摘要:

AbstractA test methodology that utilizes unidirectional, hoop‐wound tubes to determine matrix‐dominated mechanical properties of unidirectional fiber composite lamina is described. Longitudinal shear modulus and strength as well as transverse Young's modulus, transverse tensile strength, and transverse compressive strength are obtained from a single thin‐walled tube specimen and fixturing design. Data presented for two carbon‐fiber‐reinforced epoxy composite materials illustrate the simplicity and precision of the described

ISSN:0272-8397    

DOI:10.1002/pc.750130102

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThermoplastic composites in general have been found to display improved resistance to impact damage over their thermosetting counterparts. However, in earlier work, we presented data that suggested that in poly(etheretherketone) (PEEK) based composites, damage tolerance may be adversely affected if cooling rates are too slow in the processing of these parts. In this work, ultrasonic C‐scan and compression‐after‐impact testing were implemented on PEEK APC‐2 plaques cooled at three different cooling rates, in addition to toughened epoxy and bismaleimide plaques processed conventionally as a comparison. It was found that the damaged areas as measured ultrasonically varied significantly between the PEEK samples cooled at different rates, and that under the slowest cooling conditions, the damaged areas approached those of the thermosetting systems tested. However, because compressive strengths before impact were found to be greater on slow cooling, the differences in compression‐after‐impact were less dramatic than one would have expected from the C‐scan results alone. Variations in crystallinity as well as spherulite size were the source for the differences in damaged areas as well as in compres

ISSN:0272-8397    

DOI:10.1002/pc.750130103

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of surface treatment of pitch‐based carbon fiber on a new engineering thermoplastic resin, polyethernitrile, was investigated. Pitch‐based carbon fiber (CF) was treated in two separate oxidizing solutions. In the first method, a nitric acid solution was used as an oxidizing agent. In the second method, a hydrogen peroxide solution was used. Both methods demonstrated that each of these solutions was a satisfactory oxidizing agent for the pitch‐based CF. These treated fibers were combined with polyethernitrile polymer by the powder impregnation method, and unidirectional laminates were obtained. Improvements in both interlaminar shear strength and transverse flexural strength were achieved. The laminates fabricated from the treated CF maintained the same longitudinal flexural strength as laminates from the untreated control. In addition, scanning electron micrographs of composite fracture surfaces also showed excellent bonding of the treated

ISSN:0272-8397    

DOI:10.1002/pc.750130104

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractAn isothermal two‐dimensional shear‐thinning model of the compression molding of long‐glass‐fiber–reinforced thermoplastic is presented. A transverse isotropic behavior is introduced by considering two different pairs of power‐law coefficients. First (K1,m1) is linked to the shear deformations through the thickness and to the compression deformation; second (K2,m2) is associated to the expansion motions in the plane.K2is significantly greater thanK1because of the influence of the glass mat structure, which resists stretching in the plane of the part. These coefficients are determined by fitting the computed and experimental mold closing forces in a circular isothermal compression‐molding test. The average velocity through the thickness is obtained by a variational method. Incompressibility is ensured by penalization. A finite element method is used, with a convected mesh and remeshing technique. The agreement between this model and experimental results (shape of the sample, mold closing force, pressure) performed on a rectangular

ISSN:0272-8397    

DOI:10.1002/pc.750130105

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractAn investigation was conducted to evaluate the effect of blending thermoplastic filament fibers with carbon filament fibers in varying yarn forms to study the efficiency of matrix wetting and infiltration into a laminate. Poly(etheretherketone) (PEEK) and poly(phenylene sulfide) (PPS) were studied in commingled, DREF, and powder form, as a flat triaxial braid. The as‐braided and laminated specimens were both subjected to tensile testing and optical microscopy to establish the efficiency of the impregnation process. It was observed that both thermoplastic matrices commingled with carbon yarn maximized the tensile properties and produced the best quality laminate. To impart the best translational properties of the thermoplastic matrix to the carbon/thermoplastic composite, improvements are necessary in the commingling and powder infiltration processe

ISSN:0272-8397    

DOI:10.1002/pc.750130106

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractMechanical properties such as tensile and flexural properties as well as impact behavior of nickel‐powder–filled isotactic polypropylene composites were investigated in the composite composition range 0–3.5 volume % Ni. Tensile modulus, strength, and elongation‐at‐break decreased with increase in Ni content, which is attributed to the introduction of discontinuity in the structure. Analysis of tensile strength data indicated the introduction of stress concentration consequent upon addition of Ni into polypropylene. Izod impact strength at first increased up to a critical Ni content beyond which the value decreased inappreciably while flexural modulus and strength increased with filler conc

ISSN:0272-8397    

DOI:10.1002/pc.750130107

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractThe effect of filler content, temperature, and frequency of the applied electric field on DC and AC electrical conductivities of composites of nickel‐coated carbon fibers and polypropylene are considered. The impedance behavior and the dielectric properties of these composites were studied in the low frequency range 10 Hz–30 kHz. It was found that the volume electrical resistivity shows filler content and temperature dependence. The calculated activation energy of the thermal rate‐process decreases with the filler concentration, while the shielding effectiveness increases. The overall observed permittivity of the composites increases with the filler concentration, and the dielectric behavior is discussed in terms of the space charge, electronic and interfacial polarization within the covered frequency range. It was observed that the AC conductivity is nearly independent of the frequency below 100 Hz and increases with frequency above this range. Finally, it was concluded that addition of nickel‐coated carbon fibers could alter the electrical conduction mechanism and the polarization process of the polymeric

ISSN:0272-8397    

DOI:10.1002/pc.750130108

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

摘要:

AbstractAn experimental method is presented to determine the amount of resin flow within a composite laminate during cure. The method is analogous to the use of radioactive tracers in other applications. Heavier elements such as chlorine and bromine, which may be naturally present in small amounts in epoxy resins are used to follow resin flow and mixing. The presence and the quantity of these “tags” is determined using wavelength dispersive X‐ray analysis in a scanning electron microscope. With the resins in this study, it is shown that it is possible to measure volume fractions of resin with accuracies ranging from ±0.5 to ±3 volume %. By using brominated resin in only one layer of a laminate, the degree of flow and mixing can be followed accurately. The results suggest that there is considerable resin mixing as well

ISSN:0272-8397    

DOI:10.1002/pc.750130109

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY

ISSN:0272-8397    

DOI:10.1002/pc.750130101

出版商:Society of Plastics Engineers    

年代:1992

数据来源: WILEY