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.
During the efforts of this work, the development of an integrated numerical and test approach for composite wing leading edge hailstone impact with electrical ice protection system was accomplished. The work was divided into testing of a building block of coupons, flat and curved panels, and wing leading edge with de-icer and the simulation which accurately modelled the tested structures. The tool showed quick results to determine the effect of wing leading edge and heater damage on the heating capabilities. The toolset is a validated tool to determine wing leading edge ice impact damage and survivability.
Damage sizes for all components tested were comparable to those predicted by simulation. The heating capability of the heater in simulation pre impact matched test and furthermore, post impact was able to show that heater damage can affect the wing leading edge temperature distribution.