A Stiffness Degradation Model for FRP Laminates Under Biaxial Fatigue Loading

Abstract

A stiffness degradation model for fiber-reinforced polymer (FRP) laminates under biaxial fatigue loading is presented in this paper. The degradation of biaxial stiffness in the FRP laminate due to matrix cracking is computed using a mesoscopic matrix crack damage model, and these results constitute the “Damage domain.” Subsequently, a new stiffness degradation model, termed the “Damage searching algorithm,” is applied within the “Damage domain” to forecast biaxial stiffness degradation in tandem with the damage evolution process. The model's validity is confirmed through a comparison of predictions with the combined tension-torsion fatigue test results of tube specimens. The findings demonstrate that the predicted axial and torsional stiffness degradation align well with experimental results. Furthermore, the projected matrix crack density evolution corresponds closely to the observation in the experiment, further affirming the effectiveness and rationality of the proposed model.