3644 S. Tariolle et al /Journal of the European Ceramic Sociery 25(2005)3639-3647 没转 500pm 500pm (a)ed/ep=0.27 (b)ed/ep=0.9 (c)ed/ep=1.85 Fig. 10.(a-c)Macrostructure of composites( CS55)with interlayers obtained by the use of com starch(p=0. 51)with different relative thicknesses 3.2. Weak interfaces Two different weak interfaces were studied: some with graphite spray (l-G)and some with boron nitride spray (I- BN). Dense layers had a thickness of approximately 100 um and were separated by thin interfaces of graphite or boron nitride(less than 5 um). The vaporization of the spray did not lead to a constant thickness of interfaces (Fig. 13). Long 60 crack deflections and sometimes layer delaminations were bserved on these two types of composites( Figs. 14 and 15) An increase of the work of rupture was also observed. A significant reinforcement by crack deflection was observed in composites with weak interfaces, either for weak inter- faces in graphite(l-G)or in boron nitride(I-BN). The prob- lem encountered in this type of composite is linked in the difficulties to reproduce the weak interfaces. This was re- Fig. Il. Work of rupture in function of the relative thickness in composites lated to the method used to pulverize the spray that could be (CS55) with interlayers with corn starch. The dote line correspond to the value of work of rupture for the dense boron carbide.3644 S. Tariolle et al. / Journal of the European Ceramic Society 25 (2005) 3639–3647 Fig. 10. (a–c) Macrostructure of composites (CS55) with interlayers obtained by the use of corn starch (p = 0.51) with different relative thicknesses. 3.2. Weak interfaces Two different weak interfaces were studied: some with graphite spray (I-G) and some with boron nitride spray (I￾BN). Dense layers had a thickness of approximately 100
m and were separated by thin interfaces of graphite or boron nitride (less than 5
m). The vaporization of the spray did not lead to a constant thickness of interfaces (Fig. 13). Long crack deflections and sometimes layer delaminations were observed on these two types of composites (Figs. 14 and 15). An increase of the work of rupture was also observed.8 A significant reinforcement by crack deflection was observed in composites with weak interfaces, either for weak inter￾faces in graphite (I-G) or in boron nitride (I-BN). The prob￾lem encountered in this type of composite is linked in the difficulties to reproduce the weak interfaces. This was re￾lated to the method used to pulverize the spray that could be improved. Fig. 11. Work of rupture in function of the relative thickness in composites (CS55) with interlayers with corn starch. The dote line correspond to the value of work of rupture for the dense boron carbide