Strength loss and aging life of single-lap CFRP bonded joints under hygrothermal environment

Strength evolution of CFRP laminates and bonded joints because of moisture absorption was investigated experimentally. Experiments of accelerated moisture absorption under different temperatures, quasi-static tension, and fracture surfaces morphology observations were conducted. Strength loss and failure modes change due to moisture absorption were discussed in detail. An empirical model of predicting strength loss of the CFRP bonded joints due to moisture absorption was presented using a direct and an indirect method. Based on the time-temperature equivalent principle, a new approach of predicting the aging life of the CFRP bonded joints using the laboratory experimental data was proposed. Experimental data from references were extracted to check the strength loss model. The results demonstrated that the strength loss ratio of CFRP bonded joints soaked in 50°C water for 39 days exceeds 27.4%. The large degradation can attribute to the failure modes change from the interfacial failure to the cohesive failure and then return to the interfacial failure. The ratio of strength loss can be predicted by a first order decay exponential equation.