Micromechanical approach to the tensile strength of a knitted fabric composite

Abstract

This paper describes a micromechanical approach to estimate the tensile strength of a knitted fabric reinforced composite. In this new approach, the state of stress in each constituent phase of the composite is explicitly expressed as a function of externally applied overall stress, by means of a bridging matrix. The maximum normal strength theory of isotropic materials is applied to each constituent phase at every load increment level. Once either the fiber or the matrix attains its ultimate strength, the corresponding applied overall stress is defined as the ultimate strength of the composite. In this way, the failure mode of the composite is automatically indicated and so is the strength margin of the constituent phases. The developed strength theory has been applied to several unidirectional composites and also to a plain weft knitted glass fiber fabric reinforced epoxy composite. The predicted tensile strengths in all cases are in good agreement with the corresponding experimental data. Parametric studies have also been carried out to investigate the effects of various geometric and material parameters of the constituent phases on the tensile strength of knitted fabric composites. Useful insights have been gained.