DIRECT EXAMINATION OF INTERPHASES IN MODEL COMPOSITES USING PHASE-STEPPING PHOTOELASTICITY

摘要

A phase-stepping photoelastic technique has been used to evaluate quantitatively the effect of an interphase region on interfacial shear stress at a fibre-break and hence the efficiency of the interfacial bond. E-glass fibres were coated with an epoxy resin of lower Young's modulus and yield strength than that of the matrix resin as well a plasma copolymer. This enables the effect of sizing or modified matrix region to be quantified. The micro-mechanical response in the matrix at the interface/interphase has been described in detail using contour maps of isochromatic fringe order. From these, the profile of the interfacial shear stress at fibre-breaks has been calculated. In the presence of an interphase region the stress transfer profile was modified and the stress concentration associated with a transverse crack reduced.