Nonlinear Mechanical Behavior of Angle-Plied CFRP Laminates with Different Ply Thickness
Hayato NAKATANI, Kenji TAKAGI, Asao KOIKE and Shinji OGIHARA
Abstract:This paper evaluates effect of ply thickness on nonlinear mechanical behavior of angle-plied CFRP laminates. To begin with, stress-strain behavior of unidirectional laminates under off-axis tensile loading is obtained. The laminates have exhibited nonlinear mechanical behavior in all off-axis angles investigated. It has been also shown that this nonlinear behavior can be predicted well by the one-parameter plasticity model. Angle-plied CFRP laminates have been manufactured using 16 plies of 0.15 mm thick prepreg ([(+45)4/(-45)4]S) or 48 plies of 0.05mm thick prepreg ([(}45)12]S). When neighboring plies in same fiber orientation are regarded as one blocked plies for 16-ply laminates, this ply thickness is 12 times thicker than that in 48-ply laminates. Tensile tests have been demonstrated that 48-ply laminates show complicated nonlinear behavior until maximum strain of about 20% and intense fiber-matrix debondings as with interlaminar delamination. An attempt has been made to predict the stress-strain behavior of the angle-plied laminates by the one-parameter plasticity model in conjunction with classical laminate plate theory. The predicted behavior of the 16-ply laminates has agreed well with the experimental results without any modification. As for the 48-ply laminates, the model has predicted comparable results of the nonlinear behavior in large strain region when changes in fiber orientation angle due to deformation of the plate has been also taken into account. Key Words:Carbon fiber/epoxy composites, Nonlinear behavior, Off-axis loading, Plasticity, One-parameter plasticity model, Classical laminate plate theory, Unidirectional laminates, Angle-plied laminates