Fatigue Failure Mechanisms in a Unidirectionally Reinforced Composite Material

The fatigue failure mechanisms in a unidirectional glass fiber-epoxy material were studied. Specimens were made by filament winding the glass fiber roving and vacuum impregnating with a low viscosity room temperature curing resin. The fatigue response could be divided into three distinct life ranges. In the first region ( 10 6 reversals), the applied stress was below the microcrack initiation stress and none of the few specimens tested failed. Unlike behavior in the first two regions, where defects were formed in the first cycle and subsequently propagated, most of the cycles in this region were used in crack nucleation.