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

Authors: Chen, Zhaofeng; Li, Shibo

Source: Composite Interfaces, Volume 12, Number 5, 2005 , pp. 473-479(7)

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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.

Keywords: MECHANICAL PROPERTIES; NEXTEL 720/SIC COMPOSITE; LPCVI; PYC INTERFACE; GAP; RESIDUAL THERMAL STRESS

Document Type: Letter section

DOI: http://dx.doi.org/10.1163/1568554054275706

Publication date: 2005-06-01