Experimental characterisation of fibre failure and its influence on crack growth resistance in fibre reinforced titanium metal matrix composites

Abstract

The present paper addresses the effects of fibre failure on the fatigue crack growth resistance of a Ti-6AI-4V (wt-%) alloy matrix unidirectionally reinforced with continuous Sigma (SM1240) SiC fibres. Fibre fracture was monitored in situ using a PAC Locan acoustic emission (AE) analyser, and the exact spatial locations of the individual fibre failure events were identified using novel experimental techniques. A fibre probe technique has been illustrated to be a viable method with which to identify whether a fibre is broken or remains intact within a testpiece. Examination of exact spatial locations of fibres is possible, and evidence suggests that individual fibre failure is of ten followed by another fibre failure within the same row of a single mat lay up. Experimental observations and AE data reveal that crack arrest occurs if relatively few fibres fail in the crack wake as they are breached by matrix fatigue crack growth, and that fibre failure occurs only in the crack wake and behind the growing fatigue crack tip.