Study On The Dynamic Responses Of The Active Materials Under Impact Loadings

When subjected to impact loadings, active materials could react and release chemical energy, which can improve the target damage degree. Therefore, active materials have wide appliations in weapon systems. Research on the mechanical properties of active materials under impact loadings is very important for the design and safety of these materials in warhead structures. In this thesis, three typical active materials were fabricated, and their quasi-static and dynamic behaviors were studied by using universal material machine(MTS), Split Hopkinson Tensile Bar(SHTB) as well as Split Hopkinson Pressure Bar(SHPB) experiments. The tensile, compression and ignition properties of the materials were studied. The main conclusions are as follows:(1) Different quasi-static tensile specimens were prepared and quasi-static tensile mechanical properties were obtained. The tensile specimens were fabricated by powder mixing, pressing, inert gas atmosphere sintering. The quasi-static tensile behaviors of the active materials were studied by using MTS universal material machine. The results showed that PTFE/Al/Cu, PTFE/Al/W materials were elastic-plastic materials. The ductility of material and the static tensile strength depends on the density of materials. With the increase of material density, the tensile ductility and the tensile strength of the material decreased.(2) Dynamic mechanical properties tests were conducted and the mechanical constitutive equations were built. The dynamic behaviors of the active materials with different proportions and densities were studied by using Split Hopkinson Tensile Bar(SHTB) and Split Hopkinson Pressure Bar(SHPB). The dynamic tensile and compression stress-strain curves in different strain rates of active materials were obtained. Then,Johnson-Cook elastic-plastic model was chosen to describe the constitutive of materials.The results showed that the dynamic compressive strength of materials could be improved by adding a moderate amount of metals. But the dynamic tensile strength and ductility would be reduced when more copper or W-powder were added.(3) The ignition characteristics of these materials were exmained. The influences of the Copper or W mass fraction and the pulse length on the ignition threshold of these materials were studied by means of improved SHPB experimental instrument. The results showed that ignition threshold only depends on the material’s characteristic.