The Blast Response of Sandwich Composites with Bi-Axial In-Plane Compressive Loading Erheng Wang1 and Arun Shukla2 1. Dept. of Aerospace Engineering, The University of Illinois, Urbana-Champaign, 104 S Wright St, Urbana, IL, 61801, erhengwang@gmail.com 2. Dynamic Photomechanics Lab, Dept. of Mechanical, Industrial and Systems Engineering The University of Rhode Island, 92 Upper College Road, Kingston, RI 02881, shuklaa@egr.uri.edu ABSTRACT The in-plane compressive loading in the ship hull structures during their whole service life will likely change the dynamic behavior of these structures under transverse blast loading. In the present study, the dynamic behavior of E-glass Vinyl Ester composite face sheet / foam core sandwich composites with bi-axial in-plane compressive loading were investigated under a transverse blast loading. A special test fixture which enables bi-axial in-plane compressive loading on the specimens was designed prior to transverse shock wave loading generated by a shock tube apparatus. Blast tests are carried out for three levels compressive loading. A high-speed back-view 3D Digital Image Correlation (DIC) system is utilized to acquire the real time deformation of the sandwich composites. The real time deformation and post mortem analysis were carefully conducted to study the failure mechanisms. The results show that the in-plane compressive loading induces the buckling and failure in the front face sheet. This mechanism highly reduces the blast resistance of the sandwich composites. INTRODUCTION Sandwich composites may undergo in-plane compressive loading in their application in the naval, aerospace, transportation and defense industries. For example, a ship’s hull will undergo longitudinal (in-plane) compressive loading during its service life [1], a missile’s shell will experience an in-plane inertia force when it is launched, and some residual stresses may be present in composites from the manufacturing and assembling processes. These in-plane compressive loadings will affect the dynamic response of sandwich composites when they are subjected to transverse blast loading and consequently affect their blast resistance. However, recent investigations on the behaviors of sandwich composites under blast loading mainly focus on the transverse behavior without longitudinal compressive loading [2-8]. Nurick [2], Zhu [3], and Dharmasena et al. [4] have tested sandwich structures with a metallic honeycomb core. Radford et al. [5] conducted blast experiments on sandwich composites with a metal foam core. They all found that the ability of sandwich panels to resist dynamic loading is far superior to that of monolithic metal plates with the same areal density. Tekalur et al [6] have studied the blast performance of sandwich structures with reinforced polymer foam cores. They concluded that the imparted damage was substantially reduced when Z-direction pin reinforcements (through thickness direction) were introduced into the core material. Wang et al. [7] constructed a sandwich structure with stepwise graded core materials and subjected it to transverse blast loading. They found that monotonically increasing the wave impedance of the core layers enhanced the blast resistance of the sandwich structures. Many of the above results have been summarized in Ref [8]. Some investigations on the dynamic response of pre-stressed composite structures under low-velocity transverse impact loadings can be found in literature [9-13]. Robb et al. [9] carried out the first experimental investigation on the low-velocity impact response of E-Glass reinforced/polyester laminated plates under different in-plane uniaxial and biaxial pre-stress. They found that the effects of the pre-stress were significant only at the highest level preT. Proulx (ed.), Dynamic Behavior of Materials, Volume 1, Conference Proceedings of the Society for Experimental Mechanics Series 99, 383 DOI 10.1007/978-1-4614-0216-9_53, © The Society for Experimental Mechanics, Inc. 2011
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