No process variable (other than, perhaps, molecular cross linkage) is likely to significantly improve the tendency toward compressive failure in these highly oriented materials. Process parameters are also unable to affect use temperatures, which will remain in a range well below those of ceramics.

The application of blend concepts has been exploited to a relatively small extent. The field of engineering resins has demonstrated the potential of blending to result in order-of-magnitude property changes.

The commercially announced fibers from liquid crystalline melts illustrate the strong Japanese effort toward development of fibers discovered in the United States. This reflects the unwillingness of American industry to commercially develop new materials with a limited current market.

Although industry is doing little fundamental research on organic fibers, development in general will be handled by industry more effectively than for the other fibers discussed in this report because the organics have a broader commercial market. This indicates that limited government resources should be applied to the more specialized inorganics.

The use of precursors that can be pyrolyzed to form continuous inorganic filaments has provided a route to the manufacture of synthetic inorganic fibers of many different compositions. The precursor materials include polymers, concentrated salt solutions that may behave like polymeric materials, polymer-modified solutions and slurries, and sol-gel systems. Polymeric precursors are used for the fabrication of continuous nonoxide filaments such as carbon, graphite, and silicon carbide (sic). Oxide fibers are produced from all of the precursor types listed above.

Since the rheological properties necessary for spinning continuous filaments at high speed are provided by the polymeric-type material present in the fiber-forming precursor composition, spinability of the final fiber composition in its fused form is not a necessary property, as it is in the forming of traditional glass filaments. Therefore, materials such as aluminum oxide (A1₂O₃) or zirconium oxide (ZrO₂) and many others may be prepared in fiber form, even though the properties of their liquid phases would not normally permit fiber spinning at any practical rate. Similarly, fibers of materials not generally considered to melt, such as carbon (c) and SiC, are also prepared by this technology. Polymeric materials may embody in their composition all of the precursor components of the final solid inorganic, such as SiC or C, or they may be present principally for their contribution to fiberizing properties. In the latter case, the polymer may be completely fugitive, while the actual fiber components exist in the precursor formulation as decomposable salt compounds or as colloids added as particles or compatible sols such as aqua sols.¹ Thus, formation of the inorganic fiber precursor (or organic in the case of carbon fibers) involves spinning melted polymeric

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)