On dynamic response and fracture-induced initiation characteristics of aluminum particle filled PTFE reactive material using hat-shaped specimens

Abstract

Dynamic response and fracture-induced initiation characteristics of aluminum particle filled polytetrafluoroethylene (PTFE/Al) reactive material was studied in two experimental configurations: (a) thin disks for compression and (b) hat-shaped specimens with predesigned shear bands of different widths for compression-shear, at elevated strain rates and temperatures. Compression stress-strain curves demonstrate typical elasto-plastic behavior with prominent strain hardening, strain rate strengthening, as well as thermal softening effects of the material. While growing oscillations and marked strength decrease due to shear band widths decrease observable on the shear stress-strain curves illustrate the localized shear induced adiabatic thermal effect and size effect of polymer materials. Post compression-shear to initiation phenomenon recorded by high-speed photography reveals the necessity of fracture process to initiation, apart from the intense shear work and loading rate effect. Employing the constitutive parameters determined at elevated strain rates and temperatures, 3D full size finite element modeling was performed. On the basis of a good agreement of the simulated and tested shear stress-strain curves for specimens of different shear band widths, a more direct insight into the deformation and stress evolution at the vicinity of the predesigned shear zones was analyzed and obtained.