PLY-BY-PLY BASIS OFF-AXIS FATIGUE LIFE PREDICTION FOR CROSS-PLY CFRP LAMINATES AT ROOM TEMPERATURE

摘要

Off-axis fatigue behavior of a symmetric cross-ply carbon/epoxy laminate is examined at room temperature and a fatigue life prediction method that considers inelastic deformation and in-situ strength of embedded plies is developed. The fiber orientation dependence of the off-axis fatigue data on the cross-ply laminate can be removed by normalizing them with respect to static strength. The distribution of the normalized off-axis fatigue data of the cross-ply laminate almost agrees with the result for the unidirectional laminates made of the same prepreg tape. Then, off-axis fatigue analysis of cross-ply laminates is performed on a ply-by-ply basis. For this purpose, a ply fatigue model that takes into account in-situ static strengths of plies embedded in a laminate is proposed. Stresses in the cross-ply laminate are evaluated using a CLT-based laminate constitutive model that considers nonlinear deformation of embedded plies. Predicted off-axis fatigue lives of the cross-ply laminate are shown to correlate well with experimental results.