Nonlinear behavior and compressive strength of unidirectional and multidirectional carbon fiber composite laminates

Nonlinear mechanical behaviors and strengths of carbon fiber reinforced plastics (CFRP) laminates under compressive loadings are investigated. Nonlinear behaviors that are specifically addressed in this study are elastic material nonlinearity in the fiber direction and plastic deformation of matrix origin. Compressive behaviors and strengths of unidirectional laminates, along with quasi-isotropic laminates, are measured using T800H/3633 and interlayer-toughened T800S/3900-2B systems. The compressive strength of unidirectional laminates is predicted based on the kink band formulation incorporating nonlinear behaviors. It yields a non-conservative prediction that typically contrasts with experimental results. However, nonlinear behaviors of quasi-isotropic laminates are well predictable using classical lamination theory with nonlinear properties. Predicted compressive strengths based on strength criteria of a 0° layer concur with experimental results. Discussion of the compressive strength of CFRP laminates is provided through comparison of experimental results for unidirectional and multidirectional laminates.