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The aerospace industry is incessantly investigating innovative techniques to increase aircraft fuel efficiency. As a consequence of innovative efforts, the cost of flying is continuously reduced and the aircraft’s mechanical performance improved. To achieve an important weight reduction, the fuselage of aircrafts like the Boeing 787 ‘‘Dreamliner’’ is mainly made of carbon fiber based composites. Having a high material specific strength-to-weight ratio, carbon fiber reinforced composites are state of the art materials in the aerospace industry. The in-flight concern of having the aircraft subjected to lightning is an ongoing safety issue. In the event of a lightning striking the fuselage, localized melting of the composite will commonly occur, as carbon fiber reinforced composites are highly resistive materials. A current design solution to prevent the fuselage from extended damaging/melting is to integrate an embedded metallic mesh between the carbon fiber composite plies. Upon lightning strike on the external skin of the composite material, the electrical current dissipates through the metallic mesh, thus minimizing damages of the composite part to localized melting. In addition to the integrated mesh, another solution to minimize/prevent localized melting of the composite is to rivet relatively thick and heavy metallic protective plates over the components prone to lightning such as the nose and wing tips of the aircraft. To resolve weight issues arising from heavy riveted plates, it would be advantageous to deposit thin layers of conductive material on the carbon fiber based composite surface. Unfortunately, high operating temperatures of conventional thermal spray processes used to apply a metallic overlay would degrade the carbon fiber based composites. For the purpose of producing metallic coated carbon fiber based composites, a new innovative technique which combines Cold Gas Dynamic Spray and lay-up moulding of composites is envisioned. This current study presents a detailed description of the experimental approach developed to produce metallic coated composites and demonstrates the manufacturability of such components at the commercial scale. Technical prerequisites, such as obtaining a low resistivity metallized composite and producing an easily removable metallic layer from the mould during lay-up moulding, are essential for the production of such aerospace materials. The thesis results obtained at the University of Ottawa Cold Spray Laboratory show that highly conductive and dense metallized composites could be produced. |
