Abstract
As a novel energetic material with quite a high energy density, titanium hydride (TiH2) was introduced into a polytetrafluoroethylene/aluminum (PTFE/Al) reactive material system for the first time. The effects of TiH2 on the reaction energy, dynamic mechanical responses, and reaction properties of the composites were investigated through adiabatic bomb calorimeter, split-Hopkinson pressure bar, and drop-weight experiments. The results show that the reaction heat of the composites improved significantly as the content of TiH2 increased. Under dynamic compression, these composites show obvious strain hardening and strain rate hardening effects. Besides, a certain amount of TiH2 granules helps to improve the material’s compressive strength, and the maximum would even reach 173.2 MPa with 5% TiH2 percentage, 10.1% higher than that of PTFE/Al. Mesoscale images of the samples after dynamic compression indicate that interface debonding between the particles and PTFE matrix and the fracture of the PTFE matrix are the two major mechanisms resulting in the material’s failure. In addition, the drop-weight experiments indicate that the material’s impact sensitivities are sensitive to the content of TiH2, which would be increased to within 20% of the content of TiH2 compared with PTFE/Al, and the reaction degree is also improved to within 10% of the content of TiH2. The retrieved reaction residues after drop-weight experiments imply that the reaction is initiated at the edges of the samples, indicating a shear-induced initiation mechanism of this kind of reactive material.
Highlights
Metal/fluoropolymer composites are normally considered to be inert and not sensitive to friction, heat, light, or shockwaves
When the stoichiometric mass fraction of PTFE/Al is set at 73.5/26.5 for a complete reaction, the two components will react according to the following chemical equation [4]: 4Al + 3(–C2 F4 –) → 4AlF3 + 6C + 8.67 MJ/kg
Feng et al [6] conducted numerous quasi-static compression experiments to research the mechanical properties of PTFE/Al composites, and observed a violent reaction phenomenon for the first time
Summary
Metal/fluoropolymer composites are normally considered to be inert and not sensitive to friction, heat, light, or shockwaves. Feng et al [6] conducted numerous quasi-static compression experiments to research the mechanical properties of PTFE/Al composites, and observed a violent reaction phenomenon for the first time. They investigated the influences of sintering temperature, component ratio, and Al particle size on the mechanical and reactive properties of PTFE/Al through quasi-static compressive tests, and proposed a crack-induced initiation mechanism [7]. The results show that TiH2 particles help to improve the material’s strength within a certain amount, and they could be activated by the heat produced by the reaction between PTFE and Al, releasing hydrogen and generating titanium carbide (TiC), which makes TiH2 completely release its energy. Of the composites, during processes which the are reaction processes are recorded by a high-speed photography system
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