DAMAGE AND FRACTURE OF A CROSS WOVEN C SIC COMPOSITE SUBJECT TO COMPRESSION LOADING/

In order to understand the mechanical behaviours of ceramic matrix com posites under various loading conditions, the compression stress-strai n behaviour of a cross woven C/SiC ceramic matrix composite was charac terized in terms of damage and fracture mechanisms, which were observe d by scanning electron microscope (SEM) on a side-polished sample. The compression stress-strain curve was found to consist of two stages. T he first stage, which extends to about 300 MPa, covers linear elastic deformation with a compression modulus of 140 GPa. The second stage st arts with the occurrence of compression damage modes, which include pl y delamination, bundle separation and transverse bundle cracking. Depe nding on the local structure of the sample, the second stage of the st ress-strain curve can be either mostly linear or non-linear. The fract ure of the composite under compression is by kinking, shearing and ben ding fracture of fibre bundles individually or in groups, forming a ma croscopic shear band in the sample.