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

In order to uncover the influence of localized deformation in the soft inte rphase layer on the global elastoplastic behavior of a fiber-reinforced com posite, a dual homogenization and finite-element study is presented in this paper. The homogenization approach makes use of the concept of secant modu li and an energy-based effective stress which is evaluated by a field fluct uation method. In the finite-element analysis NASTRAN was used, with the tr iangular elements carefully constructed in the unit cell to deliver the loc al stress and strain fields of the constituent phases. These dual investiga tions are complementary in that the homogenization theory could readily pro vide the overall stress-strain curves of the composite whereas the finite-e lement analysis could give the local stress fields which are important to t he onset of damage or crack initiation. The results of finite-element metho d (FEM) could also be used to assess the accuracy of the homogenization the ory. Detailed comparisons between the two have indicated that the homogeniz ation theory is sufficiently accurate. The propagation of plastic zone in b oth ductile phases are also vividly demonstrated. In addition, the soft int erphase is found to be a region of high strain concentration, rendering the entire system with a lower elastoplastic strength as compared to an ordina ry 2-phase composite. (C) 2000 Published by Elsevier Science S.A. All right s reserved.