Fabrication and testing of all-oxide CFCC tubes

Abstract

A novel, low-cost processing method was used to manufacture all-oxide ceramic composite tubes. Fibre cloths were infiltrated with a pre-consolidated slurry composed of a mixture of mullite and alumina powders. The pre-consolidated slurry was first formulated at a low volume fraction of powder to produce a short-range repulsive interparticle pair potential that allowed consolidation via pressure filtration, yet produced a consolidated body that could be fluidised by vibration. Efficient infiltration of fibre tows and a homogeneous microstructure were demonstrated. The infiltrated cloths, which could be frozen for latter use, were rolled to tubular shapes. After drying, the powder matrix was strengthened by cyclic infiltration and pyrolysis of an alumina precursor. When the tubes were pressurised, they delaminated at an average hoop stress of 47 MPa. Delamination initiated within the porous matrix where the outer most layer terminated. A failure analysis is presented using a strain energy release rate function for this specimen/crack configuration. Values of fracture energy inferred from the analysis were in close agreement with literature data for porous ceramics.