Study On Dynamic Responses Of Bird Striking An Aircraft Windsheild And Virtual Test Platform

The bird impact against aircraft structures can cause catastrophic damages. The statistical data from U.S.Air Force in 1987 showed that the probability of windshield and cockpit impacted by birds was about 21.4%, the biggest probability comparing with the other components of the aircraft. The records also presented that the impacted windshield and cockpit was much more dangerous than the other components. At present, the common way to determine the windshield's capabity against bird-stike is to carry out a full-scale bird-strike experiment. In the meantime, finite element (FE) analysis is taken as an important method to simulate the whole process of bird strike windshield. But numerical results of current models are not in good agreement with the experimental data. It is difficult for the numerical simulation of bird strike against windshield to meet the engineering requirement. Therefore, it is necessary to continue studying on the bird strike behavior of aircraft windshield by the means of both experiments and numerical analysis, and to build a virtual bird-strike test platform as well. The investigation has much more important academic value and practical engineering significance.Firstly, an experimental study was performed on bird impact against a full-scale aircraft windshield. The whole dynamic response process of bird impact on windshield was recorded with the high speed video cameras and the data acquisition system. A comprehensive discussion was presented on the deformation of bird and windshield, and the damage modes of the windshield. Experimental results, the history curves of the displacement and the strain of all the measure points on the windshield, were obtained. The experimental study provides an important physical basis and verification cases for establishing a reasonable finite element model of bird strike on the aircraft windshield.Secondly, the bird FE model was studied through the combination analysis of three kinds of geometry shapes and several constitutive equations. The impact force and displacement histories were calculated and compared with the experimental data of bird impact on a flat aluminum plates. A reasonable bird geometry shape and a constitutive model were obtained, of which the analysis results was the most agreeable with the experimental data. The parameters of the bird constitutive model were optimized by the optimization methods.Thirdly, based on the experiment investigation, a finite element model of bird impact on the windshield was established to predict the damage initiation and propagation of the windshield after bird impact via the nonlinear finite element method, combined with the user-defined materials subroutine (VUMAT) of the ABAQUS/Explicit software. By comparing the instantaneous deformation of bird and windshield, the damage modes of the windshield, displacement curves and strain curves of the measured points on the windshield, it was shown that the simulation results and the full-scale bird impact test results had a good agreement. The boundary conditions of the windshield FE model were discussed via two modeling strategies. One way was to simplify the supporting structures around the windshield glass as the fixed constraint boundary condition acting on the windshield glass directly. The other way was to take into account the surrounding structure of the windshield glass in the FE model. The sensitivities of the design parameters of aircraft windshield, including skin thickness, skin elastic modulus, rubber thickness, and rubber elastic modulus, were discussed to the windshield's capability against bird-strike comprehensively. In addition, the capability of the layered windshield against bird-stike, composed of inorganic glass, PVB and organic glass, was discussed with the different adhesive film (PVB) thickness, inorganic glass thickness, organic glass thickness, as well as the different numbers of layer.Finally, based on the previous study, a virtual test platform of bird impact on aircraft windshield was studied and established for the engineering application. Presented in the paper were the general schematic of the platform, the key technology, the detail design of each function modules. An expample of the bird strike test of aircraft windshield showed the efficiency and practicability of the virtual test platform. It was shown that the virtual test platform could be helpful for designing and modifying an aircraft windshield.