Modeling the stress/strain behavior of a knitted fabric-reinforced elastomer composite

This paper presents a micromechanical analysis procedure for predicting the stress/strain behavior of a composite made of weft-knit polyester fiber interlock fabric and a polyurethane elastomer matrix. For analysis, a representative volume element (RVE) of the composite was initially identified. The RVE was divided into a number of sub-volumes, each of which was considered as a unidirectional fiber-reinforced composite oriented according to the fiber architecture in the RVE. The analysis was then carried out for such a unidirectional composite by using a bridging matrix that correlates the stresses generated in both the fiber and the matrix materials. The bridging matrix is sensitive to the geometrical and physical properties as well as the constitutive relationships of the fiber and matrix materials. The Prandtl–Reuss theory was used to describe the elasto-plastic behavior of the polyester fiber and an accurate incremental theory was applied to represent the rubber-elastic constitutive relationship of the polyurethane matrix. A volume-average scheme was used to assemble the contributions of all the sub-volumes to obtain the overall response charecteristics of the RVE. By means of the bridging matrix, the stress state of each constituent phase of the composite is explicitly known at every load step. The procedure was repeated for a series of load increments to obtain the stress/strain behavior of the composite. A strength criterion based on maximum normal stress theory was applied to determine the maximum load that the composite can sustain. The predicted stress/strain behavior is validated by comparison with experimental data.