Predicting tensile behaviors of short flax fiber-reinforced polymer–matrix composites using a modified shear-lag model

Abstract

Natural fiber-reinforced composites are increasingly being used in the industry. The fiber–matrix interfacial properties of the composites are influenced by many factors, including chemical treatment of the natural fiber, type of polymer matrix, composites fabrication method, and process and the service environment of the composites. In this paper, a modified shear-lag model based on a cohesive fiber/matrix interface is proposed and applied to the analysis of the stress–transfer characteristics and the tensile properties of unidirectional short flax fiber-reinforced composites. The model takes into account of the interfacial shear stiffness, bonding strength between fiber end face and matrix, fiber aspect ratio and fiber volume fraction. 3D finite element models of the composites using a cohesive zone method are used to verify the accuracy of the modified shear-lag model. The fiber tensile strength and the composite tensile elastic modulus are significantly influenced by the interfacial shear stiffness, fiber aspect ratio, and fiber volume fraction. The bonding strength between the fiber end face and the matrix only has an effect when the interfacial shear stiffness is low. The predicted results from the modified shear-lag model show good agreement with the finite element analysis and experimental results in the literature. The modified cohesive shear-lag model provides a simple and effective method for analyzing fiber axial stress, shear stress in the fiber/matrix interface, and tensile elastic modulus of the final composite.