Life-prediction for constant-stress fatigue in carbon-fibre composites

A detailed analysis has been carried out of the strength and fatigue behaviour under constant-stress cycling of four modern aerospace CFRP laminates, all having the common lay-up [(+/-45,O-2)(2)](s). Despite some important differences in their basic material characteristics, the fatigue responses of the four materials were similar. This pattern of behaviour has resulted in the development of a descriptive model of constant-life fatigue which has then been used as the basis for a life-prediction procedure. Preliminary attempts at validation of the method have met with a reasonable degree of success and suggest that it could provide designers with a means of selecting newly developed composites for fatigue applications on the basis of far less experimental data than are currently needed for confidence in design.