The Mechanical Behavior Of Clamped Circular Sandwich Plates Subjected To Impact Loading

Because of the well mechanics, thermology and acoustics properties, the cellular metal is a kind of excellent engineering materials. It is able to withstand large plastic deformation due to its large stress plateau. In recent years, it has been used in various fields such as packaging, military, transportation and construction and so on.In this paper, deformation and failure modes, energy absorption and deformation mechanism of clamped sandwich circular plates were investigated by experimental research and numerical simulation. In the experiments, the aluminum foam bullets were employed to simulate impact loading. The main conclusions are drawn as follows:The effects of initial velocity of the bullets, edge length of single honeycomb and thickness of honeycomb core and other parameters on failure modes and shock resistance of clamped circular sandwich panels was studied. The experimental results show that when the honeycomb edge length increases, the number of cellular wall per unit area decreases, thus the deflection of back panel increases which weakens its shock resistance ability. The panel and core fails while the thickness of honeycomb core increase. Therefore the honeycomb core height has important significance on shock resistance of the circular honeycomb sandwich plates. In addition, there will be a plastic hinge and it moves from plate center to the clamped border in the dynamic response. The front plate of circular sandwich panels takes on three failure modes:intrusion failure, overall deformation and penetration failure. Because of the anisotropic characteristics of the corrugated panel, the corrugated sandwich front panel folds in the line of symmetry of the circular plate.The honeycomb core takes on shear failure and compression deformation which is a gradual compression deformation mode. Local compression and shear near the line of symmetry appeared in the corrugated core-There are three failure modes of the back face-sheet of circular honeycomb sandwich plate:large inelastic deformation, tearing failure and flower petal shaped tearing failure.The back face-sheet of circular corrugated sandwich plate also folds near the line of symmetry of clamped border.Based on the experiment results, response process, energy absorption and deformation mechanisms of the circular honeycomb and corrugated sandwich panels under aluminum foam impact are simulated by LS-DYNA3D970.It is found that the deflection of back face-sheet of circular sandwich plate increases with bullet impact velocity increase. The deflection of back face-sheet reduces with increase the thickness of face-sheet, thickness of core, height of core and decrease single honeycomb edge length, thus the shock risistance ability of the circular sandwich plate can be approved.The energy dissipation of sandwich panels increases along with the impact load increases, but decrease with the thickness of face-sheet and the thickness of core increase. The absorbing energy of circular honeycomb sandwich plate increases with the increase of single honeycomb edge length.while due to the core fully densified it remains unhchaged after the first rise.With the core height increase energy absorption of circular honeycomb sandwich plate decrease, but the importance of the core in the the whole energy dissipation becomes much more great.It should be noted that face-sheet and core is likely to fail was observed in experiments when the height of core is large. Therefore the core height should be choosed reasonably in order to achieve a better protective effect. When aluminum foam bullets are used to simulate explosion loads on sandwich plate, the load time is much longer than that under the explosive loads which may be due to the densification of the foam bullets.And it will generate secondary impact on sandwich panels after the foam bullets densification. The secondary core compression which caused by secondary impact is obviously improved under the high impact velocity.The core shape has a great influence on resistance ability of sandwich plates. The back face-sheet deflection of the diamond core shape is the smallest under same impulse.Therefore its resistant ability is the best.