Effect of bird strike on residual strength and vibration of fan blades for aero-engines

Bird strikes represent a critical threat to aviation safety, causing severe damage to aero-engine fan blades and compromising flight integrity. The impact introduces sudden unbalance and inertia asymmetry, leading to time-varying nonlinear dynamic properties and complex system vibrations. This study investigates post-impact strength and vibration characteristics of damaged fan blades. A validated SPH-FEM (Smoothed Particle Hydrodynamics–Finite Element Method) framework, calibrated through experimental bird strike tests, was developed in PAM-CRASH to replicate three damage modes: bending, tearing, spalling. Post-impact analyses revealed that leading-edge damage redistributes stress concentrations toward the blade root while amplifying tip deformations. Tearing and spalling damages significantly increase structural stresses (up to 280 % above baseline) and reduce natural frequencies in higher-order modes (up to 15 %). Severe damage creates critical operational risks, including stress concentration that accelerate crack propagation. These findings demonstrate that tearing damage necessitates prioritized inspection due to its severe stress amplification, while leading-edge reinforcement is essential for damage tolerance. This work establishes a validated framework for assessing blade residual strength and dynamic behavior, supporting predictive maintenance strategies for aviation safety.