bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental analysis and simulation of flow through multi‐layer fiber reinforcements in liquid composite molding
Authors: Diallo M. L. , Gauvin R. , Trochu F. 
Published: April 2004

AbstractLiquid composite molding (LCM) is a process in which a reactive fluid is injected into a closed mold cavity with preplaced reinforcement. Combined layers of different permeabilities are often used in LCM, which creates through thickness and inplane porosity and permeability variations. These inhomogeneities may influence the flow front profile in the thickness direction. To investigate the effect of the through thickness inhomogeneities, mold filling experiments were performed using preforms containing layers of two different fiber architectures. Aqueous corn syrup solutions were injected into a tempered glass mold containing the reinforcement stack. The progress of the flow front at various locations within the reinforcement was measured by an electrical conductivity technique based on the insertion of small wires between the reinforcement layers. Experimental data reveal the details of the flow front shape as the fluid penetrates the preform. Using these data, a model is proposed to calculate the overall in‐plane permeability of the preform. Numerical simulations of the flow front progression performed with the computer software RTMFLOT developed in our laboratory are compared to the experimental flow front for various stacking arrangements. Results show good agreement between simulations and experiments and demonstrate the capability of the software to simulate multi‐layer flow process.
Inverse gas chromatography as a tool to characterize ligno‐cellulosic fibers modified for composite applications
Authors: Coupas A.‐C. , Gauthier H. , Gauthier R. 
Published: April 2004

AbstractInverse gas chromatography (IGC) was used to characterize ligno‐cellulosic fiber modified for composite applications. The surface properties of the paper fiber was modified by solution grafting of maleic anhydride functionalized polypropylene (PPgMA): We have investigated the influence of the maleic anhydride content and the chain length of the PPgMA on the surface modifications involved in the solution grafting process. Using IGC at infinite dilution, the evolution of the dispersive component of surface energy with such treatments and the variation of the paper fiber acid/base behavior was determined. The treatment by PPgMA was found to reduce the acidic character of the paper fiber and to enhance its basic character. Moreover, increasing the chain length of the PPgMA resulted in a reduction of both the hydrophilic character of the fiber and its acidic character, while increasing the anhydride content of the PPgMA enhanced the basic character of the fiber. Finally, using IGC at finite concentration, it is observed that reducing the chain length of PPgMA contributes to reducing the specific area of the paper fiber.
The relationship between zeta‐potential and pull‐out shear strength on modified UHMWPE fiber reinforced epoxy composites
Authors: Chiu Hsien‐Tang , Wang Jyh‐Horng 
Published: April 2004

AbstractUHMWPE fiber exhibits high performance, featuring high tensile strength and modulus, because of its extended chain structure. However, this fiber demonstrates some defects, such as low melting point, creep, and poor interfacial bonding with resin. Therefore, it is still not widely applied in composites. This research attempted to improve the performance by applying interfacial treatment to the fiber, using polypyrrole (PPy) synthesized through oxidation. The interfacial shear strength was evaluated using the results of a pull‐out test and a Zeta Potential. The UHMWPE fiber was exposed to PPy treatment at various temperatures. The PPy‐modified fiber was then impregnated with epoxy to generate the composites. The effects of the modification were also examined. The performance of the composites was determined by the Zeta Potentials of the fiber and resin, using an EKA electrokinetic analyzer. The interfacial shear strength was determined by the pull‐out test. The morphology of fiber was observed by SEM. Results show that the shear strength of the interface between the PPy‐treated UHMWPE fiber and epoxy increased 215%. The correlation between the Zeta Potential and the interfacial shear strength was also observed.
Fabrication and mechanical response of commingled GF/PET composites
Authors: Svensson Niklas , Shishoo Roshan , Gilchrist Michael 
Published: April 2004

AbstractThe mechanical properties and the response to mechanical load of continuous glass fiber reinforced polyethylene terephthalate (GF/PET) laminates have been characterized. The laminates were manufactured by compression molding stacks of novel woven and warp knitted fabrics produced from commingled yarns. The laminate quality was examined by means of optical and scanning electron microscopy. Few voids were found and the laminate quality was good. Resin pockets occurred in the woven laminates, originating from the architecture of the woven fabric. The strength of the fiber/matrix interface was poor. Some problems were encountered while manufacturing the laminates. These led to fiber misalignment and consequently resulted in tensile mechanical properties that were slightly lower than expected. Flexural failures all initiated as a result of compression, and it is possible that the compression strength of the matrix material, rather than its tensile strength, might limit the ultimate mechanical performance of the composites. Flexural failures for both materials were very gradual. The warp knitted laminates were stronger and stiffer than the woven laminates. The impact behavior was also investigated; the woven laminates exhibited superior damage tolerance compared with the warp knitted laminates.
Forming limit measurements for random‐fiber mats
Authors: Dessenberger Richard B. , Tucker Charles L. 
Published: April 2004

AbstractIn resin transfer molding, the fabrication of the fiber preform is critical to both part quality and production efficiency. The deformation induced by preforming introduces porosity and permeability variations, which affect mold filling, and may result in defects (tears and wrinkles) in the preform. In this study we develop an experimental method for determining the formability of thermoformable random‐fiber mats, and provide a mathematical framework for expressing the results. We characterize formability of random‐fiber mats using a forming limit diagram, similar to the diagrams used for sheet metal. This diagram maps the combinations of principal stretch ratios λ1 and λ2 that cause the material to fail. The maximum load during constant‐rate extension provides the failure criterion in forming limit tests. The experiments combine uniaxial and constrained tests. The uniaxial tests reveal behavior when the sample is free to contract in the lateral direction, and also help determine the strains that cause wrinkling in the sheet. The constrained tests give data when lateral contraction is prohibited. Biaxial data is acquired by conducting a sequence of two constrained tests on a single sample, rotating the sample by 90° between the tests. Forming limit data is presented for CertainTeed's U750 thermoformable random‐fiber mat. The results are expressed mathematically in a formability function W (λ1, λ2), in which the forming limits are incorporated through a quadratic penalty function. This type of data can be used in an ideal forming theory to determine the feasibility of forming any given shape from a random‐fiber mat.
Thermoplastic composites reinforced with long fiber thermotropic liquid crystalline polymers for fused deposition modeling
Authors: Gray R. W. , Baird D. G. , Bøhn J. H. 
Published: April 2004

AbstractThis work is concerned with preliminary studies on developing thermoplastic composites for use in fused deposition modeling (FDM). Polypropylene (PP) strands reinforced with thermotropic liquid crystalline polymer (TLCP) fibrils were generated in a novel dual extruder process. The process allowed the reinforcement of PP with a melting point (Tm) of 165°C with continuous fibrils of a high melting (283°C) TLCP (Vectra A950). The strands were then re‐extruded in a capillary rheometer forming monofilaments to simulate piston actuated FDM. The effects of the thermal and deformation histories on the mechanical properties of the re‐extruded strands were evaluated. It was found that tensile properties of the strands improved with draw ratio and that the maximum modulus of the composite strands was similar to that predicted by composite theory. Strands were consolidated uniaxially via compression molding at temperatures just above the melting point of the matrix to determine the effect of thermal history. This resulted in a ∼20% reduction in tensile modulus relative to the modulus of the strands. Monofilaments were extruded from a capillary rheometer in which long fiber strands were used as feedstock to study the effects of deformation history on the tensile properties. It was found that the tensile properties of the monofilaments were dependent on capillary diameter, capillary L/D, and apparent shear rate due to fibril alignment.
Physical and numerical modeling of mold filling in resin transfer molding
Authors: Golestanian Hossein , El‐Gizawy A. Sherif 
Published: April 2004

AbstractFinite element modeling and experimental investigation of mold filling in resin transfer molding (RTM) have been performed. Flow experiments in the molds were performed to investigate resin flow behavior into molds of rectangular and irregular shapes. Silicone fluids with viscosity of 50 and 100 centistoke as well as EPON 826 epoxy resin were used in the mold filling experiments. The reinforcements consisted of several layers of woven fiberglass and carbon fiber mats. The effects of injection pressure, fluid viscosity, type of reinforcement, and mold geometry on mold filling times were investigated. Fiber mat permeability was determined experimentally for the five‐harness and eight‐harness woven mats. Resin flow through fiber mats was modeled as flow through porous media. Pressure distributions inside both types of molds were also determined numerically. In the case of resin flow into rectangular molds, numerical results agreed well with experimental measurements. Comparison between the experimental and numerical results of the resin front position indicated the importance of edge effects in resin flow behavior in small cavities with larger boundary areas. Reducing the resistance to resin flow at the edge region in the numerical model allowed for good agreement between the numerical simulation and the physical observations of the resin front position and mold filling time.
Effects of time and temperature on the tension‐tension fatigue behavior of short fiber reinforced polyamides
Authors: Jia Nanying , Kagan Val A. 
Published: April 2004

AbstractTo support the fatigue design of the cyclically stressed plastics parts, such as automotive under‐the‐hood and exterior components, we analyzed the short‐term and long‐term mechanical performance (tensile strength, fatigue strength, and fatigue life) of short glass fiber reinforced polyamides PA 6 and PA 66. Comprehensive tension‐tension fatigue tests were conducted with reference to the latest ASTM, ISO, and Japanese industrial standards for plastics, at temperatures from −40°C to 121°C, on materials aged at 121°C for 0, 100, 500, and 1000 h. Tests were conducted at a loading frequency f = 5 Hz, stress ratio R = 0.1, and in a wide range of cycles to failure from 2 × 103 to 2 × 106. Without aging and for both PA 6 and PA 66, the highest fatigue strength or fatigue life was found at −40°C; it decreased significantly at 23°C, and decreased further at 121°C. The fatigue strength of PA 6 was found to be higher than that of PA 66 at −40°C, but the reverse was seen at 23°C. At 121°C, the fatigue strengths of PA 6 and PA 66 were virtually the same. Aging at 121°C improved the tensile strength of PA 6 and PA 66 as aging time increased from 100 to 1000 h, and this process seemed to be more influential for PA 6.
Modeling and rheology of HTPB based composite solid propellants
Authors: Erişken Cevat , Göçmez Ahmet , Yilmazer Ülkü , Pekel Fikret , Özkar Saim 
Published: April 2004

AbstractThe propellant with the minimum viscosity required for a defect‐free casting can be obtained by proper selection of the size and fractions of solid components leading to maximum packing density. Furnas' model was used to predict the particulate composition for the maximum packing density. Components with certain size dispersions were combined to yield a size distribution that is closest to the optimum one given by Furnas for maximum packing. The closeness of the calculated size distribution to the optimum one was tested by using the least square technique. The results obtained were experimentally confirmed by viscosity measurement of uncured propellants having HTPB binder and trimodal solid part accordingly prepared by using aluminum (volumetric mean particle diameter of 10.4 μm) and ammonium perchlorate with four different sizes (volumetric mean particle diameters: 9.22, 31.4, 171, and 323 μm). The experimental measurements showed that the compositions for the minimum viscosity are in good agreement with those predicted by using the model for maximum packing. The propellant consisting of particles with mean diameters of 10.4, 31.4, and 323 μm was found to yield the minimum viscosity. This minimum viscosity was observed when the fraction of the sizes with respect to total solids was 0.141, 0.300, and 0.559, respectively.
Mechanical characterization of triaxially braided hybrid composites
Authors: Savino Vincenzo , Chou Tsu‐Wei 
Published: April 2004

AbstractThe use of advanced composites has been expanded to the oil and gas industry. One of the newly developed technologies is in composite coiled tubing that offers the potential of exceeding the performance of metallic tubings. The high strains due to bending and the complex state of stress in these tubes necessitate the better understanding of the correlation between fiber architecture and tube performance. Braided composites can withstand high bending deformation without severe degradation of properties. In this study, braided hybrid composites are presented as an option for achieving high performance coiled tubing under tensile and flexural loads. The effects of material and fabric microstructural parameters on the mechanical behavior of braided hybrid composites are studied. The mechanical characterization of triaxially braided composites has identified the influence of the mechanical properties of the axial yarn, the axial yarn volume fraction, and the braid angle. Overall, this study provides a sound knowledge base for the design, fabrication, and characterization of triaxially braided composites for coiled tubing applications in the petroleum industry.
Practical use of the statistically modified laminate model for injection moldings. Part 1: Method and verification
Authors: Saito Makoto , Kukula Stefan , Kataoka Yasuto 
Published: April 2004

AbstractThe fibers in injection molded FRP provide the material's strength and stiffness; however, they also supply many of the problems. Preferential orientation of fibers during molding can reduce strength and stiffness below expected values in critical directions, or induce warpage in thin walled sections. Makers of short fiber reinforced injection molded products typically use computer aided engineering packages to optimize product performance and manufacturing variables. However, the reliability of the fiber orientation simulation can be limited, and the method is not easily understood, making an assessment of accuracy for a given situation difficult. In addition, the structural module of flow analysis packages is often a basic package with many features missing. This paper presents a structural analysis system for injection molded parts made of short fiber reinforced plastics. A full‐featured commercial structural analysis code is interfaced with a flow analysis program using a practical material model that takes into account the effects of local fiber orientation. The system is completely open to the user, and can be modified as required.
Sliding mode interlaminar fracture toughness of interply hybrid composite materials
Authors: Hwang Shun‐Fa , Huang Chih‐Ching 
Published: April 2004

AbstractTo measure the sliding mode interlaminar fracture toughness of interply hybrid composites, end notched flexure (ENF) specimens with three different types of stacking sequence have been utilized. Finite element analysis is applied to separate the contribution from different modes on the strain energy release rate. In addition, the methods of beam theory, compliance, and compliance calibration to calculate the GC values are compared. The effects of interface friction, crack length, and specimen width are also discussed. The results show that the crack growth in the three types of specimens is dominated by the sliding mode and the Mode II interlaminar fracture toughness can be approximated. The compliance method is not recommended for hybrid ENF specimens and the effects of interface friction can be neglected. To get rid of the edge effect, the specimen width must be carefully chosen, while the fracture toughness does increase with the initial crack length.
Flow channels/fiber impregnation studies for the process modeling/analysis of complex engineering structures manufactured by resin transfer molding
Authors: Mohan R. V. , Shires D. R. , Tamma K. K. , Ngo N. D. 
Published: April 2004

AbstractThe success of resin transfer molding (RTM) depends upon the complete wetting of the fiber preform. Effective mold designs and process modifications facilitating the improved impregnation of the preform have direct impact on the successful manufacturing of parts. Race tracking caused by variations in permeabilities around bends, corners in liquid composite molding (LCM) processes such as RTM have been traditionally considered undesirable, while related processes such as vacuum assisted RTM (VARTM) and injection molding have employed flow channels to improve the resin distribution. In this paper, studies on the effect of flow channels are explored for RTM through process simulation studies involving flow analysis of resin, when channels are involved. The flow in channels has been modeled and characterized based on equivalent permeabilities. The flow in the channels is taken to be Darcian as in the fiber preform, and process modeling and simulation tools for RTM have been employed to study the flow and pressure behavior when channels are involved. Simulation studies based on a flat plate indicated that the pressures in the mold are reduced with channels, and have been compared with experimental results and equivalent permeability models. Experimental comparisons validate the reduction in pressures with channels and validate the use of equivalent permeability models. Numerical simulation studies show the positive effect of the channels to improve flow impregnation and reduce the mold pressures. Studies also include geometrically complex parts to demonstrate the positive advantages of flow channels in RTM.
Compaction of textile reinforcements for composites manufacturing. II: Compaction and relaxation of dry and H2O‐saturated woven reinforcements
Authors: Robitaille François , Gauvin Raymond 
Published: April 2004

AbstractPrevious analysis of published experimental results on compaction and relaxation of textile reinforcements allowed the effects of some processing parameters on the mechanical behavior of the reinforcements to be identified. However, a limited number of relaxation results are available; also, the effect of some parameters on compaction received limited attention, and the behavior observed with fluid‐saturated reinforcements has not been investigated. In this paper, the results of a structured experimental program of compaction and relaxation performed on three woven reinforcements are reported. In half the trials, a relaxation period was imposed on the samples. In the other half, samples saturated with distilled H2O were compacted. The selection of the processing parameters was found to be as important as the selection of the reinforcement itself for the definition of a manufacturing operation. The processing parameters governing the compaction and relaxation were seen not to be the same, and the fiber reorganization that occurs during the compaction phase was found to have a different effect on successive compaction cycles than the reorganization occurring during the relaxation.
Polymerization of styrene‐isoprene on glass cloth for use in composite manufacture
Authors: Grady Brian P. , O'Rear Edgar A. , Penn Lynn S. , Pedicini Angelo 
Published: April 2004

AbstractThe evaluation of a new process for promoting the adhesion of thermosetting resins to a reinforcing fiber is described. In this process, termed admicellar polymerization, monomers are polymerized inside a surfactant bilayer adsorbed on a surface. Admicellar polymerization is essentially a surface analogue of emulsion polymerization. This technique can place a variety of polymers at the surface of the reinforcing agent, so that the interfacial layer can be tailored at will. In this study, a styrene‐isoprene copolymer was polymerized on the surface of glass mats. Epoxy‐matrix composites made with untreated cloth, silane‐treated cloth, and admicellar‐treated cloth were evaluated via three‐point bend tests and single filament pull‐out tests. The epoxy‐matrix composites made from admicellar‐treated and silane‐treated cloth gave significantly higher strengths in three‐point bend tests than composites made from untreated cloth. Single filament pull‐out tests, which measure fiber‐matrix adhesion directly, and scanning electron micrographs of the failure interface gave results consistent with three‐point bend tests. This paper indicates that admicellar polymerization deserves further study as an alternative to silane coupling agents in structural composites.
Effect of fiber architecture on permeability in liquid composite molding
Authors: Shih Chih‐Hsin , Lee L. James 
Published: April 2004

AbstractThis study investigates the effect of fiber architecture on the permeability in liquid composite molding. The in‐plane permeabilities of several glass fiber mats with different architectures were measured. A conceptual model based on the observed micro‐scale flow pattern is proposed to explain the measured permeability results. It is found that the size of the pores outside the fiber tows and how these pores are connected determine the permeability of a fiber reinforcement.
Evaluation of dynamic mechanical properties of unidirectional composites in relation to their morphology
Authors: Gauthier C. , Khavandi A. , Franciosi P. , Perez J. , Gaertner R. 
Published: April 2004

AbstractWe were interested in the dynamic mechanical behavior of unidirectional composites from E‐glass fibers and an epoxy matrix with several glass fiber contents ranging from 43% to 68%. A method is proposed for the determination of the viscoelastic response of such reinforced material, based on successive applications of the three‐phase self‐consistent analysis proposed by Christensen and Lo. When we apply this model in consecutive steps, we can take into account some morphological features including nonuniform arrangement of the fibers in the transverse plane with clustering or connecting arrangements as well as particular strengthening effects of the polymer in the interphase.