EFFECTS OF IMPACT-INDUCED DAMAGE ON DEFLAGRATION-TO-DETONATIONTRANSITION OF HIGH-ENERGY PROPELLANTS
推进剂的撞击损伤状态对其燃烧转爆轰的影响

The safety of energetic materials is of importance in practice. For the sake of development of new high-energy solid propellants, this paper presents an experimental study of the effects of damage, such as voids or microcracks, on the deflagration-to-detonation transition (DDT) of the NEPE (Nitrate Ester Plasticized Polyether) propellant. The study mainly includes: (1) to induce damage into the propellants by means of a large-scale drop-weight apparatus, (2) to observe microstructural variations of the propellant with a scanning electron microscope (SEM) and then to characterize the damage with sound--velocity and density measurements, (3) to carry out DDT tests of the original and impacted propellants with the steel tubes and synchronous optoelectronic triodes and strain gauges. The NEPE propellant is found to be a kind of viscoelastic material. The matrices of damaged samples are severely degraded, but particles are not. Additionally, their longitudinal sound velocity and density are reduced. The results of DDT tests show: (1) that apparent transition rates of damaged propellants vary considerably, and the sensitivity of NEPE propellants increases with damages; (2) that DDT seems to consist of five stages (ignition, convective burning, compressive burning, stronger shock formation and detonation, (3) that optoelectronic triodes provide relatively reliable, inexpensive and simple recordings of flame propagation. A suggestion is made that mechanical properties of a propellant should be improved to restrain its damage so that the likelihood of DDT might be reduced.