THE GROWTH OF FREELY INITIATING FATIGUE CRACKS IN AN UNNOTCHED SIC TITANIUM COMPOSITE/

Crack formation and growth has been monitored in parallel-sided, unidi rectionally-reinforced SCS-6/Ti-6-4 specimens during constant amplitud e load controlled LCF tests at room temperature. It was found that ini tial growth of cracks from broken fibres is governed by the matrix str ess range. Subsequently, bridged and unbridged cracks which span sever al fibres are seen to propagate under the action of the stress range a pplied to the composite. Crack growth in the composite is related to p ropagation rates for the monolithic matrix, and it is shown that speci mens fractured from unbridged cracks at conditions determined by the m atrix fracture toughness. Bridged crack growth is successfully modelle d using an analysis due to Marshall et al. (C) 1997 Elsevier Science L td.