S. Tariolle et al. /Journal of Solid State Chemistry 177(2004)487-49 (a) Porous layers densified without sintering aid (35 vol% of porosity) 0000 mm 0.000020040060.080.100.120.140.160.18 b) Porous layers made with 50 vol %of com starch(45 vol% of porosity) FTmm 0.000.020.04060.08:160.1 displacement(mm) (c) Porous layers made with 55 vol%of corn starch(50 vol% of porosity) c (d) Weak interlayers made with a graphite spray 000 0.0 displacement (mm) Fig. 7. Fractographies and strain versus displacement curves of different B C laminar materials. of a second phase at the silicon carbide grain boundaries References formed by sintering aids. In the case of the solid phase sintered BC multi- n w. Clegg, Acta Metall. Mater. 40(11)(1992)3085-3093 layered materials, significant crack deflection was [2]H Liu, S.M. Hsu, J. Am. Ceram Soc. 79(9)(1996)2452-2457. observed in few specimens. 3 D.H. Kuo, W.M. Kriven, Mater Sci Eng. A 241(1998)241-250. f pores seems to be a crucial p (4K.S. Blanks, A. Kristoffersson. E Carlstrom, w.J. Clegg, J. Eur. Ceran.Soc.l8(1998)1945-1951 meter and elongated pores aligned with the plane of the [5]JB. Davis, A. Kristoffersson, E. Carlstrom, WJ.Clegg,J.Am layers seem to be more favorable to initiate crack (2000)2369-2374 deflection [6W. Lee, S.J. Howard, w.J. Clegg. Acta Mater. 44(10)(1996) 3905-3922. Studies on Bc multi-layered materials containing [7 C. Lacroix, D. Leguillon, E. Martin. Compos. Sci. Technol. 62 weak interfaces like platelets of graphite or boron nitride (2002)519 are lI n progress to verify these conclusions 8 M.-YHe, J.w. Hi n,J.Appl.Mech.56(1989)270-278of a second phase at the silicon carbide grain boundaries formed by sintering aids. In the case of the solid phase sintered B4C multi￾layered materials, significant crack deflection was observed in few specimens. The shape of pores seems to be a crucial para￾meter and elongated pores aligned with the plane of the layers seem to be more favorable to initiate crack deflection. Studies on B4C multi-layered materials containing weak interfaces like platelets of graphite or boron nitride are in progress to verify these conclusions. References [1] W.J. Clegg, Acta Metall. Mater. 40 (11) (1992) 3085–3093. [2] H. Liu, S.M. Hsu, J. Am. Ceram. Soc. 79 (9) (1996) 2452–2457. [3] D.H. Kuo, W.M. Kriven, Mater. Sci. Eng. A 241 (1998) 241–250. [4] K.S. Blanks, A. Kristoffersson, E. Carlstro¨m, W.J. Clegg, J. Eur. Ceram. Soc. 18 (1998) 1945–1951. [5] J.B. Davis, A. Kristoffersson, E. Carlstro¨m, W.J. Clegg, J. Am. Ceram. Soc. 83 (10) (2000) 2369–2374. [6] W. Lee, S.J. Howard, W.J. Clegg, Acta Mater. 44 (10) (1996) 3905–3922. [7] C. Lacroix, D. Leguillon, E. Martin, Compos. Sci. Technol. 62 (2002) 519–523. [8] M.-Y. He, J.W. Hutchinson, J. Appl. Mech. 56 (1989) 270–278. ARTICLE IN PRESS 0 20 40 60 80 100 120 strain (MPa) 0 20 40 60 80 strain (MPa) strain (MPa) strain (MPa) 0.0 0.2 0.4 0 10 20 30 40 50 60 70 80 90 0 20 40 60 80 100 120 1 mm 1 mm 1 mm 1 mm Porous layers densified without sintering aid (35 vol% of porosity) 0.00 0.02 0.04 displacement (mm) 0.06 0.08 0.10 0.12 0.14 0.16 0.18 0.00 0.02 0.04 displacement (mm) displacement (mm) 0.06 0.08 0.10 0.12 0.14 0.16 0.18 200 180 160 140 120 100 0.1 0.3 0.5 0.0 0.2 0.4 displacement (mm) 0.1 0.3 Weak interlayers made with a graphite spray Porous layers made with 55 vol%of corn starch (50 vol% of porosity) Porous layers made with 50 vol%of corn starch (45 vol% of porosity) (a) (b) (c) (d) Fig. 7. Fractographies and strain versus displacement curves of different B4C laminar materials. S. Tariolle et al. / Journal of Solid State Chemistry 177 (2004) 487–492 491