Availableonlineatwww.sciencedirect.com DIRECT● COMPOSITES SCIENCE AND TECHNOLOGY ELSEVIER Composites Science and Technology 65(2005)2541-2549 Effect of on-axis tensile loading on shear properties of an orthogonal 3D woven SiC/SiC composite Toshio Ogasawara , Takashi Ishikawa Tomohiro Yokozeki Takuya Shiraishi b, I, Naoyuki Watanabe b Advanced Composite Evaluation Technology Center, Japan Aerospace Exploration Agency(JAXA), Mitaka, Tokyo 181-0015, Japan ersity, Hino, Tokyo 191-006 Received 2 June 2005: accepted 2 June 2005 Available online 28 July 2005 Abstract The present study examines in-plane and out-of-plane shear properties of an orthogonal 3D woven SiC fiber/SiC matrix com- posite. A composite beam with rectangular cross-section was subjected to a small torsional moment, and the torsional rigidities were measured using an optical lever. Based on the Lekhnitskii's equation( Saint-Venant torsion theory) for a orthotropic material, the in-plane and out-of-plane shear moduli were simultaneously calculated. The estimated in-plane shear modulus agreed with the mod ulus measured from +45 off-axis tensile testing. The effect of on-axis(0%/90) tensile stress on the shear stiffness properties was also investigated by the repeated torsional tests after step-wise tensile loading. Both in-plane and out-of-plane shear moduli decreased by about 50% with increasing the on-axis tensile stress, and it is mainly due to the transverse crack propagation in 90 fiber bundles and matrix cracking in 0 fiber bundles. It was demonstrated that the torsional test is an effective method to estimate out-of-plane shea modulus of ceramic matrix composites, because a thick specimen is not required o 2005 Elsevier Ltd. All rights reserved Keywords: Ceramic matrix composites; Matrix cracking: Transverse cracking: Finite element analysis 1. Introduction composites, this change also involves initial cracking in he transverse (90o) plies as tunneling cracks [4-7] It is now well understood that continuous fiber ceramic Subsequently, transverse cracks penetrate the longitudi matrix composites(CMCs) exhibit nonlinear stress- nal plies as the load is increased. Based on the energy strain behavior under tensile loading as a result of multi- criterion and finite element analysis, transverse crack ple microcracking and fiber fragmentation. An overview propagation in cross-ply brittle matrix composites has of CMC mechanical properties has been provided by been analyzed [6, 7]. Shear-lag analysis is often used to Evans and Zok [1]. For unidirectional CMCs, the estimate transverse crack propagation within polymer change in stifness due to multiple matrix cracking has matrix composites [8], and this method has also beer been estimated by elastic analysis based on the Lame applied to an orthogonal 3D woven CMC as well as problem [2], and shear-lag analysis [3]. In cross-ply cross-ply CMCs [9] The effect of transverse crack on shear stiffness deg radation has been investigated for polymer matrix com Corresponding author. Tel +81 422 40 3561; fax: +81 422 40 posites. For example, Kobayashi et al. [10]investigated ressogasat(@chofu jaxa. jp(T. Ogasawara) the effect of on-axis tensile loading on degradation of Former graduate student, Currently in Mitsubishi Space Software in-plane and out-of-plane shear moduli of cross-ply car- Co, Ltd, Kanagawa, Japan. bon fiber/epoxy composites. The experimental results -3538/S- see front matter 2005 Elsevier Ltd. All rights reserved. . compscitech. 2005.06.003Effect of on-axis tensile loading on shear properties of an orthogonal 3D woven SiC/SiC composite Toshio Ogasawara a,*, Takashi Ishikawa a , Tomohiro Yokozeki a , Takuya Shiraishi b,1, Naoyuki Watanabe b a Advanced Composite Evaluation Technology Center, Japan Aerospace Exploration Agency (JAXA), Mitaka, Tokyo 181-0015, Japan b Aerospace Systems Department, Tokyo Metropolitan University, Hino, Tokyo 191-0065, Japan Received 2 June 2005; accepted 2 June 2005 Available online 28 July 2005 Abstract The present study examines in-plane and out-of-plane shear properties of an orthogonal 3D woven SiC fiber/SiC matrix com￾posite. A composite beam with rectangular cross-section was subjected to a small torsional moment, and the torsional rigidities were measured using an optical lever. Based on the Lekhnitskii
s equation (Saint–Venant torsion theory) for a orthotropic material, the in-plane and out-of-plane shear moduli were simultaneously calculated. The estimated in-plane shear modulus agreed with the mod￾ulus measured from ±45
off-axis tensile testing. The effect of on-axis (0
/90
) tensile stress on the shear stiffness properties was also investigated by the repeated torsional tests after step-wise tensile loading. Both in-plane and out-of-plane shear moduli decreased by about 50% with increasing the on-axis tensile stress, and it is mainly due to the transverse crack propagation in 90
fiber bundles and matrix cracking in 0
fiber bundles. It was demonstrated that the torsional test is an effective method to estimate out-of-plane shear modulus of ceramic matrix composites, because a thick specimen is not required. 2005 Elsevier Ltd. All rights reserved. Keywords: Ceramic matrix composites; Matrix cracking; Transverse cracking; Finite element analysis 1. Introduction It is now well understood that continuous fiber ceramic matrix composites (CMCs) exhibit nonlinear stress– strain behavior under tensile loading as a result of multi￾ple microcracking and fiber fragmentation. An overview of CMC mechanical properties has been provided by Evans and Zok [1]. For unidirectional CMCs, the change in stiffness due to multiple matrix cracking has been estimated by elastic analysis based on the Lame problem [2], and shear-lag analysis [3]. In cross-ply composites, this change also involves initial cracking in the transverse (90
) plies as tunneling cracks [4–7]. Subsequently, transverse cracks penetrate the longitudi￾nal plies as the load is increased. Based on the energy criterion and finite element analysis, transverse crack propagation in cross-ply brittle matrix composites has been analyzed [6,7]. Shear-lag analysis is often used to estimate transverse crack propagation within polymer matrix composites [8], and this method has also been applied to an orthogonal 3D woven CMC as well as cross-ply CMCs [9]. The effect of transverse crack on shear stiffness deg￾radation has been investigated for polymer matrix com￾posites. For example, Kobayashi et al. [10] investigated the effect of on-axis tensile loading on degradation of in-plane and out-of-plane shear moduli of cross-ply car￾bon fiber/epoxy composites. The experimental results 0266-3538/$ - see front matter 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.compscitech.2005.06.003 * Corresponding author. Tel.: +81 422 40 3561; fax: +81 422 40 3549. E-mail address: ogasat@chofu.jaxa.jp (T. Ogasawara). 1 Former graduate student, Currently in Mitsubishi Space Software Co., Ltd., Kanagawa, Japan. Composites Science and Technology 65 (2005) 2541–2549 COMPOSITES SCIENCE AND TECHNOLOGY www.elsevier.com/locate/compscitech