Nonlinear Viscoelastic Modelling of the Fiber-Matrix Interphase in Composite Materials

Abstract

A nonlinear viscoelastic analysis of the carbon fiber-thermoset (or thermoplastic) matrix interphase is presented. The second order nonlinear partial differential equation governing the state of stress at the fiber-matrix interphase is solved by using an iterative scheme involving successive differentiation and Taylor expansions to satisfy the boundary conditions. Additional iteration is used for the case with nonlinear viscoelastic matrix material. The results reveal that the thickness and material properties of the interphase have strong influence in reducing the shear stress magnitudes and distribution along the fiber. The analysis and results provide valuable insight into the application and interpretation of the single fiber tension (fragmentation) test procedure and the design of “tailored interphases.”