High strain and strain-rate behaviour of PTFE/aluminuim/tungsten mixtures

Conventional drop-weight techniques were modified to accommodate low-amplitude force transducer signals from low-strength, cold isostatically pressed 'heavy' composites of polytetrafluoroethylene, aluminum and tungsten (W). The failure strength, strain and the post-critical behavior of failed samples were measured for samples of different porosity and tungsten grain size. Unusual phenomenon of significantly higher strength (55 MPa) of porous composites (density 5.9 g/cm(3)) with small W particles (<1 mu m) in comparison with strength (32 MPa) of dense composites (7.1 g/cm(3)) with larger W particles (44 mu m) at the same volume content of components was observed. This is attributed to force chains created by a network of small W particles. Interrupted tests at different levels of strain revealed the mechanisms of fracture under dynamic compression.