Multiscale structure-processing-performance interrelations in high explosives: A review enabled by X-ray computed tomography

The performance, safety, and reliability of high explosives (HEs), especially polymer-bonded explosives (PBX), are governed by their multiscale structure, which is shaped by manufacturing processes and evolves under service loads. Establishing causality within this structure-processing-performance paradigm is thus a fundamental research goal. This review synthesizes how X-ray computed tomography (CT) has advanced the understanding of these relationships across the material hierarchy and lifecycle of pressed PBX. At the crystal scale, CT-based studies have established quantitative correlations between intrinsic defects and sensitivity, while revealing dynamic deformation and damage mechanisms under stimuli. At the granule scale, CT quantifies how particle morphology and packing architecture dictate compaction efficiency and the resulting pressed microstructure. During processing, CT elucidates the impact of formulation and pressing parameters on critical outcomes such as binder distribution, void formation, and overall homogeneity. Finally, under mechanical and thermal loads, CT uniquely captures the initiation and propagation of damage, directly linking real-time microstructural evolution to macroscopic property. Collectively, the consolidated findings underscore that the macroscopic behavior of PBX can be interpreted and guided by its engineered microstructure. We conclude by identifying key research gaps, such as the need to bridge observations across vastly different time scales and to integrate CT-derived microstructural data into predictive constitutive models. This review aims to provide a comprehensive framework for leveraging advanced characterization to establish physics-based, microstructure-informed design principles for next-generation high explosives.