Advanced aircraft engine exhaust nozzle development

Recent research to improve the properties of non-metallics for jet engine applications has centered on fabricating the carbon and ceramic material into composite structures. In these configurations carbon or a ceramic is processed into long, very thin fibers having extremely good strength and modulus characteristics. The oxidation-protection coatings for carbon-carbon have improved to the point where the material lasts hundreds of hours in laboratory life tests. For this reason, carbon-carbon and ceramic-matrix composites are ready for tests in functioning jet engines. A test conducted in 1987 with a carbon-carbon two-dimensional converging-diverging nozzle installed in a GE-J85 engine is described. Tests of ceramic composites made using ceramic fibers or whiskers imbedded in a ceramic matrix have also been carried out. Structural capabilities of carbon-carbon and ceramic composites under cyclic load and high temperature conditions were demonstrated.