The residual head velocity after the jet penetrating a target plate is an indication of the residual penetration capability of the jet, which changes obviously with the penetration time. In this study, the residual head velocity after the jet penetrating through the n-layer metal and the n-layer liquid was deduced by using the quasi-steady penetration model theory. The influence of shock wave to the residual head velocity of jet was analyzed. The calculation results show that the residual head velocity of the jet decreases with the increase of the number of layers of the composite structure, and the shock wave obviously affects the velocity of the residual head of the jet but not very strong. According to the difference between the experimental value and the theoretical value of the jet penetrating the single-layer composite structure, a method of modifying the theoretical mathematical model by using constant C as the calibration value is proposed. The mathematical model can be extended to calculate the residual head velocity of the jet penetrating the multi-layer metal-liquid composite structure with different materials and thickness.

This paper is aimed to investigate the crushing response of single square honeycomb panels under quasi-static compression loading. Two types of materials are used in this study, which refers to 100 % polylactic acid (PLA) and 70 % PLA filled 30 % carbon fibre (PLA/CF). Single honeycomb panels were fabricated through additive manufacturing technique, and assembled using slotting technique. The effect of boundary factor on the single square honeycomb panels have been studied, which refers to none, single-side, double-side boundary conditions. The effect of material properties on the crushing response has also involved. For the tensile test, it was concluded that the PLA/CF specimen offered the higher young modulus with 428.75 MPa than 360.76 MPa of PLA specimen. For the quasi-static compression test, the compressive modulus and strength of the single honeycomb sandwich panel showed 489.69 MPa and 18.32 MPa with boundary type 1, which provided the highest value compared to other two boundary condition types. Moreover, the square honeycomb sandwich panels with PLA/CF material and type 3 boundary condition offered the better crushing performance on energy absorption (EA) with 66.42 kJ and specific energy absorption (SEA) with 2282.47 kJ/kg. In addition, the crushing behaviour and failure mode were also involved and discussed in this study.

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In order to further improve the impact resistance of composite multi-cell thin-walled structures under axial loading, a new type of composite multi-cell sandwich tubular structure is proposed. Based on the MAT54 material model and the Chang-Chang failure criterion, a composite laminated shell modeling method was developed to simulate the failure behavior of the material under axial compression load and verified by quasi-static compression tests. The effectiveness of the simulation model is verified by comparing the parameters of peak load and specific energy absorption. The impact-resistance sensitivity of cell number and sandwich structure in composite multicellular structure was studied by this model. The results show that number of cells have a significant effect on the specific energy absorption of the composite multi-cell structure.