Hemitropic properties of thin non-centrosymmetric 3D woven textile composites

Due to their microstructural architecture, 3D woven textile composites, (3DWTC), exhibit complex macroscopic behavior, which cannot be effectively captured using classical continuum theories. One reason for this can be attributed to the ratio of the characteristic microscopic and macroscopic length scales, (d and L, respectively), which violates the separation of length scales requirement in micromechanics. In these instances, higher order continuum theories, such as micropolar theory, are considered to effectively describe the macroscopic behavior of a material. In this study, the 3D macroscopic constitutive relation of 3D woven textile composite (3DWTC) is reported. The three different 3DWTC considered are referred to as thin asymmetric, thick asymmetric, and thick symmetric. The lack of centro-symmetry in the asymmetric microstructures produces an interesting anisotropic response, such as stress-curvature (or couple stress-strain) coupling effect. This is analogous to asymmetric plate structures and the coupling between the resultant forces and curvatures through the B-matrix. At the macroscopic (continuum) scale, the material is modeled as a micropolar continuum, where internal couple-stresses and curvature strains are introduced. To capture the stress-curvature coupling effect, a generalized Aero-Kuvshinski type constitutive model is considered. With this, the anisotropic micropolar properties and the additional hemitropic material constants of the 3DWTC are determined numerically and their results qualitatively summarized.