【作者】 徐松林；

【导师】 张炜； 阳世清；

【作者基本信息】 国防科学技术大学 ， 航空宇航科学与技术， 2010， 博士

【摘要】 PTFE（聚四氟乙烯）/Al（铝）含能反应材料是一种新型的直接毁伤式含能材料,其高化学潜能主要通过冲击引发化学反应的形式释放出来。力学性能、能量释放反应的冲击引发和能量释放水平是其三项重要特征性能。本文主要研究了PTFE/Al含能反应材料的冲击力学性能、准静态力学性能与能量释放反应的冲击引发。系统考察了制备工艺、试验条件和材料组分对其力学性能的影响规律;构建了该材料基于试验结果的压缩应力-应变本构方程,进行了含能反应材料弹丸冲击试验过程的数值模拟;探索了该类材料在冲击加载下的能量释放反应引发特性。实验研究了PTFE/Al含能反应材料模压烧结工艺参数和组分配比对其准静态力学性能的影响规律,分析并推测了材料在单轴拉伸加载下的破坏模式及各类添加剂的增强机制。影响拉伸强度的主要因素按影响程度从大到小依次是烧结温度、降温速率、烧结时间、预成型压力、降温过程中的保温温度和预成型温度。获得的优化组合工艺使典型的PTFE/Al（质量比为73.5/26.5）材料拉伸强度和断裂伸长率分别达到24.9MPa和395%。Al含量在6%时PTFE/Al材料有最大拉伸强度,遵循了Πугачев提出的球状颗粒填充PTFE模型。Al含量35%时PTFE/Al材料有最大的准静态压缩强度。纳米粉体和晶须的少量添加可使PTFE/Al材料拉伸强度提高26.2%和9.6%。偶联剂显著提高了高Al含量PTFE/Al材料的拉伸强度,使Al含量50%时的材料拉伸强度提高了62.3%。在标准摆锤式冲击试验机基础上,改进了冲击试验装置。利用改进前后的摆锤式冲击试验机和分离式霍普金斯压杆（SHPB）试验装置,测得了PTFE/Al含能反应材料的冲击压缩比、压缩应变、开裂阈值、解体阈值和标准冲击强度等动态力学性能参数,分析并推测了材料在冲击加载下的破坏模式及其增韧机制。研究结果表明,材料冲击压缩比随摆锤冲击能的增加呈线性增加趋势。材料标准冲击强度、开裂和解体破坏阈值均在Al含量40%时达到最高值,分别为25.3 J/cm₂、71.2 J/cm₂和85.6J/cm₂,冲击压缩应变则与Al含量成反比。高密度微米颗粒、纳米粉体和晶须使材料各破坏阈值呈下降趋势,偶联剂使材料破坏阈值略微升高。同时采用SHPB试验装置,研究了PTFE/Al含能反应材料的动态压缩性能,得到了Al含量、加载应变率与材料动态压缩强度和临界应变的相关关系。在压缩实验数据基础上,构建了PTFE/Al材料基于Johnson-Cook塑性模型的压缩应力-应变本构方程,该方程包含了材料的应变硬化效应、应变率效应、温度效应和Al含量的影响。与本研究基本同步的文献报道的本构方程相比,本研究构建的本构方程具有更宽的应变率实验基础(0.006⁹000 s^-1),适用的Al含量范围更广,从26.5%到50%。用LS-DYNA模拟处理软件和自行构建的本构方程进行了PTFE/A（l质量比为73.5/26.5）含能反应材料弹丸侵彻靶板试验过程的数值模拟,且与试验结果符合较好,验证了所构建本构方程的可靠性、合理性和实用性。同时还获得了弹丸冲击速度对穿靶过程中弹-靶相互作用情况及穿靶后相关性能参数的影响规律。利用改进的摆锤式冲击试验和SHPB试验还研究了PTFE/Al含能反应材料能量释放反应的冲击引发特性,结合红外成像仪测温方法测得了试样的冲击温升。发现材料反应阈值可用摆锤的冲击能量或压杆的加载应变率表示。随着摆锤冲击能的增加,材料冲击温升也随之上升。化学计量配比的PTFE/A（l质量比为73.5/26.5）反应阈值最低,即最易被冲击引发反应。高密度微米颗粒、纳米粉体和晶须使材料反应阈值呈上升趋势,偶联剂对材料反应阈值影响较小。试样初始温度升高使材料反应阈值降低。PTFE/Al（质量比为73.5/26.5）含能反应材料绝热反应温度的计算值为4580K,绝热反应热的计算值为TNT炸药热值的2.0倍以上,其高能量释放主要源于冲击加载下被引发的氟-铝高放热反应,且能量释放水平可通过材料组分进行调节。更多还原

【Abstract】 PTFE/Al energetic reactive material is a new kind of energetic material with directly destroys ability, their high chemical potential energy are released mostly in the form of chemical reaction by impact initiated. The most important characteristic performances of energetic reactive material are mechanical performance, reaction initiation under impact and energy release level.The basic mechanical performances of PTFE/Al were studied in this paper including impact mechanical performance, quasi-static mechanical performance and reaction initiation of energy release under impact. The influence laws of preparation technics, experiment conditions and material compositions on the mechanical performances of PTFE/Al were investigated. The compressive constitutive relation of PTFE/Al was established based on the experiment results. Moreover, the numerical simulations of PTFE/Al impact test process were done by using LS-DYNA and above established constitutive relation. The initiation characteristic of energy release reaction under impact was also explored.The influences laws of pressing-sintering preparation technics parameters and material compositions on the quasi-static mechanical performance of PTFE/Al were studied experimentally, the destroy pattern of PTFE/Al under single axis tensile was analyzed and the strengthen mechanism of additives was also explained. The influence degree of technics parameters on the tensile strength of PTFE/Al is sintering temperature, cooling rate, sintering time, pressed pressure, kept temperature and pressed temperature in turn. The obtained optimized combinative technics make the tensile strength and elongation of PTFE/Al (73.5/26.5 wt %) increase to 24.9 MPa and 395%. The PTFE/Al sample with 6% content of Al particulate possesses maximal tensile strength, which follows the model of spherical particulate filled PTFE put forward byΠугачев. The PTFE/Al composite of 35% Al has the highest compressive strength. The addition of nano-powder and whisker make the tensile strength of PTFE/Al increased 26.2% and 9.6%. The coupling agent increase the tensile strength of PTFE/Al with high Al content obviously, the increase degree of PTFE/Al with 50% Al is higher to 62.3%.The impact equipment and impact test method was improved based on the standard pendulum impact tester. Multi impact parameters were obtained by using the above tester and Split Hopkins Compressive Bar (SHPB) test equipment, including impact compressive ratio, compressive strain, crack value, split value and standard impact strength. The destroy pattern of material under loaded impact and the increase mechanism of toughness was also analyzed and supposed. The results show that the impact compressive ratio is in direct ratio to the input energy of pendulum. The PTFE/Al sample with 40% content Al possesses maximal impact performance, the standard impact strength, split value and crack value was 25.3 J/cm2, 71.2 J/cm2 and 85.6J/cm2 respectively. The impact compressive strain is in inverse ratio to the Al content of samples. The addition of high density micron granule, nano-powder and whisker make the destroy value of samples decreased, and the coupling agent make the destroy value of samples increased slightly.The dynamic compressive performances of PTFE/Al energetic reactive material were studied by using SHPB test equipment at the same time, the correlativity between Al content, loaded strain rate with dynamic compressive strength and critical strain was obtained. Based on the obtained quasi-static and dynamic compressive experimental datum, the compressive stress-strain constitutive relation of PTFE/Al energetic reactive material was established according to Johnson-Cook plastic model, which takes account of strain harden effect, strain rate effect, temperature effect and the influence of Al content. Compare with the reported constitutive relation, the established constitutive relation could be put to use in broader range including strain rate of 0.006 to 9000 s-1 and Al content of 26.5% to 50%.At the same time, the numerical simulations of PTFE/Al bullet impact steel plate test process were done by using LS-DYNA software and above established constitutive relation. The simulative result is very close to experimental result, which validates the reliable, reasonable and applicable of established constitutive relation. The influences of impact speed of PTFE/Al bullet on the damage performance at impact process and after penetration were also obtained.The energy release reaction initiation characterization of PTFE/Al energetic reactive material under impact was studied by improved pendulum impact test and SHPB test, and the temperature increase of samples were obtained by using infrared imaging synchronously. The reaction value of sample can be expressed by impact energy of pendulum and loaded strain rate of bar. The increase of temperature is in direct ratio to the input energy of pendulum. The reaction initiated value of PTFE/Al (73.5/26.5 wt %) is the lowest, which means the sample is easiest to be initiated under impact. The addition of high density micron granule, nano-powder and whisker make the reaction value increased. The coupling agent has little influence on the reaction value, and the increase of sample temperature make the reaction value decreased.The calculated reactive temperature of PTFE/Al (73.5/26.5 wt %) was high to 4580K. The energy release level of PTFE/Al was more than 2.0 times to the energy of TNT explosive. The high energy release of PTFE/Al mainly roots in the reaction between fluorin and Al under impact, and the energy release level could be adjusted by the change of material compositions.更多还原