The Influence of Initial Defects on Impact Ignition of Aluminum/Polytetrafluoroethylene Reactive Material

Aluminum/polytetrafluoroethylene (Al/PTFE) reactive material is a typical multifunctional energetic material, which can release enormous energy under impact loading. To clarify its ignition mechanism, a Split Hopkinson pressure bar (SHPB) is used to conduct the impact ignition experiment on reactive materials with different initial defects. The experimental results show that the measured minimum specific incident energy that can cause the ignition for the specimen without pre-impact (MSed specimen) increases slowly from 97.5 to 101 Jcm⁻² with the molding pressure first, but drops substantially to 83.3 Jcm⁻² as the molding pressure increases to 100 MPa. In addition, only the MSed specimens with the molding pressure above 100 MPa are ignited at the third stress pulse. Combined with the results of scanning electron microscopy, it is found that the existence of local larger pores inside the MSed specimens with high molding pressures (100, 120, and 150 MPa) contributes to the increase in damage level under impact and thus reduces the ignition threshold. The impact ignition experiment on the pre-impacted specimens (MSed + PIed specimens) indicates that a phenomenon of damage sensitization exists in Al/PTFE reactive materials, confirming that the initial defects and damage evolution have significant effects on the impact ignition of the material.