Failure Analysis of Rotorcraft Composite End Plate Structure Under High-Velocity Bird Impact

Abstract

The paper discusses finite element (FE) modeling for predicting structural damage and correlation studies of dynamic responses in rotorcraft composite structures under high energy bird impact. Before these applications of numerical modeling techniques the simulations are to be accepted by the industry for design development and certification of composite aircraft structures, composites damage models have to be developed and implemented in commercial FE codes, and validation studies at specimen and substructure level have to be performed. Since the experimental tests are expensive and difficult to perform, numerical simulations can only provide significant help in designing high-efficiency bird-proof structures. The design concept is based on the absorption of the major portion of the bird kinetic energy by the composite skins, in order to protect the inner honeycomb core from damage, thus preserving the end plate functionality for safe landing. To this purpose, the end plate skin is fabricated from composite layers, which unfold under the impact load and increase the energy absorption capability. The numerical modeling of bird strike using the Lagrangian approach and smooth particle hydrodynamics formulation and the critical design parameters are considered in carrying out the analysis. A numerical model of this problem has been developed with an explicit finite element code Autodyn. Analysis is carried out for the developed model using the test parameters. Numerical results by means of bird modeling approaches and accurate simulations of composite structures phenomena during impact are substantiated with experimental test results. The results obtained from the analysis and test shows close conformity implying their appropriateness in the simulation of bird strike.