Availableonlineatwww.sciencedirect.com ScienceDirect materials letters ELSEVIER Materials Letters 61(2007)312-315 www.elsevier.com/locate/matlet Preparation and mechanical properties of c/Sic composites with carbon fiber woven preform Junqiang Ma", Yongdong Xu, Litong Zhang, Laifei Cheng, Jingjiang Nie, Hong L National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, PR China Received 19 December 2006; accepted 9 April 2006 Available online 17 May 2006 Abstract o C/SiC composites reinforced with multilayer carbon fiber woven preforms were fabricated by isothermal chemical vapor infiltration (ICVD) rocess. To characterize the mechanical properties of the composites, mechanical testing was carried out under various loading conditions, including tension, bending and shear loads. The results indicated that the composites, with superior intrinsic through-the-thickness properties exhibited high in-plane mechanical properties. Therefore, the composites developed can well meet the demands of the reusable nose cap, i.e. the easiness of near-net shaping and the capability of withstanding multidirectional mechanical and thermal stresses. o 2006 Elsevier B V. All rights reserved eywords: Composite materials; Chemical vapor infiltration: Multilayer preform; Mechanical properties 1. Introduction The objective of this paper is to assess the mechanical properties of the novel C/SiC composites under various loading Fiber reinforced composite materials are widely used in the conditions, including tension, bending and shear loads, which design of thermostructural components like nozzles, nose cap, etc. are expected to provide valuable information for effectively for its acceptable performance at elevated temperatures [1,2]. utilizing the composites to manufacture the very demanding Traditional C/C nose cap is fabricated by stacking bi-directional nose cap carbon cloth one over the other on a horizontal plane. However, when the carbon cloth is shaped around the dome-shaped mold, 2. Experimental the carbon cloth will undergo in-plane shear deformation, which is accompanied by the changes of intemal microstructure. These 2. I. Fabrication of the composites variations in intemal geometry have much influence on local thermal conductivity [3 and make it difficult to develop the The carbon fiber utilized was T300 6 K carbon fiber from the models which predict the stiffness and strength properties of the Nippon Toray corporation. The weave pattern of the carbon fiber composites [4]. Further, the very tough reentry environment [5 preforms is illustrated in Fig. 1(a) and their weave parameters are can significantly degrade the C/C nose cap and lower its reliability presented in Table 1. Composite panels were processed by and reusability isothermal chemical vapor infiltration (ICVi)to deposit pyrolytic The solution to the above problems associated with the carbon interphase (0. 2 um thickness)and Sic matrix, which has luction of the nose cap using 2D C/C composites is the use been described previously in full detail [6]. The resultant com- SiC composites reinforced with near-net shaped multilayer posites had a nominal fiber volume fraction of 45%0, an open orms. Most recently, the authors have applied the unique porosity of 14-17% and a density of 1.9-2.1 g/em multilayer preforms to successfully produce the near-net shaped C/SiC nose cap by the Icvi process 2.2. Mechanical testing s Corresponding author. Tel. +86 29 88494616: fax: +86 29 88494620 Of a total of 15 composite panels processed in the same fur nace runs, five were cut into test specimens along the warp and 0167-577X/S-see front matter e 2006 Elsevier B V. All rights reserved. doi:10.1016 malet006.04.099Preparation and mechanical properties of C/SiC composites with carbon fiber woven preform Junqiang Ma ⁎, Yongdong Xu, Litong Zhang, Laifei Cheng, Jingjiang Nie, Hong Li National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi'an, Shaanxi 710072, PR China Received 19 December 2006; accepted 9 April 2006 Available online 17 May 2006 Abstract C/SiC composites reinforced with multilayer carbon fiber woven preforms were fabricated by isothermal chemical vapor infiltration (ICVI) process. To characterize the mechanical properties of the composites, mechanical testing was carried out under various loading conditions, including tension, bending and shear loads. The results indicated that the composites, with superior intrinsic through-the-thickness properties, exhibited high in-plane mechanical properties. Therefore, the composites developed can well meet the demands of the reusable nose cap, i.e. the easiness of near-net shaping and the capability of withstanding multidirectional mechanical and thermal stresses. © 2006 Elsevier B.V. All rights reserved. Keywords: Composite materials; Chemical vapor infiltration; Multilayer preform; Mechanical properties 1. Introduction Fiber reinforced composite materials are widely used in the design of thermostructural components like nozzles, nose cap, etc. for its acceptable performance at elevated temperatures [1,2]. Traditional C/C nose cap is fabricated by stacking bi-directional carbon cloth one over the other on a horizontal plane. However, when the carbon cloth is shaped around the dome-shaped mold, the carbon cloth will undergo in-plane shear deformation, which is accompanied by the changes of internal microstructure. These variations in internal geometry have much influence on local thermal conductivity [3] and make it difficult to develop the models which predict the stiffness and strength properties of the composites [4]. Further, the very tough reentry environment [5] can significantly degrade the C/C nose cap and lower its reliability and reusability. The solution to the above problems associated with the production of the nose cap using 2D C/C composites is the use of C/SiC composites reinforced with near-net shaped multilayer preforms. Most recently, the authors have applied the unique multilayer preforms to successfully produce the near-net shaped C/SiC nose cap by the ICVI process. The objective of this paper is to assess the mechanical properties of the novel C/SiC composites under various loading conditions, including tension, bending and shear loads, which are expected to provide valuable information for effectively utilizing the composites to manufacture the very demanding nose cap. 2. Experimental 2.1. Fabrication of the composites The carbon fiber utilized was T300 6 K carbon fiber from the Nippon Toray corporation. The weave pattern of the carbon fiber preforms is illustrated in Fig. 1(a) and their weave parameters are presented in Table 1. Composite panels were processed by isothermal chemical vapor infiltration (ICVI) to deposit pyrolytic carbon interphase (0.2 μm thickness) and SiC matrix, which has been described previously in full detail [6]. The resultant com￾posites had a nominal fiber volume fraction of 45%, an open porosity of 14–17% and a density of 1.9–2.1 g/cm3 . 2.2. Mechanical testing Of a total of 15 composite panels processed in the same fur￾nace runs, five were cut into test specimens along the warp and Materials Letters 61 (2007) 312–315 www.elsevier.com/locate/matlet ⁎ Corresponding author. Tel.: +86 29 88494616; fax: +86 29 88494620. E-mail address: junqiangma@kcnh.com (J. Ma). 0167-577X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2006.04.099