Test and numerical simulation on fragmentation behavior of an aircraft PMMA windshield under bird strike by using a novel coupled SPH-DEM method

The bird striking the windshield of an aircraft poses a great threat to the safety of flight. Moreover, the fragmentation behavior of aircraft windshield under bird strike is still unknown and requires further research. In this paper, a systematic methodology on Polymethyl methacrylate (PMMA) windshield combining material level test, a smoothed particle hydrodynamics-discrete element method (SPH-DEM) numerical simulation, and bird strike test was carried out to investigate the dynamic response mechanisms and fragmentation behavior of PMMA windshield under bird strike. The electromagnetic-driven composite expansion ring tests on PMMA material were conducted to systematically obtain the typical fragmentation characteristics and parameters of PMMA at different strain rates. The contact and bond parameters of DEM for PMMA were calibrated by using the key results of material level tests such as expansion velocity, fragmentation onset time, and fragment number. Considering the significant difference in size between material level test specimen and windshield structures, a cross-scale method of “calibration-scaling-verification-application” on parameters scaling of DEM was proposed and validated, the computational accuracy and efficiency were effectively improved. Based on this, the tests of bird strike with PMMA windshield were carried out at impacting velocities of 88m/s, 118m/s, and 154m/s, and the corresponding coupled SPH-DEM model was established to simulate the dynamic response of PMMA windshield impacted by bird. The results comparison between numerical simulation and tests demonstrated that the coupled SPH-DEM model could accurately reproduce both the fluid-like response of the bird projectile and the fragmentation process of the PMMA windshield. A high level of consistency was achieved between tests and numerical simulations in terms of damage morphology, fragmentation degree, and strain response for the PMMA windshield, consequently the reliability and applicability of the proposed coupled SPH-DEM were validated.