Temperature dependence of the interfacial shear strength in glass–fibre epoxy composites

The present work focuses on further investigation of the hypothesis that a significant fraction of apparent interfacial shear strength (IFSS) in fibre-reinforced composites can be attributed to a combination of residual radial compressive stress and static friction at the fibre-polymer interface. The temperature dependence of the interfacial properties of a glass fibre-epoxy system has been quantified using the laboratory developed TMAmicrobond technique. The temperature dependence of apparent IFSS of glass fibre - epoxy in the range 20°C up to 150°C showed a significant inverse dependence on testing temperature with a major step change in the glass transition region of the epoxy matrix. It is shown that the magnitude of the residual radial compressive stress at the interface due to thermal and cure shrinkage is of the same order of magnitude as the measured IFSS. It is concluded that it possible to suggest that residual stress combined with static adhesion could be the major contributor to the apparent interfacial adhesion in glass fibre – epoxy systems.