Toward a Methodology for the Design of Bird-Proof Intakes Made with Composite Materials

Every year, collisions between aircraft and birds cause remarkable losses. Modern aircrafts have to be certified for a proven level of bird impact resistance before being put into operational service. Nevertheless, it is not surprising if the structure of a turbofan-engine intake (basically designed to carry aerodynamic and thermal loads) collapses when colliding with a bird. The collapse of the intake is tolerated, but the fly-home capability must be guaranteed. The research work that eventually led to a methodology to develop bird-proof intakes made in composite materials is here described. It consists of two phases. In a first phase, referring to the experimental data, a bird model, feasible for the analysis of birdstrike and penetration, was developed and the dynamic behaviour of the composite material used in the intake manufacture was characterised. The numerical model of a full-scale birdstrike test was hence validated referring to a postcertification test of an actual intake and used to improve the design of the same intake. In a second phase, a full-scale birdstrike test on the improved structure was carried out using a prototype and the evidences collected are compared with the numerical results. Eventually the close numerical-experimental correlation obtained demonstrates the validity of the proposed methodology and indicates that the same approach is feasible to be extended to similar cases. Indeed, the use of this methodology leads to evident benefits: highefficiency (low-weight and high-resistance) structures and drastic reductions in design times and costs.