C Wang et al./ Materials Science and Engineering C 11(2000)9-1 scales in these kinds of composites: the lst-grade toughen- toughening and elongated matrix grain toughening leads to ing mechanism is weak interfacial layer toughening, which fairly high toughness and work of fracture of the compos- is considered as the main reason for the very high tough ness of the composites; the 2nd-grade toughening mecha- nism is whisker toughening in the matrix cells; and the 3rd-grade toughening mechanism is elongated Si N grain References ghening toughening mechanisms leads to fairly high toughness and I1 R.Z. Wang, Biomimetic preparation and research of perlite and natural bone, Report of postdoctoral research, Tsinghua University work of fracture of the composites [8] China, 1995. [2] w.S. Coblenz, Fibrous monolithic ceramic and method for produc tion, US Patent 4772524, 1988 4. Conclusion [3]S. Baskaran, S D. Nunn, D. PoPovic, J W. Halloran, Fibrous mono- ithic ceramics: I. Fabrication, microstructure and indentation behav- ior,J.Am. Ceram.Soc.76(9)(1993)2217-2224 According to the structures of trees and nacres, two [4] w.J. Clegg, K. Kendall, N.M. Alford, A simple way to make tough kinds of biomimetic structure ceramic composites, fibro eramics, Nature 347(10)(1990)445-44 monolithic and laminated structure Si, N4/BN composi [5] Z. Benlian, The biomimetic design of worst bonding interface for have been successfully prepared with more than 20 ceramic matrix composites, Comp. Eng. 5(10)(1995)1261-1273 m'/2 of high toughness and 4000 J/m2 of work of 16] H Guo, Structure and preparation of Si N, matrix composites with high toughness, Dissertation for PhD, Tsinghua University, China, fracture. The load-displacement curves show that both of 1997 the composites exhibit non-brittle fracture properties. The [] H. Liu, M.S. Hsu, Fracture behavior of multilayer silicon nitride/ size of the structure cell (fiber or layer)is an important (8)Y. Huang, H. Guo, S.Y. Cai, CA.Wang, ZP.Xie, The biomimetic boron nitride ceramic. J. Am. Ceram Soc. 79(9)(1996)2452-2457 structure parameter influencing the mechanical behavior of structure design and preparation of Si, Na matrix composites with the composites. The synergy of multilevel toughening high toughness, In: Ninth Cimtec World Ceramic Congres mechanisms, weak interfacial phase toughening, whisker (CIMTEC 98), Italy, 199812 C. Wang et al.rMaterials Science and Engineering C 11 2000 9–12 ( ) scales in these kinds of composites: the 1st-grade toughen￾ing mechanism is weak interfacial layer toughening, which is considered as the main reason for the very high tough￾ness of the composites; the 2nd-grade toughening mecha￾nism is whisker toughening in the matrix cells; and the 3rd-grade toughening mechanism is elongated Si N grain 3 4 toughening in the matrix cells. The synergy of multilevel toughening mechanisms leads to fairly high toughness and work of fracture of the composites 8 . w x 4. Conclusion According to the structures of trees and nacres, two kinds of biomimetic structure ceramic composites, fibrous monolithic and laminated structure Si N rBN composites, 3 4 have been successfully prepared with more than 20 MPa m1r2 of high toughness and 4000 Jrm2 of work of fracture. The load-displacement curves show that both of the composites exhibit non-brittle fracture properties. The size of the structure cell fiber or layer is an important Ž . structure parameter influencing the mechanical behavior of the composites. The synergy of multilevel toughening mechanisms, weak interfacial phase toughening, whisker toughening and elongated matrix grain toughening leads to fairly high toughness and work of fracture of the compos￾ites. References w x 1 R.Z. Wang, Biomimetic preparation and research of perlite and natural bone, Report of postdoctoral research, Tsinghua University, China, 1995. w x 2 W.S. Coblenz, Fibrous monolithic ceramic and method for produc￾tion, US Patent 4772524, 1988. w x 3 S. Baskaran, S.D. Nunn, D. PoPovic, J.W. Halloran, Fibrous mono￾lithic ceramics: I. Fabrication, microstructure and indentation behav￾ior, J. Am. Ceram. Soc. 76 9 1993 2217–2224. Ž .Ž . w x 4 W.J. Clegg, K. Kendall, N.M. Alford, A simple way to make tough ceramics, Nature 347 10 1990 445–447. Ž .Ž . w x 5 Z. Benlian, The biomimetic design of worst bonding interface for ceramic matrix composites, Comp. Eng. 5 10 1995 1261–1273. Ž .Ž . w x 6 H. Guo, Structure and preparation of Si N matrix composites with 3 4 high toughness, Dissertation for PhD, Tsinghua University, China, 1997. w x 7 H. Liu, M.S. Hsu, Fracture behavior of multilayer silicon nitrider boron nitride ceramic, J. Am. Ceram. Soc. 79 9 1996 2452–2457. Ž .Ž . w x 8 Y. Huang, H. Guo, S.Y. Cai, C.A. Wang, Z.P. Xie, The biomimetic structure design and preparation of Si N matrix composites with 3 4 high toughness, In: Ninth Cimtec World Ceramic Congress Ž . CIMTEC’98 , Italy, 1998