bluuebunny/crossref_metadata_2025_split huggingface dataset:
In‐situ reinforcement of PBT/ABS blends with liquid crystalline polymer
Authors: Tjong S. C. , Jiang Wei 
Published: April 2004

AbstractTernary in‐situ poly(butylene terephthalate) (PBT)/poly(acrylonitrile‐butadienestyrene) (ABS)/liquid crystalline polymer(LCP) blends were prepared by injection molding. The LCP used was a versatile Vectra A950, and the matrix material was PBT/ABS 60/40 by weight. Maleic anhydride (MA) copolymer and solid epoxy resin (bisphenol type‐A) were used as compatibilizers for these blends. The tensile, dynamic mechanical, impact, morphology and thermal properties of the blends were studied. Tensile tests showed that the tensile stregth of PBT/ABS/LCP blend in the longitudinal direction increased markedly with increasing LCP content. However, it decreased sharply with increasing LCP content up to 5 wt%; thereafter it decreased slowly with increasing LCP content in the transverse direction. The modulus of this blend in the longitudinal direction appeared to increase considerably with increasing LCP content, whereas the incorporation of LCP into PBT/ABS blends had little effect on the modulus in the transverse direction. The impact tests revealed that the Izod impact strength of the blends in longitudinal direction decreased with increasing LCP content up to 10 wt%; thereafter it increased slowly with increasing LCP. Dynamic mechanical analyses (DMA) and thermogravimetric measurements showed that the heat resistance and heat stability of the blends tended to increase with increasing LCP content. SEM observation, DMA, and tensile measurement indicated that the additions of epoxy and MA copolymer to PBT/ABS matrix appeared to enhance the compatibility between PBT/ABS and LCP.
Synthesis and properties of a low hygrothermal stress epoxy molding compound for electronic encapsulation
Authors: Tai Horng‐Jer , Wang J. B. , Chou Hui‐Lung 
Published: April 2004

AbstractA vinyl siloxane‐modified cresol novolac epoxy (CNE)/cresol novolac hardener (CNH) molding compound with both siloxane and epoxy components capable of further crosslinking is synthesized. Through careful adjustment of TPP dosage, the Tg of CNE/CNH resins can be effectively controlled. The VS‐modified CNE/CNH compound possesses a lower Young's modulus, a lower linear coefficient of thermal expansion (LCTE), and a higher break strain than those of its unmodified counterpart. The combination of lower mechanical moduli and lower LCTE results in a 33% reduction in thermal stress caused by thermal mismatch. In addition to thermal mismatch, chemical shrinkage in a molding process is also an important factor that affects the interfacial strain between a compound and a substrate. The incorporation of vinyl siloxane (VS) incurs a 25% reduction in the equilibrium moisture uptake and a 16% reduction in the coefficient of diffusion for the VS‐modified compound. This modified compound can help alleviate the popcorning problems in IC packages resulting from hygrothermal stresses.
Rheological behavior of (short) carbon fiber/thermoplastic composites. Part II: The influence of matrix type
Authors: Carneiro O. S. , Maia J. M. 
Published: April 2004

AbstractThis study is the second of a series of two papers on the rheological properties of VGCF/thermoplastic composites, its aim being to compare the performance of different thermoplastic matrices when reinforced with sub‐micron Vapor Grown Carbon Fibers (VGCF). For this purpose, two polymers (polypropylene, PP, and polycarbonate, PC) were used to produce composites with different levels of fiber incorporation. The highest content VGCF composites were produced, in pellet form, using a co‐rotating twin‐screw extruder. These were subsequently diluted during the injection molding stage to obtain composites with different levels of fiber content. The rheological characterization was performed, using the latter materials, by means of both capillary and rotational rheometries, results being presented and discussed in terms of reinforcing capability and its susceptibility to temperature, for the relevant functions in both shear (steady and oscillatory) and extensional flows. The results show that VGCF have a higher reinforcing capability, both rheological and mechanical, when incorporated in the PP matrix. This better performance can be due either to better adhesion between the fibers and PP in comparison to PC, or to a higher degree of melt penetration of non‐wetted fiber rich areas and lower fiber length degradation, owing to the lower viscosity of PP in the extrusion shear rate range.
Morphological development during injection molding of self‐reinforcing composites. II: Numerical simulations and analytical predictions
Authors: Li Zhigang , Narh Kwabena A. 
Published: April 2004

AbstractIn this study, combined numerical simulation of injection molding and analytical calculations have been used to determine the velocity and elongational strain in the advancing melt front (AMF) region, during the molding of PET/LCP blends, at various injection molding conditions. A model is proposed that establishes the relationship between the aspect ratio of LCP fibers and elongational strain, based on the assumption of an affine deformation of the LCP domains. This model enables us to predict the processing dependent morphology of injection molded PET/LCP blends. The effect of processing parameters on the morphology development during injection molding were investigated. The studies show that injection speed and mold temperature have significant effects on the morphological development of the blends, compared with the effect of the melt temperature. A good correlation between calculated and scanning electron microscopy results was obtained.
Statistical characterization of fiber permeability for composite manufacturing
Authors: Pan Rong , Liang Zhiyong , Zhang Chuck , Wang Ben 
Published: April 2004

AbstractResin transfer molding (RTM) is considered one of the most promising composite fabrication techniques because of its relatively low equipment and tooling costs, short cycle times, and excellent design flexibility. Yet several technical issues impede wider application for this process. One of those issues is the measurement and characterization of fiber preform permeability, which plays a key role in process design and control. In this study, an automatic permeability measurement apparatus with automatic data acquisition and processing capabilities has been developed to improve measurement accuracy and reliability. Four major factors and their effects on permeability for a knitted and a woven fabric performs are investigated. Design of experiments, ANOVA analysis, and distribution characterization techniques are used to analyze the permeability‐influencing factors and statistical properties of fiber preform permeability. It is found that the fiber preform permeability values vary significantly for different mold shapes and fiber handling conditions. It is also revealed that permeability values for both fabrics follow normal distributions, even though their means and variances are different. These results can be used to better understand the behavior of the RTM process and to improve process design and control.
Effect of impregnation conditions on prepreg properties and honeycomb core crush
Authors: Martin C. J. , Putnam J. W. , Hayes B. S. , Seferis J. C. , Turner M. J. , Green G. E. 
Published: April 2004

AbstractThe effects of fiber tension, line speed, and impregnation temperature and pressure in the prepregging process used to manufacture a commercial high temperature toughened epoxy prepreg were investigated in a Design of Experiments (DOE) to understand core crush in honeycomb composite structures. The prepregs developed in this DOE were characterized by tack, permeation, optical microscopy, and frictional resistance. Of these methods, frictional resistance was found to correlate with core crush. Tack, permeation, and optical microscopy provided a basis for understanding this relationship through impregnation and morphology. Prepregs manufactured with high fiber tension showed greater crush and less frictional resistance than prepregs with manufactured low fiber tension. These low tension prepregs were found to have more fibers at the prepreg surface, allowing them to grip the adjacent surface and resist slippage. By identifying the key factors influencing honeycomb core crush, the prepregging process was modified, producing a crush‐resistant prepreg for end use manufacture.
A review of methods for improving the interfacial adhesion between carbon fiber and polymer matrix
Authors: Tang Long‐Gui , Kardos John L. 
Published: April 2004

AbstractThe interfacial properties between carbon fibers and surrounding matrix of a composite are drastically affected by interfacial structure. This structure mainly relates to the surface physico‐chemistry of the fiber, which includes its surface chemical groups and microstructure, morphology, surface area, and surface free energy. These properties can be changed by various surface treatments, including various dry and wet oxidation steps, plasma treatment, electrodischarge, and fiber sizing or coating. These methods improve the interfacial properties significantly and synergistically, although each treatment has its specific application area.
Improvement of carbon fiber/PEEK hybrid fabric composites using plasma treatment
Authors: Jang Jyongsik , Kim Hyuncheol 
Published: April 2004

AbstractA carbon fiber (CF)/polyetheretherketone (PEEK) composite was manufactured using hybrid fabrics composed of CF and PEEK fiber. The fiber/matrix interface was modified by low temperature oxygen plasma treatment. Scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS) and Fourier transform attenuated total reflection infrared spectroscopy (FTIR‐ATR) were used to relate the roughness and the functionality of the CF surface with the interfacial adhesion strength of the CF/PEEK composite. Scanning electron micrographs showed that plasma treatment increased the roughness of the CF surface up to 3 min of plasma treatment time; and prolonged treatment resulted in overall smoothing. XPS results confirmed that increasing treatment time marginally increased surface functionality: treatment for more than 5 min decreased the surface functionality by removing the active site of the CF surface. In addition, flexural strength and interlaminarshear strength (ILSS) of the CF/PEEK composite were measured. Their maximum values were observed at 3 min of plasma treatment time as a result of surface roughening by plasma etching. The SEM results were correlated with mechanical properties of the CF/PEEK composite.
Kinetic studies of thermoset cure reactions: A review
Authors: Yousefi A. , Lafleur P. G. , Gauvin R. 
Published: April 2004

AbstractThis article presents a review of the kinetic studies on the cure reactions of thermosetting resins. The emphasis is placed on those conducted using the thermal analysis by differential scanning calorimetry. Two important categories of kinetic models are discussed and some existing parameter estimation techniques are presented. A variety of factors affecting the cure reactions, including the formulation of cure and process variables, are discussed. At the end, two different approaches in modeling the chemoviscosity of polymeric reactive systems are presented and some existing chemorheological models developed based on these approaches are briefly reviewed.
Fatigue delamination growth under cyclic compression in glass/epoxy composite beam/plates
Authors: Kardomateas G. A. , Malik B. 
Published: April 2004

AbstractResults are reported on the fatigue growth of internal delaminations in glass/epoxy composite beam/plates subjected to constant amplitude cyclic compression. Because of compressive loading, these structures undergo repeated buckling/unloading of the delaminated layer with a resulting reduction of the interlayer resistance. A noteworthy feature of the problem is that the state of stress near the delamination tip is of mixed mode (I and II). The present combined experimental/analytical investigation for the glass/epoxy composites complements our earlier studies on delamination growth under cyclic compression in unidirectional graphite/epoxy specimens. Several configurations are studied with the delamination located at different depths (through the thickness) and with different applied maximum compressive displacements. The experimental data are correlated with the predictions from a combined delamination buckling/postbuckling and fracture mechanics model. A mode‐dependent fatigue delamination growth law is used together with an initial postbuckling solution for the deformation pattern of the delaminated layer and the substrate, which does not impose any restrictive assumptions on the delamination thickness and plate length. The experimental data seem to be adequately correlated with the theory and the fatigue delamination growth is found again to be strongly affected by the relative location of the delamination through the plate thickness. Finally, a comparison of the cyclic growth rate in glass/epoxy specimens with the corresponding one in graphite/epoxy specimens of the same geometry and applied loading shows that the delamination would grow much faster in the graphite/epoxy specimens.
Effect of moisture content on the properties of silanized jute‐epoxy composites
Authors: Gassan Jochen , Bledzki Andrzej K. 
Published: April 2004

AbstractThe composites investigated in this article were epoxy resins reinforced with jute‐fibers. The jute‐fibers were modified with an epoxyfunctional‐γ‐glycidoxypropyltrimethoxy‐silane (A‐187 from Osi‐Specialtis GmbH, Germany), which works as a coupling agent between fiber and matrix. The introduction of the coupling agent distinctly influences the mechanical properties of the composite: Dynamic modulus was doubled, damping was reduced by about 50%, and the Wöhler curves showed fatigue limits increased by about 20%. The investigations pointed out further that the moisture uptake of composites with silanized fibers was reduced by about 10–20%. Moisture at equilibrium and kinetics of absorption increase with increasing fiber content. Finally, the application of the coupling agent caused a reduction of moisture effects on mechanical properties. Tensile strength, tensile modulus, and fatigue strength under repeated tensile stress were reduced up to 30%. This tendency was not duplicated in the results for flexural strength and flexural modulus.
Aqueous powder slurry manufacture of continuous fiber reinforced polyethylene composite
Authors: Tang Longgui , Li Lin , Yi Xiaosu , Pan Zuren 
Published: April 2004

AbstractA model and experiment of an aqueous slurry process are reported. According to an ideal structure of a fiber‐reinforced composite, we present a square geometrical model to build up the relationships among some important parameters in the process such as power particle diameter, wet slurry concentration, flow distance of melting power particle, and fiber volume fraction of the composite. Practical experiments based on these relationships provide the optimum parameters for manufacturing the continuous fiber reinforced polyethylene matrix composite.
Synthesis and characterization of two novel maleimides containing an epoxy backbone
Authors: Liang Guozheng , Gu Aijiuan 
Published: April 2004

AbstractTwo novel maleimides containing an epoxy backbone, diglycidyl ether of bisphenol A and TDE‐85 epoxy, were synthesized and characterized. The maleimides, coded EMs were prepared by reacting the corresponding epoxy resin with N‐(p‐carboxy phenyl) maleimide. EMs have lower softening and curing temperature and a wider processing window than the common bismaleimide. Properties of cured resins show that EMs have improved toughness and good thermal properties. Composites based on EMs and woven glass cloth were also prepared and their properties determined.
Mechanical behavior of textile composite materials using a hybrid finite element approach
Authors: Gowayed Yasser , Yi Li 
Published: April 2004

AbstractA novel analytical solution is presented to describe the mechanical behavior and failure of textile reinforced composites. This solution is constructed from two parts. First a geometrical model, based on a processing science approach coupled with graphical rendering, is utilized to quantify the spatial characteristics of the fabric preform inside the composite. A 3‐D iterative hybrid finite element analysis is then used, utilizing data acquired from the geometrical model, to predict the stressstrain behavior of the composite. Inelastic behavior is modeled using an expanded Hahn and Tsai model and maximum stress criterion is used to predict initial failure. Damage progression is predicted based on a stiffness reduction approach. AS4 carbon/epoxy plain weave composite laminates, with a range of fiber volume fractions, have been tested. A 3‐D woven E‐glass/poly‐vinyl‐ester (PVE) angle interlock composite was also tested. Analytical results are compared with results from this experiment as well as other analytical models and experimental data in the literature. Theoretical model predictions are in agreement with most experimental data.
Accurate permeability characterization of preforms used in polymer matrix composite fabrication processes
Authors: Lai Yen‐Huang , Khomami Bamin , Kardos John L. 
Published: April 2004

AbstractThe permeabilities of fabrics composed of carbon and glass fibers have been determined by utilizing both simple 1‐dimensional and 2‐dimensional radial flow measurements using silicone oil and motor oil as permeants. The carbon fabric is typical of that used in fabrication of aerospace grade polymer matrix composites, while the glass fabric is a 3‐dimensional woven fabric that has been proposed as a standard reference material for permeability characterization. Our results indicate that reliable permeability data for fiber preforms with varying architectural complexity can be obtained provided that the experiments are performed with utmost care and that appropriate equations are used to analyze the data. In‐plane permeabilities for the carbon fiber preforms from transient unidirectional constant flow rate and constant pressure experiments agreed within 5%, regardless of the preform orientation to the flow direction. Steady‐state results on the same preforms showed agreement within 2% between constant flow rate and constant pressure experiments. The capillary pressure effect was shown to be negligible for the transient experiments. The maximum difference between the transient and steady state permeability values was 3%. The maximum difference between a permeability measured with unidirectional flow and the same permeability measured with radial flow is less than 10%.
Composites as friction materials: Recent developments in non‐asbestos fiber reinforced friction materials—a review
Authors: Bijwe Jayashree 
Published: April 2004

AbstractReplacement of conventional asbestos based friction materials has been called for because of bans on the use of asbestos. Research in this direction in the last decade has led to the development of more efficient asbestos‐free friction materials for automobiles. Fiber reinforced polymers show great promise for applications in modern vehicles. This review article focuses on the recent developments in the application of composites as friction materials. The first part of the article contains brief information about brakes, their action, brake materials, their desired properties, etc. The second part deals with the recent developments in non‐asbestos fiber reinforced friction materials.
A nonlinear control method for resin transfer molding
Authors: Mogavero J. , Sun J. Q. , Advani S. G. 
Published: April 2004

AbstractIn performing permeability measurements on the fiber reinforced preforms typically used in the resin transfer molding (RTM) process, two types of fluid injection are commonly utilized: constant fluid pressure and constant fluid flow rate. The constant pressure condition is often enforced by placing the test fluid within a pressure pot and supplying a constant gas pressure, thereby forcing the fluid into the mold under a constant pressure. In the case of constant fluid flow rate, the fluid is often supplied by forcing a piston through a fluid‐filled cylinder at a constant rate of displacement through the use of a press or Instron machine. This paper presents a nonlinear control method for providing constant flow rate RTM processes with a pressure pot solely through the use of a regulator. Computer simulations of the control examined the effect of various parameters on the ability to maintain constant flow rate. Rectilinear flow experiments were carried out to evaluate the theoretical development. Experimental results are in good agreement with the computer simulations. Both computer simulations and experiments show significant promise for the proposed control methodology.
Measurement of the electromagnetic shielding properties of mechanically loaded composites
Authors: Laight A. , Court R. , Treen A. , Buijs J. 
Published: April 2004

AbstractThe use of fiber reinforced plastic (FRP) composites for large structures is becoming more widespread. With composites increasingly called upon to replace structures traditionally fabricated from metals the requirement to find suitable methods of providing adequate electromagnetic shielding (EMS) is often of prime importance. This paper describes a measurement technique employing induced magnetic eddy currents for assessing electromagnetic shielding. The technique does not require costly screened rooms or large test panels and is portable and easy to use. The effectiveness of the technique for comparing the electromagnetic shielding of material samples after mechanical loading is demonstrated, and it is concluded that the method offers a cheap and reliable means of comparing screening solutions for composite materials in high loading or fatigue applications. The potential for development of the method into a through‐life shielding monitoring tool is also highlighted.
A comparison of compounding processes for wood‐fiber/thermoplastic composites
Authors: Park Byung‐Dae , Balatinecz John J. 
Published: April 2004

AbstractThis study was carried out to investigate the feasibility of developing a continuous compounding process for wood‐fiber/thermoplastic composites using the Szego mill, a unique, high speed planetary ring‐roller grinding mill. Prior to compounding, air‐dried sawdust was ground to evaluate the grinding effect in the mill. As the feed rate and the mill speed increased, the particle size increased and decreased, respectively. Sawdust particles were successfully compounded in linear low‐density polyethylene using the Szego mill without any major heat application. A Gelimat mixer, used for the compounding of wood fiber through a high‐shear thermokinetic mixing process, was also employed for comparison. Composites with 30 wt% wood fiber were prepared by both compounding processes, and their mechanical properties were evaluated. The use of a compatibilizer in compounding improved the mechanical properties of the composites regardless of the compounding process. The composites prepared by Szego mill compounding showed comparable strength properties with their counterparts from the Gelimat mixer. Power consumption during mill compounding was in the range of twin‐screw extruder processing.