Study On Damage Of Composite Materials Under Heat - Mechanical Load Coupling

Application of composite material in the key parts of artillery-barrel, which can not only reduce the weight, but also improve the stiffness and strength of the barrel. When the gun is firing, the inner wall of the barrel is serious erosion due to the propellant gas with instantaneous high temperature and high pressure. In addition it is also subjected to belt guiding turns action and axial tension action of the recoil mechanism. In this complex condition, the inner wall of composite material barrel is very easy to produce micro crack, the crack propagation and evolution in the following load.In order to study the damage of composite material barrel under thermal-mechanical loading. Firstly, the anisotropic finite element model of composite material barrel was established, and the influence of material nonlinearity on the heat conduction and temperature distribution was studied. Then the damage mode and its influence factors were analyzed and calculated. Finally, the crack propagation and evolution of composite material barrel were studied by using the extended finite element method. The main research contents and conclusions are as follows:(1) The mechanism of coupling thermal-mechanical load. The numerical simulation results show that:due to the differences in thermal properties of materials, the temperature will be assembled at the interface between metal and composite materials. Under the impact of thermal load, the temperature of the inner wall of the barrel is changed dramatically and the thermal stress is large. Heat conduction and temperature distribution can be improved by increasing the thermal conductivity of the composites.(2) Damage modes of composite material barrel under thermal-mechanical impact load. Through the analysis of the results of the calculation:high temperature can easily lead to the inner wall of the barrel ablation. High pressure can cause the inner wall to swell and deform, and it is easy to cause the composite material layer to tear. While maintaining the wall thickness unchanged, the thicker the metal layer, the lower the peak temperature of barrel, the longer the barrel ablation life.(3) Generation, propagation and evolution law of the crack in the composite material barrel under the thermal-mechanical impact load. The study found:When the loading is different, the pressure plays an important role in the crack growth. Although the crack definition is different from the initial cracking angle, but the crack propagation path is mainly affected by stress state.