The KES Shear Test for Fabrics

Abstract

Many fabric mechanics researchers have reported that specimens being tested on the KES shear tester are not subjected to pure shear deformation; therefore, test results cannot lead directly to a determination of the fabric shear modulus and stress/strain relationship, particularly in the nonlinear range of stress-strain. Combined with finite element analysis, this paper presents an analytical solution for the distribution of shear stresses and strains in fabric specimens tested on the kes tester. A fabric is treated as an orthotropic sheet during the analysis, which leads to a closed-form solution for the shear modulus as a function of fabric tensile and shear moduli from the kes shear test. A modified shear stress-strain relationship can also be derived. From calculations for fabrics used here, the difference between modified and tested shear modulus values is about 25–30%. The study also suggests that although the shear modulus and curves obtained on the kes shear tester are significantly different from those under the pure shear state, the kes results can still reflect the nature of a fabric under shear deformation and are valid for general objective evaluations. The exact shear stress-strain relationship and actual shear modulus may be modified only when they are required for fabric complex deformation analysis.