The plastic behavior of matrix and its effect on the interface stress transfer in fiber-reinforced composites

Existing shear-lag models for fiber-reinforced elasto-plastic composites always assume a rectangular-shaped plastic zone in the matrix, which is not consistent with numerical simulations. In this paper, a shear-lag model considering a more realistic parabolic shape of the plastic zone in an elasto-plastic matrix is proposed, in order to investigate the effect of matrix plasticity on the interface stress transfer. A closed-form solution to the profile of parabolic shape related to the applied stress is obtained so that the plastic zone evolution can be analytically characterized. Compared with the case with a purely elastic matrix, a plastic matrix could lead to a decrease in the interfacial shear stress (ISS) and an increase in the fiber stress. The smaller the plastic tangent modulus of the matrix, the lower the ISS is and the larger the fiber stress becomes, and the ISS and fiber stress keep being on same magnitudes of yielding strength and Young’s modulus of matrix, respectively. The present model with a parabolic plastic shape is more accurate to describe the mechanical behaviors of plasticity in matrix, which is of guiding value for the design of elasto-plastic composites used in vehicle accessories, medical devices, civil engineering and so on.