Delayed Failure of Hi‐Nicalon and Hi‐Nicalon S Multifilament Tows and Single Filaments at Intermediate Temperatures (500°–800°C)

Previous results have shown that tows of SiC Nicalon fibers are sensitive to the phenomenon of delayed failure, at temperatures below 700°C. The present paper examines the static fatigue of Hi-Nicalon and Hi-Nicalon S when subjected to constant load, at temperatures between 500° and 800°C in air. Multifilament tows and single filaments were tested. Experimental data show that the rupture times of tows depend on the applied stress according to the conventional power law tσn=A. In contrast, the stress-rupture time data obtained on single filaments exhibit significant scatter. A model based on slow crack growth in single filaments shows that the stress-rupture of fiber tows follows the conventional time power law. The dependence on temperature was introduced. The model allowed sound calculations of tow lifetimes and characteristics of the slow crack growth phenomenon to be extracted from the tow stress-rupture time data.

[1]  J. Lamon,et al.  Oxidation of Silicon Carbide Fibers During Static Fatigue in Air at Intermediate Temperatures , 2009 .

[2]  T. Kurauchi,et al.  Static fatigue of rubbery polymers: statistical approach to the failure process , 1984 .

[3]  J. Lamon,et al.  Tensile creep behaviour of a silicon carbide-based fibre with a low oxygen content , 1995, Journal of Materials Science.

[4]  Jacques Lamon,et al.  Delayed Failure at Intermediate Temperatures (600°–700°C) in Air in Silicon Carbide Multifilament Tows , 2004 .

[5]  Jacques Lamon,et al.  A micromechanics-based approach to the mechanical behavior of brittle-matrix composites , 2001 .

[6]  A. Kohyama,et al.  Tensile properties and microstructure characterization of Hi-NicalonTM SiC fibers after loading at high temperature , 2007 .

[7]  E. Lara‐Curzio.  Stress-rupture of Nicalon/SiC continuous fiber ceramic composites in air at 950 C , 2005 .

[8]  Y. Gogotsi,et al.  Oxidation and properties degradation of SiC fibres below 850 °C , 1994 .

[9]  M. Hori.  Statistical Aspects of Fracture in Concrete, I. : An Analysis of Flexural Failure of Portland Cement Mortar from the Standpoint of Stochastic Theory , 1959 .

[10]  Tadanobu Inoue,et al.  Fracture Toughness of a Crystalline Silicon Carbide Fiber (Tyranno‐SA3®) , 2006 .

[11]  E. Lara‐Curzio.  Oxidation Induced Stress-Rupture of Fiber Bundles , 1998 .

[12]  J. Lamon,et al.  Damage and failure in ceramic matrix minicomposites: Experimental study and model , 1997 .

[13]  T. Shimoo,et al.  Oxidation behavior and mechanical properties of low-oxygen SiC fibers prepared by vacuum heat-treatment of electron-beam-cured poly(carbosilane) precursor , 2003 .

[14]  I. Smith,et al.  The intrinsic reactivity of carbons to oxygen , 1978 .