Paper number 174

BALLISTIC IMPACT BEHAVIOUR OF SIC FIBRE REINFORCED TITANIUM MMCS

N.J.Bowman¹ and M.P.Thomas²

1Imperial College of Science Technology & Medicine,
Exhibition Road, London, SW7 2AZ, UK
2 Structural Materials Centre, Defence Evaluation & Research Agency (DERA), Farnborough, Hampshire, GU14 OLX, UK

Summary

The room temperature ballistic impact behaviour of four unidirectionally fibre reinforced titanium MMCs has been studied together with corresponding monolithic Ti alloys. Monolithic Timetal 834 exhibits a lower ballistic limit, and more brittle failure modes, than monolithic Ti-6-4, perhaps due to a limited ductility resulting from silicide precipitates. The MMCs exhibit ballistic limits significantly lower than the monolithic alloys, as a result of preferential crack growth along fibre/matrix interfaces. This crack growth results in targets splitting longitudinally at and above the ballistic limit. Ti-6-4 / Sigma SM1140+ MMC exhibits the best ballistic limit due to crack meandering and bifurcation. The ballistic limit in the Sigma SM1240 fibre reinforced MMCs is reduced compared to Ti-6-4 / SM1140+ because of the deleterious effect of cracks at the SM1240 fibre/matrix interface which grow into the matrix. Timetal 834 / SM1140+ MMC has a poor ballistic limit due to a weak fibre/matrix bond and an embrittled matrix.

Keywords

titanium, MMC, ballistic impact, SiC fibres