Velocity Impact Damage on a Composite Plate

Rosario Borrelli (CIRA - Italian Aerospace Research Centre)

Laminate composite structures suffer from poor resistance to impact, resulting in internal damage that often cannot be detected by visual inspection, which may cause severe reductions in strength and increase under load. In order to simulate the impact event the LS-DYNA FE model was developed and coupled with modeFRONTIER. The test case used to assess the capability of the procedure in investigating the impact event consists in a rectangular plate impacted at an energy level of 40J by a hemispherical steel impactor with a diameter of 25.4mm and a mass of 1.85kg. The material of the plate was a laminate composite with a symmetric, quasi-isotropic lay-up of 24 plies. The definition of some numerical parameters of the LS-DYNA model may be a considerable challenge and in order to better understand the influence of such parameters on the simulation results, a sensitivity analysis was performed by coupling the LS-DYNA FE model with modeFRONTIER. The modeFRONTIER workflow was simplified according to the findings of the statistical analysis and a multi-objective optimization analysis with the algorithm MOGA-II was performed. The optimization strategy provided several candidate optimal solutions. The procedure allowed to study the influence of some numerical parameters on the simulation results and to find the configuration that provides the best correlation between the numerical and the experimental results in terms of contact force, deflection and absorbed energy time history. Moreover, the procedure allowed to take advantage of the modeFRONTIER automation: once the workflow was set in modeFRONTIER, the calculations run automatically and all the available time (night, weekend, etc.) is fully used.