C. Reynaud et al. /Journal of the European Ceramic Society 25(2005)589-597 200um Fig. 10. SEM micrograph of typical surface of fracture showing that the rupture is intergranular Monolithic laminate, PFA= CS, porosity= inates studied by Vandeperre and Van Der Biest24 can also shed light on our results. These authors have fabricated, by electrophoretic deposition, laminar composites with alter nating layers of dense B-Sic and B-SiC containing different amounts of graphite(21, 34, 52 and 76 vol %C, respectively labelled types B, C, D and E). The mechanical behaviour tested in 3-point bending, showed no crack deflection for the 公 100um two lowest graphite contents(types B and C)but only slight deviation from the straight-through path. In the case of the composite with layers containing 52 vol. of graphite, some Fig 9. SEM micrographs of side surfaces of representative broken laminar specimens did not show a completely brittle failure but ex omposites( CSLC).(a)P=47vol % sequence 1/2; (b)P=43.5 vol %, hibited a load-deflection curve similar to that observed for sequence 3/1. Though the crack changes direction, it kinks out of the porous interlayer giving no useful toughening the GPlC specimens of the present work. Crack deflection occurred reliably only for type E material (i.e, the highest graphite content). The fracture energy of CSLC is compared with that of the materials studied by Vandeperre and Van in the two curves reflects the opening of a crack in a plane Der Biest in Fig. 11. The fracture energy of their type D perpendicular to the applied load and corresponds to a de- interlayers(52 vol%C)is the same as that of our highest lamination porous CslC samples and the behaviour of the correspond 5.2. Discussion Contrary to was expected, deflection was not observed for specimens that meet relation 2. As the only obvious difference between our samples and those of Blanks et al. 7 is that Blanks' ones were densified by solid state sintering 30505 whereas ours are densified by liquid phase sintering, the lack of crack deflection in our specimens might be linked to the presence of an intergranular amorphous phase. An argument that might support this hypothesis is the fact that, whereas in solid state sintered SiC crack propagation is transgranular, 3 the propagation in the present case is intergranular(Fig. 10) that suggests an influence of the intergranular amorphous SiC content(vol%) films on the mechanical behaviour Fig. 11. Fracture energy of porous SiC layers() in CSLC as a function However, the comparison of the behaviour of the present of the volume fraction of Sic compared to that of SiC+graphite interfaces laminar composites with those of the SiC/SiC-graphite lam-(A)in SiC/SiC-graphite laminar compositesC. Reynaud et al. / Journal of the European Ceramic Society 25 (2005) 589–597 595 Fig. 9. SEM micrographs of side surfaces of representative broken laminar composites (CSLC). (a) P = 47 vol.%, sequence 1/2; (b) P = 43.5 vol.%, sequence 3/1. Though the crack changes direction, it kinks out of the porous interlayer giving no useful toughening. in the two curves reflects the opening of a crack in a plane perpendicular to the applied load and corresponds to a de￾lamination. 5.2. Discussion Contrary to was expected, deflection was not observed for specimens that meet relation 2. As the only obvious difference between our samples and those of Blanks et al.7 is that Blanks’ ones were densified by solid state sintering whereas ours are densified by liquid phase sintering, the lack of crack deflection in our specimens might be linked to the presence of an intergranular amorphous phase. An argument that might support this hypothesis is the fact that, whereas in solid state sintered SiC crack propagation is transgranular,23 the propagation in the present case is intergranular (Fig. 10) that suggests an influence of the intergranular amorphous films on the mechanical behaviour. However, the comparison of the behaviour of the present laminar composites with those of the SiC/SiC–graphite lam￾Fig. 10. SEM micrograph of typical surface of fracture showing that the rupture is intergranular. Monolithic laminate, PFA = CS, porosity = 15 vol.%. inates studied by Vandeperre and Van Der Biest24 can also shed light on our results. These authors have fabricated, by electrophoretic deposition, laminar composites with alter￾nating layers of dense -SiC and -SiC containing different amounts of graphite (21, 34, 52 and 76 vol.% C, respectively labelled types B, C, D and E). The mechanical behaviour, tested in 3-point bending, showed no crack deflection for the two lowest graphite contents (types B and C) but only slight deviation from the straight-through path. In the case of the composite with layers containing 52 vol.% of graphite, some specimens did not show a completely brittle failure but ex￾hibited a load–deflection curve similar to that observed for the GPLC specimens of the present work. Crack deflection occurred reliably only for type E material (i.e., the highest graphite content). The fracture energy of CSLC is compared with that of the materials studied by Vandeperre and Van Der Biest in Fig. 11. The fracture energy of their type D interlayers (52 vol.% C) is the same as that of our highest porous CSLC samples and the behaviour of the correspond￾Fig. 11. Fracture energy of porous SiC layers () in CSLC as a function of the volume fraction of SiC compared to that of SiC+graphite interfaces () in SiC/SiC–graphite laminar composites.24