The use of advanced composite materials brings to the aircraft design the benefits coming from a reduction in part counts and a simplification in the inspection and maintenance procedures. Hail, bird impacts and runway debris represent a big threat for aircraft structures and their effects shall be taken into account in the design phase leading to a redundant design and reducing the advantages coming from the use of CFRP. This problem affects in particular the regional aircrafts with their reduced fuselage thickness.
CFRPs reinforced with a structure capable to increase significantly the impact-resistance and the damage tolerance characteristics could solve most of the problems coming from the use of composite materials on sensible aircraft parts. In particular, the adoption of a metallic mesh embedded into a CFRP panel seems to be one of the most promising solutions to improve the overall performance; in particular, the SMA fibres offer the possibility to realise a high-performance composite allowing a significant increase of mechanical properties opening also the way to the multifunctionality of the future aircraft structures Cytec Engineered Materials (CEM), relying on the great experience acquired in decades of research, manufacturing and application of advanced epoxy systems to the aerospace market, can bring to this problem the know-how required to reach a smart and sustainable solution. CEM selected the most suitable materials (carbon reinforcement, resin system and metallic mesh) and identified a method for prepreg manufacturing. The activities were then focused on manufacturing and characterisation of coupons and small panels realised with the selected base constituents. Specific characterisation tests were carried out to validate the results and the results were summarised in a report including assessment and benefits.
The Resin Film Infusion process proved to be an excellent manufacturing option, given the cost and commercial availability of the selected “dry” products. The process can be easily controlled and scaled-up to satisfy the aerospace market material quantities and quality standards. NiTiNol knitted fabrics and hybrid Carbon/NiTiNol woven textiles were successfully impregnated and tested in CEM laboratories. The resulting material showed controlled resin contents and excellent levels of impregnation, visual quality and handle-ability.
Hybrid composite structures were characterised to assess the impact of NiTiNol wires in different product forms, contents and positions on key laminates mechanical performance. In addition, shape memory materials potential to enhance composite structures impact resistance and tolerance properties was evaluated. Finally, a complete microscopic (SEM) evaluation was carried out to study the fiber/matrix interface of the selected products. A technology assessment study was completed specifically focusing on the balance between SMA materials driven impact resistance/tolerance improvements versus weight penalty for each investigated material and configuration.