High Strain and Strain-Rate Behaviour of PTFE/Aluminium/Tungsten Mixtures

TL;DR

This study investigates the high strain-rate behavior of PTFE/Al/W composites, revealing that porous composites with small tungsten particles exhibit significantly higher strength due to force chain networks, with insights into fracture mechanisms.

Contribution

It introduces a modified drop-weight technique for low-force signals and uncovers the impact of porosity and tungsten grain size on composite strength and fracture behavior.

Findings

Porous composites with small W particles reach 55 MPa strength.

Dense composites with larger W particles reach 32 MPa strength.

Force chains from small W particles enhance composite strength.

Abstract

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.