Effects of nonlinear hyper-viscoelasticity and matrix/fiber debonding on mechanical properties of short carbon fiber/SBR composites under cyclic uniaxial loads using an RVE-based multiscale finite element model

This research work is devoted to the development of an RVE-based finite element analysis of short carbon fiber (SCF) reinforced rubber composites under uniaxial tensile loads by a novel approach. A micro model was developed with periodic geometry and random distribution of the short fiber in it. Three different zones including rubber matrix, SCF as the inclusion phase, and a thin layer as the interphase were considered. A nonlinear hyper-viscoelastic model was selected for the matrix in conjunction with linear viscoelastic and elastic models for the interphase and reinforcing parts, respectively. The analyses were carried out at two loading-unloading rates of 10 mm/min and 100 mm/min subjected to incrementally-increased cyclic loads. Two interface conditions were taken into account. In the first case, a perfect bonding was assumed between matrix and SCF while in the second, partial debonding between fiber and polymer was considered. The latter was modeled via XFEM with a crack initial criterion. An integral averaging technique was employed to predict the stress and strain at the macro-scale. Comparison of the predicted results with experimentally measured data revealed that the adopted methodology and modeling techniques are quite able to predict the stress and strain and thus confirmed the accuracy and correctness of the multiscale approach and selected material models.