Push-out tests have been performed on unidirectional SiCfibre/Ti-6242-matrix composites, with samples of variable thickness and fibre volume fraction. Experimental results show the existence of two distinct decohesion types. SEM observations establish that these two types are characterised by two decohesion sites. Since these mechanisms appear to be linked with geometrical parameters, a finiteelement analysis has been developed. This allows us to evaluate the stress field induced by the material manufacture process, the preparation of the sample and the test itself. Two mechanisms are proposed to explain both types of behaviour.