HYGROTHERMAL AGING EFFECTS ON THE STATIC FATIGUE OF GLASS EPOXY COMPOSITES

A study of the effects of water ageing on the static fatigue behaviour of unidirectional glass/epoxy composites is presented. The failure mechanisms associated with fatigue damage were investigated under three-point bending loading. Depending on the ageing temperature, two failure features were identified: either fibre microbuckling on the compressive side of the specimen, or progressive cracking on the tensile side. Microbuckling has been found to be related to the reversible plasticization of the epoxy matrix, as measured by dynamic mechanical thermal analysis. On the other hand, tensile failure was associated with an irreversible weakening of the fibres and interfaces at elevated ageing temperatures. Some similarity is identified between damage processes in static and dynamic bending fatigue.