Availableonlineatwww.sciencedirect.cor ° Science Direct CERAMICS INTERNATIONAL ELSEVIER Ceramics International 33 (2007)1395-1398 www.elsevier.com/locate/ceramint Short communication Unidirectional carbon fiber and Sic particulate Co-reinforced fused silica composite G H. Zhou a, b S W. Wang a, * X.X. Huang a. J.K. Guo a Graduate School of Chinese Academy of Sciences, Beijing 100049, PR China Received 8 September 2005: received in revised form 3 March 2006: accepted 14 April 2006 Available online 25 September 2006 Abstract Unidirectional carbon fiber (uni-Cr) reinforced fused silica composite with the addition of 20 wt %o SiC particulate(SiCp)(uni-CH SiO2+ 20 wt% SiCp) was prepared by slurry infiltration and hot-pressing. The room temperature mechanical properties were investigated and the fracture features of composites were observed. While the flexural strength parallel to the fiber direction decreased from 667.3 to 431.8 MPa, that of perpendicular to the fiber direction increased from 18.0 to 54.3 MPa for uni-C /SiO, composite after the addition of SiCp. Obviously, the anisotropy of mechanical properties was strongly modified. The increased flexural strength might be ascribed to the increase of the fiber/matrix interfacial bonding strength caused by the SiCp addition C 2006 Elsevier Ltd and Techna Group S.r. l. All rights reserved Keywords: B. Composites; C Mechanical properties; D. Glass ceramics; D. SiC; Fused silica 1. Introduction in mechanical properties. That is, flexural strength parallel to the fiber direction was up to 600 MPa. However, its strength In the area of space lightweight structural materials, carbon perpendicular to the fiber direction was lower than 20 MPa In fiber reinforced glass matrix composites have demonstrated a 1990s, Han et al. prepared a fused silica matrix composite wide range of attributes which include high strength, high reinforced by chopped carbon fiber and si3N4, BN particle [9- stiffness, excellent toughness, low density, unique wear 11]. Though mechanical properties of this composite did not resistance, and environmental stability for structural applica- show anisotropy, a flexural strength of 73.2 MPa was obtained tions [1-4]. Fused silica is one of the glass matrix material for and the reinforced effort was far from being comparable with heat shields and space lightweight structural applications those of fiber yarn [8, 12]. The present work was undertaken to cm), low coefficient of thermal expansion (CTE), low forced SiO2 composite (uni-C/SiO2)with the addition of thermal conductivity, high softening temperature and excel- submicron SiC particulate (SiCp). The mechanical properties lent chemical inertness [5,6]. However, monolithic fused and microstructure of the hot-pressed composites were silica is rarely used due to its intrinsic brittleness and very low investigated. The toughening mechanism of the composite mechanical properties [7]. In 1970s, Guo et al. studied the was discussed unidirectional carbon fiber reinforced fused silica glass composite. The results showed its flexural strength was 12- 2. Experimental procedures fold that of fused silica, its impact strength was upgraded by 40-fold, and its work of fracture was increased by three orders Fused silica powder (SiO2 >99 wt %o pure, and average of magnitude [8]. However, this composite showed anisotropy particle size around 2.8 um), PAN-based carbon fit (2800 MPa average tensile strength, and 6-7 um in diameter), and silicon carbide powder (a-Sic >98 wt. pure, and Corresponding author. Tel: +86 21 52414320 fax: +86 21 52413903. average particle size around 0.5 um) were used as starting ang51@ mail sic ac cn(S.w. Wang) naterials. The powders were mixed in deionized water with 2-8842/$3200C 2006 Elsevier Ltd and Techna Group S.r.L. All rights reserved 10.1016 1-ceramint.2006.04008Short communication Unidirectional carbon fiber and SiC particulate Co-reinforced fused silica composite G.H. Zhou a,b , S.W. Wang a, *, X.X. Huang a , J.K. Guo a a Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050, PR China b Graduate School of Chinese Academy of Sciences, Beijing 100049, PR China Received 8 September 2005; received in revised form 3 March 2006; accepted 14 April 2006 Available online 25 September 2006 Abstract Unidirectional carbon fiber (uni-Cf) reinforced fused silica composite with the addition of 20 wt.% SiC particulate (SiCp) (uni-Cf/ SiO2 + 20 wt.% SiCp) was prepared by slurry infiltration and hot-pressing. The room temperature mechanical properties were investigated and the fracture features of composites were observed. While the flexural strength parallel to the fiber direction decreased from 667.3 to 431.8 MPa, that of perpendicular to the fiber direction increased from 18.0 to 54.3 MPa for uni-Cf/SiO2 composite after the addition of SiCp. Obviously, the anisotropy of mechanical properties was strongly modified. The increased flexural strength might be ascribed to the increase of the fiber/matrix interfacial bonding strength caused by the SiCp addition. # 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Keywords: B. Composites; C. Mechanical properties; D. Glass ceramics; D. SiC; Fused silica 1. Introduction In the area of space lightweight structural materials, carbon fiber reinforced glass matrix composites have demonstrated a wide range of attributes which include high strength, high stiffness, excellent toughness, low density, unique wear resistance, and environmental stability for structural applica￾tions [1–4]. Fused silica is one of the glass matrix material for heat shields and space lightweight structural applications because of its prominent properties such as low density (2.2 g/ cm3 ), low coefficient of thermal expansion (CTE), low thermal conductivity, high softening temperature and excel￾lent chemical inertness [5,6]. However, monolithic fused silica is rarely used due to its intrinsic brittleness and very low mechanical properties [7]. In 1970s, Guo et al. studied the unidirectional carbon fiber reinforced fused silica glass composite. The results showed its flexural strength was 12- fold that of fused silica, its impact strength was upgraded by 40-fold, and its work of fracture was increased by three orders of magnitude [8]. However, this composite showed anisotropy in mechanical properties. That is, flexural strength parallel to the fiber direction was up to 600 MPa. However, its strength perpendicular to the fiber direction was lower than 20 MPa. In 1990s, Han et al. prepared a fused silica matrix composite reinforced by chopped carbon fiber and Si3N4, BN particle [9– 11]. Though mechanical properties of this composite did not show anisotropy, a flexural strength of 73.2 MPa was obtained and the reinforced effort was far from being comparable with those of fiber yarn [8,12]. The present work was undertaken to modify the anisotropy of unidirectional carbon fiber rein￾forced SiO2 composite (uni-Cf/SiO2) with the addition of submicron SiC particulate (SiCp). The mechanical properties and microstructure of the hot-pressed composites were investigated. The toughening mechanism of the composite was discussed. 2. Experimental procedures Fused silica powder (SiO2 >99 wt.% pure, and average particle size around 2.8 mm), PAN-based carbon fiber (2800 MPa average tensile strength, and 6–7 mm in diameter), and silicon carbide powder (a-SiC >98 wt.% pure, and average particle size around 0.5 mm) were used as starting materials. The powders were mixed in deionized water with www.elsevier.com/locate/ceramint Ceramics International 33 (2007) 1395–1398 * Corresponding author. Tel.: +86 21 52414320; fax: +86 21 52413903. E-mail address: swwang51@mail.sic.ac.cn (S.W. Wang). 0272-8842/$32.00 # 2006 Elsevier Ltd and Techna Group S.r.l. All rights reserved. doi:10.1016/j.ceramint.2006.04.008