Prediction of Tensile Fatigue Life for Unidirectional CFRP

Abstract

Tensile fatigue strength in unidirectional CFRP depends on time and temperature as well as number of cycles. A prediction method of fatigue strength proposed [14] for polymer composites meeting certain conditions and confirmed 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 principle for all failure strengths, (C) linear cumulative damage law for monotonic loading, and (D) linear dependence of fatigue strength upon stress ratio. Data are provided for tensile CSR, creep, and fatigue tests at various temperatures in the longitudinal direction of unidirectional CFRP. Experimental verification of the prediction method for the tensile fatigue strength of the unidirectional CFRP is presented.