Prediction of tensile fatigue life for unidirectional CFRP

Tensile fatigue strength in unidirectional CFRP depends on time and tempera ture as well as number of cycles. A prediction method of fatigue strength p roposed [14] for polymer composites meeting certain conditions and confirme d for flexural fatigue strength of satin-woven CFRP laminates is applied to the tensile fatigue life of unidirectional CFRP. The method is based upon the four hypotheses: (A) same failure mechanisms for constant strain-rate ( CSR), creep, and fatigue failure, (B) same time-temperature superposition p rinciple for all failure strengths, (C) linear cumulative damage law for mo notonic loading, and (D) linear dependence of fatigue strength upon stress ratio. Data are provided for tensile CSR, creep, and fatigue tests at vario us temperatures in the longitudinal direction of unidirectional CFRP. Exper imental verification of the prediction method for the tensile fatigue stren gth of the unidirectional CFRP is presented.