A discrete meshless Lagrangian based approach for soft impact damage modeling in advanced propulsion systems

Soft impact on aircraft occurs in several forms, such as bird and hail strike. A discrete meshless Lagrangian based approach has been developed for modeling the fluidic behavior of soft objects during impact. This approach shows promise for developing an overall predictive methodology for accurately capturing and assessing dynamic damage in jet engines. This paper focuses on a part of this study aiming to develop a methodology capable of predicting full details of soft impact damage in turbofan engine forward sections. The initial scenario being simulated was a bird strike. Through modeling of the bird in a Lagrangian domain, the method's suitability for simulating soft impact damage in fan section structures was evaluated. Three-dimensional explicit finite element analysis models were employed to simulate the highly nonlinear and transient response of the interactions between the non-Newtonian bird and the forward engine section resulting from impact and to capture the associated turbofan blade damage, fan assembly vibrations, and subsequent engine casing destruction. Critical features under investigation were the degradation and fracture of the turbofan blades and the engine casing. Results indicated that a meshless soft impactor model was able to produce the fluid-solid interactive behavior expected from a bird. The methodology further succeeded in effectively predicting the intricate subsequent fluid-fan assembly violent interactions. Several important considerations for crashworthiness analysis of forward sections were highlighted.