Bird Impact Forces in Aircraft Windshield Design
DAYTON UNIV DAYTON United States
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In order to design transparent aircraft windshield and canopy panels which can withstand the impact of birds, and at the same time meet other equally important operational requirements, it is necessary to define the forces generated during the birdstrike event. The total force as a function of time was measured by impacting birds onto a large diameter Hopkinson bar. The local pressures and pressure distribution during the bird impact were measured by flush mounting piezo-electric pressure transducers in a heavy rigid flat plate and impacting the platetransducer assembly. The forces and pressures are a function of the relative impact velocity and angle, the weight and average density of the bird and the stiffness of the impacted structure. In order to define the temporal and spatial distribution of the bird impact forces, a parametric birdplate impact test program was initiated. These tests cover a velocity range from 30 ms to 350 ms, impact angles from 15 to 90 deg in trajectory and bird weights from 0.05 kg to 3.6 kg. The results at the 90 deg test angle indicate that 1 Birds behave essentially as a fluid during impact 2 Birds do not bounce at impact -- the impuse is equal to the initial impact momentum 3 The high-frequency component of pressure superimposed on the base pressure-time pulse is caused by breakup of the bird flesh and inhomogeneities in the bird and 4 The duration of loading is approximately equal to the squash up time.