Characterization and modeling of the ratcheting behavior of unidirectional off-axis composites

The ratcheting behavior of unidirectional carbon/epoxy composites under cyclic off-axis loading with non-zero average stress was investigated, with a focus on the influence of peak stress (stress ratio R = 0) and fiber orientation. The experimental results show that nonlinear hysteresis and ratcheting behaviors heavily depend on fiber orientation and loading stress. Herein, the evolutionary features of the nonlinear hysteresis behavior and ratcheting deformation of the material are discussed. Furthermore, a creep damage-coupled viscoplastic cyclic constitutive model based on the nonlinear hysteresis behavior and cyclic creep is proposed to simulate the ratcheting behavior of carbon fiber composites under different stress levels and with various fiber orientations. The proposed model can adequately predict the nonlinear response during loading, hysteresis behavior during unloading and reloading, and ratcheting phenomena after a large number of cycles.