bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulations of cyclic, transient variations of mold temperatures in the SMC compression molding process
Authors: Hu Sheng Yan , Chen Shia Chung , Twu Jun‐Tien , Lee L. James 
Published: April 2004

AbstractThe dual reciprocity boundary element technique is used to simulate the cyclic SMC compression molding process, taking into account the heat transfer within the whole mold. The cyclic, transient variations in mold temperatures at different mold locations are illustrated through the analysis of a plate mold. The transient temperature fluctuation near the mold cavity surface is much larger than that away from it. It was also found that owing to the high heating fluid temperature (compared with the ambient air temperature), the heat transfer at the mold exterior surface shows a significant effect on the mold temperature distribution, especially when the mold is a small or medium size. The present method provides a complete and more accurate description of the mold temperature variation during the whole cycle history by including the mold as the analysis domain, meanwhile minimizing the computation time. Other analysis methods, including the constant mold wall temperature approach, the hybrid shape‐factor/finite element method, as well as the cycle‐averaged boundary element technique imposed with 1‐D transient analysis, basically overestimate mold wall temperatures and the associated charge conversion rate.
Shrinkage anisotropy in fiber reinforced injection molded products
Authors: Jansen K. M. B. , Van Dijk D. J. , Freriksen M. J. A. 
Published: April 2004

AbstractThis paper includes a systematic study of the effect of fiber concentration and molding conditions on fiber orientation and shrinkage in injection molded composites. Closed‐form expressions were derived to relate shrinkage and internal stresses to the molding pressure and fiber orientation. The shrinkage predictions were seen to agree well with experimentally measured shrinkages.
Modeling of injected pultrusion processes: A numerical approach
Authors: Kommu S. , Khomami B. , Kardos J. L. 
Published: April 2004

AbstractInjected pultrusion (IP) is an attractive process for high volume, high performance, and low cost manufacture of continuous fiber reinforced polymer matrix composites. In this work we focus our attention on development of a computer simulation model for the IP process. First, the governing equations for conservation of mass, momentum, and energy are developed using a local volume averaging approach. In turn, a computer simulation model of the IP process is developed using finite element/control volume (FE/CV) and finite difference techniques. Specifically, the equation of continuity and conservation of momentum are solved in 2‐D using a Galerkin FE/CV technique. The energy and chemical species balance equations are solved in 3‐D, where streamline upwind Petrov‐Galerkin (SUPG) or streamline upwind (SU) FE/CV are used to discretize the equations in two dimensions while finite differences have been used in the third dimension. The chemical species balance equation is solved in the Lagrangian frame of reference using finite differences. Different numerical formulations (Galerkin, Lagrangian, SU, and SUPG) are used to solve a number of benchmark problems to determine the best numerical formulation. It is shown that for coarse discretization, Streamline Upwind methods perform consistently better than the other methods. However, for refined meshes, the Lagrangian method produces the best solution for a given CPU time. Also, using the simulation model, the effect of fiber pull speed, reinforcement anistropy, and taper of the die on the quality of the product is studied. It is shown that the simulation model can be effectively used to design the die geometry as well as to optimize the operating conditions for a given product.
Short term flexural creep behavior of wood‐fiber/polypropylene composites
Authors: Park Byung‐Dae , Balatinecz John J. 
Published: April 2004

AbstractShort term flexural creep tests were conducted to investigate the creep behavior of wood‐fiber polypropylene composites. Three experimental parameters were selected: the addition of a wetting agent, temperature, and wood‐fiber concentration. All creep curves are presented in terms of relative creep as a percentage of instantaneous (initial) strain. The creep power law model was used to accurately fit the creep data. The addition of a wetting agent greatly reduced the creep at high stress, but had little effect at a lower stress level. The extent of relative creep increased with increasing temperature. It was found that the slope of the power law model was directly proportional to the temperature. The addition of wood‐fibers into pure polymer greatly improved the creep resistance of the matrix polymer. The relative creep of the composites decreased with an increase in wood‐fiber concentration. However, the composite showed relatively large creep compared with that of solid wood. It was found that both the time exponent and slope of the power law model were inversely related to wood‐fiber concentration. The flexural modulus of the composites also had an inverse relationship with the time exponent.
The development of glass fiber reinforced polystyrene for pultrusion. I: Process feasibility, dynamic mechanical properties, and postformability
Authors: Chen Chin‐Hsing , Wang Wen‐Si 
Published: April 2004

AbstractA feasibility study on the pultrusion of a glass fiber reinforced polystyrene (PS) has been conducted using a proprietary method. The styrene prepolymer synthesized in this study was prepared from blends of styrene monomer and benzoyl peroxide (BPO). The process feasibility, dynamic mechanical properties, and postformability of the glass fiber reinforced PS by pultrusion have been investigated. By means of gel permeation chromatography, 1H nuclear magnetic resonance (1H‐NMR), and a Brookfield viscometer, the molecular weight, conversion, and viscosity of the styrene prepolymer were obtained. From the investigations of the long pot life of styrene prepolymer, the high reactivity of styrene prepolymer, and excellent fiber wet‐out, it was found that the PS resin showed excellent process feasibility for pultrusion. The dynamic storage modulus (E') of pultruded glass fiber reinforced PS composites increased with increasing die temperature, filler content, postcuring and glass fiber content, and with decreasing pulling rate. The composite can be postformed by thermoforming under pressure, and mechanical properties of postformed composites can be improved.
The development of glass fiber reinforced polystyrene for pultrusion. II: Effect of processing parameters for optimizing the process
Authors: Chen Chin‐Hsing , Wang Wen‐Si 
Published: April 2004

AbstractThis paper presents a novel process developed to manufacture polystyrene (PS) pultruded composites. The effects of the processing parameters on the mechanical properties (tensile strength, flexural strength, flexural modulus, etc.) of the glass fiber reinforced PS composites by pultrusion have been studied. The processing parameters investigated include die temperature, pulling rate (in‐line speed), postcure temperature and time, filler type and content, and glass fiber content. The optimum die temperature was determined from DSC diagrams, molecular weight, and mechanical properties tests. It was found that the mechanical properties increased with increasing die temperature and glass fiber content, and with decreasing pulling rate. The optimum die temperature, pulling rate, and glass fiber content were determined to be 160–200°C, 20–60 cm/min and 50–60 vol%, respectively. The mechanical properties reached a maximum value at 10 phr kaolin, and then decreased. However, the properties decreased with increasing tale content. The mechanical properties increase at a suitable postcure temperature and time. Furthermore, the properties that decreased as a result of composite degradation after long postcure time are discussed.
Influence of interfacial interactions on the properties of PVC/cellulosic fiber composites
Authors: Matuana Laurent M. , Woodhams Raymond T. , Balatinecz John J. , Park Chul B. 
Published: April 2004

AbstractThe surface properties at the interface between thermoplastic and cellulosic fibers strongly influence the mechanical properties of plastic/cellulosic fiber composites. This paper examines the role of surface acid‐base properties of plasticized PVC and cellulosic fibers on the mechanical properties of the composites. The acid‐base surface characteristics of cellulosic fibers were modified by treating the fibers with γ‐aminopropyltriethoxysilane (A‐1100), dichlorodiethylsilane, phthalic anhydride, and maleated polypropylene. The empirical acid (KA) and base (KD) characteristics (i.e., electron donor/acceptor abilities) of untreated and treated fibers, as well as plasticized PVC, were determined using inverse gas chromatography (IGC) technique. These parameters were used to yield information on the acid‐base pair interactions that were correlated with the tensile and notched Izod impact properties of the composites. Acid‐base pair interactions have been found to be a valuable parameter in the design of surface modification strategies intended to optimize the tensile strength of the composites. By tailoring the acid‐base characteristics of cellulosic fibers and plasticized PVC, a composite with equal tensile strength and greater modulus than unfilled PVC was developed. However, the acid‐base factors did not correlate with tensile modulus, the elongation at break, and the notched Izod impact property of PVC/newsprint fiber composites. Aminosilane has been observed to be a suitable adhesion promoter for PVC/wood composites improving significantly the tensile strength of the composites. Other treatments (dichlorodiethylsilane, phtalic anhydride, and maleated polypropylene) were found to be ineffective, giving similar strength compared to the composites with untreated cellulosic fibers. FTIR spectroscopy results suggested that aminosilane was effective because treated cellulosic fibers can react with PVC to form chemical bonds. The resulting bond between PVC and cellulosic fibers accounts for the effectiveness of aminosilane, when compared with other coupling agents.
Effect of post‐curing on the mechanical properties of carbonized phenolic resins
Authors: Ko Tse‐Hao , Ma Tsu‐Sheng 
Published: April 2004

AbstractAfter curing, phenol‐formaldehyde resins were post‐cured at 160°C, 230°C, and 300°C in air for several hours, and then those post‐cured samples were carbonized at 1000°C. The effect of post‐curing on the physical properties and microstructure of the carbonized phenolic resin is reported in this article. The purpose of post‐curing was to improve the mechanical properties of the carbonized resins. The post‐curing process promoted the crosslinking reaction and the evolution of gases. The cured resin post‐cured at a higher post‐curing temperature (300°C) had a significantly higher weight loss, greater linear shrinkage and lower density than others samples. During carbonization the post‐curing process not only decreased the weight loss but also limited the shrinkage. Post‐curing also promoted the formation of carbon basal planes and the chemical densification in structures of the final carbonized resins. The increase in post‐curing temperature and time had the effect of reducing the linear shrinkage of the resin during carbonization. The TGA thermal analysis showed that the post‐cured resins improved the total weight loss more than 15 wt% over the unpost‐cured resin. The carbonized resins developed from the post‐cured resins had a greater flexural modulus by about 10–50% and improved the linear shrinkage by about 10% over that developed from unpost‐cured resin.
Analysis of an injection/compression liquid composite molding process
Authors: Han Kerang , Ni Jun , Toth James , Lee L. James , Greene Joseph P. 
Published: April 2004

AbstractThe injection/compression liquid composite molding (LCM) process is simulated by using the control/volume finite element method (CV/FEM). The flow in the runner and the fiber‐free areas is simplified by using an equivalent permeability approach. Several molding experiments were conducted using a tub‐shaped mold and the structural reaction injection molding (SRIM) process for a poly(urethane/isocyanurate) matrix and a glass fiber preform. Good agreement is found between the experimental results and the simulation.
A generalized self‐consistent mori‐tanaka scheme for prediction of the effective elastic moduli of hybrid multiphase particulate composites
Authors: Dai L. H. , Huang Z. P. , Wang R. 
Published: April 2004

AbstractA generalized self‐consistent Mori‐Tanaka method (GSCMTM) is developed in this paper. The method starts with the formulation of the problem of heterogeneous elasticity proposed by Dederichs and Zeller and incorporates the strain equivalence condition of Christensen's generalized self‐consistent method (GSCM) and Hill's interfacial operator theory into the evaluation of the strain concentration tensors of constituents. For a two‐phase composite with spherical inclusions, the effective moduli predicted by GSCMTM coincide with those predicted by the Mori‐Tanaka method (MTM). By a two‐step homogenization technique, GSCMTM was successfully extended to multiphase composites. The effective moduli predicted by GSCMTM for multiphase hybrid particulate composites agree well with the existing theoretical and experimental results and can be expressed in a simple explicit form.
Creep and relaxation behavior of woven glass/epoxy substrates for multilayer circuit board applications
Authors: Shrotriya P. , Sottos N. R. 
Published: April 2004

AbstractThe creep behavior of a common woven glass/epoxy composite substrate for multilayer circuit board applications was characterized using dynamic mechanical analysis (DMA). The creep compliance was measured in both the warp and fill directions of the composite over a temperature range of 30°C to 155°C. The creep compliance of the neat FR‐4 epoxy matrix was also characterized for comparison with the composite response. Master creep curves were obtained for the neat resin and the composite in the warp and fill directions assuming thermorheologically simple behavior and applying the time‐temperature superposition principle. The creep data was fit to a Prony series and then converted to relaxation data in the Laplace domain. Micromechanical models were developed to predict the relaxation behavior of the woven glass/epoxy composite from the elastic properties and the geometry of the glass fabric and relaxation behavior of the neat resin. Model predictions were compared with experimental data.
Anisotropic modeling of isothermal squeezing flow of Glass‐Mat reinforced thermoplastics (GMT)
Authors: Dweib M. A. , Brádaigh C. M. Ó 
Published: April 2004

AbstractLubricated isothermal compression molding of Glass‐Mat Thermoplastic (GMT) was carried out using a circular mold on a 100 kN test machine to characterize the rheological parameters for squeezing flows of the material. Flow was found to be anisotropic with the main flow direction perpendicular to the main fiber direction. In‐plane flow of circular specimens was found to follow an elliptical shape, which allows a relationship to be derived between extensional strain rates in the two main in‐plane directions. A transversely isotropic incompressible Newtonian fluid model was successfully applied to interpret the squeezing data parallel and perpendicular to the main flow direction. Longitudinal and transverse extensional viscosities were calculated for two squeezing temperatures, 180°C and 200°C. The results were compared to the standard isotropic power law interpretation, showing the largest anisotropic viscosity to be 20% higher than the isotropic viscosity at low closing speeds and 9.5% higher at fast closing speeds. A very significant difference in the viscosities was found between the two different temperatures as the viscosity at 200°C dropped to about 65% of its value at 180°C. In this work, original material sheets were also confirmed to display anisotropic mechanical properties. The final squeezed specimens were found to have different fiber volume fractions in the same specimen.
Impact behavior of carbon fiber/polyethylene fiber hybrid composite: The effect of surface treatment of polyethylene fiber
Authors: Park Rohchoon , Jang Jyongsik 
Published: April 2004

AbstractHybrid composites were prepared by adding one or two plies of polyethylene (PE) fabric to the bottom side of four‐ply carbon fiber/vinylester composites. The effect of the surface treatment of PE fiber on the impact properties of carbon fiber/PE fiber hybrid composites was investigated using oxygen plasma, γ‐MPS, and γ‐MPS‐modified polybutadiene (PB/γ‐MPS) as surface modifiers. Carbon fiber/vinylester composite exhibited brittle failure with cross‐shaped crack at the back side. The addition of PE fabric on the bottom side resulted in a change of the impact behavior of hybrid composites. After hybridization, the absorption of much impact energy was attributed to a considerable degree of plastic deformation in PE plies and the delamination at the interface between carbon and PE layer. However, the surface treatment of PE fiber reduced the impact energy of composites with restriction of deformation at the interface between the carbon and the PE layer. Moreover, the addition of a treated PE layer decreased the degree of deformation with a dagger‐shaped deformation zone at the back side. The extent of the deformation area had a significant effect on the impact energy of the hybrid composites.
Effect of carbon fabric type on the mechanical performance of 2D carbon/carbon composites
Authors: Ko Tse‐Hao , Kuo Wen‐Shyong 
Published: April 2004

AbstractA stabilized PAN fabric was carbonized and graphitized from 800°C to 2500°C. Two‐dimensional (2D) carbon/carbon composites were made using the stabilized PAN fabric, carbonized fabrics, and a resol‐type phenol‐formaldehyde resin. These composites were heat‐treated from 600°C to 2500°C. The influence of different heat‐treated fabrics and heat treatment on the fracture and flexural strength of these composites was also studied. The composite reinforced with higher heat‐treated fabrics showed a lower weight loss than that with lower heat‐treated fabrics. When the composites were graphitized at 2500°C, the loss was 49.7 wt% for the composite made with stabilized PAN fabric and 26 wt% for that with carbonized fabric at 2500°C. Those composites also have a higher density than composites produced by other methods. Composites made with stabilized PAN fabric exhibited a strong bonding in the fiber/matrix during pyrolysis. This composite showed catastrophic fracture and a smooth fracture surface with no fiber pullout. Composites made with higher carbonized fabrics exhibited a weak interface bonding. These composites showed a pseudo‐plastic fracture pattern with fiber pullout during pyrolysis. Composites made with carbonized fabrics at 2000°C and 2500°C showed the highest flexural strength at the prolysis temperature of 1000°C. Composites made with carbonized fabric at 1300°C showed the highest flexural strength above 1500°C to 2500°C. The composite made with stabilized PAN fabric exhibited the lowest flexural strength during pyrolysis.
Dynamic mechanical properties of spherical inclusions in polymer composite: A self‐consistent approach considering morphology
Authors: Shaterzadeh M. , Gauthier C. , Gerard J. F. , Mai C. , Perez J. 
Published: April 2004

AbstractIn this work, the dynamic mechanical behavior of epoxy/A‐glass bead composites is investigated considering the influence of the volume fraction of the beads and their surface treatments. The main differences between the different samples are observed in the rubbery modulus plateau. The “Self‐Consistent Scheme” is used to calculate the effective shear modulus of the composite with spherical inclusions, i.e., a macroscopically isotropic polymer medium containing spheres. The 3‐phase model first introduced by Christensen and Lo accurately predicts results for the composite with treated glass beads (sizing agent), but fails for the other one (untreated surface). For the latter composite, other related models (4‐phase models) are also applied without satisfactory results. Then, the 3‐phase model is applied in successive steps to account for the specific distribution of glass.
Moisture absorption effect on adhesive filled bonded joints
Authors: Ouddane M. , Boukhili R. 
Published: April 2004

AbstractThe effect of filler type and content on the performance and durability of adhesive bonded joints upon exposure to damp heat (water immersion) has been investigated using concurrently step lap shear and thermo mechanical analysis (TMA) experiments. A TMA based approach is developed in order to predict the strength of the bonded constructions. Two types of fillers were used in order to achieve the objectives: glass beads (GB) and alumina ceramic powder (ACP). It is shown that ACP filled adhesives have higher strength retention than GB filled ones. It is also demonstrated that valuable information can be extracted from TMA measurements. Generally, the increase of the coefficient of thermal expansion (CTE) of the bonded joints is found to be in agreement with the decrease of the step lap joint strengths after exposure. The increase of the CTE of the bonded joints resulting from exposure to hot water seems to increase the stresses, which in turn affect the overall strength. Similarly, bulk adhesive results show that GB filled systems are more susceptible to water than ACP filled ones, which confirms the decrease in strength of GB filled bonded constructions.
Crystallinity of isothermally and nonisothermally crystallized poly(ether ether ketone) composites
Authors: Chen Ming , Chung Chia‐Ting 
Published: April 2004

AbstractPEEK/carbon fiber composites were prepared by a modified diaphragm forming machine under vacuum. The study of the degree of crystallinity versus the differential scanning calorimetry (DSC) heating rate indicated that 50°C/min was an optimal heating rate to suppress the reorganization of the specimens crystallized between 315°C and 255°C and to avoid superheating the specimens. A high volume of fibers constrained the spherulitic growth by an impingement mechanism, which depressed the crystallization rate and reduced the crystallinity. Thus the crystallization was still in process even after 240 min annealing at 300°C. The effect of the cooling rate on the degree of crystallinity was simulated and investigated in DSC at a heating rate of 50°C/min. The results indicated that the cooling rates ranging from 1°C/min to 100°C/min could be divided into five regions that were associated with a high volume of fiber and the crystallization regime. A Time‐Temperature‐Transformation diagram superposed on the Continuous‐Cooling‐Transformation curves allows us to predict the amount of crystallization in different regimes. The data points for the DSC method deviated from the prediction at the cooling rates above 60°C/min because of the recrystallization during DSC heating scans.