A reduced integration-based solid-shell finite element formulation for gradient-extended damage

The present contribution is concerned with the incorporation of gradient-extended damage into a reduced integration-based solid-shell finite element formulation. To this end, a purely mechanical low-order solid-shell element based on the isoparametric concept is combined with a gradient-extended two-surface damage plasticity model. Due to a tailored combination of the assumed natural strain (ANS) as well as the enhanced assumed strain (EAS) method, the most important locking phenomena are eliminated. A polynomial approximation of the kinematic as well as the constitutively dependent quantities within the weak forms enables the definition of a suitable hourglass stabilization. In this way, the element stiffness contributions coming from the hourglass stabilization can be determined analytically, since they represent polynomials with respect to Cartesian coordinates. Several numerical examples on elastic as well as elasto-plastic plates and shells under various loading scenarios show the ability of the present methodology to predict various degradation processes such as damage initiation, propagation, merging as well as branching. (C) 2021 Elsevier B.V. All rights reserved.