The CoSPI project aimed at developing and manufacturing a flat stiffened skin composite panel using the infusion process. This kind of process often leads to the reduction of manufacturing costs while lessening the environmental impact of the production.
Before manufacturing the panels, we proposed to study three different processes: cold infusion, Liquid Resin Infusion and Resin Film infusion. The major development efforts were on the impact behaviour. This behaviour was a critical issue for parts obtained by infusion and has to be acceptable for primary structure parts. Several parameters were studied such as the resins, the weaving, the preform type, curing in an oven or an autoclave, in order to optimise the triptych process-composite preform-resin. Thus a trade-off study was carried out in order to choose the best infusion process in terms of mechanical behaviour, costs and environmental impact.
The environmental impact was at the heart of the CoSPI project. Minimising waste, energy consumption and the use of noxious products was one of the main objectives of this project. To achieve the objectives, the CoSPI experimented with some innovative ideas, such as the use of resins usually dedicated to pre-pregs in LRI and RFI techniques. Some new weaving method was also investigated. Thus, multiaxial warp knit fabrics were tested, again for improving the impact resistance of the panels.
Three partners were part of this project: UBO a French university, CC a Swiss SME and FMC a French SME. UBO has a wide experience of infusion processes and had already been part of projects on this topic. FMC and CC are two SMEs specialised in high technology composite parts manufacturing. They will both bring to the project solid know-how and high value equipment for coupon manufacturing.
Expected impacts involve both dissemination and training material for the academic partners and exploitation of new infusion techniques for the SMEs.
The trade-off study led to the conclusion that out-of-autoclave Liquid Resin Infusion process with powdered preforms was the best compromise to optimise the triptych process-composite preform-resin. This process had compared to well-known prepregs resins cured in autoclave. The mechanical results on static and impact tests had shown that out-of-autoclave LRI process can meet the standards required for primary structure parts. Thus, final demonstrators were manufactured using this process and the selected resin (PRISM EP2400 by Cytec). Those demonstrators were blade and J stiffened panels representing a fuselage section. Their dimensions were 1200x750mm with 5 stiffeners.