Probabilistic modeling of stiffness degradation for fiber reinforced polymer under fatigue loading.

• The inherent correlation between stiffness degradation and strength degradation of FRP is explored. • A probability model of stiffness degradation is proposed based on the same damage state principle. • The proposed model is flexible enough to fit the stiffness degradation data of FRP laminates with good agreement. The stiffness degradation of fiber reinforced polymer (FRP) has significant effects on its fatigue life and reliability. In this study, the inherent correlation between stiffness degradation and strength degradation is explored, and a probability model that describing stiffness degradation of FRP is presented. Firstly, the evolution of fatigue damage in FRP is analyzed, and then it is characterized by stiffness degradation and strength degradation, respectively. Secondly, the randomness of initial stiffness and critical stiffness of FRP is considered, and a probability model of stiffness degradation is proposed based on the same damage state principle. Finally, the test data of FRP laminates are used to verify the proposed model, and the fitting accuracy is compared with several existing models. The results show that the stiffness degradation of FRP presents a fast-slow-fast trend during fatigue failure process, and the proposed model is capable of fitting stiffness degradation data of FRP with good agreement. [ABSTRACT FROM AUTHOR]