高聚物粘结颗粒体裂纹萌生与自愈机理研究

The initiation and evolution of cracks in polymer bonded explosive (PBX) in service of weapon and equipment will affect the safety, reliability and detonation performance of explosives and their structures. Polymer bonded granula is a substitute material for PBX. Granula and polymer and bonding interface constitute the basis of mechanical behavior of substitute materials. The micro-scale material structure requires an introduction of rotation deformation. In view of effects of rotation deformation and temperature, the elastic-plastic and elastic visco-plastic constitutive relations in terms of stress-strain and couple stress-curvature tensor for granula and polymer, and the interfacial cohesion constitutive relation are established. The finite element equations and the numerical algorithm are properly formulated. In concern of rotation deformation, the stress and couple stress concentration as well as the changes of bonding forces and moments are demonstrated so that the mechanism of crack initiation and granula debonding is revealed. It is further studied that the reversibly and irreversibility of cracks are related to the temporal-spatial evolution of microstructure and internal tractions, the loading environment and the visco-plasticity of polymers, as a result, the mechanism of crack self-healing is explored. Mechanical properties test under thermal environment are carried out, with which parameters determination, microstructural observation and theoretical verification are carried out. PBX substitute material model and mechanical analysis method considering rotational deformation and temperature as well as strain rate effect are provided, which may be regarded as the theoretical basis of deformation and failure analysis of PBX.

高聚物粘结炸药（PBX）在武器装备服役过程中会出现裂纹的萌生和演化，影响炸药及其结构的安全性、可靠性和爆轰性能。高聚物粘结颗粒体是PBX替代材料，颗粒体和高聚物以及粘结界面构成替代材料力学行为的基础，微米级尺度的材料结构要求考虑材料的转动变形。本项目计及转动变形和温度影响，建立颗粒体和高聚物关于应力与应变、偶应力与曲率张量的弹塑性和弹粘塑性本构关系以及粘结界面的内聚力本构关系，建立适合的有限元方程和数值算法。研究计及转动变形时应力和偶应力的集中以及粘结力和力偶的变化，揭示颗粒体裂纹萌生和界面脱粘的机理。研究裂纹可逆和不可逆性与微结构变形和内力的演化、载荷环境、高聚物粘塑性的关联性，探索裂纹自愈的机理。开展原位观测和热力环境下的力学性能试验，进行参数确定、微结构演变观测及理论合理性验证。计及转动变形和温度及应变率效应的PBX替代材料建模及力学行为分析方法，为PBX的损伤破坏分析提供理论基础。

高聚物粘结炸药（PBX）是用于导弹战斗部装药、推进剂、水雷、鱼雷、反坦克导弹及核武器起爆装置等，在存储、运输、服役时经受载荷和温度环境下，炸药原生缺陷和微结构会发展演化，微裂纹和微缺陷可形成异常起爆等重大安全事故，影响炸药爆轰等物理力学性能。. 拓展了拉压弹性-转动弹塑性的材料力学理论，转动塑性的累计造成屈服应力的下降，形成材料的劣化以及微裂纹的萌生。建立了计及转动塑性的有限元数值分析模型，分析了微观缺陷导致的转动塑性及屈服应力和偶应力的演变，预测裂纹萌生趋势，提出了屈服应力与转动塑性的依赖关系。针对聚合物的超大变形特点，创新了计及转动变形的大变形度量理论，研制了平面超大变形的数字图像度量技术及其设备。建立了高聚物粘结颗粒体的微观特性几何模型，改进了材料细观结构的二维几何建模方法。探索了温压环境下高聚物粘结颗粒体的力学行为，表明降温及其温度循环易导致界面脱粘、颗粒尺寸突变易形成界面损伤，适当水平的压力有利于降低材料损伤。探索了不同体积分数的TATB基PBX在降温过程中界面的损伤差异，随着炸药晶粒体积分数的提高，降温过程中界面的残余刚度就越高，表明降低晶粒体积分数有助于减少界面脱粘。. 拉压弹性-转动弹塑性力学理论拓展了对传统弹塑性力学的认识，为裂纹的萌生和材料疲劳等问题提供了新的视角。创立计及转动变形的大变形理论，为连续介质力学的创新和改造奠定新的变形理论基础。改进的PBX细观结构的二维几何建模方法，更符合真实PBX的细观结构。升温和降温过程中PBX界面损伤机理和低压对变温环境下PBX 界面损伤的抑制作用，以及不同体积分数TATB基PBX在降温过程中界面损伤差异的研究，为炸药在存储、运输、服役时，避免极端环境下异常起爆提供重要参考意义。