Evaluation of the ammonium nitrate fuel oil-nitromethane energetic material sensitivity

Abstract Ammonium Nitrate Fuel Oil is a widely used non-ideal explosive, though its relatively low detonation performance and high insensitivity limit its efficiency. This study examines the effect of partial substitution of ammonium nitrate(V) with nitromethane (4.0–9 wt%) on energetic material sensitivity, and thermal exposure. Brisance was evaluated using the Hess method at 40 mm and 60 mm diameters to capture scale effects, while friction and impact sensitivities were determined according to standardized procedures. Thermal stability was assessed after 48 h at 75 °C. Brisance increased systematically with nitromethane content, however, the magnitude of improvement was strongly diameter-dependent. The 40 mm configuration reflected near-critical detonation, whereas 60 mm enabled more complete energy release. Sensitivity results, revealed a selective response: friction sensitivity remained unchanged (> 360 N), while impact sensitivity increased, with thresholds decreasing from > 50 J for ANFO to approximetly 40 J for modified systems. This indicates that sensitization is governed by compressive hot-spot formation rather than shear mechanisms. Thermal testing showed no bulk decomposition, though minor phase redistribution occurred. Overall, nitromethane enables controlled enhancement of ANFO performance without compromising safety, emphasizing the importance of scale-dependent interpretation in non-ideal explosives.