The influence of core height and face plate thickness on the response of honeycomb sandwich panels subjected to blast loading Y. Chi, G.S. Langdon * , G.N. Nurick Blast Impact and Survivability Research Unit (BISRU), Department of Mechanical Engineering, University of Cape Town, Private Box, Rondebosch 7701, South Africa article info Article history: Received 15 September 2009 Accepted 29 October 2009 Available online 31 October 2009 Keywords: Honeycomb Sandwich Panels Blast loading abstract This paper reports on an investigation into the behaviour of circular sandwich panels with aluminium honeycomb cores subjected to air blast loading. Explosive tests were performed on sandwich panels con- sisting of mild steel face plates and aluminium honeycomb cores. The loading was generated by detonat- ing plastic explosives at a pre-determined stand-off distance. Core height and face plate thickness were varied and the results are compared with previous experiments. It was observed that the panels exhibited permanent face plate deflection and tearing, and the honeycomb core exhibited crushing and densifica- tion. It was found that increasing the core thickness delayed the onset of core densification and decreased back plate deflection. Increasing the plate thickness was also found to decrease back plate deflection, although the panels then had a substantially higher overall mass. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Sandwich panels, which consist of face plates separated by a core, are finding increasing use in structural applications because of their high specific stiffness and strength. While the response of monolithic structures subjected to blast loading has been stud- ied for many years [1–6], it has only be in recent years that researchers have begun to focus on the blast response of sandwich panels [7–12]. Fleck and Deshpande [7] developed analytical for- mulae to characterise the structural response of clamped metallic sandwich beams subjected to uniformly distributed air and water blasting loads. The study reviewed and compared the blast perfor- mance of a monolithic plate and various core topologies. Qui et al. [8] extended the analytical model [7] for clamped circular sand- wich plates. In addition, Xue and Hutchinson [9,10] performed fi- nite element calculations to compare the blast response of a monolithic plate and a metal sandwich plate, of the same material and total mass. In addition to these studies, Zhu et al. [11] pre- sented a review on impact and blasting of metallic and sandwich structures, and Kim Yuen et al. [12] presented an overview on sandwich panels subjected to blast loading. A variety of core topol- ogies were investigated in these studies and the results have shown that metal sandwich panels have the potential to perform better than monolithic plates under certain impact and blast situations. Metal honeycombs have been used as cores for blast, impact and quasi-statically loaded sandwich panels since they are light- weight, have good energy absorption properties and exhibit high strains to failure [13–19]. Dharmasena et al. [20] and Zhu et al. [21,22] have studied the air-blast response of square metal honey- comb sandwich panels. Dharmasena et al. [20] identified three stages of the response of the sandwich components to blast load- ing. It was found that the sandwich panel had lower back plate deflection than the solid plate. However, after complete core crush- ing, the advantages of the sandwich panel (as compared to the so- lid plate) are diminished. Furthermore, Zhu et al. [22] investigated the effect of foil thickness, cell size, mass of charge, relative density of the core, and the face-sheet thickness. Zhu and Lu [22] found that there is a compromise between strength and weight. The re- ported results [22] focused on the back plate response and showed that increasing the face-sheet thickness increased the mass of the panel but decreased the back plate deflection. Increasing the foil thickness and increasing the honeycomb relative density both de- creased the back plate deflection. Conversely, increasing the cell size increased the back plate deflection; this effect was especially noteworthy for panels with thinner face-sheet [22]. Despite a wealth of literature on the response of sandwich structures with various core topologies, and on the quasi-static and impact loading of honeycomb sandwich panels, there are rel- atively few studies that investigate the air-blast response of circu- lar aluminium honeycomb sandwich panels [23–26]. Nurick et al. [25] investigated the behaviour of a particular configuration of cir- cular aluminium honeycomb sandwich panels subjected to intense air blasts. The face plates were made of 1.6 mm thick low carbon steel and the core was an aluminium honeycomb of thickness 13 mm. This paper presents experimental results for other config- urations of fully clamped circular sandwich panels with aluminium 0261-3069/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2009.10.058 * Corresponding author. E-mail address: genevieve.langdon@uct.ac.za (G.S. Langdon). Materials and Design 31 (2010) 1887–1899 Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes