Influence of SiC Nanowires on the Damage Evolution of SiCf/SiC Composites

doi:10.15541/jim20210045

Abstract

Abstract:

SiC fiber (SiC_f)/SiC composites were modified by SiC nanowires (SiC_nw) grown in-situ on SiC fiber to obtain hierarchical structure. Effects of this hierarchical structure on the properties of composites, such as microstructure, fracture strength and damage evolution, were evaluated. Results show that the introduction of SiC_nw significantly improves the matrix infiltration efficiency. SiC_nwand BN-coated SiC_nwreinforced SiC_f/SiC composites acquire better performance in bending tests by comparison with conventional SiC_f/SiC. SiC_nw coated by BN interphase obviously enhances the strength owing to weak-bonded interface. Besides, results of acoustic emission and Coated Vickers Hardness Impresses reveal that SiC_nw delay early damage evolution at early state and mainly make contribution to hindering and bridging of microcracks, which is further enhanced by BN-coated SiC_nw.

Key words: hierarchical composites, SiC nanowire, mechanical properties, acoustic emission

CLC Number:

TQ174

LI Longbin, XUE Yudong, HU Jianbao, YANG Jinshan, ZHANG Xiangyu, DONG Shaoming. Influence of SiC Nanowires on the Damage Evolution of SiC_f/SiC Composites[J]. Journal of Inorganic Materials, 2021, 36(10): 1111-1117.

Figures/Tables 10

Fig. 1 Schematic figure of three-point test within-situ AE monitoring system

Fig. 2 Typical SEM images of (a, b) as-grown SiCnw, (c) BN-coated SiCnw, and typical SEM images demonstrating the pore size of (d) SiCf/SiC and (e) SiCf/SiC-SiCnw composites

Composite	SiC_f/SiC	SiC_f/SiC- SiC_nw/BN	SiC_f/ SiC-SiC_nw
Bulk density/(g·cm^-3)	(1.98±0.03)	(2.02±0.04)	(2.08±0.03)
Open porosity/%	(17.64±1.08)	(14.39±0.60)	(11.58±1.35)

Composite	SiC_nwcontent / wt%	Flexural strength, σ_u/MPa	Proportional limit stress, σ_PL/MPa	Strain at flexural strength, ε_u/%	First AE stress, σ_min/MPa	AE onset stress, σ_onset/MPa
SiC_f/SiC	0	(356.7±16.2)	(153.9±6.4)	(0.39±0.05)	(58.8±7.5)	(116.1±8.9)
SiC_f/SiC-SiC_nw	2.0	(412.6±22.4)	(185.1±7.7)	(0.63±0.06)	(66.1±6.2)	(155.8±7.7)
SiC_f/SiC-SiC_nw/BN	2.0	(506.4±28.3)	(247.7±8.6)	(0.88±0.12)	(78.5±5.2)	(171.6±15.9)

Fig. 3 SEM fractural morphologies of (a) as-grown SiCnw, (b, c) BN-coated SiCnw in composites Local parts marked by white rectangular borders demonstrating that SiCnw tends to break (a) or pull out (b, c)

Fig. 4 Fracture morphologies of composite (a) SiCf/SiC, (b) SiCf/SiC-SiCnw and (c) SiCf/SiC-SiCnw/BN The images demonstrating the pull-out length of fibers

Fig. 5 Representative normalized cumulative AE energy curves as a function of stress (a) for composite SiCf/SiC (orange), SiCf/SiC-SiCnw (black) and SiCf/SiC-SiCnw/BN (blue) To clarify the difference of damage threshold among these three groups, initial key part (grey area) in (a) is magnified in (b). Colorful figures are available on website

Fig. 6 Typical stress-strain curves of SiCf/SiC(orange), SiCf/SiC-SiCnw (black) and SiCf/SiC-SiCnw/BN (blue) The proportional limit is pointed out in the picture. Colorful figures are available on website

Fig. 7 Scatter diagrams of the energy of individual AE events as a function of time in composites (a) SiCf/SiC, (b) SiCf/SiC-SiCnw, and (c) SiCf/SiC-SiCnw/BN Considering the massive amount of data, diagrams are depicted after compression

Fig. 8 SEM micrographs of crack propagation around the indentation in composites (a) SiCf/SiC; (b) SiCf/SiC-SiCnw; (c) SiCf/SiC-SiCnw/BN

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