Experimental and numerical investigation on a multi-layer protective structure under the synergistic effect of blast and fragment loadings

The main function of a multi-layer protective structure of a combatant ship is to prevent the inner cabins from being destroyed by anti-ship weapons. The damage effect of these weapons on ship structures mainly comes from the blast wave and fragments. The motivation of this study was to investigate the synergistic effect of blast wave and fragment impact loadings on the multi-layer protective structure. A protective structure model with four layers and a metal casing filled with TNT charge (MCTC) which was used to simulate the warhead of an anti-ship weapon were designed and manufactured. An experiment was conducted in which the MCTC exploded inside an empty cabin of the first layer of the multi-layer protective structure. The distribution of fragments and the equivalent bare charge of the MCTC were determined by a numerical method. From experimental results, the failure pattern of the multi-layer protective structure under the synergistic effect of blast wave and fragment impact loadings was presented. The synergistic effect for the stiffened plates was also presented in the experiment by comparing the deformation and the rupture of the air-backed and water-backed stiffened plates. On the other hand, the agreement between numerical results and experimental results validated the numerical method, which enabled the numerical model to be used to predict the response of a full scale structure under loadings of anti-ship weapons. Finally, a discussion of synergistic effects of blast and fragment loadings on a multi-layer structure was presented and suggestions for the design of a protective structure are put forward.