Bionic stab-resistant body armor based on triangular pyramid structure

A stab-resistant substrate was designed and realized with a triangular pyramidal structure, inspired by the biological armor model in nature. The stab-resistance behavior and dynamic response mechanisms were studied through numerical simulation and experimental testing of a knife impacting a substrate, and an optimal structural design was obtained accordingly, with a tilted angle of 22.5° and optimal thickness of 1.2 mm. It was shown that the triangular pyramidal structure generated twice the internal energy of the knife than the flat substrate due to the dispersing effect of the structure. The force parallel to the inclination caused a significant scratch on the substrate surface, while the force perpendicular caused obvious substrate deformation. A new riveting method was used to form the total layer, which passed the GA 68—2008 standard. The stab-resistant clothing coupled with the reduced wearing burden could provide effective protection and avoid fatal injuries on security personnel working in dangerous environments. The method provided may enlighten the future design and manufacturing of stab-resistant clothing.     

Damage of multi-layer spaced metallic target plates impacted by radial layered PELE

Three different kinds of PELE (the penetrator with lateral efficiency) were launched by ballistic artillery to impact the multi-layer spaced metal target plates. The impact velocities of the projectiles were measured by the velocity measuring system. The damage degree and process of each layer of target plate impacted by the three kinds of projectiles were analyzed. The experimental results show that all the three kinds of projectiles have the effect of expanding holes on the multi-layer spaced metal target plates. For the normal structure PELE(without layered) with tungsten alloy jacket and the radial layered PELE with tungsten alloy jacket, the diameters of holes on the second layer of plates are 3.36 times and 3.76 times of the diameter of the projectile, respectively. For radial layered PELE with W/Zr-based amorphous composite jacket, due to the large number of tungsten wires dispersed after the impact, the diameter of the holes on the four-layer spaced plates can reach 2.4 times, 3.04 times, 5.36 times and 2.68 times of the diameter of the projectile. Besides, the normal structure PELE with tungsten alloy jacket and the radial layered PELE whit tungsten alloy jacket formed a large number of fragments impact marks on the third target plate. Although the number of fragments penetrating the third target plate is not as large as that of the normal structure PELE, the area of dispersion of fragments impact craters on the third target plate is larger by the radial layered PELE. The radial layered PELE with W/Zr-based amorphous composite jacket released a lot of heat energy due to the impact of the matrix material, and formed a large area of ablation marks on the last three target plates.     

Experimental study on ceramic balls impact composite armor

Ceramic balls represent a new type of damaging element, and studies on their damaging power of composite armor are required for a comprehensive evaluation of the effectiveness of various types of weapons. The goal of this study was to determine the impact of ϕ7 mm toughened Al₂O₃ ceramic balls on a composite ceramic/metal armor. The influences of the ceramic panel and the thickness of the metal backing material on the destroying power of the ceramic balls were first determined. Based on the agreement between numerical simulation, experimental results, and calculation models of the target plate resistance, the response mechanism of the ceramic balls was further analyzed. The results indicate that for a back plate of Q235 steel, with an increasing thickness of the ceramic panel, the piercing speed limit of the ceramic balls gradually increases and the diameter of the out-going hole on the metal back decreases. Different conditions were tested to assess the effects on the piercing speed, the diameter of the out-going hole, the micro-element stress, and the integrity of the recovered ceramic bowl.     

Growth model of cavity generated by the projectile impacting liquid-filled tank

The high-speed impact of a projectile on a liquid-filled tank causes the hydraulic ram, in which a cavity is formed. To study the growth characteristics of the cavity, the formation mechanism of the cavity is analyzed. The effect of Reynolds number and Mach number on drag coefficient is considered, the axial and radial growth models of the cavity are established respectively. The relative errors between the cavity length calculated by the axial growth model, the cavity diameter calculated by the radial growth model and Ma L. Y. test results are less than 20%, which verifies the effectiveness of the axial and radial growth models. Finally, numerical simulation is carried out to study the growth characteristics of the cavity caused by the projectile impacting the satellite tank at the velocity of 4000 m/s. The cavity length and diameter calculated by the axial and radial growth models agree well with those obtained by simulation results, indicating that the cavity length and diameter in satellite tank can be accurately calculated by the axial and radial growth models.     

Consequence of reinforced SiC particles and post process artificial ageing on microstructure and mechanical properties of friction stir processed AA7075

Friction stir processing and post process artificial ageing was successfully carried out on AA7075 with and without reinforcement of SiC particles producing defect free processed zone with uniform distribution of filler material. Effect of SiC particle reinforcement and artificial ageing times on the microstructural modifications was characterized using optical and electron microscopy, electron backscattered diffraction and X-Ray diffraction. Hardness, impact and wear tests were carried out to investigate mechanical behaviour before and after processing. Reinforcement of SiC particles during FSP and subsequent age hardening treatment brought about nearly twofold increase in hardness and impact toughness values by the combined effect of grain refinement, Zener pinning, dispersion strengthening and precipitation hardening. Significant improvement in wear resistance in terms of wear loss was also observed after processing compared to the reference material AA7075-T6. Fractured surface of post FSP age hardened AA7075 alloy exhibited features of ductile fracture during Charpy impact test.