Evaluation of the Fibre-Matrix Debond Strength of a Ti-22Al-23Nb (AT.%)/Trimarc Metal Matrix Composite

Abstract

Silicon carbide fibre reinforced titanium metal matrix composites are of interest for engineering applications which require high strength, high temperature, low weight and damage tolerance [12-14]. Developing experimental methods to characterize and analyze their mechanical properties is of critical importance so that deformation and failure mechanisms can be established. It has been found that mechanical test specimen geometry is important for determining the fibre-matrix debond strength in continuous fibre reinforced metal matrix composites (MMCs) [2,4-8,10,11,15-19]. Specimens containing exposed fibres lead to edge stress singularities at the fibre/matrix interface for fibre orientations which are perpendicular to the applied stress. This stress singularity leads to fibre/matrix debonding at the specimen edge without the application of an externally applied mechanical load. Accurate determination of the debond strength is difficult using such a specimen geometry. A cruciform specimen geometry mitigates this edge effect by requiring the greatest stresses to be at the centre of the sample, thereby forcing the debond to occur at the centre of the cruciform [2,4-8]. Fig. 1 gives the dimensions of the experimental cruciform specimen designed to promote debond occurrences at the centre of the cruciform. The centre wing has been added to the traditional dogbone specimen so that the free edges of the wing are stress free. The largest stress occurs in the centre region of the specimen. The strain can be measured at this location using a strain gage placed Letter