摘要:

AbstractThe nine independent stiffness constants of injection‐molded tensile bars of poly(phenylene sulfide) reinforced with 30 and 40% by weight of carbon or glass fibers have been measured by ultrasonic techniques. The thermal conductivities along the three principal directions of these thermoplastic composites have also been determined by the laser‐flash radiometry method. The elastic moduli (tensile and shear) and thermal conductivity increase with increasing fiber volume fraction,vf, with the tensile modulus and thermal conductivity along the mold flow direction showing the greatest change. For a composite, containing 40 weight % of carbon fibers, the Young's modulus and thermal conductivity along this direction exceed those of the polymer matrix by a factor of 8. Using the known values ofvfand the observed aspect ratio and orientation factor of the fibers, the elastic moduli and thermal conductivity have been calculated on the basis of the laminate theory. The agreement between theoretical predictions and experimental data is better than 10% on the aver

ISSN:0272-8397    

DOI:10.1002/pc.750130202

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of hot fuming nitric acid (FNA) treatment on the adhesion of ultra‐high modulus polyethylene fabrics to an epoxy resin has been investigated. Mechanical and molecular characterization of the interface has been attempted. Fourier transform infrared diffuse transmittance spectroscopy has been used to monitor the chemical changes introduced by the FNA treatment as well as the nature of the interface between the fibers and the epoxy resin on the molecular level. Scanning electron microscopy has been used to examine the morphological consequences of the FNA treatment. Flexural and interlaminar shear properties of the composites have been measured as a function of the extent of surface treatment. Esterification of the FNA treated polyethylene fibers is used to examine the role of surface functionality to the mechanical performanc

ISSN:0272-8397    

DOI:10.1002/pc.750130203

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractA model capable of predicting the process‐induced macroscopic in‐plane material response of semicrystalline thermoplastic matrices and their composites was developed. Thi sinvestigation focused on the material response of a single layer or ply of neat PEEK matrix and its carbon fiber composite (APC‐2) when subjected to various processing histories. Specifically, the response of the material moduli and processing strains as a function of temperature and the degree of crystallinity were studied. The kinetic‐viscoelastic response of the matrix was determined from a modified form of the Standard Linear Solid model. A constitutive relation was proposed to quantify resign shrinkage as a function of thermal history, which incorporated crystallization. For a specific process history, the effective composite mechanical properties were determined from micromechanics models. Both neat and composite processing strains were evaluated to show the effect of fibers on the matrix dominated response (90° direction). In addition, comparisons of model moduli predictions with experimental measurements were performed. This study demonstrated that an increase in the degree of crystallinity results in an asymmetric shift of the modulus in the glass transition region to higher temperatures. Also, strains due to crystallization were predicted to be much smaller in comparison to the strains resulting from thermal contraction of the PEE

ISSN:0272-8397    

DOI:10.1002/pc.750130204

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractA study on anisotropic material flow of polymeric composites in compression molding was conducted. Flow resistance and material anisotropy were measured by compression and tension tests to quantify the inhomogeneity of chopped fiber reinforced polymeric composites. The material was assumed to obey Hill's anisotropic yield criterion with its associated flow rule. An anisotropic finite element formulation was developed to simulate the material flow under various conditions. This two‐dimensional model was applied to plane strain compression in a mold with plate‐rib type geometry to substantiate the effect of fiber induced anisotropy. The predictions were compared with experimental resu

ISSN:0272-8397    

DOI:10.1002/pc.750130205

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThree‐point‐bend testing of a continuous unidirectional glass reinforced unsaturated polyester composite was chosen as a model to study the acoustic emission (AE) response and associated damage events in composite materials. Conventional three‐point‐bend samples were tested over a wide range of span‐to‐depth ratios, with failure modes established by post‐failure scanning electron microscope (SEM) analysis. In addition,in‐situAE monitoring with simultaneous SEM recording was undertaken during three‐point‐bend testing inside an SEM vacuum chamber. These two test methods, using different equipment and sample geometry, were found to yield similar mechanical and AE results. Thein‐situtests enabled the development of the various stages of damage to be observed while the AE response was simultaneously monitored. This enabled the AE signals to be unambiguously assigned to specific damage accumulation mechanisms. It was concluded that the AE amplitude distribution can be divided into three main ranges in this system: 60 to 65 dB, 75 to 85 dB, and larger than 90 dB corresponding to matrix damage, fiber‐matrix debonding, and fiber breakage, respectively. It has been demonstrated that the coupling of AE monitoring with SEM recording of a composite system undergoing mechanical loading is a very powerful technique in the study of damage accumulation in advan

ISSN:0272-8397    

DOI:10.1002/pc.750130206

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThis paper is concerned with the creep behavior of short fiber‐reinforced thermoplastics, especially with regard to the role of fiber orientation. Rectangular samples of low density polyethylene (LDPE) and polycarbonate (PC) containing varying amounts of carbon fibers were prepared by compression and injection molding. The materials were compounded using a technique producing a concentration independent fiber length distribution. The orientation distribution, on the other hand, was found to be strongly influenced by fiber concentration. The creep parameters were measured for both LDPE and PC. The contraction ratio was determined for the PC samples. In the case of LDPE reliable data could not be obtained due to the low modulus of the matrix. The creep properties of the PC and LDPE samples varied significantly with the orientation of the fibers. The creep strain was measured as a function of time for both polymers for different fiber concentrations and orientations. The predictions of the Halpin‐Tsai equation underestimated the experimental strain figures somewhat when the stress direction coincided with that of the fiber orientation. When the stress acted across the fibers the theoretical and experimental results showed satisfactory agreement. A plausible explanation is that incorporation of carbon fibers changes the morphology of the matrix material. We conclude that the contraction ratio is an important measure of the volume and its changes during deformation, especially with regard to its relation to the free volume and similar quantities. We have shown that the necessary data can be obtained, in spite of experimental difficulties even for anisotropic samp

ISSN:0272-8397    

DOI:10.1002/pc.750130207

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractFranklin Fiber whisker‐reinforced silicone rubber composites were molded using both transfer and compression molding. Processing parameters, such as sprue design, milling procedure, and mold temperature were varied. The fiber orientation in the composites is anisotropic and independent of sprue design and mold temperature, but dependent on milling procedure. Fiber attrition is significant for all samples. The Young's modulus is affected by fiber orientation. The experimental modulus values are higher than those predicted by the Halpin‐Tsai equations for short fib

ISSN:0272-8397    

DOI:10.1002/pc.750130208

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750130201

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY