Bicomponent extrusion of ceramic fibers

One of the main problems facing composite fabricators is finding high-temperature ceramic reinforcement fibers that are compatible with their matrices. Unlike metal-matrix composites, which require relatively large diameter fibers and a good bond between fibber and matrix, ceramic-matrix composites requires small diameter fibers having a weaker bond between fiber and matrix. Furthermore, they require an interfacial barrier that dissipates crack propagation energy without being absorbed by the matrix. Process speed is another important concern, because it influences the ultimate cost of the reinforcement fiber. To overcome these problems, a process has been developed to extrude, in a one-pass operation, a bicomponent (core/sheath) fiber system. It is designed to handle either oxide or non-oxide reinforcement core material, with a matching sheath material that acts as an interface between the core and its matrix, and also absorbs crack propagation energy. This article provides a closer look at the patented bicomponent extrusion process, which was developed by the author. Initial development has been undertaken with simple laboratory equipment. Therefore, only the very smallest scale extrusion has been attempted, and no characterizations have been made apart from simple bend tests against such commercially available fibers as Sigma (DRA), Tyranno (Ube), and Nicalon NL607 (Nipponmore » Carbon).« less