Experimental and simulation study on micro damage of HTPB propellant under multi angle tensile shear loading

The damage evolution of composite solid propellants is influenced by the stress state. In order to investigate the in-situ damage evolution mechanism of hydroxyl terminated polybutadiene (HTPB) propellant under tensile shear conditions, computer tomography (CT) technology was used to scan and reconstruct micro samples of HTPB propellant loaded at different angles. The variation of propellant internal damage with loading process and the influence of different representative volume element (RVE) sizes on porosity were analyzed. Subsequently, numerical simulations of relaxation loads were conducted using 12 different finite element models with 4 RVE sizes and 3 mesh sizes. The experimental results show that under tension shear loading conditions, the porosity increases exponentially with the equivalent effect, and the propagation direction of macroscopic cracks formed by the convergence of microcracks tends to be perpendicular to the tensile stress component. When the side length of RVE reaches and exceeds 600 μm, the porosity tends to stabilize. The numerical simulation study of variable angle tension shear loading found that when the RVE size is 800 μm and the grid size is 10 μm, the calculation effect considering calculation accuracy and efficiency is the best. As the loading angle increases, the dewetting stress first decreases and then increases, the dewetting strain shows a linear increasing trend.