Prediction of tensile fatigue life for unidirectional CFRP

A prediction method of fatigue strength of polymer composites under an arbitrary frequency, stress ratio and temperature is proposed. The method is based upon the four hypotheses: (A) same failure mechanism for static, creep and fatigue failure, (B) same time-temperature superposition principle for all failure strengths, (C) linear cumulative damage law for monotone loading and (D) linear dependence of fatigue strength upon stress ratio. Tensile static, creep and fatigue tests at various temperatures were conducted in the longitudinal direction of unidirectional CFRP. The validity of the prediction method and the applicability of the hypotheses for the tensile fatigue strength for this unidirectional CFRP are discussed.