Study Of Dynamic Mechanical Property And Anti-penetration Mechanism Of Ti B₂-B₄C Composites

B₄C have been wildly used in armor structure for its excellent physical and mechanical properties, such as low density, high strength, and transmitted X-ray abilities, etc. As a new type of composites material, the fracture toughness, elastic modulus and micro hardness of the TiB₂-B4 C composites was improved compared with pure B4 C. Nowadays, related researches on TiB₂-B4 C composites has already become a hot topic. Many important researches have been conducted in the sintering process and microstructure of the composites. However, the systematic and comprehensive mechanics behaviors of TiB₂-B4 C composites still need further discussions for engineering applications. In this paper, both dynamic mechanical properties of the TiB₂-B4 C composites and anti-penetration performance of ceramic/metal composites armor with adhesive were studied in conjunction with experiments, theoretical analysis and simulation methods.Firstly, the microstructure, tensile and compressive mechanical properties under static/dynamic loadings were carried out. Results showed that the grain of TiB₂ distributed uniformly in the grown B4 C particles. Both the TiB₂ and B4 C particles have regular shapes. The micro-void distributed uniformly on the boundary between TiB₂ and B4 C phases. Intergranular and transgranular fracture were discovered in the boundary of TiB₂ grain and the internal of B4 C grain respectively.The issue of stress concentration was solved by employing Flattened Brazilian disc experiments in studying the tensile mechanical properties of TiB₂-B4 C composites materials. The crack propagation characteristics were obtained, validated by 2D-DIC calculations. The material strength, failure strain, elastic modulus and strain rate sensitivity of TiB₂-B4 C compositess were acquired based on modified SHPB experimental apparatus. The tensile/compressive strength of TiB₂-B4 C both increases with the increase of loading strain rate due to the effect of the crack propagation. Furthermore, the TiB₂ dopant strengthens the composites by improving the size and distribution of internal grains and micro void, resulting in a greater strength than elemental B4 C and TiB₂ ceramics.The dynamic mechanic performance of TiB₂-B4 C compositess under one dimension strain loadings was also discussed together with the micro-crack extension mechanism and propagation property of failure wave. The Rankine-Hugoniot relation helped getting the curves of D-u and p-μ type. The strain rate sensitivity of TiB₂-B₄C’s Hugoniot elastic limit under extreme high strain rate loadings was analyzed. The Hugoniot elastic limit of TiB₂-B4 C was found to be close to that of the B4 C base under planar shock wave loadings with relatively small influence from the TiB₂ dopant. Failure waves were discovered in the TiB₂-B4 C compositess in the impact conditions beneath the Hugoniot elastic limit, the propagation velocity of which was deduced using the characteristic line method of wave equation. On the other hand, the influence of delayed effect on the failure wave velocity was brought up.The strength model of fractured TiB₂-B4 C composites have been obtained by the improved triaxial confining pressure test system. The completed constitutive model of TiB₂-B4 C composites was established conducting static/dynamic loading experiments and plate impact experiments and damage constants inversion of BP neural network. The validity of the model was verified by penetration experiments and numerical simulation.Eventually, the anti-penetration performance of the ceramic/metal composites armor with different thickness of adhesives and different form of ceramic plates were studied in the present study. The stress wave propagation characteristic inside the target plate was obtained. The results showed that the anti-penetration performance of layered ceramic composites armor is prior to targets with monolithic form ceramic plate. And the anti-penetration performance of armor was increased with the thickness of adhesive. The propagation characteristic of stress wave inside the adhesive layers and attenuation characteristic in the whole targets was gained by the wave impendence anayssis of targets materials. Finally, it was found that the shear capacity of the adhesive was increased with the increasing of target thicknesses, after analyzing the shear stress and shear strain rate of the adhesive layer.