DETERMINATION OF THE INTERFACIAL SHEAR-STRENGTH OF GLASS-FIBER-REINFORCED PHENOLIC COMPOSITES BY A BIMATRIX FRAGMENTATION TECHNIQUE

The stress transfer in bimatrix fragmentation specimens has been succe ssfully analysed by finite element methods. When a bimatrix specimen i n which a glass fibre coated with phenolic resin was embedded in a duc tile epoxy resin block and tensile tested, it was found that the pheno lic resin coating first fractures transversely, but the transverse fra cture does not affect the stress transfer from epoxy to the phenolic r esin coating and to the fibre. There ave two characteristic values of the interfacial shear stress at the two interfaces, and they are relat ed to the yield and cold-draw strengths of the epoxy resin. The bimatr ix fragmentation technique cart be used to determine the interfacial s hear strength of a composite with any combination of failure strains o f the fibre and the matrix: The maximum shear stress developed at the interface is limited by the yielding of the support resin. It was foun d, in using the bimatrix fragmentation technique, that fibre treatment with Epikote 828 resin significantly improved the interfacial shear s trength of glass-fibre-reinforced phenolic composites. (C) 1996 Elsevi er Science Limited