MIATERIALS SENE S ENGEERING ELSEVIER Materials Science and Engineering A345 (2003)28-35 Mechanical properties of several advanced Tyranno-SA fiber reinforced CVI-SiC matrix composites Wen Yang a, b *, Tetsuji Noda Hiroshi Araki, Jinnan Yu, Akira Kohyama d Kohyama laboratory, Institute of Adranced Energy, Kyoto University, Kyoto 611-0011, Japan Nano-Material Laboratory, Nano-Fabrication Research Group, 5th Sub-Group, National Institute for Materials Science, CREST, 1-2-1 Sengen Tsukuba, Ibaraki 305-0047, Japan China Institute of Atomic Energy, 102413 Beijing, PR China CREST, Japan Science and Technology Corporation, 4-1-8 Kawaguchi, Saitama 332-0012, Japan Received 30 November 2001: received in revised form 7 March 2002 Co A recently developed SiC fiber, Tyranno-SA (2D plain-woven ) was used as the reinforcement in several SiC/SiC composites. The re fabricated by chemical vapor infiltration(CVi)process. The mechanical properties and fracture behaviors were investigated using three-point bending test. The Tyranno-SA fiber possesses rough fiber surface with pure SiC surface chemistry, which may result in strong fiber/matrix bonding and fiber sliding resistance. Various pyrolytic carbon(PyC) and SiC/PyC interlayer coatings were applied in the composites to modify the mechanical properties of the interface. The interlayers were deposited by isothermal CVI process. The test results revealed a close Pyc layer dependence of the strength of the composites. The ultimate flexural strength(UFS)increased with the increasing of the Pyc layer thickness up to 100 nm, and then, kept at similar level till 200 nm. The Tyranno-SA/SiC composites exhibited relatively high proportional limit stresses due mainly to the large Youngs modulus of the fiber. Fiber pullouts were observed at the fracture surfaces of all the interlayered composites. Attractive promising was exhibited on further improvement of the mechanical properties of the composites through further improvement of the interfacial properties and the matrix densification process C 2002 Elsevier Science B V. All rights reserved Keywords: Tyranno-SA fiber; Chemical vapor infiltration(CVn) process; PyC and SiC/PyC interlayer coatings; Flexural properties 1. Introduction For SiC/SiC composites, the property of fiber/matrix interface is one of the key factors [7-ll] that determine There is a strong and increasing interest in the r&d the materials performance, primarily because that of continuous SiC fiber reinforced Sic matrix compo- damage tolerance results from the deviation of matrix sites(SiC/SiC composites)for a variety of high-tem- cracks into the interfaces. This phenomina can be perature, high-stress applications in aerospace, hot controlled through deposition of a thin coating layer engine and energy conversion systems [1-4]. They are on the fibers. Carbon remains the most frequently used also quite attractive candidates for blanket first wall interlayer. Recently, an alternating multiple interlayers structures in nuclear fusion power systems due mainly to (pyrolytic carbon(PyC)-SiC)n, have been developed for their inherent low induced radioactivation. radiation improved oxidation and radiation resistance [12-14 resistance and chemical stability at elevated tempera- However, the understandings already established are tures [1, 5, 6 mostly for the old-generation SiC-based fibers such Nicalon-CG. Recently an advanced fiber, Tyranno-SA which is predominantly B-Sic crystals with a near stoichiometric C/Si atomic ratio, has been developed Corresponding author. Tel: +81-298-59-2842: Fax: +81-298-59 Ube Industry Ltd Japan[15]. Several selected proper ties of the Tyranno-SA fiber are listed in Table 1. This E-mail address: yang wen(@nims.go. jp (W. Yang). fiber exhibits excellent mechanical properties, coupled 0921-5093/02S ter c 2002 Elsevier Science B.V. All rights reserved. PI:S092150Mechanical properties of several advanced Tyranno-SA fiber￾reinforced CVI-SiC matrix composites Wen Yang a,b,
, Tetsuji Noda b , Hiroshi Araki b , Jinnan Yu c , Akira Kohyama d a Kohyama laboratory, Institute of Advanced Energy, Kyoto University, Kyoto 611-0011, Japan b Nano-Material Laboratory, Nano-Fabrication Research Group, 5th Sub-Group, National Institute for Materials Science, CREST, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan c China Institute of Atomic Energy, 102413 Beijing, PR China d CREST, Japan Science and Technology Corporation, 4-1-8 Kawaguchi, Saitama 332-0012, Japan Received 30 November 2001; received in revised form 7 March 2002 Abstract A recently developed SiC fiber, Tyranno-SA (2D plain-woven), was used as the reinforcement in several SiC/SiC composites. The composites were fabricated by chemical vapor infiltration (CVI) process. The mechanical properties and fracture behaviors were investigated using three-point bending test. The Tyranno-SA fiber possesses rough fiber surface with pure SiC surface chemistry, which may result in strong fiber/matrix bonding and fiber sliding resistance. Various pyrolytic carbon (PyC) and SiC/PyC interlayer coatings were applied in the composites to modify the mechanical properties of the interface. The interlayers were deposited by isothermal CVI process. The test results revealed a close PyC layer dependence of the strength of the composites. The ultimate flexural strength (UFS) increased with the increasing of the PyC layer thickness up to 100 nm, and then, kept at similar level till 200 nm. The Tyranno-SA/SiC composites exhibited relatively high proportional limit stresses due mainly to the large Young’s modulus of the fiber. Fiber pullouts were observed at the fracture surfaces of all the interlayered composites. Attractive promising was exhibited on further improvement of the mechanical properties of the composites through further improvement of the interfacial properties and the matrix densification process. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Tyranno-SA fiber; Chemical vapor infiltration (CVI) process; PyC and SiC/PyC interlayer coatings; Flexural properties 1. Introduction There is a strong and increasing interest in the R&D of continuous SiC fiber reinforced SiC matrix compo￾sites (SiC/SiC composites) for a variety of high-tem￾perature, high-stress applications in aerospace, hot engine and energy conversion systems [1/4]. They are also quite attractive candidates for blanket first wall structures in nuclear fusion power systems due mainly to their inherent low induced radioactivation, radiation resistance and chemical stability at elevated tempera￾tures [1,5,6]. For SiC/SiC composites, the property of fiber/matrix interface is one of the key factors [7/11] that determine the materials performance, primarily because that damage tolerance results from the deviation of matrix cracks into the interfaces. This phenomina can be controlled through deposition of a thin coating layer on the fibers. Carbon remains the most frequently used interlayer. Recently, an alternating multiple interlayers, (pyrolytic carbon (PyC)/SiC)n , have been developed for improved oxidation and radiation resistance [12/14]. However, the understandings already established are mostly for the old-generation SiC-based fibers such as Nicalon-CG. Recently an advanced fiber, Tyranno-SA, which is predominantly b-SiC crystals with a near stoichiometric C/Si atomic ratio, has been developed (Ube Industry Ltd. Japan) [15]. Several selected proper￾ties of the Tyranno-SA fiber are listed in Table 1. This fiber exhibits excellent mechanical properties, coupled
Corresponding author. Tel.: /81-298-59-2842; Fax: /81-298-59- 2801 E-mail address: yang.wen@nims.go.jp (W. Yang). Materials Science and Engineering A345 (2003) 28/35 www.elsevier.com/locate/msea 0921-5093/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 5 0 9 3 ( 0 2 ) 0 0 4 6 8 - 9