Development of a workflow for the virtual optimization of a nanofiber-interleaved composite laminate subjected to impact loading

Delamination is one of most common failure mechanisms for composite materials. By interleaving nanofibers between laminate plies, the authors showed that it is possible to control the interlaminar fracture toughness. In particular, either a toughening or an embrittlement of the interface could be obtained by varying fibre diameter, fiber arrangement (random, aligned) and mat thickness. The modification induced by the nanomat can be therefore exploited in order to tailor the delamination strength of the laminate. The aim of this work is to identify a way to optimize the impact strength of a composite laminate with interleaved nanomats with respect to the maximization of the energy dissipated by delamination under impact. Impact damage is simulated using the Finite Element Method (FEM) with the Abaqus software. Cohesive elements are placed at the interfaces between groups of plies with different orientation of a plain weave composite laminate. Each interface can be assigned three different cohesive properties. The cohesive zone properties of virgin and nanomodified interfaces were identified in a previous work. The optimization workflow took into account also the possibility of changing the initial ply orientation. A multiobjective optimization was run for the counteracting objectives of max damage-dissipated energy and minimum decrease of composite stiffness.