G. de Portu et al. /Composites: Part B 37(2006)556-567 consideration that such architectures can exhibit a significant References improvement in selected aspects of mechanical and tribologi cal behaviour [1] Evans AG. Perspective on the development of high-toughness ceramics. Theoretical model useful to guide the design of laminated J Am Ceram Soc 1990: 73(2): 187-206 structures have been discussed and the parameters that need to [2 Tu wC, Lange FF. Evans AG be taken into account in the development of a complete model [3] Suresh S, Mortensen A. Fundamentals of functionally graded materials. suggested. ondon: Institute of Materials: 1998 A route to prepare layered structures in the system [4] Suresh S Graded materials for resistance to contact deformation and AlO3-ZrO, have been showed damage. Science 2001: 292: 2447-51 The attention has been focused on composites that foster 5 Moya Js. Layered ceramics Adw Mater 995. 72) strong adhesion among the layers of dissimilar materials. These tural engineering with duplex and laminar ceramic composites. J Am structures develop in-plane residual stresses within the ceramic Ceram Soc1992;7507):1715-28. layers, which lead to increased strength, apparent fracture [7] Chan HM. Layered ceramics: processing and mechanical behaviour toughness, contact damage and wear resistance, with respect to Annu Rey mater Sci 1997: 27: 249-82 the properties of monolithic ceramics [8] Hutchinson JW, Suo Z Mixed mode cracking in layered materials. Adv ppl Mech199229:63-191 A couple of methods to assess the residual stresses have (9)Ho S. Hillman C. Lange FF, Suo Z. Surface cracking in layers under been analyzed. The residual stress at the surface of a layered biaxial, residual compressive stress. J Am Ceram Soc 1995: 78(9): 2353-7 composite has been assessed by indentation technique while [10] Chartier T, Merle D, Besson JL. Laminar ceramic composites. JEur Ceram Soc1995;15:101-7. different thickness ratio among the layers have been Il Hillman C Suo z, Lange F Cracking of laminates subjected to biaxial determined by piezo-spectroscopic analysis. With the latter (12) Chartier T Rouxel T. Tap lumina-zirconia laminates: processing chnique the dramatic increase of residual stresses in the and mechanical properties. J Eur Ceram Soc 1997; 17: 299-308 vicinity of the interfaces and the surface effect have been [13] Sergo V, Lipkin DM, De Portu G, Clarke DR. Edge stress in evidenced alumina/zirconia laminates. J Am Ceram Soc 1997: 80(7): 1633-8. The superior response to fatigue damage in Tertian contact [14]Perez-Unzueta configuration of such composites both under static and cyclic atmosphere on the wear of sintered alumina. Wear 1991: 140: 179-96 [15] Hutchings IM. Tribology: friction and wear of engineering materials. loading have been demonstrated. Similarly the higher wear London: Edward Arnold: 1992 resistance under sliding and abrasive conditions of layered [16] Lakshminarayanan R, Shetty DK, Cutler RA. Toughening of layered ceramics have been illustrated. The tribological behaviour has ceramic composites with residual surface compression. J Am Ceram Soc been related to the presence of compressive residual stress at 1996:79(1):7987 the surface. In the studied system when the stress is higher than [17 Kuo DH, Riven WM. A strong and damage-tolerant oxide laminate. 30 MPa the laminated structures behaves better than the monolithic material Al2O,ZrO2 hybrid laminates. J Eur Ceram Soc 1998: 5: 2025-34 Concerning the strength we have observed that laminates [19] She J, Scheppokat S, Janssen R, Claussen N Reaction bonded three-layer not only have higher values but exhibit reduced scatter and alumina-based composites with improved damage resistance. J Am higher Weibull modulus, which implies superior reliability Ceram soc19988(5):13746 So far the main efforts have been addressed to model the [20] Tomaszewski H, Strzeszewski J, Gebicki w. The role of residual stresses in layered composites of Y-ZrO2 and Al2O3. J Eur Ceram Soc 1999: 19 system in order to demonstrate the potentiality of structures in improving the properties of ceramics and [21] De Portu G, Micele L, Guicciardi S, Fujimura S, Sekiguchi Y, Pezzotti G understand the underlining mechanisms. The future challenge will be the production of components of complex shape with composites loaded in flexural geometry. Compos Sci Technol such microstructural architecture 2005:65:1501-1506 [22] Pascual J, Chalvet F, Lube T, De Portu ramic laminates. Mater Sci Forum 2005: 4 :492-3193-581-4uuons [23] Jimenez-Pique E, Ceseracciu L, Anglada M, Chalvet F, De Portu G Acknowledgements Hertzian contact fatigue sites. J Eur Ceram Soc 2005: 25: 3393-401 The authors are grateful to Japan Society for the Promotion [24] Conoci S. Melandri C, De Portu G. Wear of Y-TZP containing of Science ( SPS)and Italian National Research Council compressive residual stresses at the surface. J Mater Sci 1999: 34 ( CNR)for the financial support to G. de portu to work in Japan 1009-15 [25 De Portu G, Micele L, Prandstraller D, Palombarini G, Pezzotti G. The contribution of Italian Ministry for Foreign Affair (MAE), Abrasive wear in ceramic laminates composites. Wear, in press, available which supported the creation of rin is also gratefully acknowledge. Some results illustrated in the paper belong [26] Sanchez-Herencia A, Pascual C, He J, Lange FF. ZrO the activity carried out in the framework of the European 2. tsnposites for crack bifurcation. J Am Ceram Soc 1999: 82(6) Community's Human Potential Programme under contract (27) Sanchez-Herencia AJ, James L, Lange FF. Bifurcaion in alumina plates HPRN-CT-2002-00203, [SICMAC]. The activity of colleagues produced by a phase transformation in central alumina/zirconia thin involved in this project are greatly recognized layers. J Eur Ceram Soc 2000: 20(9): 1297-300.consideration that such architectures can exhibit a significant improvement in selected aspects of mechanical and tribologi￾cal behaviour. Theoretical model useful to guide the design of laminated structures have been discussed and the parameters that need to be taken into account in the development of a complete model suggested. A route to prepare layered structures in the system Al2O3–ZrO2 have been showed. The attention has been focused on composites that foster strong adhesion among the layers of dissimilar materials. These structures develop in-plane residual stresses within the ceramic layers, which lead to increased strength, apparent fracture toughness, contact damage and wear resistance, with respect to the properties of monolithic ceramics. A couple of methods to assess the residual stresses have been analyzed. The residual stress at the surface of a layered composite has been assessed by indentation technique while the whole stress profiles across the section of samples with different thickness ratio among the layers have been determined by piezo-spectroscopic analysis. With the latter technique the dramatic increase of residual stresses in the vicinity of the interfaces and the surface effect have been evidenced. The superior response to fatigue damage in Hertian contact configuration of such composites both under static and cyclic loading have been demonstrated. Similarly the higher wear resistance under sliding and abrasive conditions of layered ceramics have been illustrated. The tribological behaviour has been related to the presence of compressive residual stress at the surface. In the studied system when the stress is higher than K30 MPa the laminated structures behaves better than the monolithic material. Concerning the strength we have observed that laminates not only have higher values but exhibit reduced scatter and higher Weibull modulus, which implies superior reliability. So far the main efforts have been addressed to model the system in order to demonstrate the potentiality of laminated structures in improving the properties of ceramics and understand the underlining mechanisms. The future challenge will be the production of components of complex shape with such microstructural architecture. Acknowledgements The authors are grateful to Japan Society for the Promotion of Science (JSPS) and Italian National Research Council (CNR) for the financial support to G. de Portu to work in Japan. The contribution of Italian Ministry for Foreign Affair (MAE), which supported the creation of RIN is also gratefully acknowledge. Some results illustrated in the paper belong to the activity carried out in the framework of the European Community’s Human Potential Programme under contract HPRN-CT-2002-00203, [SICMAC]. The activity of colleagues involved in this project are greatly recognized. References [1] Evans AG. Perspective on the development of high-toughness ceramics. J Am Ceram Soc 1990;73(2):187–206. [2] Tu WC, Lange FF, Evans AG. Concept for a damage-tolerant ceramic composite with ‘strong’ interface. J Am Ceram Soc 1996;79(2):417–24. [3] Suresh S, Mortensen A. Fundamentals of functionally graded materials. London: Institute of Materials; 1998. [4] Suresh S. Graded materials for resistance to contact deformation and damage. Science 2001;292:2447–51. [5] Moya JS. Layered ceramics. Adv Mater 1995;7(2):185–9. [6] Harner MP, Chan HM, Miller GA. Unique opportunities for microstruc￾tural engineering with duplex and laminar ceramic composites. J Am Ceram Soc 1992;75(7):1715–28. [7] Chan HM. Layered ceramics: processing and mechanical behaviour. Annu Rev Mater Sci 1997;27:249–82. [8] Hutchinson JW, Suo Z. Mixed mode cracking in layered materials. Adv Appl Mech 1992;29:63–191. [9] Ho S, Hillman C, Lange FF, Suo Z. Surface cracking in layers under biaxial, residual compressive stress. J Am Ceram Soc 1995;78(9):2353–7. [10] Chartier T, Merle D, Besson JL. Laminar ceramic composites. J Eur Ceram Soc 1995;15:101–7. [11] Hillman C, Suo Z, Lange FF. Cracking of laminates subjected to biaxial tensile stresses. J Am Ceram Soc 1996;79(8):2127–33. [12] Chartier T, Rouxel T. Tape-cast alumina–zirconia laminates: processing and mechanical properties. J Eur Ceram Soc 1997;17:299–308. [13] Sergo V, Lipkin DM, De Portu G, Clarke DR. Edge stress in alumina/zirconia laminates. J Am Ceram Soc 1997;80(7):1633–8. [14] Perez-Unzueta AJ, Beynon JH, Gee MG. Effect of surrounding atmosphere on the wear of sintered alumina. Wear 1991;140:179–96. [15] Hutchings IM. Tribology: friction and wear of engineering materials. London: Edward Arnold; 1992. [16] Lakshminarayanan R, Shetty DK, Cutler RA. Toughening of layered ceramic composites with residual surface compression. J Am Ceram Soc 1996;79(1):79–87. [17] Kuo DH, Kriven WM. A strong and damage-tolerant oxide laminate. J Am Ceram Soc 1997;80(9):2421–4. [18] Cai PZ, Green DJ, Messing GL. Mechanical characterization of Al2O3/ZrO2 hybrid laminates. J Eur Ceram Soc 1998;5:2025–34. [19] She J, Scheppokat S, Janssen R, Claussen N. Reaction bonded three-layer alumina-based composites with improved damage resistance. J Am Ceram Soc 1998;81(5):1374–6. [20] Tomaszewski H, Strzeszewski J, Gebicki W. The role of residual stresses in layered composites of Y–ZrO2 and Al2O3. J Eur Ceram Soc 1999;19: 255–62. [21] De Portu G, Micele L, Guicciardi S, Fujimura S, Sekiguchi Y, Pezzotti G. Effect of residual stresses on the fracture behavior of notched laminated composites loaded in flexural geometry. Compos Sci Technol 2005;65:1501–1506. [22] Pascual J, Chalvet F, Lube T, De Portu G. Strength distributions of ceramic laminates. Mater Sci Forum 2005;492–493:581–6. [23] Jime´nez-Pique´ E, Ceseracciu L, Anglada M, Chalvet F, De Portu G. Hertzian contact fatigue on alumina/alumina–zirconia laminated compo￾sites. J Eur Ceram Soc 2005;25:3393–401. [24] Conoci S, Melandri C, De Portu G. Wear of Y-TZP containing compressive residual stresses at the surface. J Mater Sci 1999;34: 1009–15. [25] De Portu G, Micele L, Prandstraller D, Palombarini G, Pezzotti G. Abrasive wear in ceramic laminates composites. Wear, in press, available on line. [26] Sa´nchez-Herencia AJ, Pascual C, He J, Lange FF. ZrO2/ZrO2 layered composites for crack bifurcation. J Am Ceram Soc 1999;82(6): 1512–8. [27] Sa´nchez-Herencia AJ, James L, Lange FF. Bifurcaion in alumina plates produced by a phase transformation in central alumina/zirconia thin layers. J Eur Ceram Soc 2000;20(9):1297–300. 566 G. de Portu et al. / Composites: Part B 37 (2006) 556–567