V M. Sglavo, M. Bertoldi Acta Materialia 54(2006 )4929-4937 Fig. 13 shows typical fracture surfaces of the engineered [2] Davis JB, Kristoffersson A, Carlstrom E, Clegg WJ. J Am Ceram Soc laminate(AMZ) subjected to bending tests. The markings 2000:83:2369-7 on the fracture surface show that the surface flaw extends B] Clegg WJ, Kendall K, Alford McN. Nature (London)1990: 347 at first along the surface and is then arrested by the engi-[4 Kriven wM, Kuo D-H. US Patent 5,948.5167 September1999 peered residual stress profile in the in-depth propagation; [5]Mistler RE. US Patent 3,652.,378: 28 March 1972. then, after such stable growth stage only, the through 6 Harmer MP, Chan HM, Miller GA. J Am Ceram Soc 1992: 75: 1715-28 thickness notch can become instable and lead to sample [7 Russo CJ, Harmer MP, Chan HM, Miller GA. J Am Ceram Soc failure. Such behaviour demonstrates further the insensi 1992:75:3396400 tiveness of the engineered laminate to surface defects [8]Latkshminarayanan R, Shetty DK, Cutler RA. J Am Ceram Soc 1996;79:79-87 9]Rao MP, Sanchez- Herencia AJ, Beltz GE, McMeeking RM, Lange FF. Science 1999:286:102-5. 6. Conclusions [0] Orlovskaya N, Lugovy M, Subbotin V, Radchenko O. Adams J, Chheda M. et al. J Mater Sci 2005: 40- 5483-90 The present study shows that it is possible to produce [ll] Orlovskaya N, Kuebler J, Subbotin V, Lugovy M. J Mater Sci highly reliable ceramic materials whose"constant 2005:40:5443-50 strength can be a priori defined and controlled through [2 mugovy M. slyunyayev v orlovskaya N, Blugan G, Kuebler ), Lewis an innovative design procedure. The material can be also [13] Cai PZ, Green DJ, Messing GL. J Am Ceram Soc 1997: 80: 1929-39 designed to support bending loads in a more efficient way [14] Donald w. J Mater Sci 1989: 24:4177-208 than homogeneous materials, since it is improved only [15] Bartolomew RF, Garfinkel HM. In: Uhlmann DR, Kreidl NJ where needed, i.e. near the surface. These laminates are editors. Glass science and technology, vol 5. New York(NY) :Aca- therefore natural candidates for structural applications, demic Press: 1980 particularly when high mechanical reliability and damage [16 Lange FF. J Am Ceram Soc 1989: 72: 3-15 ge[17] Yu BC, Lange FF. Adv Mater 2001 tolerance in severe conditions are required, as in the case [18]Sglavo VM, Larentis L, Green DJ. J Am Ceram Soc 2001: 84: 1827-31 of load-bearing components in the automotive and aircraft [19] Sglavo VM, Green DJ. J Am Ceram Soc 2001: 84: 1832-8 industry, biomedical prostheses, chemical plant linings and [20] Green DJ, Tandon R, Sglavo VM Science 1999 283: 1295-7 safety systems [21] Green DJ. An introduction to the mechanical properties of ceram- Cambridge: Cambridge University Press: 1998 It is important to point out that the principle outlined is [22]Sglavo VM, Bertoldi M. In: Proceedings of the 29th international general. It can be applied to different material systems and conference on advanced ceramics and composites, 23-28 January production processes. The design requires knowledge of the 2005. Cocoa Beach(FL): American Ceramic Society: 2005 arce of the residual stresses and the availability of suit- [23] Moon RJ, Hoffman M, Hilden J, Bowman KJ, Trumble KP, Rodel J able processing techniques to assemble layers with different Eng fract Mech 2002: 69: 1647-65 composition and/or microstructure 224] Chung TJ, Neubrand A, Rodel J, Fett T. Ceram Trans 2001:114:78996 225] Halpin JC. Primer on composite materials analysis. 2nd ed. Lancas- ter(PA): Technomic: 1992. Acknowledgements [28] Ledbetter H, Kim S, Crudele DB, Kriven W. J Am Ceram Soc 1998:8l:1025-8. Te acknowledge the University of Trento for financial [27] Sergo V, Wang X, Becher PF, Clarke DR. J Am Ceram Soc 1995; support and Massimo Paternoster for technical assistance Professor Rishi Raj( Colorado University, USA)is 28] Ledbetter H, Kim S, Crudele DB, Kriven w JAm Ceram Soc 1998:8l:1025-8. acknowledged for reviewing the manuscript aternoster M. Sglavo VM. Ceram Tr 2003;153:89-102 [0] Greenwood R, Roncari E, Galassi C. J Eur Ceram Soc References 31] Mistler RE, Twiname ER. Tape casting: theory and practice. Wes- []Lawn BR. Fracture of brittle solids. 2nd ed. Cambridge: Cambridge berville(OH): American Ceramic Society: 2000. University Press: 1993 32] Cesarano Ill J, Aksay IA, Bleier A. J Am Ceram Soc 1988: 71: 250-5Fig. 13 shows typical fracture surfaces of the engineered laminate (AMZ) subjected to bending tests. The markings on the fracture surface show that the surface flaw extends at first along the surface and is then arrested by the engi￾neered residual stress profile in the in-depth propagation; then, after such stable growth stage only, the through￾thickness notch can become instable and lead to sample failure. Such behaviour demonstrates further the insensi￾tiveness of the engineered laminate to surface defects. 6. Conclusions The present study shows that it is possible to produce highly reliable ceramic materials whose ‘‘constant’’ strength can be a priori defined and controlled through an innovative design procedure. The material can be also designed to support bending loads in a more efficient way than homogeneous materials, since it is improved only where needed, i.e. near the surface. These laminates are therefore natural candidates for structural applications, particularly when high mechanical reliability and damage tolerance in severe conditions are required, as in the case of load-bearing components in the automotive and aircraft industry, biomedical prostheses, chemical plant linings and safety systems. It is important to point out that the principle outlined is general. It can be applied to different material systems and production processes. The design requires knowledge of the source of the residual stresses and the availability of suit￾able processing techniques to assemble layers with different composition and/or microstructure. Acknowledgements We acknowledge the University of Trento for financial support and Massimo Paternoster for technical assistance. Professor Rishi Raj (Colorado University, USA) is acknowledged for reviewing the manuscript. References [1] Lawn BR. Fracture of brittle solids. 2nd ed. Cambridge: Cambridge University Press; 1993. [2] Davis JB, Kristoffersson A, Carlstrom E, Clegg WJ. J Am Ceram Soc 2000;83:2369–74. [3] Clegg WJ, Kendall K, Alford McN. Nature (London) 1990;347: 455–7. [4] Kriven WM, Kuo D-H. US Patent 5,948,516; 7 September 1999. [5] Mistler RE. US Patent 3,652,378; 28 March 1972. [6] Harmer MP, Chan HM, Miller GA. J Am Ceram Soc 1992;75:1715–28. [7] Russo CJ, Harmer MP, Chan HM, Miller GA. J Am Ceram Soc 1992;75:3396–400. [8] Latkshminarayanan R, Shetty DK, Cutler RA. J Am Ceram Soc 1996;79:79–87. [9] Rao MP, Sa´nchez-Herencia AJ, Beltz GE, McMeeking RM, Lange FF. Science 1999;286:102–5. [10] Orlovskaya N, Lugovy M, Subbotin V, Radchenko O, Adams J, Chheda M, et al. J Mater Sci 2005;40:5483–90. [11] Orlovskaya N, Kuebler J, Subbotin V, Lugovy M. J Mater Sci 2005;40:5443–50. [12] Lugovy M, Slyunyayev V, Orlovskaya N, Blugan G, Kuebler J, Lewis M. Acta Mater 2005;53:289–96. [13] Cai PZ, Green DJ, Messing GL. J Am Ceram Soc 1997;80:1929–39. [14] Donald W. J Mater Sci 1989;24:4177–208. [15] Bartolomew RF, Garfinkel HM. In: Uhlmann DR, Kreidl NJ, editors. Glass science and technology, vol. 5. New York (NY): Aca￾demic Press; 1980. [16] Lange FF. J Am Ceram Soc 1989;72:3–15. [17] Yu BC, Lange FF. Adv Mater 2001;13:276–80. [18] Sglavo VM, Larentis L, Green DJ. J Am Ceram Soc 2001;84:1827–31. [19] Sglavo VM, Green DJ. J Am Ceram Soc 2001;84:1832–8. [20] Green DJ, Tandon R, Sglavo VM. Science 1999;283:1295–7. [21] Green DJ. An introduction to the mechanical properties of ceram￾ics. Cambridge: Cambridge University Press; 1998. [22] Sglavo VM, Bertoldi M. In: Proceedings of the 29th international conference on advanced ceramics and composites, 23–28 January 2005. Cocoa Beach (FL): American Ceramic Society; 2005. [23] Moon RJ, Hoffman M, Hilden J, Bowman KJ, Trumble KP, Ro¨del J. Eng Fract Mech 2002;69:1647–65. [24] Chung TJ, Neubrand A, Ro¨del J, Fett T. Ceram Trans 2001;114:789–96. [25] Halpin JC. Primer on composite materials analysis. 2nd ed. Lancas￾ter (PA): Technomic; 1992. [28] Ledbetter H, Kim S, Crudele DB, Kriven W. J Am Ceram Soc 1998;81:1025–8. [27] Sergo V, Wang X, Becher PF, Clarke DR. J Am Ceram Soc 1995; 78:2213–4. [28] Ledbetter H, Kim S, Crudele DB, Kriven W. J Am Ceram Soc 1998;81:1025–8. [29] Bertoldi M, Paternoster M, Sglavo VM. Ceram Trans 2003;153:89–102. [30] Greenwood R, Roncari E, Galassi C. J Eur Ceram Soc 1997;17:1393–401. [31] Mistler RE, Twiname ER. Tape casting: theory and practice. Wes￾terville (OH): American Ceramic Society; 2000. [32] Cesarano III J, Aksay IA, Bleier A. J Am Ceram Soc 1988;71:250–5. V.M. Sglavo, M. Bertoldi / Acta Materialia 54 (2006) 4929–4937 4937