Micro-CT-based HTPB propellant double-axis stretch test design

In order to study the microstructural damage evolution of solid propellants under biaxial tension, firstly, based on finite element numerical calculation, small specimens of HTPB propellant that can simultaneously meet the requirements of biaxial deformation characteristics were designed, and stress cloud maps of deformation were obtained for three different configurations of HTPB propellant small specimens under typical tensile ratios. Then, based on the 1172 Micro-CT and its corresponding biaxial tensile fixture, biaxial tensile microtests were conducted to verify the confirmed configuration of small specimens. The results show that under the same loading displacement conditions, the stress distribution in the central test area of the three configurations of small HTPB propellant specimens is relatively uniform. The average stress value, plane stress dispersion, and overall stress stability coefficient of the central test area are calculated, and the optimal configuration of the small specimen with a thinning radius of R = 2 mm in the center circle is analyzed and compared. The central test area shows a more significant biaxial tensile state; the damage evolution process of the microstructure of small specimens was obtained through biaxial tensile tests, and the changes in force and porosity of small specimens with loading displacement were obtained. Finally, by analyzing the experimental results, the design requirements for small specimens of HTPB propellant under biaxial tension were met, and the rationality and effectiveness of the small specimen configuration were verified.