  The dynamic mechanical properties of reactive materials (e.g., high density
mixtures of polytetraflouroethylene (PTFE), aluminum (Al) and tungsten (W)
powders) can be tailored by changing the morphology of the particles and
porosity. Cold isostatically pressed PTFE-Al-W powder composites with fine
metallic particles and a higher porosity exhibited higher ultimate compressive
strength than less porous composites having equivalent mass ratios with coarse
W particles. The mesoscale force chains between the fine metallic particles are
responsible for this unusual phenomenon. We observed macrocracks below the
critical failure strain for the matrix and a competition between densification
and fracture in some porous samples in dynamic tests.
