JOURNAL OF MATERIALS PROCESSING TECHNOLOGY 209(2009)572-576 ELSEVIER journalhomepagewww.elsevier.com/locate/imatprotec Microstructure and tensile behavior of multiply needled C/Sic composite fabricated by chemical vapor infiltration Jingjiang Nie*, Yongdong Xu, Litong Zhang, Laifei Cheng, Jungiang Ma National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi'an Shaanxi 710072, China ARTICLE INFO A BSTRACT Article history: The microstructure and tensile behavior of a multiply needled C/SiC composite fabricated by chemical vapor infltration were investigated. Results showed that the tensile stress-strain Received in revised form curves exhibited a typical nonlinear behavior and can be divided into three regions: a very 16 January 2008 small initial linear region followed by a large nonlinear region and finally a quasi-linear gion Needling process caused a crimp around needling fibers and reduced the bearing fibers in plane Needling process induced damages were the main reasons for the failure of the composite. The fracture mainly occurred at the cross of needling fibers and uni- directional fibers, with the fibers showing multi-step fracture and extensive pullout. The Microstructure lulti-step fracture of clusters and nonlinear curves indicated a typical non-brittle failure Tensile behavior behavior of the multiply needled C/SiC composite due to the various damage patterns Multiply needled @2008 Elsevier B V. All rights reserved. C/SiC composite Chemical vapor infiltration Introduction properties and high fracture toughness(Camus et al., 1996; Wang and Laird, 1995; Wu et al., 2006). However, the 2D Carbon fiber reinforced silicon carbide ceramic matrix(C/Sic) composites have some fabrication problems and poor delam- omposites are widely used as structural materials in aero- ination resistance. 2. 5D and 3D braided composites have a nautic and space industries(.e, thermal protection systems superior delamination resistance(Ma et al., 2006; Boitier et al (Naslain, 2005; Christin, 2002), advanced propulsion(Schmidt 1997; Xu and Zhang, 1997)but have a high cost. To improve et al, 2004; Bouquet et al., 2003)and braking systems(Krenkel the delamination resistance and save cost, a unique kind and Berndt, 2005) due to their high damage tolerance with of multiply preform was developed by the means of the pseudo-ductility and strain-to-failure compared with mono- through-the-thickness needling technique. The multiply nee- lithic ceramics. Chemical vapor infiltration(cvn) is the most dled preforms have 3D architecture in real sense, which ar promising process for fabricating composites with advan- similar to that of Novoltex preforms reported in literatures tages of manipulating and modifying the microstructure of(Lacoste et al., 2002 )but differ significantly from the multiply the matrix, tailoring the fiber/matrix interface, and fabricat- stitched preforms reported in literatures(Mattheij et al., 2000 ing complex net or near-net shaped components at relatively Lomov et al., 2002). The multiply needled preforms consisted low temperatures(Chiang et al., 1989; Cao et al., 199 of unidirectional plies arranged in the desiredorientations and The mechanical properties and microstructure of 2D, 2.5D short-chopped fiber fabrics. The individual plies and fabrics and 3D C/Sic composites have been investigated extensively. were kept together by needling yarns. This structure led to 2D laminated composites have good in-plane mechanical an advantageous combination of high material properties and E-mail address ingiangnieosohucom 4. Niey 0924-0136/$-see front matter e 2008 Elsevier B V. All rights reserved. doi: 10.1016/j jmatprotec. 2008.02.035journal of materials processing technology 209 (2009) 572–576 journal homepage: www.elsevier.com/locate/jmatprotec Microstructure and tensile behavior of multiply needled C/SiC composite fabricated by chemical vapor infiltration Jingjiang Nie ∗, Yongdong Xu, Litong Zhang, Laifei Cheng, Junqiang Ma National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi’an Shaanxi 710072, China article info Article history: Received 3 February 2007 Received in revised form 16 January 2008 Accepted 16 February 2008 Keywords: Microstructure Tensile behavior Multiply needled C/SiC composite Chemical vapor infiltration abstract The microstructure and tensile behavior of a multiply needled C/SiC composite fabricated by chemical vapor infiltration were investigated. Results showed that the tensile stress–strain curves exhibited a typical nonlinear behavior and can be divided into three regions: a very small initial linear region followed by a large nonlinear region and finally a quasi-linear region. Needling process caused a crimp around needling fibers and reduced the bearing fibers in plane. Needling process induced damages were the main reasons for the failure of the composite. The fracture mainly occurred at the cross of needling fibers and uni￾directional fibers, with the fibers showing multi-step fracture and extensive pullout. The multi-step fracture of clusters and nonlinear curves indicated a typical non-brittle failure behavior of the multiply needled C/SiC composite due to the various damage patterns. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Carbon fiber reinforced silicon carbide ceramic matrix (C/SiC) composites are widely used as structural materials in aero￾nautic and space industries (i.e., thermal protection systems (Naslain, 2005; Christin, 2002), advanced propulsion (Schmidt et al., 2004; Bouquet et al., 2003) and braking systems (Krenkel and Berndt, 2005)) due to their high damage tolerance with pseudo-ductility and strain-to-failure compared with mono￾lithic ceramics. Chemical vapor infiltration (CVI) is the most promising process for fabricating composites with advan￾tages of manipulating and modifying the microstructure of the matrix, tailoring the fiber/matrix interface, and fabricat￾ing complex net or near-net shaped components at relatively low temperatures (Chiang et al., 1989; Cao et al., 1990). The mechanical properties and microstructure of 2D, 2.5D and 3D C/SiC composites have been investigated extensively. 2D laminated composites have good in-plane mechanical ∗ Corresponding author. Fax: +86 29 8849 4620. E-mail address: jingjiangnie@sohu.com (J. Nie). properties and high fracture toughness (Camus et al., 1996; Wang and Laird, 1995; Wu et al., 2006). However, the 2D composites have some fabrication problems and poor delam￾ination resistance. 2.5D and 3D braided composites have a superior delamination resistance (Ma et al., 2006; Boitier et al., 1997; Xu and Zhang, 1997) but have a high cost. To improve the delamination resistance and save cost, a unique kind of multiply preform was developed by the means of the through-the-thickness needling technique. The multiply nee￾dled preforms have 3D architecture in real sense, which are similar to that of Novoltex preforms reported in literatures (Lacoste et al., 2002) but differ significantly from the multiply stitched preforms reported in literatures (Mattheij et al., 2000; Lomov et al., 2002). The multiply needled preforms consisted of unidirectional plies arranged in the desired orientations and short-chopped fiber fabrics. The individual plies and fabrics were kept together by needling yarns. This structure led to an advantageous combination of high material properties and 0924-0136/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2008.02.035