Research On The Micro-mechanics And Constitutive Relation For Solid Propellant

As a specific functional energetic composite material, solid propellant is a critical driving force for launching rockets, missiles, tactical missiles, etc. Its performances especially its mechanical properties might directly impact the survivability and combat effectiveness of strategic and tactical missiles. Therefore, to carry out the micro-mechanical research, explore the damage and failure mechanism, as well as establish the constitutive relation for solid propellants are of great significances for a new generation of solid propellant's research and development.In this paper, a solid propellant has been studied on its mechanical behavior from both micro-mechanical and constitutive relation kinds of way.1,Adopting SEM-Micro-test Tensile Stage to do in-situ tensile test for solid propellant. Observing its micro-damage and tension failure mechanism; analyzing the influences on its micro-structure evolution caused by initial damage, volume and size of solid particles in it.2,Results of in-situ tensile test showed that:There are main three initial damage forms in solid propellant: (1) Cracked grain, mainly exhibits in AP. (2) Micro-cracks and cavity, mainly reveal in matrix; (3) Incomplete binder package, mainly shows of the interface de-bonding between HMX and binder, as well as between big size particles of AP and binder. However, the third form of damage has the biggest influence on tension destruction of solid propellant. Besides the greater volume of solid particles, the larger diameter, plus the more severe degree of de-bonding between two-phase of the interfaces, the greater impact on the tension destruction.Different volume and size of the three solid particles: HMX, Al and AP have different influences on the micro-structure evolution of solid propellant, and have different destruction ways: (1) HMX particles' destruction is because of the de-wetting between HMX solid particle and binder interfaces. (2) Al particles' destruction is because of the break of binder and the matrix. (3) AP particles' destruction is because of the co-existence of de-wetting and binder fracture, while the latter dominated.3,Quasi-static tensile tests for the solid propellant are carried out by universal testing machines at room temperature, tensile rate is fixed at 10mm/min. According to the experimental results and its stress and strain response characteristics, this paper keeps on improving the Ramberg-Osgood model upon the precious's amendment, and takes into account the damage observed in micro-mechanical experiments, finally establishes the constitutive equation. After fitting by Origin software, it's found that the improved constitutive model can be a very good description of the solid propellant's mechanical behavior at room temperature and at 10mm/min tensile rate.4,Compared the in-situ tensile test with quasi-static tensile test shows that: The results of these two experiments matched very well, they have consistent shapes of stress-strain curve, in addition, both of them show obvious non-linear behavior.