Comparison of the properties of Nextel 720/SiC composites at room temperature and 1300°C

Author: Chen Zhaofeng   Li Shibo  

Publisher: Taylor & Francis Ltd

ISSN: 1568-5543

Source: Composite Interfaces, Vol.12, Iss.5, 2005-06, pp. : 473-479

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Abstract

Continuous Nextel 720 fibers reinforced SiC composites with PyC interface are fabricated by LPCVI at 1000°C for 200 h using SiCH3Cl3 as precursor. The mechanical properties at RT and 1300°C are measured by three-point bending. The microstructures of the interface are characterized by TEM. The results indicate the composites have the metal-like behavior of fracture, whether they are at RT or high temperature. The RT and 1300°C strengths are 310 MPa and 140 MPa, respectively. The RT and 1300°C strains are 0.32% and 0.12%, respectively. The loss of flexural strength and strain of the Nextel 720/SiC composites at high temperature result from stronger residual thermal stress caused by the mismatch of CTE between fibers and matrix. A gap appears between fibers and PyC interface after the 1300°C test, which could be resulted from 7.7% compressive strain of PyC interface caused by the residual thermal stress and 0.1% sintering shrinkage of Nextel 720 fiber.