1996 L Zou et al. Journal of the eure eramic Society 23(2003)1987-1996 Youngs modulus of the Si3N4 matrix in the nitride/boron nitride ceramic. J. 4m. Ceram. Soc. 1996. 79 sandwiching sample due to its indirectly deter mination. However, this was solved by con 6. Kovar. Desiderio. Thouless. M. D. and Halloran. J W. Crack centrating all the deviations from the effecting deflection and propagation in layered silicon nitride/boron nitride factors upon the Youngs Modulus in Eqs. (5) 7. Kovar, D. King. B. H,Trice, R.W. and Halloran,J.w and (10). In this way, The e value was success Fibrous monolithic ceramics. J. Am. Ceram Soc. 1997 80 2471 fully adjusted to offset these influences. 8. Hai Guo, Yong Huang and Chang-an Wang, Preparation and Acknowledgements ng an Wang, Yong Huang. Qingfeng Zan, Hai Guo and Shengyou Cai, Biomimetic structure design-a possible approach The authors gratefully acknowledge Professor Z. D to change the brittleness of ceramics in nature. Materials science Guan for his much help in doing three-point bending Engineering C, 2000, 11, 9-12. tests; also this work was supported by National Natural 10. Charalambides. P. G. Lund. J. Evans. A. G R. M. A test specimen for determing the fracture resistance of Science Foundation of China(No. 59632090) bimaterial interfaces. J. Appl. Mech, 1989, 56. 77-82 I1. Phillips, A.J. Clegg, w.J. and Clyne, T.W., Fracture behavior of ceramic laminates in bending-lI. Comparison of model pre- References dictions with e data. Acta Metall. Mater. 1993. 41 819-827 12. Phillips, A.J., Clegg, w.J. and Clyne, T.w Fracture behavior 1. Clegg. W.J., Kendall. K, Alford, N. M., Birchall, D. and But- hates in bending-1. Modelling of crack propa- s. Nature. 1990 gation. Acta Metall. Mater., 1993, 41. 805-817 13. Clyne, T. w. and Phillips, A. J, Interfacial control and macro- 2. Baskaran, S, Nunn, S. 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