The dynamic response of clamped rectangular Y-frame and corrugated core sandwich plates

Abstract

The dynamic response of fully clamped, monolithic and sandwich plates of equal areal mass has been measured by loading rectangular plates over a central patch with metal foam projectiles. All plates are made from AISI 304 stainless steel, and the sandwich topologies comprise two identical face-sheets and either Y-frame or corrugated cores. The resistance to shock loading is quantified by the permanent transverse deflection at mid-span of the plates as a function of projectile momentum.At low levels of projectile momentum both types of sandwich plate deflect less than monolithic plates of equal areal mass. However, at higher levels of projectile momentum, the sandwich plates tear while the monolithic plates remain intact.Three-dimensional finite element (FE) calculations adequately predict the measured responses, prior to the onset of tearing. These calculations reveal that the accumulated plastic strains in the front face of the sandwich plates exceed those in the monolithic plates. These high plastic strains lead to failure of the front face sheets of the sandwich plates at lower values of projectile momentum than for the equivalent monolithic plates.Keywords: Sandwich plates, dynamic response, FE simulations, lattice materials. 1 Author to whom all correspondence should be addressed. . Full-scale ship collision trials reveal that the Y-frame design is more resistant to tearing than conventional monolithic designs, see Wevers and Vredeveldt (1999) and Ludolphy (2001). Likewise, the finite element simulations by Konter et al. (2004) suggest that the Y-frame confers improved perforation resistance. Naar et al. (2002) have argued in broad terms that the ability of the bending-governed Yframe topology to spread the impact load over a wide area, combined with the high inplane stretching resistance of the Y-frame, gives the enhanced performance of the Yframe sandwich construction over conventional single and double hull designs. The corrugated sandwich core (Fig. 1b) is a competing prismatic topology to that of the Yframe. Pedersen et al. (2006) and Rubino et al. (2007b) have investigated the quasi-static structural response of Y-frame sandwich beams while Côté et al. (2006) studied the response of sandwich beams with a corrugated core . These studies reveal that geometrical imperfections and/or non-uniform loading (such as indentation loading) induce bending within the struts of the corrugated core and reduce the compressive strength of the corrugated core to approximately that of the Y-frame core. Tilbrook et al. (2007) have performed a combined experimental and numerical investigation into the dynamic compressive response of these cores. They found that buckling of the webs is delayed at low impact velocities by inertial stabilization of the webs while plastic shock wave effects dominate the response at higher impact velocities. Radford et al. (2005) have developed an experimental technique to subject structures to high intensity pressure pulses using metal foam projectiles. The applied pressure versus ti...

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