Longitudinal yielding behaviour of SiC-fibre-reinforced titanium-matrix composites

Four fibre-reinforced titanium metal-matrix composites (TiMMCs) have been t ensile tested and the results compared with those from unreinforced titaniu m alloys. There is no significant difference in the mechanical properties o f the MMCs, suggesting that the properties of the two fibres used, Sigma SM 1140+ and SM1240, are similar. The MMC failure strains are higher than that expected of virgin SiC fibres, because of matrix load transfer and residua l compressive strain in the fibres. MMC proportional limits are very simila r to those of the unreinforced alloys and are caused, in all but the IMI834 /SM1140+ MMC, by shear deformation of the matrix. The proportional limit of the IMI834/SM1140+ is caused by brittle cracking of the matrix, possibly i nduced by a high matrix carbon content. The rule of mixtures is successful in predicting the MMC proportional limit if the residual fibre strain is ac counted for and provided that the matrix yields by the same mechanism as th e monolithic alloy. Crown copyright (C) 1999 Published by Elsevier Science Ltd. All rights reserved.