bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of water absorption on the behavior of E‐glass fiber/nylon‐6 composites
Authors: Bian X. S. , Ambrosio L. , Kenny J. M. , Nicolais L. , Dibenedetto A. T. 
Published: December 2004

AbstractThe effect of water absorption on the stress transferability across E‐glass fiber/nylon 6 interface has been studied using the embedded single fiber composite technique. The behavior of silane coated fiber and untreated fiber composites after periods of water immersion were compared. The silane coating provided both higher interfacial shear stress transferability and protection from permanent water damage in the interphase region. It was found that water absorption in the nylon matrix reduced the shear stress transferability through plasticization of the matrix, weakening of the interface, and the development of tensile swelling stresses at the phase boundaries. In untreated materials the shear stress transferability was limited by decoupling of the matrix from the broken fiber ends by either interface slippage or local plane strain fracture in the interphase region near the fiber end. In the silane treated materials the shear stress transferability was limited by constrained yielding of the polysiloxane/nylon interphase at the fiber end, thus indicating plasticization of the matrix was the primary factor. After 20 days of water immersion, there was permanent deterioration of stress transferability in the untreated samples, but very little permanent damage in the treated samples.
The interphasial regions in interlayer fiber composites
Authors: Sanadi A. R. , Subramanian R. V. , Manoranjan V. S. 
Published: December 2004

AbstractThe interaction between the fiber and matrix in a fiber‐reinforced material plays an important role in determining the mechanical behavior of the composite. An efficient technique to simultaneously improve fiber‐matrix interfacial shear strength and impact behavior of the composite is to deposit a flexible interlayer onto the fiber. This results in the creation of three bulk phases, the fiber, matrix, and the interlayer and two interphasial regions. A phenomenological model that defines the variation of the fiber‐interlayer interphase and that of the interlayer‐matrix interphase has been developed. In the model, the elastic moduli of these regions vary continuously, so as to bridge the two bulk phases on either side of the interphase. The interaction between the bulk phases is also taken into consideration. The model has the potential for the use of dynamic mechanical analysis to obtain, relatively, adhesion/interaction parameters of different fiber‐interlayer‐matrix systems. These parameters can be used to determine the optimum interlayer thickness for improved toughness and good stress transfer efficiency.
Influence of hot compaction pressure on the interfacial properties in the amorphous metallic ribbon/thermoplastic matrix composite system
Authors: Varin R. A. , Ruutopold A. , Wronski Z. 
Published: December 2004

AbstractThe application of rapidly solidified amorphous metal ribbons as continuous reinforcements for thermoplastic composites is examined. The metallic glass alloy Fe40Ni40B20 (at. percent), with good stiffness, strength, and magnetic properties, was selected as the ribbon alloy. The mechanical properties of the ribbons (elastic modulus and fracture strength) were determined by tensile testing under plane‐stress conditions. The continuous FE40Ni40B20 amorphous ribbons were incorporated as reinforcements into a polypropylene (thermoplastic) matrix. To evaluate the quality of the composites formed, ribbon pullout tests were performed to measure the interfacial ribbon/matrix bond strength. It was noted that increasing the hot compaction pressure during fabrication and the surface texture of the ribbons by etching significantly improved the interfacial shear strength between the ribbon and thermoplastic matrix.
Evaluation of carbon‐fiber‐reinforced thermoplastic matrices in a flat braid process
Authors: Hasselbrack Sally A. , Pederson Christopher L. , Seferis James C. 
Published: December 2004

AbstractAn investigation was conducted to evaluate the effect of blending thermoplastic filament fibers with carbon filament fibers in varying yarn forms to study the efficiency of matrix wetting and infiltration into a laminate. Poly(etheretherketone) (PEEK) and poly(phenylene sulfide) (PPS) were studied in commingled, DREF, and powder form, as a flat triaxial braid. The as‐braided and laminated specimens were both subjected to tensile testing and optical microscopy to establish the efficiency of the impregnation process. It was observed that both thermoplastic matrices commingled with carbon yarn maximized the tensile properties and produced the best quality laminate. To impart the best translational properties of the thermoplastic matrix to the carbon/thermoplastic composite, improvements are necessary in the commingling and powder infiltration processes.
A method to determine resin flow during curing of composite laminates
Authors: Poursartip Anoush , Riahi Golnar , Frederick Laurie , Lin Xie 
Published: December 2004

AbstractAn experimental method is presented to determine the amount of resin flow within a composite laminate during cure. The method is analogous to the use of radioactive tracers in other applications. Heavier elements such as chlorine and bromine, which may be naturally present in small amounts in epoxy resins are used to follow resin flow and mixing. The presence and the quantity of these “tags” is determined using wavelength dispersive X‐ray analysis in a scanning electron microscope. With the resins in this study, it is shown that it is possible to measure volume fractions of resin with accuracies ranging from ±0.5 to ±3 volume %. By using brominated resin in only one layer of a laminate, the degree of flow and mixing can be followed accurately. The results suggest that there is considerable resin mixing as well as flow.
A strain‐based parametric biaxial failure criterion for fiber‐reinforced composites
Authors: Makinde A. , Neale K. W. , Sacharuk Z. 
Published: December 2004

AbstractOrthotropic, fiber‐reinforced composite laminae under biaxial plane stress loading conditions are considered. A new strain‐based strength criterion for such laminae is proposed. This failure criterion, which is cast in parametric form, is completely general. A parametric equation that is expressed as a Fourier series is proposed for describing the failure surface for the laminae. This equation is shown to be valid for most fiber‐reinforced composite laminae through comparisons with experimental data taken from the literature. The advantages of the failure theory are discussed in comparison with the quadratic form of the tensor polynomial theory. Also presented is a biaxial apparatus for testing cruciform specimens under biaxial loading conditions. Efforts under way to characterize composite laminae and laminates under complex stress states are discussed.
Modified Tsai‐Wu failure criterion for fiber‐reinforced composite laminates
Authors: Pang Su‐Seng , Pandian Annamalai , Bradshaw Roger D. 
Published: December 2004

AbstractThe Tsai‐Wu Quadratic Failure Criterion provides satisfactory strength predictions for fiber‐reinforced composite materials but requires five experimental tests to determine the strength parameters. This paper presents two modifications of this criterion, which employ micromechanics to determine these parameters. Experiments on uniaxial and multiaxial vinyl ester/fiberglass composite laminates show that the first modified failure criterion, which is based solely on fiber and resin properties, predicts strength within an average absolute error of 25.4% in comparison to the experimentally determined strength. The addition of a single longitudinal tensile test to the modified expression (second modified failure criterion) reduces the average absolute error to 15.9%. This compares well with the Tsai‐Wu Failure Criterion, which gives an average absolute error of 9.4%. The proposed modified criteria are shown to provide satisfactory failure predictions, while greatly reducing the amount of testing required.
Fiber orientation in simple injection moldings. Part I: Theory and numerical methods
Authors: Bay Randy S. , Tucker Charles L. 
Published: December 2004

AbstractThis paper sets out the theory and numerical methods used to simulate filling and fiber orientation is simple injection moldings (a film‐gated strip and a center‐gated disk). Our simulation applies to these simple geometry problems for the flow of a generalized Newtonian fluid where the velocities can be solved independently of fiber orientation. This simplification is valid when the orientation is so flat that the fibers do not contribute to the gapwise shear stresses. A finite difference solution calculates the temperature and velocity fields along the flow direction and through the thickness of the part, and fiber orientation is then integrated numerically along pathlines. Fiber orientation is three‐dimensional, using a second‐rank tensor representation of the orientation distribution function. The assumptions used to develop the simulation are not valid near the flow front, where the recirculating fountain flow complicates the problem. We present a numerrical scheme that includes the effect of the fountain flow on temperature and fiber orientation near the flow front. The simulation predicts that the orientation will vary through the thickness of the part, causing the molding to appear layered. The outer “skin” layer is predicted only if the effects of the fountain flow and heat transfer are included in the simulation.
Fiber orientation in simple injection moldings. Part II: Experimental results
Authors: Bay Randy S. , Tucker Charles L. 
Published: December 2004

AbstractExperimental measurements of fiber orientation are reported for two parts injection molded from nylon 6/6 reinforced with 43 wt% of glass fibers. The parts are a center‐gated disk and a film‐gated strip. Orientation is measured from polished cross sections and reported as a function of position, both across the thickness and in the flow direction. Both parts have a layered structure, with outer shell layers of flow‐aligned fibers surrounding a central core of either random‐in‐plane (strip) or transversely aligned fibers (disk). The disk also has surface skins with less alignment. The experiments are compared with predictions of the simulation presented in Part I. The simulation predicts the presence, nature, and location of the layers very well. However, it overpredicts the small out‐of‐plane fiber orientation and places the core‐shell transition too close to the midplane. A comparison with selected experimental results suggests that the major source of error is the closure approximation used by the fiber orientation equation. The simulation is exercised for a variety of cases to show the importance of material and process parameters. A polymer matrix with a small power‐law index or a large heat of fusion gives a thicker core and is less likely to have a skin. Injection time is an important parameter, but injection temperature and mold temperature have little effect on fiber orientation.
The meaning of the critical length concept in composites: Study of matrix viscosity and strain rate on the average fiber fragmentation length in short‐fiber polymer composites
Authors: Monette L. , Anderson M. P. , Grest G. S. 
Published: December 2004

AbstractComputer modeling is used in order to provide a theoretical understanding of the concept of critical length in composites, and of the factors influencing the critical aspect ratio. The effects of interphase and matrix properties have been investigated. We have identified the interphase parameters which minimize the critical length. Contrary to the assumption that the critical aspect ratio is related to interfacial shear strength and fiber strength only, we find a significant dependence on matrix viscosity and strain rate, for fixed interphase properties. We therefore conclude that the fragmentation test, which relates the measured critical aspect ratio to a value for the interfacial shear strength, has to be reinterpreted in terms of more parameters than those simply present in the Kelly‐Tyson formalism. Moreover, the significance of the concept of critical length for tailoring mechanical properties of composites needs to be reassessed.
Microstructure of long‐ and short‐fiber reinforced injection molded polyamide
Authors: Toll S. , Andersson P.‐O. 
Published: December 2004

AbstractThe variation of fiber orientation and content within injection molded rectangular plates is investigated. Fiber orientation and volume fraction are measured using metallographic polishing and a newly developed image‐analysis system; fiber weight‐fractions are measured using an ashing method. Three different moldings are studied; two of the long‐fiber compound Verton, Molded at different injection speeds, and one of the short‐fiber compound Maranyl. Microstructural regions are identified and characterized, and the flow mechanisms by which they are formed are discussed. The results show that the long fibers segregate extensively, whereas the short ones do not. The major differences between the two compounds are found in the core: the core of the long‐fiber compound has a higher content and orientation of fibers than that of the short‐fiber compound.
Preform permeability predictions by self‐consistent method and finite element simulation
Authors: Berdichevsky Alexander L. , Cai Zhong 
Published: December 2004

AbstractThe self‐consistent method and finite element simulations have been used to estimate the permeability of an aligned fiber bundle. The self‐consistent method gives out formulas for both longitudinal and transverse permeabilities as functions of the fiber volume fraction. The finite element simulation presents the solutions of various periodic fiber packings. The results for square and hexagonal fiber packings are found coincident with the literature results. It is shown that the permeability is not only related to the fiber volume fraction of porosity, but is also greatly influenced by the packing structure or micro‐level disturbance. A unified empirical model is proposed, which uses as variables ultimate fiber volume fraction in addition to fiber volume fraction. The model predications agree with numerical simulation results in different cases.
Influence of processing and material variables on resin‐fiber interface in liquid composite molding
Authors: Patel N. , Rohatgi V. , Lee L. James 
Published: December 2004

AbstractIn this study, systematic investigation of influence of processing variables on the tensile strength and resin‐fiber interface of composites prepared by liquid composite molding process was carried out. The variables studied included injection pressure and mold/fiber mat temperature. Fibers were better wetted and bonded at lower injection pressure and higher molding temperature, which resulted in a higher tensile strength of molded composites. Single filament composite tests were also used in conjunction with birefringence studies to characterize interface bonding. Improved interfacial behavior was observed in the case of compatible systems.
Rheological behavior of two‐ and three‐phase fiber suspensions
Authors: Shuler Stephen F. , Binding David M. , Byron Pipes R. 
Published: December 2004

AbstractThe rheology of two polyamide 6.6 systems filled with long glass fibers, as well as at of a three‐phase polyamide 6.6‐glass fiber‐gas bubble system, was studied using capillary rheometry, To investigate the influence of fiber concentration, the shear and extensional viscosities were determined for both 30 and 40 vol% fiber filled suspensions as well as for the base polymer. Comparison revealed a modest increase in both the shear and extensional viscosities with increased fiber fraction. The shear viscosities, ηs, of both suspensions are shown to be close to one order of magnitude greater than the base matrix fluid viscosity, η. However, the extensional viscosities, ηE, of the suspensions are determined to be approximately four orders of magnitude greater than the shear viscosity of the matrix fluid for strain rates from 100 s−1 to 102 s−1. The addition of a gas bubble phase to the neat polymer and polymer‐fiber suspensions was accomplished through the decomposition of various percentages of an azodicarbonamide blowing agent. The presence gas bubbles resulted in reduced shear and extensional viscosities for both the neat and fiber‐filled polyamide with greater reductions observed for the neat polyamide. Greater viscosity reductions were observed as the blowing agent centration was increased.
Simultaneous interpenetrating networks for tough matrix composites
Authors: Prakash N. A. , Liu Y. M. , Jang B. Z. , Wang J. B. 
Published: December 2004

AbstractGraphite fiber reinforced epoxy composites normally exhibit low impact strength, poor delamination resistance, and low damage tolerance. Because delamination is a matrix‐dominated failure mode, tougher matrix resins may be utilized to reduce or eliminate the adverse effects of delamination on the structural integrity of fiber composites. The effects of modifying epoxy network morphology by introducing polyurethane in the form of an interpentrating network were studied. The compatibility, toughness, and tensile properties of the matrix as well as the properties of the resultant laminates were evaluated. One of the conclusions arising was that the interpenetrating network morphology results in superior resin and composites toughness with increasing polyurethane content. However, the benefits of increased resin toughness did not necessarily translate into proportionally increased composite owing to the geomertical limitations placed on the plastic deformation zones in laminates.
Mechanical properties of carbon fiber reinforced polyester/urethane hybrid network composites
Authors: Yu J. L. , Liu Y. M. , Jang B. Z. 
Published: December 2004

AbstractHybrid resins of unsaturated polyester/urethane were synthesized and characterized. Both the toughness and stiffness of the polyester were improved significantly by incorporating 20 wt% urethane. Unsaturated polyester, styrene, and ethane showed good compatibility during blending and probably formed a simultaneous interpenetrating network (IPN) during polymerization. The resultant IPN morphology possessed a unique glass transition temperature. This IPN morphology not only imparted great fracture resistance to the otherwise brittle polyester, but also changed the fracture mode of new resin composites. The molecular weight of unsaturated polyesters did not have significant effect on the mechanical properties, but did exert an apparent influence on the fracture mode. During the cure process the side reaction, an amine reaction, could be suppressed addition of suitable promoter and catalyst.
Prediction of fiber orientation in the thickness plane during flow molding of short fiber composites
Authors: Ko Jin , Youn Jae Ryoun 
Published: December 2004

AbstractFiber orientations caused by the flow in the thickness plane during injection molding of short fiber reinforced polymer composites has been simulated. The Lagrangian scheme was employed for the finite element analysis. Flow fields were solved by using a penalty method with Uzawa's scheme and orientation fields were also solved by using the second order orientation tensor. A generalized Newtonian fluid whose rheological behavior is independent of fiber orientation was assumed. Automatic mesh generation using an elliptic grid generator was developed for quadrilateral elements. Mold filling and orientation analyses were performed for a cavity of rectangular cross section. To determine the orientation state in other cross‐sectional geometries, numerical analyses were also performed for two different typical cross sections. As the result, orientation of short fibers in the flow field was analyzed qualitatively and quantitatively. According to the state of short fiber orientation in the thickness plane, the orientation field can be classified into three regions in the flow direction and three layers in the thickness direction. Orientation of short fibers was mainly influenced by elongational and shear flows. It was observed that critical values are present for upper limits of orientation. Effects of initial orientation at the inlet on the orientation field were examined.
The effects of a nucleating agent and of fibers on the crystallization of nylon 66 matrices
Authors: Klein N. , Selivansky D. , Marom G. 
Published: December 2004

AbstractCrystallization from the melt of nylon 66 in the presence of carbon fiber, aramid fiber, or nucleating agent was studied using differential scanning calorimetry (DSC) and hot stage microscopy. The use of the nucleating agent resulted in an increase in crystallization rate and a decrease of induction time under both isothermal and nonisothermal conditions. The fibers were found to behave like a giant nucleating site producing a uniform transcrystalline layer having morphology and crystallization kinetics different from those of the bulk matrix. The influence of the cooling rate on the process of nonisothermal crystallization was analyzed, and the values of activation energy, calculated from the cooling rate—crystallization temperature relationship, appeared to be higher for the nucleated and for the reinforced nylon compared with that of the neat nylon 66. This implied that the presence of fibers or nucleating agent led to the development of a more ordered structure, which required a larger amount of energy for crystallization.
Thermoplastic composites from maleic anhydride modified post‐consumer plastics
Authors: Xanthos M. , Grenci J. , Patel S. H. , Patel A. , Jacob C. , Dey S. , Dagli S. S. 
Published: December 2004

AbstractIn attempts to identify potential applications for refined commingled postconsumer plastics, a feedstock containing about 80% polyethylene (PE) and lesser amounts of poly(ethylene terephthalate) (PET), polystyrene (PS), polypropylene (PP), and poly(vinyl chloride) (PVC) was modified through functionalization with maleic anhydride in a co‐rotating intermeshing twin‐screw extruder. The modified and unmodified blends were compounded with various fillers and reinforcements such as glass fibers, mica flakes, talc, and calcium carbonate. Injection molded composites based on the modified matrix had, in general, superior mechanical and thermal properties. These findings are discussed in view of the improved adhesion resulting from reactions and/or enhanced polar interactions at phase boundaries. Several compounds prepared in this work had overall property data comparable to, or approaching those, of equivalent commercial HDPE molding compounds that are commonly used in “durable” applications.
Dielectric studies of mineral‐filled epoxy
Authors: Wu Shiann‐Long , Tung I‐Chung 
Published: December 2004

AbstractDielectric studies in epoxy and epoxy composites, containing different volume fractions of three different dielectric fillers, have been performed using the impedance bridge method for the high frequency region, 102 to 105 Hz, and the d.c. transient current method for the low frequency region, 10−4 to 10−1 Hz. It has been observed that, in the high frequency region, the dielectric constants of the epoxy composites increased with the addition of the dielectric filler and with the increase of the dielectric constant of the filler. The intensity of the β‐relaxation was reduced for the composites compared to an equal volume of epoxy, owing to the decrease in the concentration of the diester segments in the composites. From the low frequency data, the epoxy and epoxy composites behaved more debye‐like with increasing temperature. Also, the dielectric loss factor increased, but the thermal activation energy value to relaxation decreased two to four times in going from the unfilled to filled materials, which was thought to be attributed to Maxwell‐Wagner buildup of interfacial charges at the epoxy/fillers interfaces.