A dual homogenization and finite-element study on the in-plane local and global behavior of a nonlinear coated fiber composite Original Research Article

In order to uncover the influence of localized deformation in the soft interphase layer on the global elastoplastic behavior of a fiber-reinforced composite, a dual homogenization and finite-element study is presented in this paper. The homogenization approach makes use of the concept of secant moduli and an energy-based effective stress which is evaluated by a field fluctuation method. In the finite-element analysis NASTRAN was used, with the triangular elements carefully constructed in the unit cell to deliver the local stress and strain fields of the constituent phases. These dual investigations are complementary in that the homogenization theory could readily provide the overall stress–strain curves of the composite whereas the finite-element analysis could give the local stress fields which are important to the onset of damage or crack initiation. The results of finite-element method (FEM) could also be used to assess the accuracy of the homogenization theory. Detailed comparisons between the two have indicated that the homogenization theory is sufficiently accurate. The propagation of plastic zone in both ductile phases are also vividly demonstrated. In addition, the soft interphase is found to be a region of high strain concentration, rendering the entire system with a lower elastoplastic strength as compared to an ordinary 2-phase composite.