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Fracture behavior and mechanical properties of SiC nanofiber (SiCNF) reinforced SiC nanocomposites as influenced by the thickness of amorphous carbon (a-C) coatings are studied via molecular dynamics simulations using Tersoff potential. To simulate the condition that a matrix crack arrives at the interface between matrix and coating, a pre-setting matrix crack is created. Results show that the tensile stress-strain curve of nanocomposites without and/or with thin a-C coatings (e.g., t≤ 0.3 nm) demonstrates an abrupt drop after achieving a maximum value, while nonlinear tails appear in the curves of nanocomposites with thick a-C coatings (e.g., t >2.0 nm). It is demonstrated that the SiCNF is penetrated by the matrix crack when it is uncoated and/or coated by a thin a-C layer (t ≤ 0.3 nm) and the nanocomposite fails in a typical brittle mode; whereas the crack deflection path changes and the SiCNF is pulled out from the matrix when the a-C coatings are thick enough (e.g., 4 nm), showing a different fracture mode in nanocomposites. Compared to nanocomposites without an a-C coating, the tensile strength of nanocomposites with a-C coating of 4.0 nm thickness is about four times higher, and the fracture energy increases around an order of magnitude. Furthermore, the average stress concentration factor for SiCNF in nanocomposites, defined as the ratio of tensile strength of single SiCNF to the average stress of the nanofiber in the composite when it is broken, is extracted and shows a decreasing trend with increasing coating thickness, indicating that a-C coating can therefore be expected to simultaneously enhance the tensile strength and fracture energy of the SiCNF/SiC nanocomposites. This work sheds light on the toughening mechanism in SiCNF/C/SiC nanocomposites where a-C coating plays a significant role, indicating that the toughening mechanism in conventional ceramic matrix composites on a microscale is still valid on a nanoscale. Simulation results suggest that coating thickness in material design is efficient for engineering SiCNF/SiC nanocomposites with high strength and toughness.
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Keywords:
- molecular dynamics simulations /
- tensile behavior /
- nanocomposite /
- a-C coating
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[7] Xia Z H, Curtin W A 2001 Cer. Eng. Sci. Proc. 22 371
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[11] Yang W, Noda T, Araki H, Yu J, Kohyama A 2003 Mater. Sci. Eng. A 345 28
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[13] Yang W, Araki H, Tang C, Thaveethavorn S, Kohyama A, Suzuki H, Noda T 2005 Adv. Mater. 17 1519
[14] Xia Z H, Riester L, Curtin W A, Li H, Sheldon B W, Liang J, Chang B, Xu J M 2004 Acta Mater. 52 931
[15] Xia Z H, Curtin W A, Sheldon B W 2004 J. Eng. Mater. Technol. 126 238
[16] Fan J P, Zhuang D M, Zhao D Q, Zhang G, Wu M S, Wei F, Fan Z J 2006 Appl. Phys. Lett. 89 121910
[17] Fan B B, Guo H H, Li W, Jia Y, Zhang R 2013 Acta Phys. Sin. 62 148101 (in Chinese) [范冰冰, 郭焕焕, 李稳, 贾瑜, 张锐 2013 物理学报 62 148101]
[18] Li L, Niu J B, Xia Z H, Yang Y Q, Liang J Y 2011 Scripta Mater. 65 1014
[19] Li L, Solá F, Xia Z H, Yang Y Q 2012 J. Appl. Phys. 111 094306
[20] Tersoff J 1989 Phys. Rev. B 39 5566
[21] Brenner D W, Shenderova O A, Harrison J A, Stuart S J, Ni B, Sinnott S B 2002 J. Phys. Condensed Matter. 14 783
[22] Pastewka L, Pou P, Pérez R, Gumbsch P, Moseler M 2008 Phys. Rev. B 78 161402
[23] Pastewka L, Moser S, Gumbsch P, Moseler M 2011 Nature Mater. 10 34
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[1] Karnitz M A, Craig D F, Richlen S L 1991 Am. Ceram. Soc. Bull. 80 430
[2] Donald I W, Mcmillan P W 1976 J. Mater. Sci. 11 949
[3] Marshall D B, Evans A G 1985 J. Am. Ceram. Soc. 68 225
[4] Besmann T M, Stinton D P, Kupp E R, Shanmugham S, Liaw P K 1997 Mater. Res. Soc. Symp. Proc. 458 147
[5] Evans A G 1990 J. Am. Ceram. Soc. 73 187
[6] Curtin W A 1991 J. Am. Ceram. Soc. 74 2837
[7] Xia Z H, Curtin W A 2001 Cer. Eng. Sci. Proc. 22 371
[8] Kerans R J, Parthasarathy T A 1999 Composites:Part A 30 521
[9] Kerans R J 1995 Scripta Metall. et Mater. 32 505
[10] Yang W, Kohyama A, Katoh Y, Araki H, Yu J, Noda T 2003 J. Am. Ceram. Soc. 86 851
[11] Yang W, Noda T, Araki H, Yu J, Kohyama A 2003 Mater. Sci. Eng. A 345 28
[12] Wong E W, Sheehan P E, Liebert C M 1997 Science 277 1971
[13] Yang W, Araki H, Tang C, Thaveethavorn S, Kohyama A, Suzuki H, Noda T 2005 Adv. Mater. 17 1519
[14] Xia Z H, Riester L, Curtin W A, Li H, Sheldon B W, Liang J, Chang B, Xu J M 2004 Acta Mater. 52 931
[15] Xia Z H, Curtin W A, Sheldon B W 2004 J. Eng. Mater. Technol. 126 238
[16] Fan J P, Zhuang D M, Zhao D Q, Zhang G, Wu M S, Wei F, Fan Z J 2006 Appl. Phys. Lett. 89 121910
[17] Fan B B, Guo H H, Li W, Jia Y, Zhang R 2013 Acta Phys. Sin. 62 148101 (in Chinese) [范冰冰, 郭焕焕, 李稳, 贾瑜, 张锐 2013 物理学报 62 148101]
[18] Li L, Niu J B, Xia Z H, Yang Y Q, Liang J Y 2011 Scripta Mater. 65 1014
[19] Li L, Solá F, Xia Z H, Yang Y Q 2012 J. Appl. Phys. 111 094306
[20] Tersoff J 1989 Phys. Rev. B 39 5566
[21] Brenner D W, Shenderova O A, Harrison J A, Stuart S J, Ni B, Sinnott S B 2002 J. Phys. Condensed Matter. 14 783
[22] Pastewka L, Pou P, Pérez R, Gumbsch P, Moseler M 2008 Phys. Rev. B 78 161402
[23] Pastewka L, Moser S, Gumbsch P, Moseler M 2011 Nature Mater. 10 34
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