Effect of Temperature on the Fracture Toughness of Al‑PTFE Reactive Material by J‑integral Method

To investigate the influence of temperature‑induced phase transition of polytetrafluoroethylene (PTFE) on the fracture toughness of Al‑PTFE reactive material, the quasi‑static tensile test and fracture toughness test were performed, and the normalization data reduction technique with single specimen in ASTM E1820 was applied for analyzing the elastic‑plastic fracture toughness of Al‑PTFE by J‑integral method. Combined with the microstructures analysis of the fracture surface, the effect of temperature on the fracture toughness of Al‑PTFE was revealed. The results show that the strength of Al‑PTFE reactive material decreases with the increase of temperature, while the fracture toughness increases. Moreover, the yield strength and fracture toughness of this material change obviously after crossing the phase transition temperature. The crack propagation pattern changes from brittle fracture to ductile fracture. Furthermore, when PTFE is in phase Ⅱ, less PTFE fibrils can be formed by stretching. However, increasing temperature can lead to the transform of the crystal phase for PTFE to phase Ⅳ and Ⅰ. Besides, the stable formed PTFE fibrils can effectively dissipate the external energy in the form of local plastic deformation. The crack tip is passivated by winding bridging, so as to prevent the crack propagation and improve the fracture toughness of this material. © 2022, Editorial Board of Chinese Journal of Energetic Materials. All right reserved.