Study On The Mechanical Performance Of Polytetrafluorethylene/A1 Energetic Reactive Materials

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.