Abstract:

To achieve accurate observation and characterization of the meso-damage and its evolutionary behaviour of the Nitrate Ester Plasticized Polyether（NEPE） solid propellant， an imaging scan test was conducted in the monotonic stretching process of the NEPE solid propellant at a stretching rate of 0.1 mm/s based on the self-developed in-situ monotonic loading test system and the third-generation high-resolution Synchrotron Radiation X-ray Computed Tomography （SR-μCT） technology. The meso-morphology of the solid propellant at the initial state and its evolution with the tensile load are obtained， and the evolution of the volume and sphericity of the typical damage within the solid propellant with the load is extracted. Results show that the SR-μCT can successfully acquire the mesoscale structure inside the NEPE solid propellant， and identify the AP particles， Al particles， matrix， and defects inside the solid propellant based on the grayscale difference. Mainly two types of initial defects exist inside the NEPE solid propellant， one being the pores inside the particles and the other the initial debonding at the AP particle/matrix interface. The meso-damage of the solid propellant has firstly appeared as pores formed by initial interface debonding. With the small tensile load， the meso-damage of the solid propellant has mainly appeared as the pores formed by the debonding of larger AP particles， while the large tensile load enables observation of the Al particle debonding in addition to the debonding of AP particles， and the macroscopic fracture of the solid propellant is due to the fusion of the pores formed by the debonding of a large number of AP particles with each other. The volume of pores increases with increasing tensile load， while the sphericity is related to the initial defects， and those with initial defects show a monotonically decreasing trend， while those without initial defects show a first increasing and then decreasing trend. Current results can enable a deeper understanding of the meso-damage of solid propellants， providing a theoretical basis for the next step of establishing the meso-damage model and constitutive relation.

Key words: synchrotron radiation in situ tomography, NEPE solid propellant, interface debonding, void nucleation, meso-damage evolution