Research On The Method To Predict The Quasi-static Mechanical Property For Solid Propellant

The main task of this paper was to study the prediction method of the quasi-static mechanical properties of the solid propellant, totally using three methods to carry out the numerical calculation of the samples provided by cooperation unit. The first method was a computational micro-mechanics method based on the description of Lagrange, in this part it established a two-dimensional, multi-component, multi-scale, high filling rate particle random distribution model, taking effect of the volume content of particles and the particle scale which has to the quasi-static tensile mechanical properties of the solid propellant. Its main steps are: firstly, generate a geometric model of particles random distribution, cut the grid, and build a numerical model of the samples, Then separately give proper material models to the matrix and filling particle, using bilinear plastic constitutive model for the matrix and elasticity constitutive model for filling particles. Finally, calculate with LS-DYNA. The second method considered the effect which the weak interface has to the tensile mechanical properties of the solid propellant. Based on the model of the first method, its numerical model separate the nodes within the interface between matrix and particle. Then, these nodes in the interface overlap each other, but they have independent numbers. The third method is a computational micro-mechanics method based on the coupling of Euler and Lagrange. In this method, the matrix used Euler grid, the particles used Lagrange grid , then coupling the grids though keywords *CONSTRAINED_LAGRANGE_IN_SOLID. Through comparing the experiments and numerical simulations results of the three methods, the conclusion can be drawn:In the first method, besides considering the impact of particle volume content, the volume content of HMX also has a significant impact on the limit strain of solid propellant, the higher the content of HMX particle, the greater the limit strain of the material. There is not any clear rule in the impact on limit stress. Considering the impact of particle size, the size of Al and HMX particle have significant impact on the limit stress and strain. The smaller the particles size of Al and HMX, the greater the limit stress and strain of solid propellant. In the numerical simulations of pure Al sample, it can be find when considering the impact of particle size that the smaller the size of AP particle, the greater the limit stress. In the aspect of destruction form , the sample's destruction is: the crack expand along the direction which is 45 degrees from the direction of the tensile load. Considering the size of the filling particles totality, samples filled with particles of all scale level may have better limit strain, so size gap should be avoided in preparing material.Considering the weak interface's impact on the quasi-static tensile mechanical properties of the solid propellant, it can be found that the limit stress and limit strain predicted by the weak interface are both smaller than the results of perfect interface.The third method can well predict the limit stress, the limit strain and elastic modulus of the solid propellant.