Stiffened composite panels are integral to many aircraft structures, including the wings and fuselage. Their widespread use has enabled significant reductions in aircraft load and associated fuel consumption and emissions. However, the equipment is expensive and the process consumes a significant amount of energy. The EU-funded COSPI (Composite stiffened panels infusion) project set out to compare various infusion processes as alternatives to autoclave processing in order to reduce cost and environmental impact. The goal was to optimise the combination of infusion process, composite (dry fibre) preform and resin while ensuring mechanical performance acceptable for aircraft primary structures. Researchers investigated three infusion processes with and without the use of an autoclave. The processes were exploited in combination with eight different resins and two types of preforms (powdered and stitched). The parametric evaluation demonstrated that the out-of-autoclave liquid resin infusion process with powdered preforms optimised the mechanical performance, meeting the standards required of primary aircraft structures. The final demonstrators, a blade and panels representing a fuselage section, were manufactured using this combination. The COSPI project demonstrated that the liquid resin infusion process can be used without an autoclave to produce composite stiffened panels meeting aircraft primary structure mechanical requirements. This provides an important alternative to the standard usage of expensive and energy-intensive autoclaving without compromising performance. Outcomes will be optimised in continued work within the scope of the EU's most ambitious research programme ever to reduce the environmental impact of flight.
Aircraft, composites, autoclave, fuselage, stiffened panels, infusion process, resin