Bahjat et al., JMES, 2017, 8 (6), pp. 2231-2237 2231 JMES, 2017 Volume 8, Issue 6, Page 2231-2237 http://www.jmaterenvironsci.com / Journal of Materials and Environmental Sciences ISSN : 2028-2508 CODEN : JMESCN Copyright © 2017, University of Mohammed Premier Oujda Morocco 1. Introduction Composite structures are important in different areas of industry such as aero, marine aircrafts, ships, automotive and so on. Many of the structures experience blast loading during war or terrorist attack or accidental explosions. Response of composite structures subjected to explosion has been a field of intense activity of researchers in recent decades. So composite plates and shells form one of the basic elements of the structures, therefore, studying the blast response of such structures helps understanding and improving their blast resistance. There are too many papers dealing with the blast loading on the structures. Rajendran [1] investigated the plate behavior under the blast loading. In this review paper, he focuses on the phenomenological evolution of blast damage of plates. Arora et al. [2] studied the resistance of glass-fiber reinforced polymer(GFRP) sandwich panels and laminate due blast in air and underwater environments. They used an experimental method to obtain the behavior of the plates. The dynamic response and blast behavior of metallic sandwich-walled hollow shells with graded aluminum foam cores are investigated by Liu [3]. They used finite element simulations to model the blast and compared results with those of conventional ungraded ones. Fallah et al [4] studied the dynamic response of a blast-resistant lightweight fiber composites structure alternative to steel for military applications. The results of localized air-blast loading on structure are reported and analyzed by using experimental and numerical methods. A theoretical method is used to predict the large deflection response of fully clamped rectangular sandwich plates subjected to blast loading by Qin et al. [5]. They used energy dissipation balance theory and obtained the solutions for the dynamic response of rectangular sandwich plate. A multi-layered composite structure that made of layers of aluminum alloy AA 7075 bonded with toughened epoxy resin is investigated for blast resistant applications By Johnson et al. [6]. The performance of the proposed thick composite plate made of thick AA 7075 layers, was numerically studied under localized impulsive loading. In the other article represented by Logdon et al [7] the influence of material properties on the response of plates subjected to air- blast loading is investigated using an experimental method. They obtained the failure of mild steel, armor steel, aluminum alloy and fiber reinforced polymer composite plates experimentally by detonating disks of plastic Numerical Investigation of Composite Structures under Blast Loading Reza Haghi, Bashir Behjat * , Mojtaba Yazdani Mechanical Engineering Department, Sahand University of Technology, Tabriz, Iran, P.O.Box 51335-1996 Abstract In this paper, the behavior of composite structures against the explosive phenomenon has been investigated using finite element method. Some composite shells such as composite plates and hemispheres with different layer-uppinghave been investigated using LS-DYNA software. The blast loading is simulated by explosion's pressure versus time curves and is directly defined in LS-DYNA software. The Tsai-Wu failure criterion is used to predict the behavior of the composite structure.In this paper, the effect of layer-upping on the blast resistance of the structure is investigated. The results show that, hemisphere composite has better performance against the blast loading than plate and failure occur under greater load. Also it is shown that angle ply composite structures has good resistance in comparison with cross plies one. Received 17 Aug 2016, Revised 01 Oct 2016, Accepted 04 Oct 2016 Keywords  Blast Loading,  Composite Shell,  Numerical Analysis,  Layer Upping Behjat@sut.ac.ir , Tel: +98 41 33459465, Fax: +98 41 33444309