摘要:

AbstractThis paper reviews theoretical and experimental studies conducted in organic, ceramic, and metal matrix composites containing cylindrical, lamellar, and spheroidal inclusions as reinforcements. Mathematical formulations proposed to predict thermal expansion coefficients of fiber, disc, and sphere reinforced organic and inorganic matrix composites have been reviewed. Experimental studies undertaken to confirm theoretical predictions of thermal expansion coefficients of a variety of reinforcement geometry composites have also been discussed.

ISSN:0272-8397    

DOI:10.1002/pc.750090102

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractModel composites of spherical glass particles dispersed in a matrix of high density polyethylene were prepared with controlled variations in the interfacial structure. Dynamic‐mechanical measurements of the composites in the melt state were recorded. The physical properties are found to relate to the morphology, bonding, reactivity, and other characteristics of the interfacial region which can be controlled by the applied chemistry. The interfacial reactions can be monitored in‐sity by dynamic‐mechanical analysis and differential scanning calori

ISSN:0272-8397    

DOI:10.1002/pc.750090103

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe orientation development mechanisms that take place during molding of short‐fiber reinforced liquid crystalline polymer composites, have been analyzed and consequently the orientation development and properties distribution were studied for the case of thin wall large area components. Two factors associated with orientation development were investigated. The first is related to the melt front shape for in‐plane orientation distribution, and the second to the thickness of the skin layer where the alignment of the orientable liquid crystalline matrix and the rigid reinforcing fibers are of importance. The two basic factors were first verified by flow calculations using a computer assisted design (CAD) system and then experimentally validated. Experimental results for thin wall large area plaques have shown that the control over the melt front shape could be achieved with a narrow restrictor‐type gate and that the skin layer thickness is determined by the heat transfer processes during filling of the mold. Furthermore, a clear correlation has been established between the measured tensile properties and the ratio of skin layer to total thickness of the plaque. Such correlations should be generally developed for short‐fiber polymer composites for cases where rigidity and load bearing capabilities are of imp

ISSN:0272-8397    

DOI:10.1002/pc.750090104

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA method including the effects of fiber length and orientation distribution to predict elastic moduli of short fiber reinforced thermplastics (FRTP) is presented. The fiber length distribution in FRTP has an asymmetric character with a tail at the long fiber end. Statistical distribution functions such as Weibull or log‐normal can be used to represent this kind of distribution. Orientation distribution of fibers in FRTP can be characterized by a single parameter exponential function,\documentclass{article}\pagestyle{empty}\begin{document}$F(\theta) = \frac{{1 - \lambda \theta }}{{1 - e^{ - \frac{\P}{2}\lambda } }}$\end{document}. A large λ indicates a highly oriented material whereas small λ represents a quasi‐isotropic material. As fiber length and orientation distribution functions have been characterized, the elastic moduli of FRTP can be predicted. First, the mean elastic moduli of unidirectional plies are predicted through the fiber length distribution. Then the stacking sequence of laminate is assumed to be as the fiber orientation distribution of FRTP, and the overall elastic moduli of FRTP are estimated based on the laminate‐plate

ISSN:0272-8397    

DOI:10.1002/pc.750090105

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractDynamic fiber wettability measurements are performed on T‐300 carbon and Teflon fibers immersed in hexa methyl disiloxane (HMDS) silicone oil and a difunctional liquid epoxy resin, neopentyl diglycidyl ether (NPDGE). Specifically, four types of these carbon fibers, which are used to reinforce high performance composites, are studied. Decreases in the wetting force are observed for progressive immersions of all carbon fibers in the silicone oil but not observed with Teflon fibers, indicating adsorption may be occurring on the carbon surface. Perimeters determined from these wetting measurements on carbon fibers are larger than those calculated, assuming the fibers to be smooth cylinders. Scanning electron micrographs suggest this difference is attributable to surface crenulations. All carbon fibers immersed in the epoxy resin show non‐zero contact ang

ISSN:0272-8397    

DOI:10.1002/pc.750090106

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractA bisphenol‐type epoxy resin cured with phthalic anhydride was filled with three types of SiO2(untreated, silanized and smaller particle size), CaCO3, dolomite and Al2O3. Also, the concentration of silica was varied. Interaction of filler and resin was estimated by measuring the glass transition temperature (Tg) by different methods. Electron microscopy and x‐ray diffraction were used to study the structure of the boundary layer and the bulk polymer. It was found that silica forms strong bonds with the resin and that basic fillers (CaCO3, Al2O3) probably affect the crosslinking process with anhydride as hardener causing lowering o

ISSN:0272-8397    

DOI:10.1002/pc.750090107

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractHigh‐speed turbine mixers have been adapted for compounding filled thermoplastics by the partial flux method. The extreme shearing forces exerted by the mixing impellors simultaneously mixes and delaminates mica fillers to form finely dispersed compounds in a granular, partially fused state which can be directly injection molded without pelletizing. In practice, one turbine mixing unit can be employed for compounding all types of resins and fillers. The partial flux method permits compounding to be accomplished at peak sensor temperatures that are considerably below the resin softening or melting transitions, frequently 50°C less than normal compounding temperatures. The short residence times and reduced energy requirements possible with partial fluxing results in substantial cost reduction without compromising quality or performance. Examples are provided for polypropylene, nylon 66, poly(butene terephthalate), poly(ethylene terephthalate) and poly(phenylene oxide) alloys. Impact modifiers derived from carboxylated polyolefin waxes may be dispersed by the intense shearing action to form highly subdivided submicron particles, which promote crazing and shear deformation during fracture testing, thereby contributing to increased composited toughness with minor sacrifice in modulus and strength. The mechanical properties of micafilled thermoplastics have also been compared with those of short glass fiber composites. In certain applications requiring stiffness and dimensional stability at elevated temperatures, mica composites prepared by intensive mixing in a turbine mixer may be economically substituted for glass fiber counterpar

ISSN:0272-8397    

DOI:10.1002/pc.750090108

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractIn this study, a theoretical basis for the use of conductive composites was established. A percolation simulation program was used to determine critical area fractions for dispersions of rectangles in two dimensions. Both the aspect ratio and orientations of the rectangles were varied independently, and the simulation results were used to predict the effect of these parameters on the critical concentration of conductive flakes in a filled polymer. Above a certain aspect ratio defined as the “scaling limit,” the critical area fraction for rectangles was inversely proportional to aspect ratio. The scaling limit was smallest for a set of randomly oriented rectangles, and its value became larger as greater degrees of alignment were imposed. The smallest critical area fractions belonged to high aspect ratio, randomly oriented rectangles. The predictions of percolation theory were compared with results for dispersions of nickel‐coated mica in fine glass powder and in compression molded polyethylene. The critical volume fraction of mica was inversely proportional to flake aspect ratio over the range of aspect ratios tested. Electromagnetic interference (EMI) shielding effectiveness was examined for composites containing both aligned and randomly oriented flakes. For a given filler loading, the shielding effectiveness of the aligned flake composites was substantially lower than that of the composites containing randomly oriented f

ISSN:0272-8397    

DOI:10.1002/pc.750090109

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractUsing the concept of filler coating, a study has been made of the morphology and mechanical properties of polypropylene/talc/elastomer composites with a series of polar components as added elastomers. Both impact strength and stiffness of the blends were better than those of polypropylene homopolymer. Most of the polar components showed a considerable amount of filler coating, as evidenced by morphological studies. However, the impact strength of the composites was generally lower than that of similar blends with non‐polar elastomers, probably owing to (a) the high glass transition temperatures of the polar components, (b) the poor dispersion of some of the elastomeric phases, and (c) a reduced affinity of the elastomers for polypropylen

ISSN:0272-8397    

DOI:10.1002/pc.750090110

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY

摘要:

AbstractThe electrodeposition of saturated copolymers onto carbon fibers is investigated, focusing particular attention on improvement of shear and impact properties of the corresponding composites. Carbon fibers are electrocoated with poly(ethylene‐co‐acrylic acid) and poly(methyl vinyl ether‐co‐maleic anhydride) from aqueous media, and fabricated into epoxy composites. The results of interlaminar shear strength (ILSS) tests, initially employed to assess fibermatrix adhesion, are vitiated by the occurrence of mixed‐mode failure. Interfacial shear strength (IFSS) is hence evaluated by stressing single‐fiber composite specimens to obtain ultimate aspect ratios of the fiber fragments. The data are combined with fiber strengths by a recently developed statistical theory (1) to yield adistributionfor IFSS. Both copolymer interphases improve fiber‐matrix bonding to an extent greater even than that obtained with commercial fiber surface treatment. Good fiber‐matrix adhesion is further apparent from SEM studies of fractured ILSS test specimens. A key to this improved adhesion is the interpenetration of matrix resin and interphase polymer, revealed by electron microprobe analysis (2). Notched Izod impact strength is also increased over uncoated‐fiber composites. These copolymer interphases behave as deformable interlayers, absorbing impact energy and blunting the growing crack tip. Further energy is absorbed in deflecting the crack through a more tortuous path. Simultaneous improvements in impact and shear strengths are thus obtained, which may be further enhanced by optimizing the electrodeposition parameters and the coating thickness. The influence of the interphase on composite properties is better understood from this study, paving the way for refinement in

ISSN:0272-8397    

DOI:10.1002/pc.750090111

出版商:Society of Plastics Engineers    

年代:1988

数据来源: WILEY