Design and processing of high temperature CMCs Figure 2. Model composites with self-healing multilayered matrix, reinforced with carbon fibers. according to [391 inverse composites(ER and the matrix undergoes microcracking when loaded at a high enoug level, e.g. in cyclic loading. As a result, oxygen can diffuse via the matrix microcracks and reach the oxidation-prone interphas and fibers [37 To impede or slow down the in-depth diffusion of oxygen, the oncept of multilayered ceramics has been extended to the matrix [38]. An example of a composite with a self-healing matrix reinforced with carbon fibers, has recentl been reported by Lamouroux et al.(Fig. 2)[39]. The multilayered matrix comprises mechanical fuse layers arresting the cracks and glass former layers entrapping oxygen in a low viscosity glass A variety of oxide matrices, such as alumina, mullite, stabilized zirconia or silica-based glass-ceramics can also be considered. Glass-ceramics, such as those from the Li,O-AlO3-SiO,(LAS). CaO-AlO3-SiO,(CAS)or Bao-Mgo AlO3-SiO,(BMAS)systems, have been extensively studied. One of the advan- tages of such glass-ceramic matrices lies in the fact that they are used in their low viscosity state(beyond T,) to embed the fibers and then ceramed to increase their refractoriness [401 Finally, non-oxide CMCs often receive a seal-coating to seal the open residual porosity and hence to impede the in-depth diffusion of oxygen. A variety of seal- coatings has been suggested including a single layer of a glass-former such as SiC or multilayered smart coatings [41 In the specific case of C/C composites, the oxidation protection usually comprises both inhibiting particles dispersed within the matrix and a complex external seal-coating [42, 431 3. PROCESSING CMCs are fabricated via liquid or gas phase routes, from fiber tows, fabrics or nD- reforms. Low temperature, pressureless, near net shape processes are preferred