Novel Method for UltraViolet (UV) Curing of Composite Structures

Recent work at CDI has seen development of a novel method of UV curing composite structures that can extend UV curing techniques to any size, thickness, or shape composite and with any type of reinforcing fiber by uniformly distributing UV light throughout a composite structure. UV curing of composites is at least an order of magnitude faster, significantly less expensive, does not require expensive manufacturing equipment (e.g., autoclave) or expensive tooling, produces an order of magnitude less organic volatiles, and produces less residual stress than thermally cured composites. However, UV curing currently is limited to thin layups with small fractions of UV opaque fiber, while new approaches currently under development at CDI can extend this process, resulting in a new UV curing process that can be used in many diverse areas, including aircraft, automotive, spacecraft, and marine applications. The process will significantly reduce the cost of manufacturing composite parts, improve the performance of these parts (by reducing residual stresses), and open new applications for composite materials using this fabrication technique. This novel UV curing technique - a process covered by U.S. Patent 6835359 (Dec. 2004) - is most attractive for large or complex composite parts.

(Left) Sketch of CDI UV curing process that utilizes specially tailored arrays of optical fibers embedded in the composite structure to ensure that UV light is uniformly and efficiently delivered throughout the volume; (right) photograph of illuminated fiber mat.

The proposed UV curing process has the potential to replace thermal curing for nearly all composite parts because it will achieve large cost and time savings while improving, or at least equaling, the thermally cured composite part performance. Additionally, the size limitations imposed by the use of an autoclave are removed because this UV curing process does not require an autoclave or any specialized tooling. Applications for this UV curing process exist in all fields, including next generation aerospace and marine vehicle applications. The great reduction in residual stress that can be obtained by curing at the desired temperature also makes this process an excellent candidate for integrated composite-metal structures. In addition, the process can be applied in situ, allowing composite structures to be cured where needed and eliminating joining issues, thus making this approach well suited to field repair applications.

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