Work

Femtosecond laser fabrication of cross-scale pre-microcracks in PBX: Toward accurate fracture toughness determination

Year: 2026

Type: article

Abstract: Accurate fracture toughness (KIC) assessment of polymer-bonded explosives (PBX) is critical for weapon system safety, yet persistently challenged by a fundamental limitation: the inability to fabricate pre-cracks with both controlled depth and sufficient sharpness.Conventional methods suffer from either excessively blunt notches (>300 μm)that artificially inflate KIC values, or manual techniques plagued by poor reproducibility, fundamentally compromising testing validity. To overcome this long-standing barrier, we introduce an innovative femtosecond laser “cold processing” technique. This method enables the precise fabrication of ultra-sharp pre-cracks (sub-μm tips)in TATB-based PBX while preserving material integrity (Raman-verified). Crucially, addressing the depth constraint inherent in standard SEVNB methods, we developed the Single Edge Multiple V-Notched Beam (SEMVNB)approach. SEMVNB eliminates the need for error-inducing U-notchesthrough direct multi-stage laser processing, significantly extending controllable crack depths beyond previous limits. The critical relative crack depth for stable KIC in PBX (a/W ≥ 0.17) is substantially lower than the ASTM-specified range for metals/ceramics, revealing distinct fracture characteristics. Validation on MJ-03 substitute confirms the universal applicability of this methodology to brittle composites. This work provides a robust and reliable solution for fracture resistance assessment in PBX, directly tackling a safety-critical challenge in defense engineering by enabling accurate prediction of crack propagation risks.

Source: Energetic Materials Frontiers

DOI: 10.1016/j.enmf.2026.02.007