Chemical Reaction Mechanism and Mechanical Response of PTFE/Al/TiH 2 Reactive Composites
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JMEPEG https://doi.org/10.1007/s11665-019-04397-1
Chemical Reaction Mechanism and Mechanical Response of PTFE/Al/TiH2 Reactive Composites Zhongshen Yu, Yuchun Li, Tao Guo, Jun Zhang, Shuangzhang Wu, Junyi Huang, Jiaxing Song, and Xiang Fang (Submitted April 10, 2019; in revised form August 19, 2019) In order to improve the energy density of polytetrafluoroethylene/aluminum (PTFE/Al), titanium hydride (TiH2) was added as a high-energy additive, and thermogravimetry–differential scanning calorimetry (TGDSC), quasi-static compression and Split-Hopkinson pressure bar (SHPB) tests were conducted to investigate the chemical reaction mechanism and mechanical response of PTFE/Al/TiH2. The results of TG-DSC indicate that TiH2 first decomposes to form titanium and hydrogen, and titanium reacts with PTFE to produce TiF3, and then with the temperature rising, titanium reacts with carbon and excessive aluminum to generate TiC and Al3Ti. Under quasi-static compression, the strength of PTFE/Al/TiH2 specimens can reach 108.8 Mpa, 14.2% higher than that of PTFE/Al, the special burning flames during the reaction and XRD patterns of the reaction residues consistently indicate that TiH2 has participated in the reaction and react completely, achieving its purpose as a high-energy additive. Under dynamic compression tests, PTFE/ Al/TiH2 composites show obvious strain hardening and strain rate hardening effects, and the yield strength and compressive strength are sensitive to strain rates; the established Johnson-Cook (JC) constitutive model can describe the mechanical response of PTFE/Al/TiH2 material well. In addition, the ignition threshold of PTFE/Al/TiH2 drops to 22.78 m/s, less than that of PTFE/Al (23.74 m/s), and the ignition delay time is advanced from 650-700 to 100-150 ls as the impact velocity increase. Keywords
constitutive model, mechanical response, PTFE/Al/ TiH2 composites, quasi-static compression, SHPB tests, TG-DSC
1. Introduction As a kind of impact-induced energetic material, metal/ fluoropolymer composite has certain density, strength and energy release characteristics after granulation, powder compaction and vacuum sintering, which is considered as an inert material and insensitive to friction, heat, detonation and so on, but when subjected to impact loading, it will react quickly and release a great quantity of heat. Polytetrafluoroethylene/aluminum (PTFE/Al) is one of the typical energetic reactive materials. Under the condition of chemical equilibrium ratio, the calorific value per unit mass of PTFE/Al (73.5/26.5) can reach 8.53 MJ/kg, which is twice than that of TNT (4.18 MJ/ kg). Because of the excellent mechanical properties and energy release characteristics, this material is often used in military to make various damage elements, such as active fragments, liners and warhead shells, which enable the conventional warheads to have stronger effects of penetration and perforation and even cause unique two-stage damages to the targets, namely ‘‘impact-react’’ damage mode, which has very high application value. Many s
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