bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multilayer plug flow modeling of the fast stamping process for a polypropylene/glass fiber composite
Authors: Leterrier Y. , G'Sell C. 
Published: April 2004

AbstractThe isothermal compression at 200°C of a polypropylene/glass fiber composite was investigated in both axisymmetric and unidirectional flows. The overall stress/strain behavior at various compression strain rates was recorded and the induced orientation of the fibers is investigated. It is shown that, in the high speed range, the macroscopic flow process controlled by both the viscous extension and the relative sliding of parallel fibrous layers. The evolution of the compression force is modeled as the sum of a viscous resistance and an interlaminar friction.
Physico‐Chemical and micromechanical analysis of the interface in a poly(phenylene sulfide)/glass fiber composite—a microbond study
Authors: Gonon L. , Momtaz A. , Van Hoyweghen D. , Chabert B. , Gérard J.‐F. , Gaertner R. 
Published: April 2004

AbstractThe glass fiber/PPS composite has excellent thermal and chemical properties. The main disadvantage of the composite is its poor mechanical resistance to impact. To improve this property, the fibers were coated with a new type of sizing. The equired characteristics for this sizing is to create strong interactions between the PPS matrix and the glass fiber surface. The ability of the sizings to improve the glass/PPS adhesion has been assessed by the microbond technique. An inconvenience of this technique is the difficulty in defining a parameter that is characteristic of the interfacial adhesion. The objective of this publication is to demonstrate that a plastic flow of the PPS matrix around the fiber leads to a uniform shear strength. The adhesion between these two materials can therefore be obtained by the mean interfacial shear strength.
Structuring of binary PP/PA‐6 blends and ternary PP/PA‐6/GF blends
Authors: Benderly D. , Siegmann A. , Narkis M. 
Published: April 2004

AbstractMorphological development under shear flow conditions for binary polypropylene (PP)‐polyamide‐6 (PA‐6) and ternary PP‐PA‐6‐glass fiber blends has been investigated. The shear viscosity was determined at several temperatures, and the blend morphology was investigated as a function of shear rate and temperature. Blend morphology perpendicular and parallel to the flow direction was examined to give a complete description of the structuring of the polymer blend during flow. For blends containing a PA‐6 matrix, the glass fiber (GF) and minor PP phase are separately dispersed within the matrix, and the morphological development during flow is similar for binary and ternary blends. However, for blends containing a PP matrix, the GF are mainly encapsulated by the minor PA‐6 phase. This encapsulated morphology reduces the effective amount of PA‐6 dispersed within the matrix, and the development of an “interlayer slip” morphology, typical of PP/PA‐6 blends, is reduced. These differing ternary blend structures have implications for the shear viscosity, and its correspondence to a rule of mixtures prediction. For PA‐6–rich blends, the actual viscosity is lower than the predicted, owing to slippage between the PP dispersed phase and the PA‐6 matrix. However, in PP‐rich ternary blends, the experimental viscosity data matches a modified rule of mixtures prediction. The addition of PA‐6 to a PP/GF system does not increase the amount of “slippage” sites, owing to the encapsulated morphology. Therefore, the shear viscosity is not reduced by PP‐PA‐6 slippage.
Stress distribution around inclusions, interaction, and mechanical properties of particulate‐filled composites
Authors: Pukánszky Béla , Vörös György 
Published: April 2004

AbstractStress analysis was carried out to determine the stress distribution around particles in particulate‐filled composites. The effect of interacting stress fields was also taken into account. At large filler contents, interacting stress fields compensate for the effect of stress concentration. The solutions were introduced into the Von Mises criterion for yielding. The composition dependence of tensile yield stress was determined by using different boundary conditions and averaging techniques. An analytical expression was derived that predicts particle size and adhesion dependence of the yield stress. The analysis shows that large particles and weak interaction lead to debonding. In the case of strong adhesion, the dominating micromechanical deformation process is the shear yielding of the matrix. In such cases, particle size dependence can be explained with the effect of interfacial interactions, which lead to the formation of an interphase. The dominating deformation mechanism is determined by particle characteristics and adhesion of the components. The predictions of the analysis are in good agreement with experimental observations.
A comparison of short glass fiber reinforced polypropylene plates made by conventional injection molding and using shear controlled injection molding
Authors: Hine P. J. , Duckett R. A. , Ward I. M. , Allan P. S. , Bevis M. J. 
Published: April 2004

AbstractThis paper describes a comparison of the fiber orientation structures and resulting elastic properties of samples of short glass fiber filled polypropylene made by conventional injection molding and by the SCORIM (Shear Controlled Orientation in Injection Molding) process developed at The University of Brunel. The 3D fiber orientation distributions of the composites were measured using a unique transputer based image analysis system developed at The University of Leeds. The mechanical properties of the samples were characterized using an ultrasonic velocity technique, which allows a full set of elastic constants to be determined for each material. The link between fiber orientation distributions and measured elastic properties was then investigated using theoretical models developed in this laboratory.
Crack growth and fracture behavior of fabric reinforced polymer composites
Authors: Chellappa V. , Jang B. Z. 
Published: April 2004

AbstractThe objective of this study is to understand and characterize crack deflection and sub‐crack growth in fabric laminate composites. The theory of crack digression based on the Cook‐Gordon mechanism of crack blunting and the criterion developed by Kendall were used to study the crack propagation phenomenon. A simple approach has been developed to evaluate the cohesive and adhesive fracture energies, which play a vital role in the study of strength and toughness of the fabric laminate composites. The effects of strain rate and quasi‐static crack velocity on these energy values were identified. This study explored the possibility of selftoughening in an otherwise brittle composite system. Two competing mechanisms have been identified that control crack propagation in fabric laminate composites.
Consolidation and relaxation behavior of continuous strand random glass mats with thermoplastic binders
Authors: Knight J. C. , Backes D. , Jayaraman K. 
Published: April 2004

AbstractThe consolidation and relaxation characteristics of glass mat reinforcements with a thermoplastic polyester binder have been studied. Attention has been given to the effect of preforming conditions on binder flow around the fibers, and on the rearrangement of fiber tows making up the preform. An instrumented hydraulic press was used to compress stacks of glass mat over a wide range of temperatures (51.7 to 176.7°C) and a range of platen closing speeds (0.02 to 2.00 mm/s). Scanning electron microscopy was used to examine the fiber tows after deformation. Individual fiber tows were observed to flatten during compression, more so at higher temperatures and slower closing speeds. The scanning electron micrographs also reveal changes in binder distribution around the fiber tows that are closely related to the degree of flattening of the fiber tows. This is because small gaps are opened up within the tow as it is flattened. Flow of binder along such gaps is predominantly due to the squeezing force, with only a minor contribution from capillary forces. The redistribution of binder then facilitates further compaction. The extent of binder redistribution is also governed by the binder viscosity, which was found to be a strong function of strain rate and temperature. The shear thinning viscosity of the binder leads to greater compressibility at the highest closing speed of 2 mm/s, although the compressibility of the mats was lower at moderately higher closing speeds. The compressibility was also higher at higher temperatures as expected. The loft was greater for stacks pressed at higher temperatures; this is a consequence of the lower binder viscosity at higher temperatures allowing more rearrangement of the tows. There was no loss of binder from the stacks in these runs.
The use of friction in the shaping of a flat sheet into a hemisphere
Authors: Chu Tun‐Jen , Jiang Kongren , Robertson Richard E. 
Published: April 2004

AbstractAn analysis is given for the use of friction to control the thickness distribution in a hemispherical preform shell. As the friction is changed between a hemispherical punch and an initially flat sheet that is to be formed into a hemispherical shell, the thickness distribution of the resulting shell changes. When the friction is low, the shell tends to be thinner near the pole of the hemisphere than near the equator. As the friction between the sheet and the punch surface increases, the thinning of the shell moves away from the pole toward the equator. The results of the analysis were validated by experiments with a natural rubber sheet that had the deformability necessary to test the predictions of the analysis. The friction distribution necessary to yield a shell of uniform thickness was also derived, and two‐zone and three‐zone combinations of constant friction that yield approximately uniform thickness in the resulting hemispherical shell were also obtained.
Tear resistance of sparsely reinforced elastomer sheets
Authors: Pan Rong , Wati Daniel 
Published: April 2004

AbstractA family of elastomer composites has been developed which has outstanding tear resistance, and good tensile strength and elongation to failure as measured in a standard tensile test. These composites constitute a family in that they all are sparsely reinforced by a fishnet‐like webbing of reinforcement. The members of the family differ in that the reinforcements can be as flexible as soft polyurethane rod or as stiff as carbon fiber with 3000 strands per fiber. All these composites produce outstanding tear strength and an increase in the elongation to failure in an ASTM Die‐C type of tear test. The intersections of the polyurethane rod reinforcements prove to be effective crack arrestors.
PMR‐15/carbon fiber composites produced from powder‐coated towpreg
Authors: Dugger Jeffrey A. , Hirt Douglas E. 
Published: April 2004

AbstractAn addition‐type thermosetting polyimide, PMR‐15, has a relatively high glasstransition temperature, Tg, of approximately 340°C and attractive high‐temperature composite mechanical properties after postcuring. PMR‐15 prepreg is typically produced by pulling carbon fibers through a methanol solution that contains the PMR‐15 monomers. One of the monomers, methylene dianiline, is highly toxic, thereby making the solution‐coating technique undesirable. To alleviate the toxicity problem in the prepregging step, “preimidized” PMR‐15 is now available in powder form, and this material can be used to produce towpreg using a powder‐coating method. The powder‐coating method that has been used in this work involves the use of an aqueous foam as a carrier medium to continuously deposit the PMR‐15 powder onto carbon fibers. The powder is slurried in a surfactant solution into which nitrogen is dispersed using a foam‐generating device. A predetermined amount of this foam is then applied to a moving carbon fiber tow. The foam is collapsed and the powder fused to the fiber in a set of tubular ovens. The powder appeared to be particularly sensitive to the heat treatment, but towpreg was produced and composites were consolidated successfully. The mechanical properties of the composites formed from powder‐coated towpreg compare favorably with the properties of composites fabricated from prepreg that was drum wound from a methanol solution.
Braided thermoplastic composites from powder‐coated towpregs. Part I: Towpreg characterization
Authors: Ramasamy A. , Wang Youjiang , Muzzy John 
Published: April 2004

AbstractTextile preforms offer the potential for producing low cost, complex shaped, advanced composite structures. For thermoplastic composites in particular, it is advantageous to incorporate the resin in the tow prior to textile processing since it is difficult to impregnate dry fabrics with thermoplastic melts. Incorporating resin in the tows tends to alter the properties of the tows that are critical for textile processibility. In this paper, carbon fiber tows coated with nylon powder are studied. They are characterized for flexibility and friction coefficient, which are critical for textile processibility, and for lateral compressibility, which is critical for composite moldability. These studies reveal that the powder coated tows have higher stiffness, friction coefficient, and bulk factor compared to uncoated and commingled tows. The influence of these towpreg properties on their braidability has been studied and is provided in Part II of this series.
Braided thermoplastic composites from powder‐coated towpregs. Part II: Braiding characteristics of towpregs
Authors: Ramasamy A. , Wang Youjiang , Muzzy John 
Published: April 2004

AbstractPowder coated tows have a structure that is significantly different from conventional textile fibrous strands. The properties of carbon fiber tows coated with nylon 6 powder have been characterized in Part I of this series of Papers. In this study, braiding experiments have been carried out with powder coated and commingled tows. An approach has been established to estimate the damage inflicted to the towpregs during the braiding operation using a braiding simulator. Braiding studies reveal that the towpreg properties of flexibility and friction coefficient have significant effects on the braidability of these towpregs. These towpreg properties also have similar effects on the towpreg damage assessed with the braiding simulator. Commingled tow is easier to braid than powder coated tow. Wrapping facilitates braiding both types of tows.
Stamp forming of fabric‐reinforced thermoplastic composites
Authors: Hou M. 
Published: April 2004

AbstractA stamp forming technique has been used to process a fabric woven composite made of glass fibers (GF) and polyetherimide (PEI). A hemispherical mold with a built‐in hold‐down arrangement was designed and used at room temperature to stamp parts from preheated flat preconsolidated laminates. Tensile properties of the material were measured under similar heating conditions as in the relevant stamp‐forming process. Stretch in the fiber direction was found to be smaller than the maximum elastic extension of the glass fibers. Reduction of the angle between the crossing fibers was quite large when the satin woven fabric composite was pulled in the 45° direction. The effect of die geometries and original laminate dimensions on the “shear‐buckling” were studied. The results described the correlations between processing parameters and fiber buckling. Finally, the local strain of fiber bundles was investigated in relation to different directions of fiber orientation.
Thermoplastic nanocomposites filled with wheat straw cellulose whiskers. Part I: Processing and mechanical behavior
Authors: Helbert W. , Cavaillé J. Y. , Dufresne A. 
Published: April 2004

AbstractCellulose microcrystals with dimensions of ∼5 nm × 150–300 nm were obtained from wheat straw. To evaluate the reinforcing effect of these fillers within a thermoplastic matrix, composites with a weight fraction of cellulose ranging from O to 30 wt% were processed by freeze‐drying and molding a mixture of aqueous suspensions of microcrystals and poly(styrene‐co‐butyl acrylate) latex. It was found that these microcrystals, or whiskers, bring a great reinforcing effect at temperatures higher than the glass transition temperature (Tg) of the matrix and improve the thermal stability of the composite. The relaxed modulus increased continuously with the filler content, and for a film containing 30 wt% of whiskers, it was more than a thousand times higher than that of the matrix. This effect is discussed with regard to theoretical calculations based on a mean field approach (Halpin‐Kardos model). It is concluded that the great reinforcement observed seems to be due not only to the geometry and stiffness of the straw cellulose whiskers but also to the interactions of the microcrystals, their topological arrangement, and the probable formation of whisker clusters within the thermoplastic matrix, the cellulose fillers probably being linked through hydrogen bonds.
Dynamic mechanical analysis of a uniaxial continuous carbon fiber‐thermoplastic composite subjected to anodic and cathodic currents
Authors: Pakalapati S. N. R. , Gadala‐Maria F. , White R. E. 
Published: April 2004

AbstractThe dynamic mechanical properties of a uniaxial continuous carbon fiber‐thermoplastic composite were found to degrade significantly when subjected to anodic and cathodic currents in the presence of seawater. The composite tested was made of PAN‐based graphite fibers (50 vol%) in Du Pont's J‐2 thermoplastic resin (nylonbased). The shear storage modulus,G′, and the shear loss modulus,G″, of the composite were measured by subjecting a rod‐shaped sample to small amplitude torsional oscillations. The moduli remained constant over time when the sample was in air and when it was submerged in seawater in the absence of applied currents. Both moduli decreased to ∼45% of their initial values when a constant anodic current of density 0.414 μA/cm2was applied for 2 h. A cathodic current of the same density and duration caused the moduli to decrease to ∼63% of their initial values. The moduli remained at these low levels after the current had been turned off. Inspection, under a scanning electron microscope, of the sample exposed to the anodic current revealed numerous cracks in the polymer matrix. In the sample exposed to the cathodic current, the fibers separated from the matrix of the composite.
Compressibility and flow permeability of two‐dimensional woven reinforcements in the processing of composites
Authors: Lekakou C. , Johari M. A. K. B. , Bader M. G. 
Published: April 2004

AbstractThe processing of composites under pressure is described by a viscoelastic model in which the pressure acts on the fibers in an elastic manner and on the liquid matrix in a viscous manner. Following a micro‐mechanics approach, an analytical model has been derived for the nonlinear elastic compression of two‐dimensional, orthotropic, plain woven fiber cloths, containing two empirical constants. The model is validated by experimental data and the empirical constants determined in the compression of a wet, plain woven, glass fiber reinforcement. The effects of the compression of woven cloths during processing are demonstrated by the change of their permeability.
Fiber reinforced nylon‐6 composites produced by the reaction injection pultrusion process
Authors: Cho Bong‐Gyoo , McCarthy Stephen P. , Fanucci Jerome P. , Nolet Stephen C. 
Published: April 2004

AbstractReaction injection pultrusion (RIP) combines the injection pultrusion process with reaction injection molding (RIM) techniques to yield one of the more novel methods of thermoplastic matrix pultrusion. An experimental set‐up was designed and built to pultrude nylon‐6 RIM material and continuous E‐glassfiber. Well‐impregnated nylon‐6 composites with 66.5, 68.8, 71.1, and 73.3 vol% fiber were produced. Internal temperature profile within the die was recorded during the process, and physical properties of resulting composites were measured. This paper presents results of the effect of fiber content, die temperature profile and pulling speed variations on internal temperature profile, monomer conversion, and physical properties. The study showed that increasing pulling speed lowered both peak temperature and monomer conversion. Higher die temperatures accelerated the reaction, resulting in a higher exotherm, a higher peak temperature, and a higher monomer conversion within the range investigated. Shear strength, flexual strength, flexual modulus, and transverse tensile strength were proportional to monomer conversion. Flexual modulus increased with higher fiber content within the range observed. Data allow the proper combination of die temperature profile and pulling speed to be selected to achieve a desired level of monomer conversion and physical properties. Results of this study provide basic information required for product design with nylon‐6 composites as well as tool design, selection of processing conditions, and quality control for the process.
Photodegradation of talc‐filled polypropylene
Authors: Rabello M. S. , White J. R. 
Published: April 2004

AbstractInjection‐molded talc‐filled polypropylene (PP) composites have been exposed to ultraviolet (UV) radiation in the laboratory for periods up to 26 weeks. The extent of chemical degradation has been assessed by means of Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC), and the results correlated with the mechanical properties. In the early stages of exposure, the photo‐oxidation is faster in the talc‐filled composites than in the unfilled polymer, but this trend is reversed for exposures longer than ∼12 weeks. Scanning electron microscopy (SEM) inspection has revealed that surface cracks caused by photodegradation in the filled PP occur in the surface exposed to the UV source only, resulting in much less deterioration in tensile properties when compared with the unfilled polymer which degrades significantly at the unexposed surface also. Measurements of melting temperatures by differential scanning calorimetry (DSC) gave a consistent picture of degradation with that obtained by FTIR and GPC studies. DSC analyses have also shown that an increase in the melting enthalpy for both the unfilled and filled grades occurs during exposure.
Effect of aging on the compressive yielding of PAN‐based carbon fiber/polycarbonate composites
Authors: Nofal M. M. , Zihlif A. M. , Ragosta G. , Martuscelli E. 
Published: April 2004

AbstractThe compressive yield behavior and the effect of aging in boiling water on the mechanical properties of polycarbonate composites reinforced with PAN‐based carbon fibers were studied at different filler contents and over a range of strain rates. The Young's modulus, yield stress, and yield strain are reported as a function of aging time. Other mechanical parameters such as the activation energy and volume of the yielding process were determined through the Eyring theory. The increase of both Young's modulus and yield stress with aging in boiling water is explained by structural changes. The mechanical properties of the composite were correlated with the morphology and its glass transition temperature.