J, Vicens et al./Aerospace Science and Technology 7(2003)135-146 14 500pm Fig 6 SEM micrograph of a fractured creep sample at 1223 K under 150 MPa. CL N Fig. 7. TEM micrograph of a totally debonded FM interface of the fractured crept sample shown in Fig. 6 fuse with very low interfacial debonding energy values(r) in air(Fig. 6). At the surface of the specimens exposed (up to and low medium interfacial shear resistance(ti) depending 400 um to the surface) the oxidation of the carbon induces on the state of residual stresses [4, 7, 13, 27]. The weak fi- silica formation at the fibre/matrix interface and a brittle be- bre/interphase interface(carbon-fibre)promotes a large pull- havior of the components(Fig. 6). A TEM micrograph of a out of fibres(up to 1 mm) as observed in Nicalon/YMAs totally debonded fibre/matrix interface of a fractured crept composites fractured during creep tests in air at 1223 K un- sample is shown in Fig. 7. The interface debonding took der 150 MPa[15]. An example is shown on the fractured su place at the contact zone between the carbon interphase and face of a specimen of Sic Nicalon/Y MAS composite cre the matrix which was enriched in silica. The formation ofJ. Vicens et al. / Aerospace Science and Technology 7 (2003) 135–146 141 Fig. 6. SEM micrograph of a fractured creep sample at 1223 K under 150 MPa. Fig. 7. TEM micrograph of a totally debonded FM interface of the fractured crept sample shown in Fig. 6. fuse with very low interfacial debonding energy values (Γ ) and low medium interfacial shear resistance (τi) depending on the state of residual stresses [4,7,13,27]. The weak fi- bre/interphase interface (carbon-fibre) promotes a large pull￾out of fibres (up to 1 mm) as observed in Nicalon/YMAS composites fractured during creep tests in air at 1223 K un￾der 150 MPa [15]. An example is shown on the fractured sur￾face of a specimen of SiC Nicalon/YMAS composite crept in air (Fig. 6). At the surface of the specimens exposed (up to 400 µm to the surface) the oxidation of the carbon induces silica formation at the fibre/matrix interface and a brittle be￾havior of the components (Fig. 6). A TEM micrograph of a totally debonded fibre/matrix interface of a fractured crept sample is shown in Fig. 7. The interface debonding took place at the contact zone between the carbon interphase and the matrix which was enriched in silica. The formation of