Failure optimization of geometrically linear/nonlinear laminated composite structures using a two-step hierarchical model adaptivity

The optimization problem of maximizing the safety against failure in Geometrically NonLinear (GNL) laminated composite structures is investigated through a two-step model approach. An initially coarse mesh fully three dimensional finite element model is discretized using Assumed Natural Strain and Enhanced Assumed Strain stabilized equivalent single layer solid shell elements. After solving this coarse problem, the model is refined through the laminate thickness in localized “zones of interest”, and displacement continuity is enforced through constraint equations. The resultant refined finite element model is subsequently used as the onset for solving a gradient based fiber angle optimization problem. To enable the solution of large problems, parallel programming is addressed to reduce computational wall clock time. The potential and current limitations of the approach are illustrated through two numerical examples.