Alumina/alumina composite with a porous zirconia interphase - Processing, properties and component testing

Novel oxide ceramic composites (NOCC) was a four year European programme ai med to develop an all-oxide ceramic matrix composite (CMC) and processing r oute, carry out a characterisation programme on the material and demonstrat e it in a combustor rig at conditions representative of a gas turbine engin e. The fibre used was a single crystal monofilament (Saphikon Inc.), which was chosen for its temperature and creep resistance. Alumina (aluminium oxi de) was chosen for the fibre and matrix, and zirconia as a weak interphase coating on the fibre. Tape casting followed by hot pressing was chosen as t he manufacturing route for the composite, with hot isostatic pressing (HIPp ing) as an alternative densification process. Cross-ply material with fibre volume fractions of around 30% was found to have moderate strength (100-13 0 MPa), but retained composite properties at elevated temperatures and afte r extended periods at elevated temperatures (1000 h at 1400 degrees C). In addition, the material was found to withstand thermal cycling (> 1300 cycle s to 1200 degrees C), retaining its as-fabricated properties. Computational fluid dynamics (CFD) calculations were carried out for a combustor rig, an d a CMC tile was designed. The temperatures; stresses and strains in the ti le were predicted using finite element (FE) analysis and combustor tiles we re manufactured. A tile was successfully tested in a rig at temperatures > 1260 degrees C and up to 46 cycles. Some of the issues that remain to be ad dressed with the material and manufacturing method are cost, delamination d uring manufacture, and consistency. It is likely that, due to the high cost of the fibre and relatively modest usable strength, the material will rema in as a model material. The promising results on long term static and cycli c ageing proves that the concept of an all-oxide CMC is valid and points th e way to future development of this class of material. (C) 2000 Elsevier Sc ience Ltd. All rights reserved.