CERAMICS INTERNATIONAL ELSEVIER Ceramics International 29(2003)323-326 Microstructure and fracture characteristics of alumina-based prismatic ceramic composites G.H. Min,D,, L X. Yang, T.H. Inoue a Materials Science and Engineering Institute, Shandong University, Jinan 250061, PR China Energy Conversion Department, Osaka National Research Institute, Osaka 563-8577, Jape Received 24 April 2002: received in revised form 15 June 2002: accepted 21 July 2002 Abstract e Al2O3 SiC prismatic ceramic composites have been prepared by a structure-controlled process, in which the high-aspect-ratio umina-based cells with a distinct prismatic texture were separated in three dimensions by thin SiC cell boundaries. The work-of- fracture of the composites has been improved greatly due to the developed paths for crack propagation by the weak cell bounda corresponding to longer displacement under reasonable load-carrying condition. The route of crack propagation depended greatly on the interfacial shear strength and boundary thickness. Crack deflecting and delamination are considered as two main contribu- tions at the earlier stage, whereas frictional sliding of fibrous cells becomes more dominant after cracking occurs, especially at l loading condition. These mechanisms are different from those observed in multilayered monolithic ceramics due to the conti structures of present materials. C 2002 Elsevier Science Ltd and Techna S r l. All rights reservec Keywords: B. Microstructure; C. Mechanical properties; Alumina-based composites; Fracture characteristic 1. ntroduction The objective of the present paper is to evaluate the bending properties such toughness and fracture Fibrous monolithic ceramics would prove to be can- energy, and to observe the crack propagation. The main didates for structural applications due to fabricating effort is focused to describe the differences in fracture with commercial powders and showing non-cata- behavior of fibrous ceramics against laminated ceramics strophic fracture behavior. More recently, an extensive and fiber-reinforced ceramics, and fracture mechanism effort had been made on the aspects of fabrication and of the prismatic ceramics is to be concluded fracture behavior of those fibrous ceramics, and several preliminarily systems had been developed such as by JW Holloran [1-5] and T H. Inoue and co-workers [6-9]. Those cera- mics fail non-catastrophically in a similar manner to 2. Experimental procedure whisker fiber-reinforced ceramics [10] and multilayered ceramic composites [11, 12]. However, it seems to have A commercial a-type Al_O3 powder with an average not been characterized for fracture behavior in fibrous particle size of 0.22 um and specific surface area of 12.3 monolithic ceramics. The mechanisms that govern the m/g(TM-D, Taimei Chemicals Co Ltd, Japan) was energy absorption ability of fibrous ceramics are unique, used as a fibrous'cell'. A fine B-Sic powder (UF-0741 almost referred to that of laminated ceramics or fiber Ibiden Co Ltd) was selected as the interfacial cell reinforced ceramics, which caused the experimental boundary results not to follow those existing models [1, 13-15 The prismatic fibrous ceramic was prepared by mold extruding and hot-pressing techniques. The green fibers with a diameter of 0.5 mm were prepared by mold Corresponding author. Tel: +86-531-839-5639: fax: +86-531 extrusion, and Sic slurry was sprayed on the surface of the arranged green fiber sheets as the thin inter-fiber layers. Then, dozens of sheets were stacked and com 0272-8842/03/S22.00C 2002 Elsevier Science Ltd and Techna S.r. l. All rights reserved PII:S0272-8842(02)00141-4
Microstructure and fracture characteristics of alumina-based prismatic ceramic composites G.H. Mina,b,*, L.X. Yanga , T.H. Inoueb a Materials Science and Engineering Institute, Shandong University, Jinan 250061, PR China bEnergy Conversion Department, Osaka National Research Institute, Osaka 563-8577, Japan Received 24 April 2002; received in revised form 15 June 2002; accepted 21 July 2002 Abstract Al2O3/SiC prismatic ceramic composites have been prepared by a structure-controlled process, in which the high-aspect-ratio alumina-based cells with a distinct prismatic texture were separated in three dimensions by thin SiC cell boundaries. The work-offracture of the composites has been improved greatly due to the developed paths for crack propagation by the weak cell boundaries, corresponding to longer displacement under reasonable load-carrying condition. The route of crack propagation depended greatly on the interfacial shear strength and boundary thickness. Crack deflecting and delamination are considered as two main contributions at the earlier stage, whereas frictional sliding of fibrous cells becomes more dominant after cracking occurs, especially at lower loading condition. These mechanisms are different from those observed in multilayered monolithic ceramics due to the controlled structures of present materials. # 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved. Keywords: B. Microstructure; C. Mechanical properties; Alumina-based composites; Fracture characteristic 1. Introduction Fibrous monolithic ceramics would prove to be candidates for structural applications due to fabricating with commercial powders and showing non-catastrophic fracture behavior. More recently, an extensive effort had been made on the aspects of fabrication and fracture behavior of those fibrous ceramics, and several systems had been developed such as by J.W Holloran [1–5] and T.H. Inoue and co-workers [6–9]. Those ceramics fail non-catastrophically in a similar manner to whisker fiber-reinforced ceramics [10] and multilayered ceramic composites [11,12]. However, it seems to have not been characterized for fracture behavior in fibrous monolithic ceramics. The mechanisms that govern the energy absorption ability of fibrous ceramics are unique, almost referred to that of laminated ceramics or fiber reinforced ceramics, which caused the experimental results not to follow those existing models [1,13–15]. The objective of the present paper is to evaluate the bending properties such as toughness and fracture energy, and to observe the crack propagation. The main effort is focused to describe the differences in fracture behavior of fibrous ceramics against laminated ceramics and fiber-reinforced ceramics, and fracture mechanism of the prismatic ceramics is to be concluded preliminarily. 2. Experimental procedure A commercial a-type Al2O3 powder with an average particle size of 0.22 mm and specific surface area of 12.3 m2 /g (TM-D, Taimei Chemicals Co Ltd, Japan) was used as a fibrous ‘cell’. A fine b-SiC powder (UF-0741, Ibiden Co Ltd) was selected as the interfacial ‘cell boundary’. The prismatic fibrous ceramic was prepared by mold extruding and hot-pressing techniques. The green fibers with a diameter of 0.5 mm were prepared by mold extrusion, and SiC slurry was sprayed on the surface of the arranged green fiber sheets as the thin inter-fiber layers. Then, dozens of sheets were stacked and com- 0272-8842/03/$22.00 # 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved. PII: S0272-8842(02)00141-4 Ceramics International 29 (2003) 323–326 www.elsevier.com/locate/ceramint * Corresponding author. Tel.: +86-531-839-5639; fax: +86-531- 295-5999. E-mail address: minguanghui@hotmail.com (G.H. Min)
G H. Min et al./ Ceramics International 29(2003)323-326 pressed into a perform at 523 K under a pressure of 25 3. 2. Mechanical properties MPa, and followed by hot pressing at temperature of 1773 K for I h under the same pressure, yielding the The mechanical properties of Al_O3 /SiC prismatic prismatic fib rous ceramIc opposites with various boundary thicknesses are listed The bending strength was tested by three-point bend- in Table 1. On the basis of the bending data, the tough ng with 0.5 mm/min crosshead speed. The used samples ness energy appears to be improved greatly with little had a polished tensile surface with 1.5 mm thick (in hot- increased toughness but decreased bending strength. It pressing direction), 4 mm wide and 40 mm long(in fiber can be considered that the bending strength is decreased direction). The four-point Single Edge Notched Beam due to the reduction of effective load-carrying area by method(SENB) was used for evaluation of fracture interphase SiC addition, which also results in little toughness and fracture work. The used samples were increase of fracture toughness. However, the fracture prepared 3.0 mm thick, 4 mm wide and 40 mm long, work is improved greatly because the weak interfaces per- and a notch was cut with 1. 5 mm in depth and 0. 1 mm mit the crack propagation with multi-directional routes In case of the interphase Sic thickness of 9.3-15.6 Microstructures and crack propagation of the pris- um, the fracture work of 1221.4-1481.6 J/m- is achieved matic ceramic were observed by optical microscope with good combination of bending strength and tough ness. When the thickness is higher than 15.6 um, the prismatic ceramic is easy to peel/ cleave due to weak 3. Results and discussion bonding between the layers, and shear stress along the axial direction is very low, which results from poor sin 3.. Microstructure tenability of Sic Fig. 2 shows the load-displacement curves of the Fig. I shows the microstructure in the cross section of prismatic ceramics with various SiC interphase. The prismatic composites with various boundary thick composites display a non-catastrophic and graceful nesses Flattened hexagonal Al2O3 cells about 250 um in failure with reasonable load-carrying capability, as thickness and 550 um in width are separated by a thin described in detail elsewhere [171 cell boundary (dark), this uniform structure being The work-of-fracture of the prismatic ceramic is attributed to the deformation of the green fibers during composed of two parts, earlier stage and later stage, warm-pressing and hot-pressing. With the increasing of corresponding to the displacement of lower or larger boundary thickness, the cross sections of Al2O3 cells than about 0.5 mm, respectively. During the initial stage showed an ellipse shape. It can be assumed that cells with relatively high load-carrying capacity, the deflect were permitted to move under pressure in the case of ing, delaminating and tensile fracturing occur alter thicker cell boundaries natively, yielding a saw-teeth curve. Crack deflection In practice, the fibrous monolithic ceramic is a special and delamination are two main contributions to the xample of laminated or multilayered ceramics. A con- improved fracture energy. During the later stage of trolled three-dimensional structure exists in fibrous bending test, the load-carrying capacity becomes very ceramics, and each fibrous cell is separated completely low, which means the ending of tensile fracturing and by a thin cell boundary, although the weaker interphase the starting of fiber sliding. The sliding friction among mics, uniform monolith existed within each layer(sepa- work-of-fracture in the later stage of bending te o,ng was introduced just in inter-layers in multilayered cera- fibers becomes a dominant factor for the improved rated as two-dimensional). Thus, the difference in the The total displacements are up to 1.0 mm and similar structure results in the variations of mechanical proper- to those of fiber reinforced ceramic composites [101 ties and fracture behavior [16] However, relatively short displacement occurs for the I Fig. 1. Cross-section observation of the alumina-based prismatic ceramics with SiC boundaries in various thickness of (A)4.4 um, (B)9.3 um, and
pressed into a perform at 523 K under a pressure of 25 MPa, and followed by hot pressing at temperature of 1773 K for 1 h under the same pressure, yielding the prismatic fibrous ceramic. The bending strength was tested by three-point bending with 0.5 mm/min crosshead speed. The used samples had a polished tensile surface with 1.5 mm thick (in hotpressing direction), 4 mm wide and 40 mm long (in fiber direction). The four-point Single Edge Notched Beam method (SENB) was used for evaluation of fracture toughness and fracture work. The used samples were prepared 3.0 mm thick, 4 mm wide and 40 mm long, and a notch was cut with 1.5 mm in depth and 0.1 mm in tip diameter. Microstructures and crack propagation of the prismatic ceramic were observed by optical microscope. 3. Results and discussion 3.1. Microstructure Fig. 1 shows the microstructure in the cross section of prismatic composites with various boundary thicknesses. Flattened hexagonal Al2O3 cells about 250 mm in thickness and 550 mm in width are separated by a thin cell boundary (dark), this uniform structure being attributed to the deformation of the green fibers during warm-pressing and hot-pressing. With the increasing of boundary thickness, the cross sections of Al2O3 cells showed an ellipse shape. It can be assumed that cells were permitted to move under pressure in the case of thicker cell boundaries. In practice, the fibrous monolithic ceramic is a special example of laminated or multilayered ceramics. A controlled three-dimensional structure exists in fibrous ceramics, and each fibrous cell is separated completely by a thin cell boundary, although the weaker interphase was introduced just in inter-layers in multilayered ceramics, uniform monolith existed within each layer (separated as two-dimensional). Thus, the difference in the structure results in the variations of mechanical properties and fracture behavior [16]. 3.2. Mechanical properties The mechanical properties of Al2O3/SiC prismatic composites with various boundary thicknesses are listed in Table 1. On the basis of the bending data, the toughness energy appears to be improved greatly with little increased toughness but decreased bending strength. It can be considered that the bending strength is decreased due to the reduction of effective load-carrying area by interphase SiC addition, which also results in little increase of fracture toughness. However, the fracture work is improved greatly because the weak interfaces permit the crack propagation with multi-directional routes. In case of the interphase SiC thickness of 9.3–15.6 mm, the fracture work of 1221.4–1481.6 J/m2 is achieved with good combination of bending strength and toughness. When the thickness is higher than 15.6 mm, the prismatic ceramic is easy to peel/cleave due to weak bonding between the layers, and shear stress along the axial direction is very low, which results from poor sinterability of SiC. Fig. 2 shows the load–displacement curves of the prismatic ceramics with various SiC interphase. The composites display a non-catastrophic and graceful failure with reasonable load-carrying capability, as described in detail elsewhere [17]. The work-of-fracture of the prismatic ceramic is composed of two parts, earlier stage and later stage, corresponding to the displacement of lower or larger than about 0.5 mm, respectively. During the initial stage with relatively high load-carrying capacity, the deflecting, delaminating and tensile fracturing occur alternatively, yielding a saw-teeth curve. Crack deflection and delamination are two main contributions to the improved fracture energy. During the later stage of bending test, the load-carrying capacity becomes very low, which means the ending of tensile fracturing and the starting of fiber sliding. The sliding friction among fibers becomes a dominant factor for the improved work-of-fracture in the later stage of bending test. The total displacements are up to 1.0 mm and similar to those of fiber reinforced ceramic composites [10]. However, relatively short displacement occurs for the Fig. 1. Cross-section observation of the alumina-based prismatic ceramics with SiC boundaries in various thickness of (A) 4.4 mm, (B) 9.3 mm, and (C) 15.6 mm. 324 G.H. Min et al. / Ceramics International 29 (2003) 323–326
G H. Min et al. /Ceramics International 29(2003)323-326 Table I Properties evaluation of the Al2O3/SiC prismatic composites Interlayer thickness(um) Fracture work (m-) Fracture toughness(MPa m/) Bending strength (MPa) 794.6 .70 685 253.1 15.6 481.6 5.02 210.3 0 0,000200.400600801.001.20 Fig. 3. Crack route on the side surface of the prismatic ceramics with SiC boundaries in various thickness of (a)4.4 um, (b) ceramics with SiC boundaries in thickness of 9.3 um 9.3 um, and(c)15.6 um propagation exists near the notch tip, the cracks deflect alumina-based multilayered ceramics, in which dis- but do not cause a longer delamination. However, placement showed value of 0.4-0.6 mm, similar to those of cracks occur also quickly on the multi-portions or else the prismatic ceramics in the earlier stage [11, 12, 14-16 over the entire section near or far from the main route Generally, two factors govern the fracture properties which plays an important role in the further improve of the composites: the fracture resistance of the cell and ment for crack path. Then, those cracks with small-scale cell boundary(load-carrying capacity in Fig. 2), and deflection result in long-distance delamination by inter weaker cell boundaries in comparison to the cells acting with the main route in a bridging manner, some (developed crack routes or displacement in Fig. 2) delaminations stretching up to two outer loading points of the tested sample 33. Fracture characteristics A more detailed observation is seen in Fig. 4. in which sev eral typical manners of crack growth can be As analyzed above, the controlled structure of the lyzed. While going across a fibrous layer, a crack is cellular ceramics is closely related to their mechanical deflected into a weak interface layer, causing a delani- properties, including fracture features. Fig 3 shows the nation. However, some delaminations grow only a finite crack propagating paths on the side-surface of a sample distance and deflect in the next fibrous layer or deflect after the notched bending test. The main route of crack ing and delaminating occur at same time(Fig 4A). The A FI? Fig 4. Propagating manners of cracks nearby the interlayer showing deflecting and delaminating(A)and bridging(B)
alumina-based multilayered ceramics, in which displacement showed value of 0.4–0.6 mm, similar to those of the prismatic ceramics in the earlier stage [11,12,14–16]. Generally, two factors govern the fracture properties of the composites: the fracture resistance of the cell and cell boundary (load-carrying capacity in Fig. 2), and weaker cell boundaries in comparison to the cells (developed crack routes or displacement in Fig. 2). 3.3. Fracture characteristics As analyzed above, the controlled structure of the cellular ceramics is closely related to their mechanical properties, including fracture features. Fig. 3 shows the crack propagating paths on the side-surface of a sample after the notched bending test. The main route of crack propagation exists near the notch tip, the cracks deflect but do not cause a longer delamination. However, cracks occur also quickly on the multi-portions or else over the entire section, near or far from the main route, which plays an important role in the further improvement for crack path. Then, those cracks with small-scale deflection result in long-distance delamination by interacting with the main route in a bridging manner, some delaminations stretching up to two outer loading points of the tested sample. A more detailed observation is seen in Fig. 4, in which several typical manners of crack growth can be analyzed. While going across a fibrous layer, a crack is deflected into a weak interface layer, causing a delamination. However, some delaminations grow only a finite distance and deflect in the next fibrous layer or deflecting and delaminating occur at same time (Fig. 4A). The Table 1 Properties evaluation of the Al2O3/SiC prismatic composites Interlayer thickness (mm) Fracture work (Jm2 ) Fracture toughness (MPa m1/2) Bending strength (MPa) 4.4 794.6 2.70 164.4 9.3 1221.4 6.85 253.1 15.6 1481.6 5.02 210.3 Fig. 2. Load–displacement curves of of the alumina-based prismatic ceramics with SiC boundaries in various thickness of (a) 4.4 mm, (b) 9.3 mm, and (c) 15.6 mm. Fig. 3. Crack propagation route on the side surface of the prismatic ceramics with SiC boundaries in thickness of 9.3 mm. Fig. 4. Propagating manners of cracks nearby the interlayer showing deflecting and delaminating (A) and bridging (B). G.H. Min et al. / Ceramics International 29 (2003) 323–326 325
G H. Min et al. /Ceramics International 29(2003)323-326 interlocking of delamination is attributed to the hetero- [2]D Kovar, B.H. King, J W. Holloran, Fibrous monolithic cera- geneous Sic interlayer [12]. During the middle and later mics, J. Am. Ceram Soc. 80(1997)2471 stages of the bending test, the interaction occurs among [3] R W. Trice J.W. Halloran, Influence of microstructure and tem- various propagating cracks, and the bridging is a domi erature on the interfacial fracture energy of silicon nitride/boron nant mechanism as in Fig. 4B. Finally, the sliding of nitride fibrous monolithic ceramics, J. Am. Ceram Soc. 82(1999) adjacent cells or/and cellular layers lasts a longer dis- [4] R.W. Trice, J.W. Halloran, Effect of sintering aid composition on placement at lower load-carrying. Thus, the fracture the processing of Si3N4/BN fibrous monolithic ceramics, J.Am behavior of the prismatic ceramics lies between multi Ceram.Soc.82(1999)2943 layered ceramics and fiber reinforced ceramic composites [ S.Y. Lienard, J.w.Halloran, Texture development of s nitride/boron nitride fibrous monolithic ceramics, J. Mater [6K. Ueno, Fabricating method for a prismatic ceramic compo- 4. Conclusion ites. JP Patent No 9-318910 [ K. Ueno, Prismatic structures ceramic, J. Soc. Mater. Sci. Japan By means of structure-controlled processing, pri [8 matic ceramic composites of the Al2O3/SiC system have mechanical properties of Si3 N4-based prismatic materials, in been prepared with a distinct prismatic texture of alu Proc. 16th Japan-Korea International Seminar on Ceramics mina-based cells, which are separated in three dimen 1999,pp.285-28 sions by thin Sic cell boundaries. 9J. She, T. Inoue, Mechanical properties and fracture behavior of The fracture toughness of the composites was AlO /SiC fibrous ceramics, J. Eur. Ceram Soc. 20(2000)1887 improved significantly. However, the bending strength [10 T. Inoue, K. Ueno, Mechanical properties and fracture beha- vior of SiTico fibre SiAlON composites, Ceram. Int. 24(1998) was decreased due to the reduced effective cross-section by weaker boundaries. When the thickness of Sic [l] s. Cai, Y. Huang, Infiuence of interface characteristic on the interphase is 9.3-15.6 um, a fracture work of 1221.4- echanical properties of multiplayer Si]N4 ceramics, Acta Com 81.6 J/m- was obtained with good combination of positie Sinica 16(1999)11( [2] J. She, T. Inoue, Fabrication and characterization of multiplayer bending strength and toughness umina-based composites with improved fracture behavi Generally, the composites fractured in a non-brittle Mater.Let.42(2000)155. manner. a crack deflecting and delimitating are con [3S. Baskaran, J. Holloran, Fibrous monolithic cer sidered as two main contributions for the improved mechanical properties and oxidation behavior of the silicon fracture energy, and frictional sliding of adjacent carbide/boron nitride system, J. Am. Ceram. Soc. 77(1994) rous ce lls becomes more dominant after cracking [14) J. She, T. Inoue, Fracture behavior and mechanical properties of occurs, especially at lower load condition. fracture char- acteristics of the prismatic ceramics lies between those of thickness, Mater. Sci. Lett. 19(2000)4 the multilayered ceramics and fiber reinforced ceramic [5] J. She, T. Inoue, Multilayered Al2O3/ SiC ceramics with composites due to three-dimensional controlled structure improved mechanical behavior, J. Eur. Ceram. Soc. 20(2000) [16 J. She, T. Inoue, Mechanical properties and fracture behavior of References AlO3 laminates with different architectures, Mater. Lett. 46 [S. Baskaran, S.D. Dunn, J.W. Holloran, Fibrous monolithic [17 G.H. Min, R. LiNon-catastrophic fracture of alumina-based ceramics: fabrication microstructure and indentation behavior. J. prismatic ceramic composites, Chinese J. Mater. Res. 15(16) Am. Ceran.Soc.76(1993)2209 2001)693-698
interlocking of delamination is attributed to the heterogeneous SiC interlayer [12]. During the middle and later stages of the bending test, the interaction occurs among various propagating cracks, and the bridging is a dominant mechanism as in Fig. 4B. Finally, the sliding of adjacent cells or/and cellular layers lasts a longer displacement at lower load-carrying. Thus, the fracture behavior of the prismatic ceramics lies between multilayered ceramics and fiber reinforced ceramic composites. 4. Conclusion By means of structure-controlled processing, prismatic ceramic composites of the Al2O3/SiC system have been prepared with a distinct prismatic texture of alumina-based cells, which are separated in three dimensions by thin SiC cell boundaries. The fracture toughness of the composites was improved significantly. However, the bending strength was decreased due to the reduced effective cross-section by weaker boundaries. When the thickness of SiC interphase is 9.3–15.6 mm, a fracture work of 1221.4– 1481.6 J/m2 was obtained with good combination of bending strength and toughness. Generally, the composites fractured in a non-brittle manner, and crack deflecting and delimitating are considered as two main contributions for the improved fracture energy, and frictional sliding of adjacent fibrous cells becomes more dominant after cracking occurs, especially at lower load condition. Fracture characteristics of the prismatic ceramics lies between those of the multilayered ceramics and fiber reinforced ceramic composites due to three-dimensional controlled structure. References [1] S. Baskaran, S.D. Dunn, J.W. Holloran, Fibrous monolithic ceramics: fabrication, microstructure and indentation behavior, J. Am. Ceram. Soc. 76 (1993) 2209. [2] D. Kovar, B.H. King, J.W. Holloran, Fibrous monolithic ceramics, J. Am. Ceram. Soc. 80 (1997) 2471. [3] R.W. Trice, J.W. Halloran, Influence of microstructure and temperature on the interfacial fracture energy of silicon nitride/boron nitride fibrous monolithic ceramics, J. Am. Ceram. Soc. 82 (1999) 2502. [4] R.W. Trice, J.W. Halloran, Effect of sintering aid composition on the processing of Si3N4/BN fibrous monolithic ceramics, J. Am. Ceram. Soc. 82 (1999) 2943. [5] S.Y. Lienard, J.W. Halloran, Texture development of silicon nitride/boron nitride fibrous monolithic ceramics, J. Mater. Sci. 35 (2000) 3365. [6] K. Ueno, Fabricating method for a prismatic ceramic composites, JP Patent No 9–318910. [7] K. Ueno, Prismatic structures ceramic, J. Soc. Mater. Sci. Japan 47 (6) (1998) 644. [8] T. Inoue, M.Suzuki, S. Sodeoka, K. Ueno, Fabrication and mechanical properties of Si3N4-based prismatic materials, in: Proc. 16th Japan–Korea International Seminar on Ceramics, 1999, pp. 285–288. [9] J. She, T. Inoue, Mechanical properties and fracture behavior of Al2O3/SiC fibrous ceramics, J. Eur. Ceram. Soc. 20 (2000) 1887. [10] T. Inoue, K. Ueno, Mechanical properties and fracture behavior of SiTiCO fibre/SiAlON composites, Ceram. Int. 24 (1998) 565. [11] S. Cai, Y. Huang, Influence of interface characteristic on the mechanical properties of multiplayer Si3N4 ceramics, Acta Compositie Sinica 16 (1999) 110. [12] J. She, T. Inoue, Fabrication and characterization of multiplayer alumina-based composites with improved fracture behavior, Mater. Lett. 42 (2000) 155. [13] S. Baskaran, J. Holloran, Fibrous monolithic ceramics: mechanical properties and oxidation behavior of the silicon carbide/boron nitride system, J. Am. Ceram. Soc. 77 (1994) 1249. [14] J. She, T. Inoue, Fracture behavior and mechanical properties of multiplayered alumina-based composites with different layer thickness, Mater. Sci. Lett. 19 (2000) 45. [15] J. She, T. Inoue, Multilayered Al2O3/SiC ceramics with improved mechanical behavior, J. Eur. Ceram. Soc. 20 (2000) 1771. [16] J. She, T. Inoue, Mechanical properties and fracture behavior of Al2O3 laminates with different architectures, Mater. Lett. 46 (2000) 65. [17] G.H. Min, R. LiNon-catastrophic fracture of alumina-based prismatic ceramic composites, Chinese J. Mater. Res. 15 (16) (2001) 693–698. 326 G.H. Min et al. / Ceramics International 29 (2003) 323–326