Cold spray and mechanical bonding technology for the production of aerospace hybrid composites

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Aircraft primary structures are constantly being redesigned for reducing weight without encumbering structural integrity and safety. Following this trend, industry leaders incorporate a greater proportion of carbon fibre reinforced composites (CFRCs) that improve the aircraft skin's strength-to-weight ratio and resistance to mechanical stress. However, issues regarding wear/erosion at specific locations arise, leading to swift degradation. This is currently solved through costly and labour intensive methods of shaping and gluing titanium sheets on CFRC skins in critical areas. It is envisioned that additive manufacturing processes can offer better alternatives to the current solution. Cold spray is a low temperature additive manufacturing process suitable for heat sensitive substrate materials, that enables depositing thin layers of material in variable thickness. This project proposes to use Nucap's GRIP Metal patented hook technology to create a bond coat on CFRCs prior to spraying. The combination of both technologies aims at enabling reliable and reproducible cold spray coatings on CFRCs through mechanical bonding, in a cost effective way. The project uses GRIP Metal steel and aluminium sheets instead of titanium to minimize costs while allowing validation of the proof of concept. CFRC plates integrating GRIP Metal sheets with different hook densities and sizes will be manufactured by laminating on uncured carbon fibre prepreg stacks. The quality of the resulting laminates will be probed. Steel coatings and aluminium coatings, depending on initial results obtained with steel, will be sprayed on the assemblies to assess the productibility of variable thickness coatings. The successful development and implementation of the proposed technology has the potential to result in major cost savings and reduced manufacturing time.