On the importance of nesting considerations for accurate computational damage modelling in 2D woven composite materials

The mechanical behaviour and progressive damage of two-dimensional plain woven carbon-epoxy fabrics is modelled at different length scales, taking into account the geometric and material variability of the weave, by subjecting the dry preforms to compaction simulations. Micromechanical analyses are performed using a fibre distribution algorithm, in order to obtain the mechanical properties of the tows for any given fibre volume fraction. Different Representative Unit Cells are generated, compacted, and subjected to Periodic Boundary Conditions in order to compare their mechanical performance, under different loading scenarios. Additional analyses are undertaken to evaluate the effect of nesting under different stress states. Through computational homogenisation, it is possible to study damage evolution and corresponding stiffness degradation of the material. The numerical predictions are compared with experimental observations, and show that, to model damage: i) a single ply with three-dimensional Periodic Boundary Conditions or four plies with two-dimensional Periodic Boundary Conditions may not be the most accurate approach to model damage; ii) it is important to consider the effect of nesting in such computational models, since they play a key role in the mechanical response of the material.