard layers can slide over each other because of the soft shearable layers between them. In its present stage, the model predicts, for any arbitrarily complex singly‐curved shape, the extent of relative ply sliding, the stresses generated, and the array of point forces that are required to produce the specified shape. The behavior of a beam with extensive ply sliding is very different from that described by classical beam theory. First, the ply normal stresses depend not only on the local curvature and distance from the neutral axis, but also on the position along the laminate. Second, the relative ply sliding and the bending stresses occur not only in bent sections of the laminate, but also in nearby straight sections. Thus, the response of a given element of material depends not only on local conditions, but also on the curvature distribution throughout the laminate.
Solidification in anisotropic thermoplastic composites
Authors: Gilmore Scott D. , Güçeri Selçuk İ. 
Published: May 2005

AbstractHeat transfer analysis in thermoplastic composites manufacturing offers several challenges. The melting/solidification process results in the appearance of a molving solid‐fluid interface or two‐phase zone. The presence of reinforcing fibers with thermal conductivities substantially different than those of matrix meterials causes the composite material to behave anisotropically. Furthermore, an analysis should be adaptable to complex geometries if it is to be useful for practical applications. In this paper, a numerical approach is presented to develop an analysis tool for the processing of thermoplastic‐matrix composites. A numerical grid generation technique is employed to determine the temperature distribution within the part while accounting for the heat absorption and liberation during the solidification stage. The influence of anisotropy in the domain is accounted for by considering thermal conductivity as a second‐order tensor which varies continuously throughout the domain. Sample part configurations are used to demonstrate the applicability of this technique to thermoplastic composites processing.
Design of particulate composites for optical applications
Authors: Dunlap P. N. , Howe S. E. 
Published: May 2005

AbstractThis paper reviews the basic theoretical approach to describing light scattering in filled materials with nearly matching refractive indices (Rayleigh‐Gans‐Debye Theory). The modifications necessary to handle high filler concentrations (interparticle interference and multiple scattering) are included empirically. The primary result of this analysis is an expression for the optical transmission of a polymer composite as a function of particle size, volume fraction, composite thickness, and refractive index difference between the components. The angular dependence of the scattering is included so that scattered light which falls within the aperture of the transmission detector can be accounted for, Particular attention is given to including the temperature dependence of the refractive index and the effect of fillers on the thermal expansion properties of the polymer matrix in order to predict the temperature range over which the composite will be optically useful. Similarity to analyses of the Christiansen filter is discussed.
Modified fibers for polymer composites with improved mechanical properties
Authors: Wang Q. , Ait‐Kadi A. , Kaliaguine S. 
Published: May 2005

AbstractIn this paper, a new composite material, AEG, which was developed in our laboratory by catalytic grafting polymerization of ethylene on asbestos fibers, was used to improve the properties of asbestos/HDPE composites. Tensile testing shows that the AEG modified asbestos/HDPE composites exhibit significantly higher tensile strength and elongation at break than the unmodified ones. Instrumented impact testing permits a detailed understanding of the modifying effect of AEG on impact properties. The records acquired during impact for the unmodified composites were truncated at the onset of initial fracture, showing a typical brittle cleavage fracture. In contrast, the records for the AEG modified composites showed an effective post‐initial fracture behavior. The load at peak, the energy required to initiate and propagate the fracture, and the deformation during impact increase dramatically for the AEG modified composites. SEM micrographs of the fractured surfaces also demonstrate the difference in the morphology of the two composites.
The properties of wet‐formed thermoplastic sheet composites
Authors: Bigg D. M. , Hiscock D. F. , Preston J. R. , Bradbury E. J. 
Published: May 2005

AbstractGlass fiber reinforced thermoplastic matrix sheet composites of polypropylene and poly(ethylene terephalate) were produced in a two‐stage pilot scale impregnation and consolidation process. The first stage consisted of preparing wet‐formed mats of long, discontinuous fibers and polymer powder on an inclined wire paper‐making machine. The second stage consisted of consolidating approximately 15 wet‐formed mats into a solid composite laminate by the application of heat and pressure in a compression press. The resulting composites had a nominal glass content of 26 wt% (∼12 vol %). Flexural strengths as high as 108 MPa for polyproplene composites and 132 MPa for poly(ethylene terephthalate) composites were measured on specimens cut from stamped parts. The flexural modulus of the polypropylene compsites reached 5.4 Gpa, while the modulus of the stiffest poly(ethylene terephthalate) composite was 8.1 Gpa. The impact properties of the composites were equally good. Polyproplene compsites absorbed up to 62 J/cm during an instrumented falling dart impact test, while poly(ethylene terephthalate) composites absorbed as much as 32 J/cm during the same test.
Mold filling and curing analysis in liquid composite molding
Authors: Lin R. J. , Lee L. James , Liou Ming J. 
Published: May 2005

AbstractNon‐isothermal mold filing and curing experiments of liquid composite molding were carried out in this work. To compare the experimental results with a previously developed numerical simulation model, measurements of volumetric heat transfer coefficient between the resin and the fiber, and characterization of resin kinetics and rheological changes were also conducted. Combined with the previously measured fiber perform permeability, the numerical model provided a good prediction of temperature profiles during molding for a polyurethane/glass fiber composite.
Processing effects in production of composite prepreg by hot melt impregnation
Authors: Chmielewski C. , Jayaraman K. , Petty C. A. 
Published: May 2005

AbstractThe hot melt impregnation process for producing composite prepreg has been studied. The role of the exit die is highlighted by operating without impregnation bars. Experimental results show that when a fiber two is pulled through a resin bath and then through a wedge shaped die, the total resin mass fraction and the extent of resin impregnation in the two increase with the processing viscosity. The penetration of resin into a fiber bundle is greater when the resin viscosity is higher. This trend is unchanged over a range of two speeds up to the breaking point. A theoretical model is developed to describe the effect of processing conditions and die geometry on the degree of impregnation. Calculations with this model indicate that for a given die geometry, the degree of impregnation increases from 58% to 90% as the ratio of the clearance between the two and the die wall, to the total die gap is decreased from 0.15 to 0.05. Physical arguments elated to the effective viscosity of the prepreg show that the clearance ratio is independent of the two speed, but decreases as the ratio of the effective shear viscosity of the prepareg to the resin viscosity increases. This provides a connection between the experimental results obtained with varying resin viscosity and the computational results obtained with varying clearance values at the die inlet.
Influence of the impregnating property on mechanical properties of commingled yarn composites
Authors: Hamada Hiroyuki , Maekawa Zen‐Ichiro , Ikegawa Naoto , Matsuo Tatsuki , Yamane Masachika 
Published: May 2005

AbstractThree types of glass/nylon 6 intermediate material forms‐film stacking, uncommingled yarn, and commingled yarm‐were selected study the correlations between the impregnating property and mechanical properties. The size of the glass fiber block to be filled with matrix and the porosity in glass fiber bundles by spearing out the fiber bundle was different in these materials. Unidirectional glass fiber reinforced thermoplastic composites were fabricated by compression molding. The being test was performed by using the three‐point loading system, and the fracture behavior and the degree of impregnation were observed to examine the influence of processing conditions on the bending properties, relative to the form of the intermediate material. Bending strength increased, in accordance with the impregnating property, least in the film stacking form, second most in uncommingled yarn, and most in commingled yarn. The impregnating property was affected by the size of fiber blocks and the porosity in fiber bundles, because bending strength was improved by spreading out the fiber bundles. Commingled yarn is an excellent intermediate materials, which has both the fineness of matrix/fiber mixing and large porosity in fiber bundles.