The Effect of Loading Direction and Stacking Sequence on the Strength in Quasi-Isotropic CFRP Laminates

Abstract

For quasi-isotropic CFRP laminates, the elastic stress-strain behavior is expected to be the same in any loading direction and stacking sequence of laminate. But fracture and strength of them may strongly depend on the loading direction and stacking sequence of laminate. The laminate has structurally made up many interfaces and the lamina in the laminate is anisotropic due to embedded fiber. Therefore, once matrix cracking or delamination takes place in the loading laminate, the laminates change into anisotropic ones. In this paper, the tensile tests were carried out in the constant displacement velocity for the specimens, cut out in several directions from each laminate, to investigate the influence of loading direction and stacking sequence on the damage pattern and tensile strength. A FEM code was used to analyze the stresses in the specimens, and the comparison between the calculated stressstrain curves and experimental ones was attempted.In addition, using Tsai-Wu failure criterion, the strength of the laminates were predicted in the various loading directions. And the correlations between the predicted results and experimental one are discussed.