Effects of fiber nonlinear properties on the compressive strength prediction of unidirectional carbon–fiber composites

Compressive strength of unidirectional carbon–fiber composites is analyzed with emphasis on the nonlinear elasticity of carbon fiber. The deformation and stress state in a kink band is solved numerically using an incremental form of the governing equations, and compressive strength is determined for a given kink band angle and initial fiber misalignment. Constitutive equations are based on one-parameter plasticity model and nonlinear elasticity, which is attributed to matrix plasticity and fiber nonlinearity, respectively. Effects of fiber nonlinear properties on the predicted compressive strength are investigated under various conditions of initial fiber misalignments, kink band angles, and fiber properties. Nonlinear fiber properties turn out to reduce the predicted compressive strength of unidirectional composites in the cases of small fiber misalignments.