Molecular Dynamics Simulation of Mechanical Properties of Polymer Bonded Explosive under Tension Loading
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摘要: 采用分子动力学方法研究了拉伸加载下HMX基PBX界面力学行为的应变率依赖性。模拟结果显示，PBX的拉伸强度和弹性模量随着应变率的增加而增大。HMX-F2311的断裂方式与应变率相关：初始应变主要集中于黏结剂F2311，在低应变率下形成了一条大致垂直于加载方向的主裂纹；随着拉伸应变率的增加，破坏路径将分布在整个模型上；PBX的断裂失效是由于黏结剂F2311的脱粘。在单轴拉伸加载过程中，HMX-F2311的势能随拉伸应变率的增加而迅速增大，尤其在高应变率拉伸加载下，范德华力相互作用对势能的演变起到了决定性作用。分子动力学模拟揭示了应变率对HMX-F2311界面微观结构、力学行为和断裂损伤机制的影响，对PBX的设计、制备和安全使用具有重要意义。Abstract: In this paper, molecular dynamics method is used to study the strain rate dependence of HMX-based polymer bonded explosive (PBX) interface under dynamic tension loading. Our results show that the tension strength and elastic modulus of PBX increase with the increasing of strain rate. The fracture of HMX-F2311 is dependent on the strain rate: the initial strain mainly appears on the binder F2311, a main crack perpendicular to the loading direction is formed at low strain rate, while the failure path distributes on the whole model under high strain rate; the fracture of PBX is due to the debonding of binder. With the increasing of strain rate, the potential energy of HMX-F2311 increases rapidly, and the van der Waals force interaction plays a crucial role in the evolution of potential energy under high strain rate. The simulation reveals the effect of strain rate on the interface microstructure, mechanical behavior and fracture mechanism of the HMX-F2311, providing opinions for the design, preparation and safety of PBX.
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图 1 HMX-F2311界面的初始模型(a)以及优化后HMX-F2311界面的稳定结构(b)
Figure 1. Initial model of HMX-F2311 interface (a) and the stable structure of HMX-F2311 interface after optimization (b)
图 2 优化过程中压力和能量随时间的变化
Figure 2. Pressure and energy fluctuations vs. time during optimization
图 3 HMX-F2311在不同应变率下的应力-应变曲线 (a)以及拉伸强度 (b) 和弹性模量 (c) 与对数应变率的关系
Figure 3. (a) Stress-strain curves of HMX-F2311 under different tension loading; (b) tension strength vs. logarithmic strain rate; (c) elastic modulus vs. logarithmic strain rate
图 4 不同拉伸加载应变率下HMX-F2311界面在x方向的应变分布
Figure 4. Distribution of strain field in the x direction of HMX-F2311 interface under different tension strain rates
图 5 不同拉伸应变率下HMX-F2311界面在x方向的应变分布
Figure 5. Distribution of strain field in the x direction of HMX-F2311 interface under different tension strain rates
图 6 不同应变率下总势能随应变的变化
Figure 6. Variations of potential energy with stain under different strain rates
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