Long-term Open-hole Compression Strength of CFRP Laminates based on Strain Invariant Failure Theory

This paper deals with the prediction of long-term strength of CFRP structure components based on the combined method of the strain invariant failure theory (SIFT) developed by Gosse and Christensen and the accelerated testing methodology (ATM) developed by Miyano and Nakada. The time-temperature-dependent master curves of SIFT critical parameters are constructed by tension and compression tests for the longitudinal and transverse directions of unidirectional CFRP under various temperatures based on the time-temperature superposition principle which holds for the viscoelastic modulus of matrix resin. These master curves can be used for predicting the long-term strength of composite structures with multi-directional laminations at any time, temperature. The long-term open-hole compression strength of the quasi-isotropic CFRP laminates is predicted using the master curves of SIFT critical parameters based on SIFT/ATM combined method and structural stress and strain analysis by finite element method. The applicability of SIFT/ATM combined method to predict the long-term strength of CFRP structures is experimentally confirmed.