bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanical properties and morphology of glass bead–filled polypropylene composites
Authors: Liang J. Z. , Li R. K. Y. 
Published: April 2004

AbstractThe effects of the filler content and size on the mechanical properties such as tensile modulus, Ec, yield strength, σyc, and impact strength, SIC, of glass bead–filled polypropylene (PP) composites have been investigated employing an Instron materials tester and a Ceast impact tester at room temperature. With increasing concentration of glass beads, Ec and SIC increase, but σyc decreases non–linearly, within a filler volume fraction range of 0%−20%; under the same test conditions, the values of EC and σyc for PP with bigger beads are somewhat lower than those of PP with smaller ones; the maximum values of SIC for the composites are about 1.4 times as high as the unfilled PP; the interface between the matrix and the beads is a weak bond. The results indicate that the stiffness and the toughness of the PP composites are effectively improved by addition of glass beads.
Resin transfer molding of BMIs and polymides
Authors: Colton Jonathan S. 
Published: April 2004

AbstractBismaleimdes (BMI) and experimental polyimides were resin transfer molded into carbon fiber fabrics using a custom‐built injection mold placed within a vacuum hot press. This represents the first time that the latter type of materials has been resin transfer molded. This is a critical stage in developing materials and processing methods for future aerospace applications, such as the High Speed Civil Transport (HSCT).
Interfacial properties of two SiC fiber–reinforced polycarbonate composites using the fragmentation test and acoustic emission
Authors: Park Joung‐Man , Chong Eui‐Min , Yoon Dong‐Jin , Lee Joon‐Hyun 
Published: April 2004

AbstractInterfacial shear strengths (IFSS) between the fiber and the matrix in two SiC fiber–reinforced polycarbonate (PC) composites (TFC) were investigated through the fragmentation method and the acoustic emission (AE) technique. Statistical analysis of SiC fiber tensile strength was performed mainly in terms of a Weibull distribution. The tensile strength and elongation for SiC fiber decreased with increasing gauge lengths, because of the heterogeneous distribution of flaws on the fiber surface. Using an amino‐silane coupling agent, the IFSS showed significant improvement, in the range of 150%, under dry conditions. On the other hand, in the aspect of the environmental effect, the IFSS was improved about 170% under wet conditions (immersed in hot water at 85°C for 75 min). This is probably due to chemical and hydrogen bonds in the two different interphases in the SiC fiber/silane coupling agent/PC matrix system. In‐situ monitoring of AE during straining of microspecimens showed the sequential occurrence of two distinct groups of AE data. The first group may result from SiC fiber breakages, and the second probably results from mainly PC matrix cracking. Characteristic frequencies coming from the failures of the fiber and the PC matrix were shown via fast Fourier transform (FFT) analysis. By setting an appropriate threshold level, a one‐to‐one correspondence between the number of AE events and fiber breakages was established. This AE method could be correlated successfully to the IFSS via the fragmentation technique, which can also applied to nontransparent specimens.
Effect of processing on the positive temperature coefficient of resistivity in lead metaplumbate/polyethylene composites
Authors: Huang Z. Z. , Yue R. , Chan H. L. W. , Choy C. L. 
Published: April 2004

AbstractThe positive temperature coefficient of resistivity (PTCR) effect of a barium metaplumbate/polyethylene [(BaPbO3)/PE] composite with 12 vol% of BaPbO3 was studied. The composite samples were prepared by hot‐pressing a mixture of BaPbO3 ceramic and high‐density polyethylene powders around the melting point of polyethylene. The composites exhibit a pronounced PTCR effect of up to a six‐decade increase in resistivity within a narrow range of temperature (∼10°C). The dependences of the room temperature resistivity and the magnitude of the resistivity jump on the pressing and annealing temperature, and the electrical behavior after repeated heating‐cooling cycles were investigated. The fracture surfaces of the composite samples were examined in a scanning electron microscope in order to correlate the electrical behavior with the microstructure.
Measurement and modeling of flow and mechanical properties of ASR‐filled polymer composites
Authors: Narh K. A. , Guo J. , Li Z. 
Published: April 2004

AbstractScrew extrusion process was used to evaluate the flow properties of ASR/LDPE composite whose rheological properties cannot be obtained from the conventional capillary rheometer measurements. The results show that the viscosity of the mixture increases with increasing automobile shredder residue (ASR) content. Although there exists significant scatter in the results because of the non‐homogeneity of the mixtures, the result can be used to roughly predict the flow properties of the materials. Thus, based on linear regression fits of the flow data, a second order polynomial relationship was established between the viscosity of ASR/LDPE composite and ASR concentration. HDPE was used in the mechanical tests. The results also show that the tensile modulus can be predicted, accurately, using a conventional composite model.
Comparative study of interlaminar fracture toughness of GFRP with different fiber surface treatments
Authors: Korjakin A. , Rikards R. , Buchholz F.‐G. , Wang H. , Bledzki A. K. , Kessler A. 
Published: April 2004

AbstractThis investigation is focused on the influence of glass fiber surface treatment on the interlaminar fracture toughness of unidrectional laminates. Three different fiber surface treatments were considered: polyethylene treated fibers to get poor adhesion, silance treated fibers to get good bond strength, and industrial fibers without special treatments with the coupling agents. The interlaminar fracture behavior of unidirectional glass fiber reinforced composites with different fiber surface treatments has been investigated in mode I, mode II, and for the fixed mixed mode I/II ratio 1.33. Double cantilever beam (DCB), end notched flexure (ENF), and mixed mode flexure (MMF) specimens were used. The data obtained from these tests were analyzed by using different analytical approaches and the finite element method. For the fibers treated with the silane coupling agent, a value about 2.5 times higher of mode II interlaminar fracture toughness for crack initiation was obtained in comparison with the polyethylene sized composite. For the composite made from the industrial fibers, a value about 2 times higher was obtained. Because of extensive fiber bridging and pullout in the composites with poor fiber/matrix adhesion, the results of mode I and mixed mode I/II tests did not characterize the interphase quality. In order to determine the interphase quality, the mode II tests are recommended.
Mold filling analysis in vacuum‐assisted resin transfer molding. Part I: SCRIMP based on a high‐permeable medium
Authors: Sun Xiudong , Li Shoujie , Lee L. James 
Published: April 2004

AbstractMold filling in SCRIMP based on a high‐permeable medium is complicated because of the considerable difference in the permeabilities of the fiber reinforcement, the peel ply and the high permeable medium. The objectives of this paper are to understand the flow mechanism through flow visualization experiments and to present models that can be used to predict the filling time and flow pattern. Permeabilities of a stitched fiber mat, a high‐permeable medium and a peel ply were measured. Flow visualization of SCRIMP mold filling was carried out under various molding conditions. It was found that although the resin flowed faster in the high‐permeable medium than in the fiber reinforcement, the flow front lead‐lag was not very large and it remained nearly constant through the entire mold filling process. A three‐dimensional Control Volume/Finite Element Method (CV/FEM) was adopted to solve the flow governing equations, i.e. the Darcy's law, and the influences of the flow properties of the high‐permeable medium, the fiber reinforcement and the peel ply on filling time were investigated. Based on experimental observations and CV/FEM simulation, a simplified leakage flow model is also presented. The comparison of experimental and simulation results show good agreement.
Mold filling analysis in vacuum‐assisted resin transfer molding. Part II: SCRIMP based on grooves
Authors: Ni Jun , Li Shoujie , Sun Xiudong , Lee L. James 
Published: April 2004

AbstractCompared with SCRIMP based on the high‐permeable medium, SCRIMP based on grooves has the advantage of a much higher mold filling rate. This paper analyzes the influences of various molding conditions on mold filling and presents models that can be used to predict the filling time and flow pattern in SCRIMP based on grooves. Mold filling experiments were carried out to investigate the effect of various factors such as the size of the groove, groove spacing, number of fiber layers and resin viscosity on mold filling. A leakage flow model was developed to simplify the simulation of the mold filling process in SCRIMP based on grooves. An “equivalent permeability” was introduced to represent the average flow capacity in the grooves. Compared with the Control Volume/Finite Element Method (CV/FEM) model, the leakage flow model greatly reduced computation time and yet provided simulation results that were in good agreement with experimental observations.
Analytical stress model for a composite prosthetic intervertebral disc
Authors: Hudgins R. Garryl , Muzzy John D. 
Published: April 2004

AbstractThis research develops an analytical stress model for a composite prosthetic intervertebral disc (PID) composed of an elastomeric core placed inside a braided flexible composite sleeve. The model is used to investigate the effects of interference between the core and sleeve on the axial compression behavior of the prosthesis. The model closely replicates the PID's compressive stress‐strain curve. The model combines textile crimp analysis and a newly proposed rubber elasticity constitutive relation. The stress model can be used to optimize the compressive behavior of a PID having a textile composite reinforcing phase.
Effect of volume loading and surface treatment on the thixotropic behavior of polypropylene filled with calcium carbonate
Authors: Wang Yeh , Yu Ming‐Jiann 
Published: April 2004

AbstractThe rheological properties of calcium carbonate‐filled polypropylene were examined using a Rheometrics dynamic analyzer. The study included steady shear test, transient stress growth test with sequential deformation history, and two‐step dynamic oscillatory shear flow. Thixotropic behavior was observed in transient tests for highly filled compounds when volume loading exceeding a critical value at about 20%. The material responses of these viscoelastic thixotropic materials depend on the duration of shear as well as on the rate of shear. The effects of filler on the rheological behavior of highly filled compounds are dominant at low strain rates; however, the effects of activity of the filler are almost negligible at high strain rates because of complete breakdown of the filler network. The timescales for structural changes in filled systems often become long compared with the viscoealstic time constants of the unfilled melt. The magnitudes of rheological properties and the degree of hysteresis appear to increase with increasing volume loading of filler particles. Conversely, surface treatment of fillers, which presumably reduces interaction between filler particles and the extent of agglomeration, results in major reductions of both rheological properties and the degree of hysteresis. The diverse experimental observations are interpreted in terms of a system forming a filler network due to weak interparticle forces. The thixotropy resulting from breakdown and recovery of the filler network is dependent on the characteristic time of the individual test.
Piezoresistivity in continuous carbon fiber polymer‐matrix composite
Authors: Wang Shoukai , Chung D. D. L. 
Published: April 2004

AbstractPiezoresistivity involving the volume resistivity of a continuous unidirectional carbon fiber epoxy‐matrix composite in the fiber direction decreasing reversibly upon tension in the fiber direction was observed by the four‐probe method, due to an increase in the degree of fiber alignment. Use of the two‐probe method resulted in measurement of the contact resistance rather than the volume resistance. The contact resistance increased reversibly upon tension.
On predicting elastic moduli and natural frequencies of multi‐phase composites with randomly distributed short fibers
Authors: Chao Lu‐Ping , Huang Yung‐Sung 
Published: April 2004

AbstractThis study presents a formulation to determine the overall stiffness of an n‐phase short fiber composite to include the inclusions' aspect ratio ranging from less than one to greater than one. The Mori‐Tanaka theory is initially employed to investigate the overall stress‐strain relation of a multi‐phase short‐fiber‐reinforced composite material, particularly whether or not the fibers and the matrix are isotropic, cubic, or transversely isotropic material. The effective stiffness tensor of a multi‐phase composite is then denoted as a function of the matrix's elastic moduli, the n‐phases' inclusions' elastic moduli, the n‐phases' inclusions' Eshelby tensor, and the n‐phases' inclusions' volume fractions. Utilizing the equivalent inclusion method allows us to model inclusions of n‐phases that consist of fictitious eigenstrains. In addition, the corresponding Eshelby tensors' values for ellipsoidal inclusion embedded in the isotropic matrix with the variation of aspect ratio are presented. Numerical results of the proposed formulation in solving a two‐phase composite closely correspond to the Halpin‐Tsai Equation. Results presented herein provide valuable information on the appropriate manufacturing requirements of multi‐phase composite materials or the design and optimization of multi‐phase composite structures.
Analysis of the vacuum infusion molding process
Authors: Hammami A. , Gebart B. R. 
Published: April 2004

AbstractThe vacuum infusion molding process is becoming increasingly popular for the production of large composite parts. A comprehensive model of the process has not been proposed yet, making its optimization difficult. The flexible nature of the vacuum bag coupled to the varying pressure inside the mold cavity results in a variation of the cavity thickness during the impregnation. A complete simulation model must incorporate this phenomenon. In this paper, a complete analysis of the vacuum infusion molding process is presented. The analysis is not restricted to the theoretical aspects but also reviews the effect of the main processing parameters. The parameters investigated in this paper are thought to be those of most interest for the process, i.e. the compaction of the reinforcement, the permeability, the infusion strategy and the presence of flow enhancement layers. Following the characterization experiments, a 1‐D model for the vacuum infusion molding process is presented. This model is derived assuming that an elastic equlibrium holds in the mold cavity during mold filling. Even though good agreement was found between simulation results and experiments, it is concluded that additional work is needed on the numerical model to integrate interesting findings from the experimental part.
Performance evaluation of synthesized acrylic acid grafted polypropylene within CaCO3/polypropylene composites
Authors: Rahma F. , Fellahi S. 
Published: April 2004

AbstractA polymeric coupling agent acrylic acid grafted polypropylene (AAgPP) was synthesized and its efficiency in CaCO3/PP composite was investigated. The grafting of acrylic acid monomer (AA) onto polypropylene was performed using an internal mixer. The effect of peroxyde, acrylic acid monomer content, temperature and RPM was studied. A grafting reaction between the polypropylene and the acrylic acid was evidenced through FTIR, UV, DSC and MFI testing. The highest grafting yield was obtained at 0.85 phr peroxide and 5 phr acrylic acid. The selected mixing temperature was 200°C, the rotor speed 150 rpm and the residence time 5 min. The obtained coupling agent (AAgPP) was used with 30 wt% CaCO3 filled polypropylene. Strong interactions with the composite were observed. The effect of increasing the coupling agent content on Izod impact and tensile properties was investigated. A maximum in the above properties is attained at 15 wt% AAgPP. The most important effect is clearly shown in the Izod test. In fact, a threefold increase has been observed for either notched and untoched specimen. The 15 wt% AAgPP is considered to be a critical concentration for the composite considered. This corresonds to maximum interactions occurring between the matrix and the filler. SEM analysis clearly shows strong interactions between the filler and the matrix in the presence of acrylic acid grafted polypropylene. This is another proof of the efficiency of the synthesized AAgPP as a potential coupling agent for CaCO3 filled PP.
A comparative study of using allyl alcohol based copolymers in the preservation of wood: Oak vs. cedar
Authors: Dilek Ş. , Olgun G. 
Published: April 2004

AbstractWood is an important raw material that is cheap and easily worked. However, wooden objects are subject to environmental attack and mechanical shocks. In this study, our aim is to preserve wooden objects against envrironmental deterioration and mechanical shocks on to consolidate objects already degraded. Allyl alcohol (AA), acrylonitrile (AN), methyl methacrylate (MMA) and AA/AN, AA/MMA monomer mixtures were impregnated into oak and cedar. Polymerization was accomplished by gamma irradiation. The mechanical properties and the dimensional stability of the wood‐copolymer composites were determined. The presence of polymer and copolymer in the wood increased the mechanical durability of the wood. The results of the hardness tests and the compressive strengths determined in parallel and perpendicular directions to the fibers revealed that P(AA/MMA), P(AA/AN) copolymers are effective in increasing the mechanical durability of pristine‐oak and cedar woods. Similar results were also obtained from hardness tests. The decrease in the mechanical durability of pristine‐oak and cedar woods after aging for 28 days is slight. The water uptake capacity of wood + copolymer composites was observed to decrease by more than 50% compared with the original samples. In the cedar wood, where the density is low and the quantity of copolymer is high, this decrease ranged from 100% to 50%.
Processing and properties of solution impregnated carbon fiber reinforced polyethersulfone composites
Authors: Wu G. M. , Schultz J. M. 
Published: April 2004

AbstractCarbon fiber reinforced polymer composites are attractive because of their high stiffness and strength‐to‐weight ratios. In order to fully utilize the stiffness and strength of the reinforcement fiber, it is necessary to bring the polymer matrix and the reinforcement fiber together with homogeneous wetting. In this paper, a solution processing technique and the mechanical properties of carbon fiber reinforced polyethersulfone composites were investigated. The polymer was dissolved in cyclopentanone and fed onto a continuous carbon fiber tow using a drum winder. The solution‐processed composite prepregs were then layed up and compression molded into unidirectional composite panels for evaluation. The composite samples showed uniform fiber distribution and reasonably good wetting. The longitudinal flexural modulus was as high as 137 GPa, and longitudinal flexural strength 1400 MPa. In addition, the effects of polymer grade and processing conditions on the mechanical properties of the composites were discussed. It is suggested that the transverse properties and interlaminar fracture toughness could benefit from higher polymer matrix molecular weight. A careful design in the spatial distribution of the molecular weight would be necessary for practical applications.
Rate‐Dependent function in the correlation between hardness and yield stress of polyethylene composites
Authors: Suwanprateeb J. 
Published: April 2004

AbstractA study of the validity of a correlation between compressive yield stress and Vickers hardness of CaCO3/high density polyethylene composites was carried out. Composites with calcium carbonate in the range of 0–0.40 were produced by twin screw extrusion followed by compression molding. Hardness was implemented by indenting the samples with Vickers indenter and compression test were carried out at various crosshead speeds in the range of 0.2–50 mm min−1. It was found that increasing calcium carbonate content increased both hardness and yield stress. In addition, compressive yield stress increased with increasing crosshead speed. The correlation between hardness and yield stress was observed to be independent on filler content and valid when the deformation rate employed in both tests were within the similar ranges which was in the order of 10−1 mm min−1. Tabor's equation was modified to take into account for the rate‐dependent behavior of composites and was found to be applicable and yield relatively accurate results.
Fractal permeation characteristics of preforms used in liquid composite molding
Authors: Ramakrishnan B. , Pitchumani R. 
Published: April 2004

AbstractPreform permeability plays a critical role in the analysis of mold filling during liquid composite molding processes. Because of the complex structure of the preform pore network, a quantitative description of the pore structures, and consequently, the evaluation of the permeabilities presents a major challenge. In this article, a fundamental description of the disordered preform pore structures based on fractal techniques is utilized to relate the preform permeabilities to the actual microstructures in terms of two fractal dimensions. Comparison of the fractal permeation model predictions with experimentally‐measured permeabilities demonstrates excellent agreement over a wide range of fiber volume fractions, injection pressures, and isotropic and anisotropic preform architectures.
Viscosity characterization of highly filled photopolymerizable liquid encapsulants for microelectronic devices
Authors: Baikerikar Kiran K. , Scranton Alec B. 
Published: April 2004

AbstractIn this paper the viscosity of novel photopolymerizable liquid encapsulants (PLEs) for microelectronic devices was characterized as a function of the particle size distribution of the fused silica filler. Microelectronic devices are typically encapsulated using a transfer molding process in which the molding compound flows over the leadframe and wire bonds as it fills the mold. The molding compound should have a low viscosity to minimize problems such as: (1) incomplete mold filling; (2) lead frame movement during cavity filling; and (3) displacement of the wires that connect the die with the leadframe (wire sweep). We have developed a photopolymerizable liquid encapsulant using an epoxy novolac‐based vinyl ester resin that may alleviate these problems. In this contribution, we have investigated the blending of two different particle size distributions of fused silica to tailor the viscosity of PLEs for microelectronic applications. We have characterized the viscosity of highly filled PLEs containing 70.0, 72.0, and 74.0 wt% silica, and found that a blend of particle size distributions with a particle size ratio of 3.13 resulted in the best viscosity reduction. In addition, the PLE viscosity decreased slightly with increasing concentration of a silane coupling agent. The resulting PLEs exhibit low viscosities at ambient temperature while maintaining desirable material properties for microelectronic applications.