Fatigue and residual strength of composite laminates

Abstract The mechanics of fatigue failure of laminated composite materials are completely different from that of conventional materials. The mechanics of fatigue failure of conventional materials involve the initiation and propagation of a single crack, which causes the material to fail. Laminated composite material can arrest the propagating crack to within a single lamina, thus avoiding immediate failure. Only after accumulation of cracks the laminate fails. The fatigue life of the laminate is best described by S-N curves. A theory for residual strength is developed which is based on a cumulative damage theory. The theory predicts that the static strength of the laminate is maintained almost to the final failure by fatigue. Experimental results verify this phenomenon.