Multi‐Scale Study of Propellants Aging via In Situ X‐Ray Tomography

ABSTRACT

Hydroxyl‐terminated polybutadiene (HTPB) propellants are widely used in solid rocket motors (SRMs). During storage and service, aging inevitably occurs, leading to degradation of mechanical properties and endangering the safety and reliability of SRMs. This study employed in situ x‐ray tomography and three‐dimensional reconstruction to explore the mesoscopic damage evolution of HTPB propellants before and after thermal accelerated aging under uniaxial tension, aiming to reveal its relationship with macroscopic mechanical deterioration. The results showed that thermally aged propellants were prone to brittle fracture due to weakened interfacial bonding between ammonium perchlorate (AP) particles and the matrix, which facilitated interfacial debonding. Beyond a critical strain threshold, damage accelerated sharply, featuring explosive debonding of AP particles, rapid pore growth, and coalescence into large crack bands. Aging also caused transgranular fragmentation of AP particles, changing their 3D morphology. Quantitative porosity evolution at various strain stages agreed well with experimental observations and correlated strongly with macroscopic mechanical responses. This work provides key experimental support for aging life evaluation, damage prediction and integrity analysis of HTPB composite solid propellants.