Tensile and fatigue behaviour of glassfibre epoxy laminates

The behaviour of unidirectional 45 degrees, angle-ply +/- 45 degrees and multidirectional [+/-45 degrees,0 degrees](s) fibreglass/epoxy laminates at room temperature under tensile and fatigue loadings has been investigated. Results for angle-ply +/- 45 degrees laminates show that the rate/frequency effect is significant in both tensile and fatigue loadings. In the case of tensile loading tests, the rate effect was observed in the stress-strain response. Fatigue data indicate a considerable accumulated cyclic creep which depends on the loading condition, i.e. applied load and frequency. The effect of frequency on the fatigue life is explained in terms of cyclic creep and its detrimental influence on the fatigue resistance. In contrast, laminates made of 45 degrees unidirectional and multidirectional [+/-45 degrees,0 degrees](s) show very little frequency effects.