Interfacial micromechanical characterisation of a ceramic matrix composite

摘要

The fibre push4n test has been investigated to experimentally determine the effect of radial Poisson expansion of the pushed fibre on the measured interfacial frictional shear stress,τ. The commercially available SiC fibre reinforced calciumaluminosilicate glass ceramic matrix composite (CAS/Nicalon) was studied. Recognised analytical models were applied to the test data and both a dependence ofτon the radius of tested fibre, and a significant difference betweenτmeasured on the initialpush of a fibre and any subsequent push it was subjected to, were observed. It was deduced that radial expansion of the fibre as it was compressively loaded was seriously effecting the measuredτ. A simple model was applied that accounted for thedifference inτas due to fibres experiencing different Poisson expansion during load and reload. Static friction was also observed on unloading and reloading cycles and, when included in the analysis, the frictional shear stress for CAS/Nicalon wasdetermined asτ{sub}0= 12±4 MPa. This agrees with alternative measurements ofτmade by fibre push-out testing and by matrix crack density measurements during tensile loading of CAS/Nicalon. Radial fibre Poisson expansion during a push-in test caused anincrease in the measuredτof more than 100% of its correct value.