HTPB复合固体推进剂率相关损伤机理分析与验证

固体发动机在点火过程中常由于结构完整性问题而出现爆炸或性能曲线异常等问题,结合发动机在点火状态下推进剂的受载情况,亟待探索固体推进剂的率相关损伤机理。本研究从某HTPB复合固体推进剂在宽温和宽应变率下单向定速拉伸试验的力学响应特征入手,针对应力-应变曲线呈现的“双峰”、“脱湿”点前后移位等现象阐释了推进剂的率相关界面损伤特性。然后,基于建立的推进剂细观有限元模型对推进剂的率相关损伤过程进行了仿真计算,通过提取有限元分析结果的损伤界面分析了推进剂的界面损伤机理。最后,通过高速摄像试验的结果对损伤机理进行了验证。结果表明,推进剂的界面损伤过程具有很强的率相关性,“双峰”和“脱湿”点前后移位均与推进剂在不同应变率下拉伸时内部的损伤演化过程有关。通过对比推进剂在不同应变率下拉伸时断裂前的形貌,高应变率下AP颗粒析出数量较多,在一定程度上印证了本研究对推进剂损伤机理的阐释。

Analysis and Verification of Rate-Dependent Damage Mechanism of HTPB Composite Solid Propellant

The problems such as explosion or abnormal performance can happen due to structural integrity problems during ignition state of solid rocket motor (SRM). It is urgent to do the research on the rate-dependent damage mechanism of solid propellant when considering the loading condition of propellant during ignition state of SRM. In this study, the mechanical response characteristics of a HTPB propellant at wide temperature range and different strain rates under uniaxial tensile test was investigated. The rate-dependent damage characteristics of the propellant were explained based on the phenomenon of "double peak" and "dewetting" point shifts on the stress-strain curve during the test. Then the rate-dependent damage process of propellant was analysed based on the meso-scale finite element model of propellant, and the rate-dependent damage mechanism was analysed by damage interface extraction according to results from finite element analysis (FEA). Finally, the damage mechanism was validated by results from high-speed photography experiment. The results show that the damage process of solid propellant has a strong rate dependence. The "double peak" and "dewetting" point shift are correlated to the internal damage evolution process of the propellant stretching at different strain rates. By comparing the morphology of propellant before fracture at different strain rates, more AP particles can be precipitated under high strain rate. It is a proof on the damage mechanism of propellant concluded in the study to a certain extent.