Measuring and Modelling the In-Plane Bending Stiffness and Wrinkling Behaviour of Engineering Fabrics

In this investigation two simple tests are conducted to characterise the shear, out-of-plane bending stiffness and in-plane bending stiffness of engineering fabrics and to investigate their wrinkling response during shear. A cantilever bending test [1] is first used to measure the out-of-plane bending stiffness while a modified version of the uniaxial bias extension (UBE) test is used to explore both the in-plane shear and the in-plane bending stiffness of the fabric (see Figure 1a). An estimate of the shear resistance of the fabric is obtained using normalisation theory [2]. In [3] it was shown that, for a given tensile stiffness in the two fibre directions, the in-plane deformation kinematics of the specimen are determined by the ratio between the fabric’s in-plane shear stiffness and in-plane bending stiffness. Thus, by measuring the fabric kinematics together with the shear stiffness of the fabric, the in-plane bending stiffness of the fabric is inferred using an inverse modelling approach. This is the first occasion that the in-plane bending stiffness of an engineering fabric has been estimated based on experimental data