Abstract
The ratcheting behavior of a unidirectional carbon/epoxy laminate under off-axis cyclic loading conditions at high temperature has been studied with emphasis on its dependence on load waveform and fiber orientation. Development of an engineering model for describing the off-axis ratcheting deformation in the unidirectional CFRP laminate has also been attempted. First, off-axis ratcheting tests with different levels of maximum and non-zero mean stresses were performed on coupon specimens with different fiber orientations. The experimental results showed that the accumulation of ratcheting strain occurs in the unidirectional CFRP laminate, regardless of the fiber orientation, and the off-axis ratcheting behavior is similar to the off-axis transient creep behavior in all aspects of its stress, time and fiber orientation dependence. It is shown that the proposed model allows adequately predicting the off-axis ratcheting behavior of the unidirectional CFRP laminate for different stress ratios as well as for different fiber orientations.