In addition to the above methods for producing fibers by CVD onto a premanufactured substrate fiber, there are methods for producing fibers by insitu growth of the substrate fiber followed by a CVD step to produce a fiber having the desired composition. The predominant fiber that has been produced by this method is carbon. The driving force for development of this fiber has been the potential of lower manufacturing cost when compared to conventional carbon fiber manufacturing techniques. The use of these fibers is envisioned to be limited to secondary structural applications where discontinuous randomly oriented reinforcement can be employed.

Boron fiber is a relatively mature product; boron-epoxy composites are in production use on F-14, F-15, and B-1B aircraft. Tens of thousands of pounds of boron-epoxy composites are also currently being used in sporting goods applications. Potentially large applications for boron in the future reside in boron-aluminum composites for electronic packaging materials for airborne applications, as repair materials for civilian and military aircraft, and for aeroshells for penetrating weapons for armor or earth structures.

A production-scale application for silicon carbide fiber reinforced composites has yet to be demonstrated. However, successful tests of SCS-8 aluminum composites have been achieved in a development and test program for military aircraft sections, which has encouraged moves toward larger-scale engineering development. NASP applications could call for over 20,000 lb of SiC fiber in composites, as well.

In general, the development of production CVD fibers has involved a high degree of engineering empiricism with regard to both processing methods and design of the fiber products themselves. This approach has resulted in complexity of processing methods and belated attention to important questions—for example, strength retention at elevated temperatures, matrix interactions during consolidation heat treatments, and internal stress structure in the fiber and its effect on composite performance under realistic stress and fabrication conditions. A basic science approach to these and other problems has, in general, been lacking.

• CVD fiber for advanced applications will probably not be a multipurpose fiber, but will more likely be a specialized material having a tailored surface composition specifically aimed at matrix comparability.

• Application of an appropriate surface coating on existing fiber can markedly enhance its stability relative to either the matrix composition or to thermal and environmental conditions that the composite is subjected to during fabrication or service life.

Front Matter (R1-R16)

Executive Summary, Conclusions, and Recommendations (1-8)

1 High-Performance Synthetic Fibers for Composites (9-20)

2 High-Performance Fiber Materials: Applications, Needs, and Opportunities (21-48)

3 Fiber-Forming Processes: Current and Potential Methods (49-102)

4 Important Issues in Fiber Science/Technology (103-108)

5 Important Policy Issues (109-118)

Glossary of Terms (119-126)

Appendix (127-129)