THERMOMECHANICAL PROPERTIES OF CERAMIC FIBERS FOR STRUCTURAL CERAMIC MATRIX COMPOSITES

摘要

For high-temperature applications, the structural performance of ceramic matrix composites (CMC) depends strongly on the reinforcing ceramic fibers displaying certain key properties. These include high fast-fracture, creep, and rupture strength, as well as high thermal conductivity across a wide range of CMC service conditions. Today numerous small-diameter polycrystalline ceramic fibers are commercially available which display these properties to various degrees. Fiber types of current CMC interest are the alumina-based Nextel 610, 650, and 720 fibers, the SiC-based non- stoichiometric Nicalon, Hi-Nicalon and ZMI fibers, and the SiC-based near-stoichiometric Hi-Nicalon Type S, Tyranno SA, Sylramic, and Sylramic-iBN fibers. This presentation reviews and compares the various strength properties of these fiber types as measured from room temperature to 1400℃ in various environments. It is shown that besides fiber composition, these strength properties are also strongly affected by fiber form, such as single fiber, tow, and fabric, and by the fiber environments expected during CMC fabrication and service. Underlying mechanisms are discussed in order to indicate the microstructural benefits of the best performing fiber types and to guide fiber selection for high-temperature CMC applications.