Availableonlineatwww.sciencedirect.com Scripta materialia ELSEVIER Scripta Materialia 54(2006)1967-1971 www.actamat-journals.com Microstructure characterization and tensile behavior of 2. 5D C/SiC composites fabricated by chemical vapor infiltration Junqiang Ma", Yongdong Xu, Litong Zhang, Aifei Cheng, Jingjiang Nie, Ning Dong National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, 547 Mailbox, Xian Shaanxi 710072, Peoples Republic of china Received 23 November 2005: received in revised form 18 January 2006: accepted 30 January 2006 Available online 9 March 2006 Abstract a The microstructure of 2. 5D C/SiC composite was characterized in terms of fiber architecture and processing-induced cracks. a geo- petric model of the weave architecture which can be used for visualization and further tive analysis, was generated. Tension tests along the warp and weft directions were conducted at room temperature. The results that the stress-strain curves exhibit mostly nonlinear behavior. Microstructural observations reveal that the differences in tensile be between two loading directions are attrib- uted to the characteristics of the weave architecture o 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved Keywords: Ceramic matrix composites; Weave architecture; Microstructure; Tension tests; Fracture 1. Introduction Although three-dimensional (3D) four-step braided C/SiC omposites have improved delamination resistance and Carbon fiber reinforced silicon carbide ceramic matrix can be used to fabricate complex net or near-net shaped composites(C/SiC CMCs)are promising candidates for components [8-10], they are still not applicable for manu- many applications, particularly as aerospace and aircraft facturing components with one closed end (e.g,a nose thermostructural components, since they retain the advan- cap). Most recently, the authors have develop a unique tages of silicon carbide ceramics while providing an kind of multilayer C/SiC composites with through-the- enhanced degree of damage tolerance [1, 2]. Up to now, thickness reinforcements. The composites developed have chemical vapor infiltration (CvI) has proved the most two-and-a-half-dimensional (2.5D)architecture in the real promising process for fabricate me abilities to manip- architecture reported in literature [11-15]. The characteris- ulate and modify the microstructure of the matrix, to tailor tics of the weave technique make the fabric preform partic- the fiber/matrix interface, and to fabricate complex net or ularly suitable for conforming to the mould surface of near-net shaped components at relatively low temperatures dome-shaped components(e.g, nose cap), and allow net or near-net shaping Two-dimensional C/Sic composites have been investi In order to utilize these novel composites most efi ated extensively [5-7]. However, their widespread applica- ciently, thorough understanding of their mechanical prop- ions in many structural components have been limited by erties is essential. It is well known that the fiber architecture fabrication problems and poor delamination resistance. determines the composite microstructures and microstress distribution, thereby determining the composite properties ing author. Tel. +86 29 88494616 to characterize the composite microstructures with an E-mail address: junqianqma@ kcnh com(J. Ma) emphasis on the fiber architecture and processing-induced 1359-6462/S- see front matter C 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi: 10. 1016/j-scriptamat. 2006.01.047Microstructure characterization and tensile behavior of 2.5D C/SiC composites fabricated by chemical vapor infiltration Junqiang Ma *, Yongdong Xu, Litong Zhang, Laifei Cheng, Jingjiang Nie, Ning Dong National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, 547 Mailbox, Xi’an Shaanxi 710072, People’s Republic of China Received 23 November 2005; received in revised form 18 January 2006; accepted 30 January 2006 Available online 9 March 2006 Abstract The microstructure of 2.5D C/SiC composite was characterized in terms of fiber architecture and processing-induced cracks. A geo￾metric model of the weave architecture, which can be used for visualization and further qualitative analysis, was generated. Tension tests along the warp and weft directions were conducted at room temperature. The results show that the stress–strain curves exhibit mostly nonlinear behavior. Microstructural observations reveal that the differences in tensile behavior between two loading directions are attrib￾uted to the characteristics of the weave architecture. 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Ceramic matrix composites; Weave architecture; Microstructure; Tension tests; Fracture 1. Introduction Carbon fiber reinforced silicon carbide ceramic matrix composites (C/SiC CMCs) are promising candidates for many applications, particularly as aerospace and aircraft thermostructural components, since they retain the advan￾tages of silicon carbide ceramics while providing an enhanced degree of damage tolerance [1,2]. Up to now, chemical vapor infiltration (CVI) has proved the most promising process for fabricating the composites. The pri￾mary advantages of this process are the abilities to manip￾ulate and modify the microstructure of the matrix, to tailor the fiber/matrix interface, and to fabricate complex net or near-net shaped components at relatively low temperatures [3,4]. Two-dimensional C/SiC composites have been investi￾gated extensively [5–7]. However, their widespread applica￾tions in many structural components have been limited by fabrication problems and poor delamination resistance. Although three-dimensional (3D) four-step braided C/SiC composites have improved delamination resistance and can be used to fabricate complex net or near-net shaped components [8–10], they are still not applicable for manu￾facturing components with one closed end (e.g., a nose cap). Most recently, the authors have developed a unique kind of multilayer C/SiC composites with through-the￾thickness reinforcements. The composites developed have two-and-a-half-dimensional (2.5D) architecture in the real sense, which differ significantly from the so-called 2.5D architecture reported in literature [11–15]. The characteris￾tics of the weave technique make the fabric preform partic￾ularly suitable for conforming to the mould surface of dome-shaped components (e.g., nose cap), and allow net or near-net shaping. In order to utilize these novel composites most effi- ciently, thorough understanding of their mechanical prop￾erties is essential. It is well known that the fiber architecture determines the composite microstructures and microstress distribution, thereby determining the composite properties. Therefore, the present work has two objectives. The first is to characterize the composite microstructures with an emphasis on the fiber architecture and processing-induced 1359-6462/$ - see front matter 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.scriptamat.2006.01.047 * Corresponding author. Tel.: +86 29 88494616. E-mail address: junqianqma@kcnh.com (J. Ma). www.actamat-journals.com Scripta Materialia 54 (2006) 1967–1971