Identification of Shear Stiffness of Soft Orthotropic Textile Composites: Part I – Development of a Mixed Method for Shear Elastic Constant Identification

Coated polyester/PVC fabrics are used in civil engineering for temporary inflatable structures or for emergency applications during disasters. However, they are not used to their full potential due to lack of behavioral knowledge, especially in their shear behavior, and the absence of simple design rules. The main objective of this article is to propose a mixed technique including experimental and numerical data to identify the elastic constants of composites in shear, whereby an existing experimental biaxial device is adapted to a shear test and moreover, an optical technique without contact is used to measure the displacements. The originality of the shear experimental device consists in the study of the influence of pretension on the shear properties. It also allows to avoid wrinkling and to take large deformations and softness of coated fabrics into account. In the second part of this article, we propose an alternative technique for the evaluation of the shear constants. This method is based on the Kawabata's shear deformation theory, which is adapted to the investigated fabrics and experimental device. In these conditions, it is possible to evaluate the shear behavior constitutive equation to simplify the design rules for inflatable structures.