Interfacial shear strength and failure modes of interphase-modified graphite-epoxy composites

Autor: James P. Bell, Angel S. Wimolkiatisak
Rok vydání: 1989
Předmět:
Zdroj: Polymer Composites. 10:162-172
ISSN: 1548-0569
0272-8397
DOI: 10.1002/pc.750100304
Popis: Electrocopolymerization of acrylonitrile/methyl acrylate/acrylic acid, acrylonitrile/methylacrylate, and glycidyl-acrylate/acrylonitrile interlayers onto Hercules AS4 graphite fibers was used to improve simultaneously the effective interfacial shear strength, τe, and the fracture toughness of graphite-epoxy composite materials. With a single-fiber fracture test, τe for these coated fibers (embedded in a diglycidyl ether of bisphenol A - 4,4′-methylenedianiline matrix) was determined at various temperatures and under various hygrothermal treatments. At room temperature, the coated samples showed slightly improved shear strength over the uncoated sample. At elevated temperatures, a plot of τe vs. temperature for the uncoated sample showed two distinctive regions: an interface-controlled plateau region at low temperatures, and a matrix-controlled region at high (>80°C) temperatures. Only one region, which was controlled by the matrix and the interlayer, was observed for the GA/AN coated sample. The τe values determined were slightly higher than the shear strength of the bulk matrix, possibly because of stronger matrix properties at the interface. Optical micrographs of the coated sample tested at temperatures less than 100°C showed no matrix crack perpendicular to the fiber axis, indicating that the interlayer has effectively blunted the crack tip and restricted its propagation. The effect of moisture in the sample was to reduce τe for the coated sample. Upon dehydration, the strength was partially recovered. The treatments did not affect the uncoated sample, however. The fragmentation length data were fitted well by both Gaussian and Weibull distributions.
Databáze: OpenAIRE
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