Fatigue life prediction of matrix dominated polymer composite materials

Abstract Fatigue life prediction is investigated analytically for matrix dominated polymer composite laminates having nonlinear stress/strain response, based on the fatigue modulus concept. Fatigue modulus degardation rate at any fatigue cycle was assumed as a power function of number of fatigue cycles. A new stress function describing the relation of initial fatigue modulus and elastic modulus was used to account for material non‐linearity at the first cycle. It was assumed that fatigue modulus at failure is proportional to the applied stress level. A new fatigue life prediction equation as a function of applied stress is proposed. The prediction was verified experimentally using cross‐ply carbon/epoxy laminate (CFRP) tube under torsional fatigue loading. It is shown that the proposed equation has wide applicability and agrees well with experimental data.