A Continuum Damage Mechanics Model for the Analysis of the Crashworthiness of Composite Structures: A work in progress

The crashworthiness capability of an aircraft structure is dependent on its ability to attenuate crash loading via the controlled deformation of energy absorbing devices. An energy-based constitutive relation was employed to model the behaviour of carbon fibre reinforced epoxy resin composite material under crush loading. Each of the damage modes in the fibre and matrix was treated separately with its own damage initiation and progression relationships as well as a damage parameter that tracks damage progression. Each damage parameter dictates the reduction in stiffness in the respective principal loading directions. This model was implemented for a 3D solid brick element in contrast to shell-based formulations currently available. Crushing composite structures were modelled and the results validated against experimental data. The force-displacement response / specific energy absorption and the failure modes obtained from the simulation show that the underlying physics of the crushing have been captured by the proposed model but that further work is required for reliable quantitative correlation.