High temperature structural fibers: Status and needs

The key to high temperature structural composites is the selection and incorporation of continuous fiber reinforcement with optimum mechanical, physical, and chemical properties. Critical fiber property needs are high strength, high stiffness, and retention of these properties during composite fabrication and use. However, unlike polymeric composites where all three requirements are easily achieved with a variety of commercially available carbon-based fibers, structural fibers with sufficient stiffness and strength retention for high temperature metal, intermetallic, and ceramic composites are not available. The objective here is to discuss in a general manner the thermomechanical stability problem for current high performance fibers which are based on silicon and alumina compositions. This is accomplished by presenting relevant fiber property data with a brief discussion of potential underlying mechanisms. From this general overview, some possible materials engineering approaches are suggested which may lead to minimization and/or elimination of this critical stability problem for current high temperature fibers.