Some aspects of the fatigue behaviour of fibre reinforced thermosetting resins

This paper reports the continuing work to establish the fatigue response of commercial fibre reinforced plastics now being specified by designers, particularly those materials using thermosetting resins as the matrix.

Results are reported of the flexural fatigue of balanced needled fabrics and of the tensile fatigue of filament wound E-glass and R-glass rings. Only a small dependence on the ratio of the minimum to the maximum stress (R-ratio) has been observed for flexural fatigue between R = 0·05 and R = 0·6.

It is shown that the fatigue behaviour of a wide variety of glass fibre reinforced composites (unidirectional/bidirectional, long and short fibres, epoxy and polyester resins), subject to either tensile or flexural loading, can be rationalised, like others have done, by normalising the maximum fatigue stress with respect to the corresponding ultimate tensile or flexural strength, obtained at an equivalent strain rate.