NUMERICAL AND EXPERIMENTAL STIFFNESS CHARACTERIZATIONS APPLIED TO SOFT TEXTILE COMPOSITES FOR TENSILE STRUCTURES

This paper presents numerical and experimental stiffness characterisat ion methods for soft composite textile membranes used in fabric roof s tructures. The studied material is a polyester plain-cloven fabric coa ted with PVC. We present three numerical textile composite micro-struc ture models. They are integrated in stiffness calculation software pro grams which are used to identify linear elastic characteristics for a coated fabric sample. The first two models are based on the laminated thin plate theory; the fabric is represented by a stacking of unidirec tionally-reinforced layers, or by the 'Crimp Model'. The third one con siders a geometrical approach to the basic cell of the fabric; the ela stic characteristics are calculated by assembly of the meshing element s. In addition, an inverse and experimental stiffness identification m ethod, based on biaxial tensile tests conducted (in orthotropic direct ions), is proposed. Load-controlled tests are conducted on cross-shape d samples with different loading ratios in warp and weft directions: 1 /1, 1/2, 2/1.