The Validity of a “Linearizing Method” for Predicting the Biaxial-extension Properties of Fabrics

Abstract

The “linearizing method” is a method used to predict the stress/strain relation of fabrics under biaxial extension in the warp and weft directions. The stress/strain relation is firstly linearized by using a transformed strain such as ei = ∊i n where ei is the transformed strain (i =1, 2), ∊i the strain, and n a constant, and the stress Fi is then expressed by a linear equation in ei. The elastic parameters are determined by strip–biaxial–extension experiments in the warp and weft directions. This method was proposed by Kawabata in 1985 without sufficient examination of its validity. In this paper, the validity of the method is inspected by biaxial–extension experiments for various kinds of fabric. It is concluded that the linearizing method has sufficient capacity to enable the biaxial–extension behaviour of the fabric to be estimated with considerable accuracy. For the case when the stress/strain relation is linearized in two zones of strain, the double–zone linearization is presented here to improve the accuracy of prediction and to expand the validity of this method over a wider range of strains.