SOFT IMPACT DAMAGE PROGNOSIS OF F-16 CANOPY USING PROGRESSIVE FAILURE DYNAMIC ANALYSIS

This work presents a numerical approach for predicting large deflections and damage evolution in aerospace structures subject to soft impact. The explicit finite-element code LS-DYNA is coupled with the micromechanics damage-analysis code GENOA, which is capable of predicting failure progression in a range of isotropic and orthotropic materials. The impact event studied was a bird strike on an F-16 canopy concept. Bird models were developed using three distinct finite-element modeling approaches: 1) Lagrangian, 2) arbitrary Lagrangian–Eulerian, and 3) smoothed particle hydrodynamics. Each model was studied by simulating impact at a speed that induced a large-deflection, elastic response in the canopy. Deflections at the impact location were compared against experimental data; from these results, the Lagrangian bird model was chosen for incorporation into a bird-impact progressive failure dynamic analysis methodology. Impact at velocities below and above that which induced failure were simulated and compared with test results. The completed methodology is able to accurately match the elastic deflection response and predict damage initiation and progression at higher velocities. Additionally, the progressive failure dynamic analysis methodology clearly identifies failure mechanisms and their percent contribution to multisite failure and can help guide the design process for parts that must withstand soft impacts.