Experimental and numerical investigations on polycarbonate samples and rotorcraft windshield for  bird model impacts

Abstract

One of the factors that significantly affect flight safety is bird strikes. Various aircraft parts are vulnerable to damage. For helicopters, the windshield, the front part of the fuselage, and the rotor blades are particularly sensitive to bird collisions. Experimental studies and numerical modelling of bird model impacts on polycarbonate samples and a helicopter windshield are presented in the paper. For the tests, a gelatine projectile was used as a bird substitute. In numerical studies, it was represented by a cylindrical shape with hemispherical ends. In the first stage of the experimental tests samples made of polycarbonate material were used as a target. These studies focused on determining the sample deflections and velocity at which the bird model would penetrate the target. The experimental investigations were conducted with a special set-up of a gas gun equipped with high-speed cameras, tensiometers, accelerometers, and force sensors. The simulations were conducted using LS-DYNA software by applying the SPH method to the bird model. The test stand models were developed in a CAD environment and then imported into LS-PrePost software, where they were discretized to use in numerical analyses. Results of the studies, such as impact force, acceleration, and windshield deflection were compared. Besides, the high-speed cameras allowed visualization of the impact process. It turned out that both a polycarbonate plate and a helicopter windshield were punctured at the speed of 50 m/s. It can be noted that the curves of the impact force and the deflection of samples obtained as a result of numerical analysis correlated well with the empirical ones. The correlation validated the modelling parameters and confirmed that numerical simulations could be trusted as an effective and reliable method for analyzing materials' behavior under impact loading.

Keywords

• bird strikes
• bird models
• experimental tests
• numerical simulations
• helicopter windshield