bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of resin transfer/compression molding process
Authors: Kang Moon Koo , Il Lee Woo 
Published: April 2004

AbstractResin transfer/compression molding (RT/CM) is a two‐step process in which resin injection is followed by mold closing. This process can enhance the resin flow speed and the fiber volume fraction, as well as reducing the mold filling time. In this study, a simulation program for the mold filling process during RT/CM was developed using the modified control volume finite element method (CVFEM) along with the fixed grid method. The developed numerical code can predict the resin flow, temperature, pressure, and degree of cure distribution during RT/CM. The compression force required for squeezing the impregnated preform can also be calculated. Experiments were performed for a complicated three‐dimensional shell to verify the feasibility of the RT/CM process and the numerical scheme. The compression force and the compression speed were measured. A close agreement was found between the experimental data and the numerical results. The resin front location obtained from a short shot experiment was compared with the numerical prediction. Again, a close agreement was observed. In order to demonstrate the effectiveness of the numerical code, simulations were performed for more complicated process conditions with anisotropic permeability of the preform at higher fiber volume fractions.
Effect of interfacial modification on metal fiber filled polypropylene composites and property balance
Authors: Tan Song‐ting , Zhang Ming‐qiu , Rong Min‐zhi , Zeng Han‐min 
Published: April 2004

AbstractMechanical properties and electrical conductivity of discontinuous stainless steel fiber (SSF) filled polypropylene (PP) composites were considered as candidates for shielding electromagnetic interference (EMI) applications. In order to improve the unsatisfied impact resistance, surface treatments of SSF and modified PP were introduced. By means of a microdroplet pull‐out test, polypropylene grafted maleic anhydride copolymer (PP‐g‐MAH) was found to be able to enhance the poor interfacial adhesion between fiber and matrix. On this basis, PP‐g‐MAH was used to prepare conventional composites, and the macromechanical measurements showed evidence that PP‐g‐MAH helped increase both flexural and impact strength of the composites. However, the good affinity of PP‐g‐MAH for SSF reduced composite conductivity accordingly. Finally, blends of PP and PP‐g‐MAH proved to be a solution for the problem, i.e., the impact strength was increased significantly while acceptable electrical resistivity was maintained.
Simulation of compression resin transfer molding to manufacture thin composite shells
Authors: Pham Xuan‐tan , Trochu François 
Published: April 2004

AbstractThe resin flow through fiber reinforcements in Compression Resin Transfer Molding (CRTM) has been modeled by Pham et al. (1). First the preform is partially filled by resin during the injection phase. Then it is compressed by the mobile part of the mold. The resin flow in the fiber bed is governed by Darcy's law. The consolidation of the saturated preform is described by the total mass conservation. A mathematical model is developed for thin curved composite parts. A filling algorithm based on resin conservation on a deformable grid is used to advance the flow front at each time step. Resin pressure and velocity are calculated by the finite element method. Several control parameters of the CRTM process are investigated in this study, such as the compaction speed of the mold upper wall, the injection pressure and the closing/opening of the injection gate. The numerical model allows the calculation of pressure distribution in the mold, which is compared with analytical solutions and experimental results.
Microstructures of 3‐D carbon/carbon composites using solid rods as reinforcements
Authors: Kuo Wen‐shyong , Ko Tse‐hao , Chi Yuan‐chen 
Published: April 2004

AbstractThis paper examines microstructures of 3‐D woven carbon/carbon composites. Unidirectional carbon/phenolic rods, with 1 mm in diameter, were made by the pultrusion technique and then combined into 3‐D preforms in the axial direction. The preforms were of three‐axis orthogonal structures based on 3‐D weaving. A special weaving setup to incorporate the rods has been developed, and three types of preforms with varying the weaving yarn sizes have been made. Another conventional type composed of carbon yarns in all axes was also made for purpose of comparison. The geometrical aspects of both types of preforms have been studied. Using the rods was found to effectively eliminate fiber crimp in the axial direction. The fabrication of the carbon/carbon composites has been carried out based on multiple impregnation and carbonization of the phenolic resin. Open and close pores of the materials have been measured after each densification process. The variations in open and close pores differ greatly in response to the densification process. The induced matrix cracks due to pyrolysis shrinkage have been examined based on microscopic observations. Dictated by the preform types, matrix cracks were regularly developed in the weaving yarns. While a dominant transverse crack was formed in each of the yarns, small pores were extensively created in the rods. Separation of bundle interfaces was also observed. Formation of these cracks in relation to processing and microstructures is discussed in detail.
Low moisture absorptive epoxy formulations for Gr/Ep laminates
Authors: Lin King‐fu , Yeh Ren‐jie 
Published: April 2004

AbstractThe incorporation of 2‐undecyl‐imidazole (C11Z) and chromium acetylacetonate (Cr(acac)3) additives into N, N, N′, N′‐tetraglycidyl diaminodiphenylmethane (TGDDM)/diaminodiphenylsulfone (DDS) epoxy formulations was found to significantly decrease the moisture absorption of their prepared graphite/epoxy laminates. However, the same additions did not much affect the moisture absorption of the cured TGDDM/DDS neat resins. Thus, the former case was attributed to the processing effects in view of the fact that C11Z pre‐reacting with TGDDM during lay‐up process produced the ether‐linkage polymer chains in the epoxy networks and raised the viscosity. The following compacting stage of laminates was believed to squeeze the small molecules such as unreacted TGDDM, DDS and Cr(acac)3, toward the surface of carbon fibers and increase the chance of Cr(acac)3 to block the hydroxyl groups in the epoxy networks produced by the reactions between TGDDM and DDS. Some evidence was provided to support the above hypothesis in this study.
Three‐dimensional simulations of the curing step in the resin transfer molding process
Authors: Choi Mi Ae , Lee Mi Hye , Chang Jaeeon , Lee Seung Jong 
Published: April 2004

AbstractThe curing step in resin transfer molding process involves heat transfer coupled with the curing reaction of thermoset resin. In order to examine the curing behavior under a specified cure cycle in the resin transfer molding process, numerical simulations are carried out by three‐dimensional finite elements method. An experimental study for isothermal cure kinetics of epoxy resin is conducted by using differential scanning calorimetry. Kinetic parameters based on the modified Kamal model are determined from the calorimetric data for the epoxy system, and by using these parameters, numerical simulations are performed for a hat‐shaped mold. It is found from the simulation results that the temperature profile and the degree of cure are well predicted for the region inside the mold. This numerical study can provide a systematic tool in the curing process to find an optimum cure cycle and a uniform distribution of the degree of cure.
A numerical model of the viscosity of an epoxy prepreg resin system
Authors: Theriault R. P. , Osswald T. A. , Castro J. M. 
Published: April 2004

AbstractThe development of the viscosity of a thermoset material during processing is complicated because of the dependence of the initial material state and the kinetic rate of conversion from a liquid to a solid material. Uncured thermoset materials typically have a low enough viscosity such that the consumption of energy to generate flow is relatively low. However, as the curing process advances, the flow mechanisms become hindered by the development of a network gel during crosslinking. Once the resin has reached the appropriate degree of cure for gelation, the resin system is incapable of large fluid‐like deformations. In this research, the rheological properties of an epoxy resin system used in laminate processing were measured and numerically fit with a modification to the dual Arrhenius model to predict the progression of the viscosity during cure. The numerical results were compared with the experimental measurements, and it was found that the model predicts the experimental observations quite well. It was found that the initial degree of cure of the prepreg is not as significant a factor as the temperature rate dependence on the processing time between the point of flow onset and gelation. However, the minimum viscosity during processing is strongly influenced by the initial degree of cure of the prepreg system.
A study of the thermomechanical properties of carbon fiber‐polypropylene composites
Authors: Van Hattum F. W. J. , Bernardo C. A. , Finegan J. C. , Tibbetts G. G. , Alig R. L. , Lake M. L. 
Published: April 2004

AbstractShort fiber composites were produced using polypropylene as matrix and polyacrylonitrile (PAN)‐based fibers or vapor grown carbon fibers (VGCF) as reinforcement. The strength, stiffness, and coefficient of thermal expansion (CTE) of the composites were measured. The VGCF‐composites showed strength and CTE that are competitive with those of “conventional” PAN‐fiber composites, but the stiffness was marginally lower. Micromechanical modeling of the PAN composite properties gives results consistent with the measurements. The models can be used to infer the apparent VGCF‐properties from their composites.
A study on the determination of in‐plane permeability of fiber preforms
Authors: Um Moon‐kwang , Lee Sang‐kwan 
Published: April 2004

AbstractOne of the parameters most frequently used in modeling and designing the mold filling process is the permeability of fibrous preforms. To obtain radial propagation of a viscous polymer into a homogeneous orthotropic porous medium, an approximate solution is derived and its results are compared with numerical ones obtained from boundary element method (BEM). A simple and direct procedure incorporating approximate solution with experimental data has been proposed to determine the principal in‐plane permeabilities of the reinforcements. A scheme is also suggested in order to increase the accuracy in the determination of degree of anisotropy. The effect of resin injection type on permeability is investigated through the experiments.
The effect of interface characteristics on the morphology, rheology and thermal behavior of three‐component polymer alloys
Authors: Fisher I. , Siegmann A. , Narkis M. 
Published: April 2004

AbstractImmiscible polymer blends are interesting multiphase host systems for fillers. Such systems exhibit, within a certain composition limits, either a separate dispersion of the two minor phases or a dispersion of encapsulated filler particles within the minor polymer phase. Both thermodynamic (e.g. interfacial tension) and kinetic (e.g. relative viscosity) considerations determine the morphology developed during the blending process.The effect of interfacial characteristics on the structure‐property relationships of ternary polymer alloys and blends comprising polypropylene (PP), ethylene‐vinyl alcohol copolymer (EVOH) and glass beads (GB), or fibers (GF), was investigated. The system studied was based on a binary PP/EVOH immiscible blend, representing a blend of a semi‐crystalline apolar polymer with a semicrystalline highly polar copolymer. Modification of the interfacial properties was obtained through using silane coupling agents for the EVOH/glass interface and compatibilization using a maleic anhydride grafted PP (MA‐g‐PP) for the PP/EVOH interface. The compatibilizer was added in a procedure aimed to preserves the encapsulated EVOH/glass structure. Blends were prepared by melt extrusion compounding and specimens by injection molding. The morphology was characterized using scanning electron microscopy (SEM) and high resolution SEM (HRSEM), the shear viscosity by capillary rheometry and the thermal behavior using differential scanning calorimetry (DSC).The system studied consisted of filler particles encapsulated by EVOH, with some of the minor EVOH component separately dispersed within the PP matrix. Modification of the interfaces resulted in unique morphologies. The aminosilane glass surface treatment enhanced the encapsulation in the ternary [PP/EVOH]GB blends, resulting in an encapsulated morphology with no separtely dispersed EVOH particles. The addition of a MA‐g‐PP compatibilizer preserves the encapsulated morphology in the ternary blends with some finely dispersed EVOH particles and enhanced PP/EVOH interphase interactions.The viscosity of the binary and ternary blends was closely related to the blend's morphology and the level of shear rate. The treated glass surfaces showed increased viscosity compared to the cleaned glass surfaces in both GB and GF containing ternary blends.Both EVOH and glass serve as nucleating agents for the PP matrix, affecting its crystallization process but not its crystalline structure. The aminosilane glass surface treatment completely inhibited the EVOH crystallization process in the ternary blend.In summary, the structure of the multicomponent blends studied has a significant effect on their behavior as depicted by the rheological and thermal behavior. The structure‐performance relationships in the three‐component blends can be controlled and varied.
Production of leather‐like composites using chemically modified short leather fibers. I: Chemical modification by emulsion polymerization
Authors: Madera‐Santana T. J. , Aguilar‐Vega M. J. , Márquez‐Lucero Alfredo , Vázquez‐Moreno F. 
Published: April 2004

AbstractIn order to evaluate the possible use of short leather fibers to produce leather‐like composites, five kilograms of fibers (extracted from leather wastes) were modified by in situ emulsion polymerization of methyl methacrylate (MMA). This treatment was performed in order to increase the compatibility of leather fibers with several commodity polymers used in the shoe and furrier industries. The chemical modification was carried out by aqueous emulsion polymerization initiated by a redox system (potassium persulfate and sodium metabisulfite). The effects of the monomer and redox initiator content as well as the reaction temperature were evaluated. The modified short leather fibers were characterized by instrumental techniques such as Infrared Spectroscopy (IR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), X‐ray Diffraction and Scanning Electronic Microscopy (SEM). The results show that the polymer is formed on the exterior of fibers (deposited fraction) as well as in the interior (by grafting or forming interpenetrated networks). The treatment significantly improves the thermal stability of fibers. It also reduces their water adsorption capacity, as a coating of PMMA is produced over the leather surface, as microscopic analysis has revealed. The last characteristic could be an advantage in certain applications.
Factors influencing viscoelastic properties of a poly (butylene terephthalate) reinforced with short glass fibers
Authors: Beaudoin O. , Bergeret A. , Quantin J. C. , Crespy A. 
Published: April 2004

AbstractShort glass fiber/poly(butylene terephthalate) composites with different glass fiber treatments were characterized within a temperature range from −150°C to + 150°C by dynamic tests in torsion and tensile modes. Untreated fibers or fibers coated by silane coupling agents associated or not with sticking agents were used. It was observed that the magnitude of β and α relaxations depends strongly on the microstructural parameters of such composites: fiber content, degree of crystallinity of the matrix, fiber length distribution, level of adhesion.
Interfacial strength of PTFE fiber/i‐PP composites with transcrystalline layers of different thickness
Authors: Wang Chi , Chen C.‐C. 
Published: April 2004

AbstractTranscrystallization of isotactic polypropylene (i‐PP) on the surface of polyte‐trafluroethylene (PTFE) fibers was investigated. Using the single‐fiber pull‐out test, the effect of the transcrystalline layers (TCLs) on the adhesive fracture energy was studied as well. To induce TCL with different thickness, two‐step crystallization of i‐PP was carried out; the PTFE/i‐PP composites were first crystallized at 140°C for a specified time and were subsequently quenched in 25°C water to conclude the crystallization. Specimens with TCL thickness of 45 ± 6 and 126 ± 15 μm were thus prepared for crystallization time of 1 and 3 hrs, respectively. In addition, the bulk portion surrounding the TCL showed a transparent appearance that indicated crystallization of i‐PP spherulites was much limited. In spite of the difference in the crystallization time, it is suggested that the mechanical properties of the individual constituents in the matrix (TCL and spherulites) prepared in this way remain unchanged, leaving the TCL thickness alone as the major controlling factor. Pull‐out results show that adhesive fracture energy is independent of the TCL thickness and the measured value is 3.0 ± 1.5 J/m2 in spite of the large variation in the TCL thickness. Compared to specimens without TCL whose adhesive fracture energy is 2.1 ± 1.1 J/m2, promotion of the adhesion level seems much limited, if any, through the presence of TCL and its thickness. However, the friction stress at the debonded PTFE fiber/i‐PP TCL is increased when TCL are produced at high crystallization temperatures. Toughness of composites with TCL can be enhanced in this manner although the neat adhesive fracture energy remains intact.
Analysis of void removal in liquid composite molding using microflow models
Authors: Shih Chih‐Hsin , Lee L. James 
Published: April 2004

AbstractVoid removal in liquid composite molding was studied. Two void removal mechanisms were observed during flow visualization. Owing to the complicated geometry in the fiber reinforcement, micron‐sized flow channels were fabricated in order to carry out quantitative analysis. The mobility of voids in both straight and constricted channels was investigated. It was found that the mobility of the bubble is related to both the bubble size and the wetting between the fluid and the solid surface (i.e. contact angle). A snap‐off effect of the gas bubble was observed when the bubble passed through the constricted channel. The snap‐off time was found to be a function of constriction geometry and the capillary number.
Metal particle modification of composite matrices for customized density applications
Authors: Gilbert Eric N. , Hayes Brian S. , Seferis James C. 
Published: April 2004

AbstractA key aspect of composite technology lies in the ability to design a part to a specific strength and thickness. Recently, new applications were identified where it was desirable to vary the density in specific areas of a part. In this work, a model prepreg system was modified with fine metal and thermoplastic particles for specific weight tailoring. These particles were placed on the prepreg surface, forming a partially interlayer modified composite when laid up and cured. Experiments were performed on the specific gravity and fracture toughness of laminates made from the prepregs. The results showed that it is possible to tailor the density of a composite system without changing the manufacturing process or fracture toughness requirements.
Hygrothermal cycling effects on the durability of phenolic based composites
Authors: Chung Kimo , Yoshioka Kenichi , Seferis James C. 
Published: April 2004

AbstractWork has been performed to investigate the thermal and mechanical properties of carbon fiber/phenolic resin composites as engineering materials for the aerospace industry. These materials are cost effective while displaying excellent temperature and fire resistance as well as good mechanical properties. All phenolic and epoxy composite specimens used here were prepared by resin transfer molding (RTM) to model a cost‐effective process. Hygrothermal cycling effects on the property changes of phenolic composites were evaluated through thermal, mechanical, and morphological tests. The fracture performance of a phenolic composite modified with a silicone‐based additive decreased after fewer hygrothermal cycles than unmodified phenolic and epoxy composites. Results from dynamic mechanical analysis (DMA) experiments showed that the modified phenolic composite was more significantly affected by the hygrothermal cycling than the unmodified phenolic composites. Fatigue tests showed that the phenolic composites that were not exposed to hygrothermal cycling had more resistance to fatigue cycles than the epoxy composites.
Prototypes for building applications based on thermoplastic composites containing mixed waste plastics
Authors: Xanthos M. , Dey S. K. , Mitra S. , Yilmazer U. , Feng C. 
Published: April 2004

AbstractAutomotive shredder residue (ASR) and a complex residue obtained as a by‐product in the tertiary recycling of nylon‐6 fibers from used carpets were evaluated as potential additives in thermoplastic composites to be used for building applications. Prototype blocks were prepared by the “intrusion” process using various ratios of the waste streams and low‐density polyethylene (LDPE) in the absence of compatibilizers. Hence, product morphologies and corresponding properties were largely controlled through processing. They were evaluated for their short‐term and longterm mechanical properties, flammability, thermal conductivity, and heavy‐metal and total organic carbon leaching characteristics. Encapsulation of the waste feedstock by LDPE during molding in a single‐screw extruder significantly reduced the leachable content. In an effort to further reduce the leachable content, the mixtures were processed in two stages by precompounding in adevolatilizing twin‐screw extruder prior to molding. In comparison to the as‐received wastes, improved homogenization decreased the leachable heavy‐metal content by at least 98%. The carpet residue feedstock consisting of polypropylene, styrene‐butadiene rubber and calcium carbonate appears to be an attractive low‐cost, high‐volume material with consistent properties and could be used as filler in thermoplastic composites. Comparison of their performance characteristics suggested that the carpet residue composites would be favored versus ASR composites as replacement of the wood thermal barrier components in a novel steel‐based stud assembly.