TABLE V Three layered composite design. A total thickness of a tile- 12.30 mI Thickness of Layers(um) Composition B,C- 30wtoSiC acomp(MPa) Orens(MPa) B4C-30wt %SiC/B4C formance of developed B4C-30 wt %SiC/B4C ceramic laminates. The results of this study are likely to find practical applications in the field of ballistic protec tion and mechanical behavior of advanced ceramic composites Acknowledgement This work was supported by AFOSR, the project no. F49620-02-0340 and by the European Commis- sion, the project ICA2-CT-2000-10020, Copernicus- 2 Program. This work was also partly performed at the Army Center for Nanoscience and Nanomaterials, North Carolina A&T State University References 100mm 1. J. S. STERNBERG, J Appl. Plrys 69(1989)3417 2. D. A. SHOCKEY. A. H. MARCHA S. R G BUZKETT and R. PARKER Int J. impact Eng. 9(1990)263. Figure 5 Photograph of fractured 3 layered B, C-30 wt%SiC /BC tile 3. G.R. JOHNSON and T. J. HOLMQUIST, J Appl. Phys. 85 hot pressed at2200°C. (1999)8060. 4. H. D. ESPINOSA, N. S. BRAR, G. YUAN, Y. XU and V. ARRIETA. Int J. Sol Struct. 37(2000)4893 known but the critical defect in the layer usually can- 5. W. J. CLEGG, Science 286(1999)1097 not be identified. There is a possibility to determine the 6. M. LUGOVY, N. ORLOVSKAYA, K. BERROTH and J stress for crack tunneling in the tensile layer [38]. Such KUEBLER, Comp. Sci. TechnoL. 59(1999)283 7.lem,ibid.59(1999)1429 stress depends only on the intrinsic fracture toughness 8P. HONEYMAN-COLVIN andE. F, LanGE..Am. ceram and the layer thickness. Such transverse cracking of a Soc.79(1996)1810. tensile layer is not possible if the tensile residual stress 9. M. P. RAO, A. J. SANCHEZ-HERENCIA, G.E has a lower value than the stress for crack tunneling BELTZ, R. M. MCMEEKING and F. F. LANGE, Science Therefore, some empirical value is used as a critical 286(1999)102. 10. 1. J. MCCOLM. "Ceramic Hardness"(Plenum Press, New York tensile stress. Such approach, in fact, is also rather suc- 1990) cessful to eliminate cracking in laminates I1. K. A. SCHWETZ and A. LIPP, UImann's Encyclopedia of Industrial Chemistry", A4, VCH, (1981). 295 12. E. AMBERGER. W. STUMPF and K.-C. BUSCHBECK 7. Conclusions "Handbook of Inorganic Chemistry", 8th ed.(Springer-Verlag This research represents a first step in laminate ceram Berlin, 1981). ics development that should provide sufficient ballis- 13. D. M. BYLANDER andL. KLEIMAN, Phys. Rev B 43(1991) tic protection. Boron carbide-silicon carbide ceramics 14. F. THEVENOT, J. Eur. Ceram Soc. 6(1990)205 have been used in the design and manufacturing of three 15. B. Champagne and R. angers. J Am Ceram Soc. 6 layered and multilayered composite with strong inter- 1979)149 faces for enhanced fracture toughness. The model of 16. K NIIHARA, A. NAKAHIRA andT. HIRAl, ibid. 67(1984) heterogeneous layered system was used to develop op 17.F.TREⅤENOT,in“ Properties of Ceramics”, edited by G. de with, timal design parameters. As a result, laminates with R.A. Terpstra, and R Metselaar(Elsevier AppL Sci, London and calculated high compressive residual stresses(up to New York, 1989) 650 MPa)and low tensile residual stresses(below 150 18 H. LEE and R. SPEYER, J. Am. Ceram. Soc. 85(2002) MPa)were developed. The feasibility of manufactur- 1291 19. M. L. WILKENS. Int J Eng. Sci. 16(1978)793 ing laminate composite systems with enhanced tough- 20 C.A.fOlSON by incorporation of thin layers with high compres F. w. ZoK andF. LaNGE.J Am ceram sive stresses in the ceramics was demonstrated. Both 21. N, orlovSkaya. M. lugovy and, KUEblERMe. three-layered and nine-layered B4C-30 wt%SiC/B4C chanical performance of 3 layered B C-SiC ceramic composites, opposites were manufactured using roll-forming and unpublished results hot pressing techniques. Work is currently in progress 22. S. HO, C. HILLMAN, F. F. LANGE and Z. SUo, J. Am Ceram.Soc.78(1995)2353 to study the mechanical properties, such as fracture 23. T. CHARTIER, D. MERLE and J. L. BESSON, Europ oughness, strength, hardness, as well as ballistic pe Certan. Soc. 16(1995)101 5489TABLE V Three layered composite design. A total thickness of a tile – 12.30 mm Thickness of Layers (µm) Composition B4C-30wt%SiC B4C σcomp (MPa) σtens (MPa) B4C-30wt%SiC/B4C 1650 9000 573 210 Figure 5 Photograph of fractured 3 layered B4C-30 wt%SiC /B4C tile hot pressed at 2200◦C. known but the critical defect in the layer usually can￾not be identified. There is a possibility to determine the stress for crack tunneling in the tensile layer [38]. Such stress depends only on the intrinsic fracture toughness and the layer thickness. Such transverse cracking of a tensile layer is not possible if the tensile residual stress has a lower value than the stress for crack tunneling. Therefore, some empirical value is used as a critical tensile stress. Such approach, in fact, is also rather suc￾cessful to eliminate cracking in laminates. 7. Conclusions This research represents a first step in laminate ceram￾ics development that should provide sufficient ballis￾tic protection. Boron carbide-silicon carbide ceramics have been used in the design and manufacturing of three layered and multilayered composite with strong inter￾faces for enhanced fracture toughness. The model of heterogeneous layered system was used to develop op￾timal design parameters. As a result, laminates with calculated high compressive residual stresses (up to 650 MPa) and low tensile residual stresses (below 150 MPa) were developed. The feasibility of manufactur￾ing laminate composite systems with enhanced tough￾ness by incorporation of thin layers with high compres￾sive stresses in the ceramics was demonstrated. Both three-layered and nine-layered B4C-30 wt%SiC/B4C composites were manufactured using roll-forming and hot pressing techniques. Work is currently in progress to study the mechanical properties, such as fracture toughness, strength, hardness, as well as ballistic per￾formance of developed B4C-30 wt%SiC/B4C ceramic laminates. The results of this study are likely to find practical applications in the field of ballistic protec￾tion and mechanical behavior of advanced ceramic composites. Acknowledgement This work was supported by AFOSR, the project no. F49620-02-0340 and by the European Commis￾sion, the project ICA2-CT-2000-10020, Copernicus— 2 Program. This work was also partly performed at the Army Center for Nanoscience and Nanomaterials, North Carolina A&T State University. References 1. J. S . STERNBERG, J. Appl. Phys. 69 (1989) 3417. 2. D. A. SHOCKEY, A. H. MARCHAND, S . R. SAGGS , G. E. CORT, M. W. BUZKETT and R. PARKER, Int. J. Impact Eng. 9 (1990) 263. 3. G. R. JOHNSON and T. J. HOLMQUIST, J. Appl. Phys. 85 (1999) 8060. 4. H. D. ESPINOSA, N. S . BRAR, G. YUAN, Y. X U and V. ARRIETA, Int. J. Sol. Struct. 37 (2000) 4893. 5. W. J. CLEGG, Science 286 (1999) 1097. 6. M. LUGOVY, N. ORLOVSKAYA, K. BERROTH and J. KUEBLER, Comp. Sci. Technol. 59 (1999) 283. 7. Idem., ibid. 59 (1999) 1429. 8. P . HONEYMAN-COLVIN and F . F . LANGE, J. Am. Ceram. Soc. 79 (1996) 1810. 9. M. P . RAO, A. J. SANCHEZ-HERENCIA, G. E. BELTZ, R. M. MCMEEKING and F . F . LANGE, Science 286 (1999) 102. 10. I. J. MCCOLM, “Ceramic Hardness” (Plenum Press, New York, 1990). 11. K. A. SCHWETZ and A. LIPP , “Ulmann’s Encyclopedia of Industrial Chemistry”, A4, VCH, (1981), 295. 12. E. AMBERGER, W. STUMPF and K.-C.BUSCHBECK, “Handbook of Inorganic Chemistry”, 8th ed. (Springer-Verlag, Berlin, 1981). 13. D. M. BYLANDER and L. KLEIMAN, Phys. Rev. B 43 (1991) 1487. 14. F . THEVENOT, J. Eur. Ceram. Soc. 6 (1990) 205. 15. B. CHAMPAGNE and R. ANGERS , J. Am. Ceram. Soc. 62 (1979) 149. 16. K. NIIHARA, A. NAKAHIRA and T. HIRAI, ibid. 67 (1984) C13. 17. F . TREVENOT, in “Properties of Ceramics”, edited by G. de With, R. A. Terpstra, and R. Metselaar. (Elsevier Appl. Sci., London and New York, 1989). 18. H. LEE and R. SPEYER, J. Am. Ceram. Soc. 85 (2002) 1291. 19. M. L. WILKENS , Int. J. Eng. Sci. 16 (1978) 793. 20. C. A. FOLSOM, F . W. ZOK and F . LANGE, J. Am. Ceram. Soc. 77 (1994) 689. 21. N. ORLOVSKAYA, M. LUGOVY and J. KUEBLER, Me￾chanical performance of 3 layered B4C-SiC ceramic composites, unpublished results. 22. S . H O, C. HILLMAN, F . F . LANGE and Z. SUO, J. Am. Ceram. Soc. 78 (1995) 2353. 23. T. CHARTIER, D. MERLE and J. L. BESSON, J. Europ. Certam. Soc. 16 (1995) 101. 5489