Search

Usually, carbon-fiber/polymeric composite parts have been assembled manually and cured using autoclave techniques. To reduce labor costs and to enable the manufacture of composite parts larger than available autoclaves, an automated fiber placement process is being developed. In this process composite parts are fabricated one layer at a time from polymer-impregnated carbon fibers in tapes of various widths. As the fibers come into contact with the part, heat and pressure are applied to consolidate the fibers with the part, as shown in., This article is from 'Ceramic Transactions. Volume 21. Proceedings of the Symposium on Microwave Theory and Application in Materials Processing Annual Meeting of the American Ceramic Society (23rd) Held in Cincinnati, Ohio on April 29 - May 3, 1991,' AD-A253 631, p539-546.

Nuclear magnetic resonance (NMR) was studied for use in the nondestructive evaluation of composite materials, with particular emphasis on NMR imaging. NMR parameters of potential use for generating images showing high contrast between acceptable and unacceptable regions of composites were measured for typical organic matrix materials. The attenuating effects of carbon fibers were measured and relationships were developed to compute the conditions necessary to obtain images of carbon-fiber composites. NMR images of aerospace composites containing poly(aryl-ether-ether-ketone) (PEEK) and epoxy resins were obtained using solid state 13C techniques. The contrast mechanism used for these images was the composites. NMR images of hydrogen in PEEK were also obtained using multiple-pulse techniques to reduce dipolar broadening. Selective pulses were used to obtain images of the spatial variations in the crystalline content of PEEK. The results of these experiments were used to assess the feasibility of using NMR for nondestructive evaluation of composite materials.