Bilinear Model for Coated Square Fabrics

An idealized composite model of a square biaxially loaded coated fabric is proposed. The model consists of straight linearly elastic yarns embedded in a thin layer of a linearly elastic isotropic coating material with the system loaded in the plane of the membrane. Governed by the assumptions of small strains, equations describing the material behavior are derived for a general state of two-dimensional loading. The resulting system of nonlinear simultaneous equations are then solved numerically for a range of coating and yarn properties. For relatively low stresses, the response is governed by the mechanism of crimp interchange and coating deformation, and at higher stresses the response is governed by yarn and coating properties. The general nonlinear result is further approximated by a set of bilinear equations and a procedure for evaluating definitive model parameters from data obtained from uniaxial tests is presented.