Mesoscopic failure behavior of HTPB propellant bonding interface under multi-angle pull-and-shear loading

This study aims to investigate the in -situ microscopic damage evolution mechanism of the hydroxyl -terminated polybutadiene (HTPB) propellant bonding interface under multi -angle tensile shear conditions as well as to characterize the effects of the microscopic damage on the macroscopic failure modes. To this end, microspecimens of the HTPB bonding interface with different loading angles are scanned and reconstructed using micro -computed tomography (CT), and data on the sizes, shapes, and volume fractions of the particles and inclusions inside the propellant bonding interface are obtained. The results indicate the existence of a weak interfacial layer within 150 mu m on the propellant side of the propellant-liner interface, and the initial defects have a significant impact on the location and evolution direction of the interfacial damage; moreover, regardless of the type of damage, it occurs inside the weak interfacial layer and is related to the adhesion force of the bottom -most ammonium perchlorate (AP) particles. In addition, the loading angle affects the damage evolution process; specifically, a larger angle facilitates the occurrence of interfacial damage, whereas a smaller angle facilitates the occurrence of cohesive damage on the propellant side. The evolution process of the damage near the propellant-liner interface can be quantitatively characterized by means of the porosity, and the interfacial damage criterion is obtained, which is crucial for the subsequent fine modeling and investigation of the mechanical properties of the propellant bonding interface.