Effect of processing methods on consolidation of cobonding T-stiffened skin structure using autoclave

The integral composite structures have been widely used in aircraft industry, especially for carbon fiber reinforced resin matrix composite parts. To ensure the performances of integral structure, the manufacturing quality must be carefully controlled, which depends on the design of processing methods and processing parameters. In this article, a typical integral structure, T-stiffened skin structure was chosen and was manufactured using carbon fiber/epoxy resin prepreg with cobonding autoclave process. The influences of debulking tool assembly, curing and cobonding sequence on the consolidation quality of T-stiffened skins were studied. Thickness, surface quality at the stiffener core and defects in the composites were analyzed to evaluate the processing quality. The experimental results show that the processing procedure with two rigid tools is easier to result in voids and fiber wrinkle at the corner section than the case with flexible and rigid tool assembly, and the degree of fiber wrinkle has relationship with the precompaction and stiffener corner filling process. Moreover, the difference in thickness of the flanges can be observed, which is resulted from the uneven pressure transfer. Surface texture at the corner section can be found and is attributed to the lay-up of the prepreg stacks. In addition, the sequence of prior curing of T-stringer or skin has little effect on the quality of T-stiffened skins. These results provide important information to optimize process method for the fabrication of stiffened skin structure.