Thermal spraying processes offer a wide range of coatings with multiple functionality. However, due to the low melting point of resins, and the relatively high temperatures associated with thermal spraying, it has generally proven difficult to deposit well adhered coatings on composite substrates without damaging them.

Maximum adhesion is achieved through careful selection of coating materials, control of the surface preparation, and thermal spray process optimisation. Novel spraying techniques have been developed for depositing multi-layer and graded coatings. Hard coatings, such as WC-Co, can be deposited on CFRP following application of a bond coat. Other functional layers may also be incorporated e.g. for providing thermal insulation for protecting composites in high temperature applications.

Initial tests have shown, that in four point bending, coatings remain attached even after failure of the underlying composite. Promising fatigue results have also been achieved, with coatings surviving 0.5million cycles through significant deflection in four point bending.

Thermal spraying technology shows promise for applications within the defence and aerospace sectors, where coatings can provide multiple functions including wear resistance, thermal management, reduced IR emissions and analog absorption. This paper presents recent developments that demonstrate the feasibility of coating composite materials, such as carbon fibre reinforced polymers (CRFP), using thermal spraying processes.