  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.
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/cc) with small W particles (less than 1 micron) in
comparison with strength (32 MPa) of dense composites (7.1 g/cc) with larger W
particles (44 microns) 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.
