Effects of a time-dependent interfacial layer on the thermo-mechanical response of polymer matrix composites

Abstract

In the present study, the micro-mechanical analysis of a fiber-matrix interphase is conducted. Finite-element analysis based on the generalized plane-strain condition is used to evaluate the thermo-mechanical deformation and stress fields in polymer matrix composites. Non-homogeneous visco-elastic constitutive relationships are considered for the matrix and the interphase. The analysis includes mechanical and time-dependent thermal loadings. When a unit cell is subjected to uniform transverse resultant forces, creep responses in the interphase and matrix are observed. For a uni-axial extensional load, most of the loading is carried by the fiber throughout the loading history, and stress relaxation in the matrix and interphase causes the fiber loading to increase slightly with time. Numerical evaluations also show that thermal expansion mismatches in the fiber, interphase and matrix result in the development of high residual stress at the interphase, which is responsible for debonding between the fiber and the matrix.