Buckling analysis of plain knitted fabric sheets under simple shear in an arbitrary direction

Knitting structures make plain knitted fabric different from woven fabric. With the aid of a micro-constitutive model the buckling of a knitted fabric sheet subjected to simple shear in an arbitrary direction is investigated. The large deformation of the fabric sheet in its critical configuration is considered. The theory of stability for finite deformations is applied to the analysis. All the stress boundary conditions of the knitted fabric sheet are satisfied. An equation for determining the buckling direction angle is derived. It is shown that there are two possible buckling modes: a flexural mode and a barreling mode. The buckling conditions for the two modes are also obtained, respectively. A numerical calculation reveals that only the flexural mode can occur, which agrees with experimental observations.