ACS developed an integrated numerical and test approach for composite wing leading edge hailstone impact application with electrical ice protection system. We proposed finite element free fast impact models satisfying the governing equations of impact mechanics coupled with cross-correlations of data from a series of tests organized in a building block approach.

First we developed a fast phenomenological semi-analytical impact model to provide rapid predictions of the impact force-time response. It used laminate mechanics and continuous global spatial interpolation functions to drastically reduce the size of the problem and explicit time integration; Then a reduced phenomenological impact model, which provided estimates of the maximum impact force, was integrated with material Characterization and Qualification (MCQ) software and multi-scale progressive failure dynamic analysis (PFDA), to characterise the impact resistance of composite structures and to determine: type of failure (delamination, crippling, etc), damage footprint (which ply, length and width), energy absorbed during impact, and post-impact residual strength.

The model accounted for temperature and moisture effects and is suitable for conventional and hybrid composites. We assembled team of experts in aircraft composite design and impact dynamics. We developed GENOA durability and damage tolerance software and ANSYS user material routine for implicit progressive failure analysis. We developed a user material routine for explicit dynamics.

At the end, a high-fidelity numerical GENOA-ANSYS FEA model was available for composite leading edge structures impacted by hail. Predictions validated with test data and provided a impact response database to complement the experimental validation. The numerical model captured damage not seen during general visual inspection and facilitated inspection and maintenance of critical systems for continued operational safety.