【作者】 陈华；

【导师】 汤文辉；

【作者基本信息】 国防科学技术大学 ， 力学， 2013， 博士

【摘要】 聚酰亚胺是近半个世纪发展起来的芳香杂环聚合物中最主要的品种，也是使用温度最高的一类高分子材料。由于聚酰亚胺具有十分优异的综合性能，并可用多途径合成，还可用多种方法加工，因而以多种多样的材料形式在航空、航天、电气、机械、微电子、化工等方面得到了广泛应用。本学位论文以国产YS-20聚酰亚胺材料在航天器上的应用为背景，对其动态力学性能和化学反应动力学性能进行了研究，以此为基础，研究了化学反应对聚酰亚胺超高速碰撞效应的影响。本论文的主要研究内容和研究成果如下：（1）对聚酰亚胺材料的高压物态方程开展了研究。设计并完成了聚酰亚胺材料的二级轻气炮实验，得到了聚酰亚胺材料的Hugoniot参数，即冲击波速度D与波后质点速度u关系式D=c0+su中的常数c0和s：在0~50GPa压力范围内，c0为（2.62±0.22）km/s，s为1.25±0.06；如果要考虑更高的压力范围，可取c0为（2.26±0.26）km/s，s为1.41±0.04。得到了聚酰亚胺材料在冲击压缩下的p-u关系为p=3.27u+1.76u2（0~50GPa压力范围内）。得到了聚酰亚胺材料在常态下的Grüneisen系数为0=1.53。聚酰亚胺高压物态方程的获得为其超高速碰撞效应的数值模拟研究打下了重要基础。（2）完成了聚酰亚胺材料的热分析实验研究。利用差示扫描量热实验测定出聚酰亚胺材料的分解反应为放热反应，反应热为81.96J/g。利用加压热重分析实验得到了聚酰亚胺材料热分解动力学参数随压力的变化规律：随着压力的增加，反应级数基本保持不变，指前因子和活化能逐渐减小。（3）建立了压力、温度相关的热分解动力学模型。聚酰亚胺是一种高分子材料，在强冲击压缩下由于高温高压因素将发生显著的热分解反应。经典的Arrhenius模型描述了反应速率随温度的变化关系，但没有考虑压力的影响。如果要探讨聚酰亚胺在冲击压缩下的热分解行为，压力的影响是客观存在的。本文基于加压热重分析实验结果，在Arrhenius模型中引入压力因素，从而使反应速率的描述更加客观全面，同时也为研究化学反应对超高速碰撞效应的影响打下了重要的理论基础。（4）建立了一种化学反应流体动力学算法。化学反应导致物质组元变化，质量守恒方程形式要复杂得多，而且作为流体动力学数值模拟中的基本单元（网格或粒子等）的压力、比内能以及组元份额等均在不断发生变化过程中。本文从质量作用定律出发，推导了可变多组元系统的质量守恒方程，以单元压力平衡、温度平衡和能量守恒为出发点，给出了单元压力、比内能和组元份额等量的算法。（5）编写了含化学反应的光滑粒子流体动力学（SPH）计算程序。聚酰亚胺在超高速碰撞下，碎片云团的形成及其运动过程中必然伴有显著的化学反应，并放出热量，这时的热传导也可能对物质的热力学状态产生影响，因而非常复杂，但目前还没有现成的程序能对这一过程进行数值模拟。本文基于SPH方法编写了三维程序。利用该程序对脉冲激光辐照铝靶以及脉冲激光引燃火柴问题进行了模拟，对程序的基本功能和化学反应过程的模拟进行了一定的验证。（6）研究了聚酰亚胺材料的化学反应对其超高速碰撞效应的影响。聚酰亚胺是航天器的一种常用热控涂层材料，因而可能受到空间碎片的超高速碰撞，所以研究其超高速碰撞效应具有重要意义。我们利用所获得的高压物态方程、压力和温度相关的热分解动力学模型以及自编SPH程序对聚酰亚胺的超高速碰撞现象进行了数值模拟研究，重点讨论了含化学效应与不含化学效应时碎片云特性的区别。结果表明，化学反应效应对碎片云的宽度、膨胀速度、热力学状态和靶板孔洞直径都有较大影响。分析认为，在聚酰亚胺材料超高速碰撞效应的数值模拟中，考虑化学反应是非常必要的。更多还原

【Abstract】 The Polyimide (PI) is a typical complex high-molecular polymer of imidemonomers. It is well known for excellent properties as light weight, thermal stability,good chemical resistance, low electrical conductivity, large radiation resistance, hightensile strength, large elastic module, and so on. Due to the excellent properties,polyimides are widely used along with composites based on polyimide fibers in themanufacture of parts for aerospace technology, polyimide films located in the surfacelayer are used to protect the spacecraft’s electronic equipment from damage by lowtemperature in the space, and polyimide resin are used to produce the solar cell arrays.The mechanical and chemical properties of polyimide and its influedce on hypervelocityimpact phenomena are studied in the paper.(1) The equation of state (EOS) for polyimideu in high-pressure state is determinedwith the shock compress experiments. An equation of state is a thermodynamic equationdescribing the state of matter under a given set of physical conditions, and theMie-Grüneisen EOS is a widely used EOS for solid materials. In our research, the threekey parameters of the Mie-Grüneisen EOS based on the shock adiabat for polyimide hasbeen determined with two-stage light-gas gun experiments, i.e. the bulk speed of soundof polyimide c0=(2.62±0.22) km/s, the linear Hugoniot slope coefficient s=1.25±0.063for pressure less than50GPa, and c0=(2.26±0.26) km/s and s=1.41±0.043for pressurefrom50GPa to about1TPa, and the Grüneisen parameter at initial state of1.53. TheMie-Grüneisen EOS for polyimide is finally obtained, and the parameter values areproved reliable via the comparison of Grüneisen parameter value calculated from twodifferent theoretical models and the experimental data.(2)The differential scaning calarmeutry (DSC) experiments andpressure-thermogravimetry (PTG) analysis experiments for polyimide are performed.The reaction heat is determined as81.96J/g through the DSC experiments, and thechemical reaction kinetics parameters with different pressure for polyimide aredeterminded through the PTG experiments. Finally, the laws of the kinetics parametersare obtained.(3) With the PTG results, a pressure-related and temperature-related chemicalreaction model for polyimide is established. The Arrhenius model does not contain thepressure factor when describing the thermal decomposition of materials, our modelwhich based on the Arrhenius model has considered the pressure factor to describe thethermal decomposition of materials. Our model is more accruable to describe thethermal decomposition of polyimide in shock wave compression condition.(4) A chemical reaction dynamics algorithm is established. Chemical reactionsleading to changes in substance component, the form of the mass conservation equation is much more complex. The pressure, specific internal energy and the componentpercent are all change following the numerical simulation. The unit pressure, specificinternal energy and the component percent are obtained from the balance of pressure,temperature and energy in this paper.(5) A three-dimensional hydrodynamic code employing the SPH method withFORTRAN language is compiled, and the chemical reaction is considered by theprogram. When impact by hypervelocity flyers, the debris cloud of polyimide target inthe process of formation and movement entails significant chemical reaction and releaseheat, and the heat conduction may also have an impact on thermodynamic state ofmatter, however, there is no ready-made program can simulate this process except ourSPH code. Finally, two examples are calculated with the code to vertify the accuranceof the code.(6) The hypervelocity impact between Al flyer with different impact angle andimpact velocity and polyimide target is simulated by using the equation of state, thermaldecomposition kinetic model and SPH code. Influence of chemical reaction is mainlyconsidered, characteristics of debris clouds and penetration hole produced in the impactare presented, influence of the impact angle and impact velocity on the debris cloudsand the penetration hole are discussed, and the pressure distribution and temperaturedistribution are obtained. The results show that materials around the penetration hole areboth destroyed by the mechamical factor and thermal factor (such as thermal stability).更多还原