Numerical identification of classical and nonclassical moduli of 3D woven textiles and analysis of scale effects

Homogeneous anisotropic couple-stress continuum model as substitutes of 3D woven textiles are presently developed. The architecture of the considered fabric preforms is obtained from an idealized geometry and organization of the yarns within a representative unit cell. The effective properties are obtained based on the finite element response of the representative volume element (RVE) under prescribed boundary conditions. Specific boundary conditions including both traction and displacement boundary conditions are applied on the structure boundaries. The effective classical and nonclassical mechanical moduli are deduced by an equivalent strain energy method. The characteristic bending lengths are identified from the resulting homogenized moduli. We model 2D and 3D textiles either as a one phase solid (dry textiles), or as a two-phase material consisting of the set of yarns and a softer surrounding phase representing the resin. The effects of scale on the predicted classical and nonclassical moduli of these textiles are investigated by varying the size of the textile unit cell over which the boundary conditions are applied. The analysis delivers classical moduli that are independent of unit cell size, whereas the couple stress moduli depend on the cell size. The developed approach is quite general and applicable to any composite materials. (C) 2015 Elsevier Ltd. All rights reserved.