Effect of Fiber Anisotropy and Interphase on the Stress Jumps Across the Fiber/Matrix Interface in Fuzzy Fiber Composites

Designing the interphase region in conventional fiber-reinforced plastics is an efficient strategy to enhance their interfacial and interlaminar properties. The influence of the interphase region on stress concentration surrounding the fiber is systematically studied using finite element (FE) simulations in fuzzy fiber-reinforced composites. Two-phase (fiber/matrix) and three-phase (fiber/interphase/matrix) numerical models are used in FE simulation for comparative analysis. While the matrix is taken as isotropic material, both isotropic and transversely isotropic fibers are considered in numerical simulations. Two types of interphase regions: (1) interphase having a constant modulus and (2) graded interphase with varying modulus across the thickness are studied. The predictions from FE simulations are validated with the analytical results obtained from the rule of mixtures approach. FE simulations show that the presence of interphase increases the stiffness of the representative volume element (RVE) and reduces the stress concentration around the fiber. Moreover, the graded interphase is more effective in reducing the stress jump at the fiber/matrix interface in comparison with the interphase having a constant modulus.