Modelling of dynamic flexural response of composite eco-structure beams using a 3D elastic–plastic damage model

The dynamic flexural behaviour of sandwich beams made of a composite eco-structure (plywood and flax/epoxy composite skin) is studied using an explicit 3D numerical model. The model includes a constitutive elastic–plastic behaviour with a plastic potential and its consistency multiplier-based yield stress criteria, a modified 3D-Hashin damage initiation and a strain threshold-based exponential damage evolution model. Experimental tests at different impact energies were carried out to validate the proposed model. The variation of force with time and displacement as well as the velocity–time profile are accurately predicted. The model is able to capture the stiffness degradation, post-peak softening, de-kinking and unloading phase that appear in the force–displacement curve. The validated model is employed to investigate the evolution of inter- and intralaminar damage for different impact energies. The most relevant damage modes are delamination and compressive damage modes (transverse and normal) for the impact energies studied.