Mechanical properties of crosslinked graphene oxide intercalated HMX and CL-20 crystals†

Abstract

Insensitive hybrid energetic crystals of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) were successfully synthesized by intercalation of triaminoguanidine-glyoxal crosslinked graphene oxide (GO-TAGP) at varying concentrations (0.5–2.0 wt%). The resulting composites exhibited enhanced density (3.2% increase for GO–TAGP modified HMX and 2.8% for GO-TAGP modified CL-20) and improved thermal stability, attributed to strong interfacial interactions between the GO-TAGP and the energetic molecules. This study investigates the correlation between GO-TAGP content and mechanical properties, which critically influence the initiation sensitivity of these hybrid nitramine crystals. Nanoindentation tests revealed a 14% increase in maximum load capacity (from 35 mN to 40 mN) for GO-TAGP reinforced HMX compared to pure β-HMX, along with a 10% higher displacement before failure. Similarly, GO-TAGP modified CL-20 demonstrated a 17% improvement in elastic modulus (from 8.7 GPa to 10.2 GPa) and a 22% increase in hardness (from 0.45 GPa to 0.55 GPa) at optimal GO loading. The elevated modulus values confirm that GO-TAGP reinforcement significantly enhances structural rigidity, enabling the composites to endure greater mechanical stress without deformation. Concurrently, the hardness improvements suggest superior resistance to localized plastic deformation, indicative of a more robust interfacial bonding within the modified crystal lattice. These enhancements contribute to reduced mechanical sensitivity, ensuring safer handling and storage of these high-energy materials.