An Extensive crashworthiness methodology for advanced propulsion systems, Part I: Soft impact damage assessment of composite fan stage assemblies

Jet engines are the most susceptible aircraft structures to catastrophic damage caused by soft impact events, such as ingesting birds or hail stones. Future propulsion systems will incorporate advanced composites, particularly in the fan assembly, because of their superior strength and stiffness properties compared to metals. However, reliance on physical testing to assess the crashworthiness of engine designs currently inhibits the development of novel propulsion concepts. The findings presented in this work are part of a study aimed at developing an extensive analytical methodology for predicting and assessing damage to engine forward sections containing composite structures. In this study, a modeling approach for capturing damage due to bird strike on composite fan blades and a fan assembly was developed. Impacts on a pre-stressed composite static single blade and a full rotating fan assembly were simulated. Two numerical methods were used to model the bird using an explicit finite element (FE) code: (1) an arbitrary Lagrangian-Eulerian (ALE) method, and (2) a meshless Lagrangian particle method. First, these models were calibrated, generating interface impact pressure results that correlated well with experimental data and previous extensive FE results. Next, bird strike simulations on a single blade were carried out, with each approach capable of producing damage and failure within the composite structure. Finally, an impact scenario on a full fan stage rotating at 7200 rpm was conducted. Both bird models successfully captured the impact and spread of the fluidic bird material, predicting a similar extent of damage to the composite fan assembly. It was concluded that.