R. Naslain et al/Composites: Part A 30(1999)537-547 MATRI 「atB①P Sputter time (min M 500nm nd TEM analysis of complex interphases in SiC/SiC microcomposites:(a)C (B) graded com ase; (b)AES depth profile (B)graded composition type A interphase(a being similar to A but wi sublayer V),(c)bright field TEM of a Nicalon/SiC with a type A'C(B)interphase, and(d) bright field TEM image of a Hi-Nicalon/SiC microcomposite with a(Py C-SiC)o multilayered interphase, according to Refs. [11, 12, 15, 23] according to a procedure similar to that one used for single elsewhere [5,6]. The FM-interfacial parameters were also filaments. A length of microcomposite was pasted with an assessed from push-in or push-through experiments epoxy cement on a paper holder(gauge length, L, ranging performed on polished cross-sections [14. Finally, the fail from 10 to 50 mm), as shown in Fig 3(a). The whole assem- ure surfaces were observed with a high-resolution scanning bly was then attached to the tensile tester grips and finally, microscope(HR-sEM) to identify the failure mode and to the paper holder was cut immediately before applying the calculate the in-situ failure stress of the fibers from mirror load. In a similar manner, minicomposites were attached radius measurements with the epoxy cement to two steel tubes(gauge lengt he effect of the environment, e.g. the ambient air, on the ranging from 50 to 75 mm)and strained at a constant mechanical behaviour and lifetime, was studied through speed(0.085% per min), the displacement being measured fatigue tests(static or cyclic)performed at high tempera either optically or with inductive transducers [Fig. 3(b)]. tures on either micro-or mini-composites The minicompo- Unloading-reloading hysteresis loops were systematically site specimens were prepared as described above for tests recorded in order to measure the Youngs modulus, E, and performed at room temperature, the epoxy cement being the residual permanent strain, ep, (at o=0), of the material replaced by a high temperature alumina-based cement. In as it is progressively damaged and to derive the FM-inter- the static(or cyclic)fatigue tests run on microcomposites, a facial parameters, i.e. the debond length, Id, the interfacial length of microcomposite was attached with the alumina- shear stress, Ti, and the debond energy, Ti, according to micromechanics-based models, which have been reported S4500, from Hitachi (Japan)according to a procedure similar to that one used for single filaments. A length of microcomposite was pasted with an epoxy cement on a paper holder (gauge length, L, ranging from 10 to 50 mm), as shown in Fig. 3(a). The whole assem￾bly was then attached to the tensile tester grips and finally, the paper holder was cut immediately before applying the load. In a similar manner, minicomposites were attached with the epoxy cement to two steel tubes (gauge length ranging from 50 to 75 mm) and strained at a constant speed (0.085% per min), the displacement being measured either optically or with inductive transducers [Fig. 3(b)]. Unloading–reloading hysteresis loops were systematically recorded in order to measure the Young’s modulus, E, and the residual permanent strain, ep, (at s ˆ 0), of the material as it is progressively damaged and to derive the FM-inter￾facial parameters, i.e. the debond length, ld, the interfacial shear stress, ti, and the debond energy, Gi, according to micromechanics-based models, which have been reported elsewhere [5,6]. The FM-interfacial parameters were also assessed from push-in or push-through experiments performed on polished cross-sections [14]. Finally, the fail￾ure surfaces were observed with a high-resolution scanning microscope (HR-SEM)4 to identify the failure mode and to calculate the in-situ failure stress of the fibers from mirror radius measurements. The effect of the environment, e.g. the ambient air, on the mechanical behaviour and lifetime, was studied through fatigue tests (static or cyclic) performed at high tempera￾tures on either micro- or mini-composites. The minicompo￾site specimens were prepared as described above for tests performed at room temperature, the epoxy cement being replaced by a high temperature alumina-based cement. In the static (or cyclic) fatigue tests run on microcomposites, a length of microcomposite was attached with the alumina- 540 R. Naslain et al. / Composites: Part A 30 (1999) 537–547 Fig. 4. AES and TEM analysis of complex interphases in SiC/SiC microcomposites: (a) C (B) graded composition type A 0 interphase; (b) AES depth profile analysis of a C (B) graded composition type A interphase (A being similar to A 0 but without sublayer V); (c) bright field TEM image of a Nicalon/SiC microcomposite with a type A 0 C (B) interphase; and (d) bright field TEM image of a Hi-Nicalon/SiC microcomposite with a (PyC-SiC)10 multilayered interphase, according to Refs. [11,12,15,23]. 4 S 4500, from Hitachi (Japan)