CARBON 47(2009)I034-I04 1035 to different fiber architectures. The axial TRS in the direction composites were laminated with [0/90 carbon fiber-cloth of loading and ultimate tensile strength(UTS)of these com- layers [11]. Fig. 1c illustrates that in the 2. 5D C/Sic the warp posites with different fiber architectures were predicted theo- yams take on an approximately sinusoidal path, and the weft retically and then validated by the experimentally measured yams present cross-sectional shapes of lentils and parallelo results and microstructural observations grams alternately. Obviously, the warp yams undertake dual roles: main contribution to in-plane strength and particular Experimental procedures contnbuti on to improve delamination resistance[12 Fig. 1d shows that in the 3d C/Sic all the carbon fibers are braided 2.1 Materials along the load direction with a small angle of 0 z 22[131 The fiber volume fraction of each preform approximated to There were four types of C/Sic composites involved in this 40 vol. for the woven composites and 32% for the needled dy, i.e., needled C/SiC, 2D C/SiC, 2.5D C/SiC, and 3D C/Sic. composites. The density and porosity of the infiltrated com- These composites were processed by using the same isother- posites are listed in Table 1 mal chemical vapor infiltration(cvD)of Sic into the different carbon fiber preforms at x1000C. The detailed processing 2. 2. Mechanical tests procedures of the four C/Sic composites have been described ts 3D views of Periodic loading-unloading-reloading tests were con rchitecture of the as-fabricated Sic-matrix composites with ducted at room temperature on a servo-hydraulic load-frame different carbon fiber preforms. The needled C/SiC materials, with a loading rate of 0.06 mm/min(Instron 8801, Instron Ltd as shown in Fig. 1a, composed of the layers of o non-woven High Wycombe, England). Strain was assessed directly by a Dee cloth, short fiber web, 90 non-woven fiber cloth, and contact Instron extensometer with a gauge length of 25 mm. needled fibers. The layers of o non-woven fiber cloth, short The data generated from each hysteresis cycle is stored on fiber web, and 90 non-woven fiber cloth were repeatedly hard-disc of a personal computer and then analyzed in accor- erlapped [10]. In this kind of structure, non-woven cloth dance with the loading-unloading procedures. The cyclic parallel to the loading direction to improve the load-bearing unloading-reloading tests were performed up to final rupture capacity of the materials. Fig. 1b shows that the 2D C/Sic of the composite specimens with emphasis on the achieve 15a25m×0MA Fig. 1-Three-dimensional presentations of fiber architectures in(a)needled C/Sic, (b)2D C/Sic, (c)2.5D C/sic, and (d)3D C/sicto different fiber architectures. The axial TRS in the direction of loading and ultimate tensile strength (UTS) of these com￾posites with different fiber architectures were predicted theo￾retically and then validated by the experimentally measured results and microstructural observations. 2. Experimental procedures 2.1. Materials There were four types of C/SiC composites involved in this study, i.e., needled C/SiC, 2D C/SiC, 2.5D C/SiC, and 3D C/SiC. These composites were processed by using the same isother￾mal chemical vapor infiltration (CVI) of SiC into the different carbon fiber preforms at 1000 C. The detailed processing procedures of the four C/SiC composites have been described elsewhere [10–13]. Fig. 1 presents 3D views of typical fiber architectures of the as-fabricated SiC-matrix composites with different carbon fiber preforms. The needled C/SiC materials, as shown in Fig. 1a, composed of the layers of 0 non-woven fiber cloth, short fiber web, 90 non-woven fiber cloth, and needled fibers. The layers of 0 non-woven fiber cloth, short fiber web, and 90 non-woven fiber cloth were repeatedly overlapped [10]. In this kind of structure, non-woven cloth parallel to the loading direction to improve the load-bearing capacity of the materials. Fig. 1b shows that the 2D C/SiC composites were laminated with [0/90] carbon fiber-cloth layers [11]. Fig. 1c illustrates that in the 2.5D C/SiC the warp yarns take on an approximately sinusoidal path, and the weft yarns present cross-sectional shapes of lentils and parallelo￾grams alternately. Obviously, the warp yarns undertake dual roles: main contribution to in-plane strength and particular contribution to improve delamination resistance [12]. Fig. 1d shows that in the 3D C/SiC all the carbon fibers are braided along the load direction with a small angle of h 22 [13]. The fiber volume fraction of each preform approximated to 40 vol.% for the woven composites and 32% for the needled composites. The density and porosity of the infiltrated com￾posites are listed in Table 1. 2.2. Mechanical tests Periodic loading–unloading–reloading tests were con￾ducted at room temperature on a servo-hydraulic load-frame with a loading rate of 0.06 mm/min (Instron 8801, Instron Ltd., High Wycombe, England). Strain was assessed directly by a contact Instron extensometer with a gauge length of 25 mm. The data generated from each hysteresis cycle is stored on hard-disc of a personal computer and then analyzed in accor￾dance with the loading–unloading procedures. The cyclic unloading–reloading tests were performed up to final rupture of the composite specimens with emphasis on the achieve￾Fig. 1 – Three-dimensional presentations of fiber architectures in (a) needled C/SiC, (b) 2D C/SiC, (c) 2.5D C/SiC, and (d) 3D C/SiC composite specimens. CARBON 47 (2009) 1034 – 1042 1035