Metallization of fiber reinforced composite by surface functionalization and cold spray deposition

The cold spray deposition process has gained interest as a promising technique for producing metallic coatings on polymers and composite materials thank to its low working temperatures. However, poor adhesion of metallic particles on polymeric substrates and the brittle nature of these materials lead to generation of cracks under the impact of the sprayed particles, limiting its application to polymeric matrix composite. The interposition of an intermediate metallic layer over the thermoset composite to be coated has been claimed to improve the adhesion of the sprayed particles and the formation of a stable link between the metal coating and the underlying polymer panel. The present work discusses a methodology that integrates the manufacturing of glass reinforced epoxy panels having functionalized surface and the subsequent production of a dense metallic layer by cold spray. Pure copper and titanium metallic powders, having spherical and irregular shape respectively, were placed on the top of the stack of dry glass fiber fabrics. Resin infusion process was then applied to impregnate the glass fabrics providing the simultaneous functionalization of the composite panel. In order to assess the effectiveness of the produced substrate, and of the proposed procedure, metallic coatings have been finally deposited on manufactured composite panels by means of a low-pressure cold spray facility. Regardless the spraying condition (namely gas temperature, stand-off distance, sprayed particles), copper samples showed a remarkable erosion of functionalized layer after cold spray process with pronounced damages of the composite substrate. On the other hand, effective depositions have been observed on titanium samples under specific combination of process parameters.