Micro–macro constitutive modeling and finite element analytical-based formulations for fibrous materials: A multiscale structural approach for crimped fibers

Materials with crimped fibers have special properties that can be effectively explored only when using a micro-macro perspective. In this framework, a novel constitutive model based on a multiscale structural rationale is introduced. Material micromechanics, depending on fiber straightening mechanisms, is described introducing a beam model which drives material model response. This rationale leads to a quasi-analytical formulation, coupling the advantages of purely-analytical and computational approaches. The proposed model is also proven to be polyconvex.Furthermore, a finite-element formulation is developed, enriched by a quasi-analytical core associated with the multiscale constitutive formulation. Different solution strategies are tested in order to optimize the numerical performances in terms of accuracy, robustness and cost. Moreover, a mixed finite element formulation based on a simplified-kinematics-for-anisotropy (SKA) is introduced. For the tested boundary value problems, the SKA-element is an optimal choice in terms of displacement and fiber stress convergence behavior, especially for coarse meshes. (C) 2018 Elsevier B.V. All rights reserved.