Im. Daniel et G. Anastassopoulos, FAILURE MECHANISMS AND DAMAGE EVOLUTION IN CROSSPLY CERAMIC-MATRIX COMPOSITES, International journal of solids and structures, 32(3-4), 1995, pp. 341-355
Failure mechanisms were studied under the microscope in a crossply sil
icon carbide/glass-ceramic composite under axial tensile loading. Fail
ure initiation takes place in the 90 degrees layer. It takes the form
of radial matrix cracks around the fibers, followed by interfacial cra
cks, which in turn coalesce into transverse macrocracks. These transve
rse macrocracks in the 90 degrees layer reach a characteristic saturat
ion crack density with a minimum crack spacing of the order of the lay
er thickness. Subsequently, transverse matrix cracks are generated in
the 0 degrees layer, increasing in density up to a minimum crack spaci
ng of the order of eight fiber diameters. This stage of failure is acc
ompanied by fiber-matrix debonding and some fiber-failures in the 0 de
grees layer. In the third stage of damage development, the macrocracks
of the 90 degrees layer branch off and connect with the 0 degrees lay
er cracks in a characteristic ''delta'' pattern. This is finally follo
wed by delamination and additional cracking in the 90 degrees layer pr
ior to ultimate failure. The various failure mechanisms and their inte
ractions were discussed and compared with predictions of prior experim
ental and analytical studies of unidirectional and crossply composites
.