bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electric breakdown of a poly(ethylene terephthalate)/glass composite
Authors: Schultz J. M. , Lhymn Chang 
Published: May 2005

AbstractThe voltage lifetime of a poly(ethylene terephthalate)/glass composite is measured for two different orientations of short fiber with respect to the applied electric field (perpendicular and parallel). The difference in the voltage lifetime between two configurations is attributed to the microstructural features at the (fiber/matrix) interface, particularly microvoids. The morphological observations by scanning and transmission electron microscopy (SEM, TEM), and optical microscopy reveal the presence of microvoids as well as the crazed matrix and consequent erosion channel. The tree initiation site is identified and the nature of tree propagation is explained. A theoretical model based on such microstructural features is constructed, which explains the voltage lifetimevsfiber orientation in a relative framework. It is concluded that the graseous discharge at microvoids is the main mechanism for electrical breakdown and the site of such gaseous discharge is the (fiber/matrix) interface. Therefore, the orientation dependence of the electrical breakdown is the geometrical effect of the interface voiding with respect to the direction of the applied electric field.
Polyfunctional epoxies: Part II. Nonrubber versus rubber‐toughened brominated formulations for graphite composites
Authors: Nir Z. , Gilwee W. J. , Kourtides D. A. , Parker J. A. 
Published: May 2005

AbstractInitial screening of carboxy‐terminated butadiene acrylonitrile (CTBN) rubber‐toughened brominated formulations for graphite composites has been reported previously. This study is a further investigation, focusing on the performance of the brominated polymeric additives as a potential flexibilizing agent for graphite composites, using different molecular weights of the Br source. Increasing segment lengths of the polymeric backbone chain of brominated polymeric additives (BPA) are examined in a new development, trifunctional epoxy resin and is compared with a 10 percent rubber‐toughened formulation of the same epoxy resin. Results show that when the Br content in the graphite composite was increased without the use of rubber, the mechanical properties improved. Mechanical and other properties of the graphite composites are discussed.
Induced orientational behavior of liquid crystal polymer by carbon fibers
Authors: Chung T. S. , Gurion Z. , Stamatoff J. B. 
Published: May 2005

AbstractExperimental results are presented that show that the structure of carbon fibers induces molecular orientation of liquid crystal polymers. X‐ray diffraction data are used to demonstrate final collinearity of the polymer molecular axis and carbon fiber axis independent of fabrication approaches or prefabrication orientation of the polymer relative to the carbon fiber direction. The final degree of polymer molecular orientation approximately equals the degree of carbon basal plane orientation within the carbon fiber.
The interface between glass and carbon fibers and thermosetting polymers
Authors: Piggott M. R. , Chua P. S. , Andison D. 
Published: May 2005

AbstractThe interface between the fibers and the polymer matrix controls the properties of fiber composites and has been the subject of much study. Recently, special techniques have been developed for single fiber pull‐out experiments on production fibers, which make it possible to obtain data on the frictional forces which govern sliding after the interface has fractured, as well as the adhesion strength of the interface. Tests on glass in polyester and epoxy resins show that the work of fracture of the interface is much smaller than that of the resin, and that the shrinkage pressures of these matrices, when fully postcured, are approximately the same (about 20 MPa). Coefficients of friction at the interface are 0.6 for the polyester and 1.0 to 1.6 for the epoxy. The carbon‐epoxy interface yields at shear stresses as high as 60 MPa, instead of fracturing, and the coefficient of friction during sliding is about 0.4.
Fracture of mica‐reinforced polypropylene: Mica concentration effect
Authors: Vu‐Khanh T. , Sanschagrin B. , Fisa B. 
Published: May 2005

AbstractConcepts of post‐yield fracture mechanics were used to characterize the crack initiation and propagation resistances of mica‐reinforced polypropylene containing different mica concentrations. Although mica addition leads to an apparently brittle composite, the crack initiation resistance is slightly increased with mica concentration up to 10 percent by weight; and significant improvement in crack propagation performance was found for polypropylene reinforced by up to 20 percent of mica in comparison to that of virgin polypropylene. The debonding of the interface between mica flakes and the matrix leads to a micro‐ductility ahead of the crack tip in which the matrix is able to pull‐out from mica particles and to stretch. This micro‐ductility also prevents the brittle, unstable crack propagation, which is due to the coalescence of voids in pure polypropylene. Above 20 percent of mica, the reduction of the effective amount of the matrix material results in a substantial drop in the resistance to crack growth of mica‐reinforced polypropylene.
Use of wood fibers in thermoplastic composites II: Polyethylene
Authors: Beshay Alphons D. , Kokta Bohuslav V. , Daneault Claude 
Published: May 2005

AbstractWood fibers of aspen in the form of chemithermomechanical pulp (CTMP) has been used as reinforcement in polyethylene (PE). The secant modulus, tensile strength, energy, and elongation at yield were measured. It was found that the mechanical properties of the composite were higher than those of PE by a factor of 2.6 for modulus, 2.3 for stress, and 2.1 for energy at yield. Compared to glass fiber composites, the CTMP composites showed higher elongation, about 100 percent higher energy, 106 percent higher stress, and 75 percent higher modulus. Note that the cost of treated wood fibers is several times lower than that of treated glass fibers.
Fiber matrix interactions in jute reinforced polyester resin
Authors: Semsarzadeh Mohammad A. 
Published: May 2005

AbstractThe effect on packing resulting from the filling of unsaturated polyester resin with fillers and jute fibers has been investigated. The influence of absorbed water on the interfacial interactions involved in the fiber matrix system of the jute reinforced polyester resin also are discussed. An approach to reduce water absorption and soluble matter lost from the jute reinforced polyester resin is proposed.
Fatigue of glass‐fiber‐reinforced polyester laminates
Authors: Ouellette Paul , Hoa S. V. 
Published: May 2005

AbstractMaterials used in making glass‐fiber‐reinforced plastic pressure vessels are tested in uniaxial tensile fatigue. Specimens of mat/woven roving/mat are tested with the warp direction parallel to the load axis and ±45 degrees to the load axis. Filament‐would specimens are tested at ±54.7 and ±35.3 degrees to the load. A stress ratio of R = 0.1 is used with load control. The residual properties of surviving specimens after 400,000 cycles indicate they have sustained no damage. The S′‐N curves show a strength loss of about 10 percent per decade of cycling. The failure mode of the filament‐would specimens is similar to that of angle‐ply laminates. Stress levels of one‐third the strength appear safe for the range of cycles investigated.
Void content of a viscoelastic composite melt: Reduction during mixing
Authors: Watson Robert J. , Chaffey Charles E. 
Published: May 2005

AbstractMica and polystyrene in four ratios were sheared for three different times, each at three speeds, and at two temperatures in the viscoelastic region, in a screw mixer. From precise density measurements on the resulting composites, void volume fractions were calculated and found to be proportional to mica concentration and independent of total screw rotations. Experimental void/mica ratios were represented by a kinetic model; they decreased from a single value common to all conditions to a steady‐state value proportional to the square root of the screw speed. Void formation and elimination occur simultaneously. The goodness of the fit to the data is insensitive to the details of the kinetic model. The characteristic rate constant depends only on temperature, increasing at the same rate as the reciprocal of the low‐frequency dynamic viscosity. Cavitation in regions of diverging flow of the mixer may inhibit void elimination.
Ultrasonic evaluation of filled polymers II. Elastic moduli of a resin filled with iron inclusions of different aspect ratios
Authors: Piché L. , Hamel A. 
Published: May 2005

AbstractAn ultrasonic technique is used for the nondestructive evaluation of elastic moduli of polymer composites. Samples with varying amounts of randomly oriented iron inclusions, having aspect ratios p = 0.20 (flakes) and p = 20.0 (short fibers), were fabricated and fully characterized. The results for the moduli are discussed in terms of available theoretical models. It is demonstrated that models which account for the microscopic details of the material offer a good description of the bulk properties. Also, experimental evidence is obtained for the effect of particle contiguity and allows not to evaluate the influence of particle/particle interaction.
An apparatus for measurements of thermal conductivity of neat epoxies and their composites
Authors: Mijović Jovan , Mei Henry L. 
Published: May 2005

AbstractIn the modeling studies of processing of composites one must determine the changes in thermal conductivity during cure as a function of both temperature and the extent of reaction. An apparatus for measurements of thermal conductivity of neat thermosets and their composites was designed and built in our laboratory. A detailed description of the apparatus is given in this paper. Also included are some initial results obtained with an epoxy resin formulation of the type used in filament‐wound structures.
Controlled energy dissipation in fibrous composites I. Controlled delamination
Authors: Jang B. Z. , Lieu Y. K. , Chung W. C. , Hwang L. R. 
Published: May 2005

AbstractDelamination mechanisms in continuous fiber reinforced composites were investigated. The concept of controlled interlaminar bonding (CIB) is proposed as a guideline for preparing fiber‐epoxy composite laminates with enhanced fracture toughness without significant degradation in strength properties. The interlaminar bonding was manipulated by several specialized techniques including insertion of delamination promotors and surface modification of laminae. Results indicated that the plane‐strain fracture toughness of E‐glass‐epoxy laminates could be improved by inserting perforated interlaminar films of aluminum, paper, polyester and polyimide, and fabrics. Such interlayers were used to promote delamination which dissipate strain energy by blunting and diverting a propagating crack. The fracture resistance of a laminate was found to be dependent on the degree of delamination. The competition between the growth of delamination cracks and the propagation of a main crack is controlled by the relative magnitude of the interlaminar bonding strength and the lamina cohesive strength. The interlaminar bonding is controlled by the degree of interlayer perforation and the adhesion between interlayer and lamina. The loading direction was found to be very important in dictating the failure processes. Experimental results from several composite systems are presented and discussed along with post‐failure analysis data.
Acoustic emission during fracture of short glass fiber reinforced poly(vinyl chloride)
Authors: Koenczoel L. , Hiltner A. , Baer E. 
Published: May 2005

AbstractThe fracture mechanics approach and acoustic emission (AE) analysis have been coupled in an investigation of slow crack growth of short fiber reinforced poly(vinyl chloride). It was found that AE occurs during less than one percent of the time of crack growth suggesting that so‐called continuous crack propagation is based on discontinuous microscopic damage. The time dependence of various AE parameters exhibits a good linear relationship with crack speed. For a unit of newly created fracture surface, a constant amount of acoustic energy is released independent of crack speed. At very low speeds, below 3·10−3mm/s, a change in mechanism from pure matrix related to fiber related crack growth is observed, which is also reflected by a change in the amplitude distribution of the AE events.
Nylon fiber reinforcement for polyurethane composites
Authors: Córdova C. W. , Young J. A. , Rowan H. H. 
Published: May 2005

AbstractThe potential of a nylon 6 fiber was evaluated for composite applications involving rigid polyurethane systems. A study showed that the use of COMPET N, a nylon 6 based fiber surface treated to enhance wetout and adhesion, in an ISP polyurethane system results in composites with higher impact values and lower weight than those reinforced with glass fiber. A 2 percent loading of COMPET N matt increased impact values by more than 300 percent over an unreinforced control while a 3 percent loading of glass matt resulted in increases of less than 100 percent. A drop impact test showed COMPET N fabric reinforced composites to absorb twice as much energy as an unreinforced and glass reinforced composite without major damage. These advantages have also been observed in COMPET N/Glass hybrids, in which layer orientation can be used to produce composites with specific properties. Cut fiber reinforced composites were found to exhibit similar properties as fabric reinforced ones resulting in the commercialization of a canoe end cap containing cut nylon fiber. Additional property benefits such as improved impact fatigue and decreased stress cracking have also been observed in nylon 6 reinforced composites resulting in the consideration of these materials for a wide range of applications.
Thermal and rheological properties of poly(phenylene sulfide) and poly(ether etherketone) resins and composites
Authors: Ma Chen‐chi M. , Hsia Hung‐chung , Liu Wen‐liang , Hu Jiann‐tsun 
Published: May 2005

AbstractPoly(phenylene sulfide) (PPS) and poly(ether etherketone) (PEEK) are high performance engineering thermoplastics with a unique combination of excellent environmental, mechanical, and thermal properties. Research on the thermal and rheological properties of PPS and PEEK resins and carbon fiber reinforced prepregs are described. Experimental studies of the dynamic viscoelasticity and thermal properties of these materials are summarized. The effects of processing cycles and environment on the thermal and rheological properties are discussed. The effects of the processing environment and the addition of carbon fiber on the thermal stability are reported. Crosslinking of poly(phenylene sulfide) in air, enhancing thermal stability, is also investigated.
A composite characterization of high speed spun semicrystalline fibers
Authors: Pournoor Kaveh , Seferis James C. , Vassilatos George 
Published: May 2005

AbstractA systematic study of thermo‐mechanical properties of high speed spun poly(ethylene terephthalate) fibers was undertaken as part of a broad quantitative process—structure—property examination of semicrystalline polymers through appropriate composite models. Calorimetric experiments on a series of fibers spun at different speeds show that crystallinity increases with takeup speed rapidly below 4500 m/min but at a slower rate above that speed. The glass transition, cold crystallization, and melting temperatures were also found to increase with speed. A similar increase is exhibited by both the refractive index of these fibers along the fiber axis and the fiber birefringence. Comparison of birefringence measurements with those predicted from a composite two‐phase optical model led to the conclusion that form birefringence may be a significant contributor to the overall birefringence and that it may not be ignored in calculations of orientation functions with this experimental technique.
The effect of fiber‐matrix adhesion on the fatigue fracture of glass‐fiber‐reinforced poly(vinyl chloride)
Authors: Nguyen P. X. , Moet A. 
Published: May 2005

AbstractFatigue crack propagation (FCP) of injection‐molded glass‐fiber‐reinforced poly(vinyl chloride) was examined as a function of fiber‐matrix adhesion (coupling) and fiber content at different load levels. Considering the entire FCP history, from crack initiation to critical propagation, it is shown that fatigue lifetime and fracture toughness of coupled composites increase with fiber weight fraction. Uncoupled material exhibits the highest fracture toughness at 10 wt% fiber, yet its fatigue life is considerably shorter. Damage analysis indicates that fiber debonding, pullout, and particularly fiber fracture seem to contribute to the higher fatigue lifetime noted in coupled composites. The Crack Layer Theory is employed to describe the observed FCP behavior. The effective enthalpy of damage parameterizes the resistance of the composite to FCP in terms of the observed mechanisms.
Crack‐arrest study in mode II Delamination in composites
Authors: Vu‐Khanh T. 
Published: May 2005

AbstractProcedures for measuring the crack initiation and arrest toughnesses in Mode II interlaminar fracture in composite materials were analyzed. Different techniques using flexural specimens were studied. The strain energy release rate,G, which is the energy available for crack propagation was calculated using simple beam theory. The calculation takes into account the transverse shear effect. Stable and unstable fractures are analyzed, and conditions required to measure the arrest toughness of interlaminar fracture are discussed. The methodology was applied to the measurement of fracture energy at the onset and arrest of delamination in glass/epoxy laminate.
Survey of current status and future trends in reinforced plastics composites
Authors: Vu‐Khanh T. 
Published: May 2005

AbstractThe production of reinforced plastics has constantly increased since the Second World War. With a forecast growth rate of 8 to 12 percent annually over the next decade, composites are one of the fastest growing sectors of the plastics industry. Advanced composites will show the largest expansion, due to a strong increase in demands in aerospace and military markets. Penetration of advanced composites into big‐volume markets has not occurred, but it is believed that advances in both materials and machinery will accelerate the mass‐production of these materials. High‐volume composites will see a less rapid growth rate but demands for these materials will continue to increase. Land transportation will remain the largest and will be also the fastest growing market for high‐volume composites. Current status and future trends in the uses of various reinforcing fibers and matrix resins are presented. Hurdles to the expansion of reinforced plastics are also discussed.
Weldline integrity of reinforced plastics: Effect of filler shape
Authors: Fisa B. , Dufour J. , Vu‐Khanh T. 
Published: May 2005

AbstractThe paper is a preliminary report on glass fiber and glass flake orientation in the weldline zone of injection molded reinforced polypropylene. Two types of weldlines were studied using simple shape molds: one where two melt streams meet head‐on and become immobilized, the other where the weldline formation is followed by additional flow. In the weldlines of the first type, which are characteristic of current standard molds used to test weldline strength, the anisometric particles are almost perfectly oriented perpendicular to flow. As a result, the weldlines of this type tend to be weak and brittle. In the second case when the weldline is formed by merging of melt streams separated by an insert, particle orientation in the weldline area remains different from other areas of the sample for long distances from the insert. It is shown that in molds where the weldline formation is followed by laterally expanding flow the change of particle orientation is faster than for unidirectional flow.
The characterization of thermoset cure behavior by differential scanning calorimetry. Part I: Isothermal and Dynamic Study
Authors: Lam Patrick W. K. 
Published: May 2005

AbstractA study of the isothermal cure kinetics of an unsaturated polyester resin by differential scanning calorimetry is described. An autocatalyzed second order kinetic model is adopted to elucidate the cure reaction and also assess the kinetic parameters. The rate constant, the maximum cure rate, the extent of cure, and the degree of conversion at the maximum cure rate, all increase with increasing cure temperature, while the half‐life and the time required to reach the maximum cure rate both decrease. Discrepancies between the experimental results and the predicted values of some of the kinetic parameters, especially at high degrees of conversion, are attributed to the highly different‐controlled cure reaction following the gel point. The activation energy (E) and the pre‐exponential factor (1n A) of the polyester cure reaction were estimated, using differential graphical techniques, to be 131 ± 4 kJ/mol and 39 ± 1 respectively. An ASTM method (E698) produces erroneously low values of the Arrhenius parameters, suggesting that the assumptions of the method may be overly simplified.
Effects of fiber length and orientation distribution on the elastic modulus of short fiber reinforced thermoplastics
Authors: Chin Wei‐Kuo , Liu Hsin‐Tzu , Lee Yu‐Der 
Published: May 2005

AbstractA method including the effects of fiber length and orientation distribution to predict elastic moduli of short fiber reinforced thermplastics (FRTP) is presented. The fiber length distribution in FRTP has an asymmetric character with a tail at the long fiber end. Statistical distribution functions such as Weibull or log‐normal can be used to represent this kind of distribution. Orientation distribution of fibers in FRTP can be characterized by a single parameter exponential function, \documentclass{article}\pagestyle{empty}\begin{document}$F(\theta) = \frac{{1 - \lambda \theta }}{{1 - e^{ - \frac{\P}{2}\lambda } }}$\end{document}. A large λ indicates a highly oriented material whereas small λ represents a quasi‐isotropic material. As fiber length and orientation distribution functions have been characterized, the elastic moduli of FRTP can be predicted. First, the mean elastic moduli of unidirectional plies are predicted through the fiber length distribution. Then the stacking sequence of laminate is assumed to be as the fiber orientation distribution of FRTP, and the overall elastic moduli of FRTP are estimated based on the laminate‐plate method.
Mechanical properties and morphology of polypropylene composites II. Effect of polar components in talc‐filled polypropylene
Authors: Stamhuis J. E. 
Published: May 2005

AbstractUsing the concept of filler coating, a study has been made of the morphology and mechanical properties of polypropylene/talc/elastomer composites with a series of polar components as added elastomers. Both impact strength and stiffness of the blends were better than those of polypropylene homopolymer. Most of the polar components showed a considerable amount of filler coating, as evidenced by morphological studies. However, the impact strength of the composites was generally lower than that of similar blends with non‐polar elastomers, probably owing to (a) the high glass transition temperatures of the polar components, (b) the poor dispersion of some of the elastomeric phases, and (c) a reduced affinity of the elastomers for polypropylene.