Deposition of silicon-like hybrid films by PECVD on carbonfiber-reinforced polymers for high-precision engineering applications

Hybrid silicon-like films have been deposited by PECVD on the surface of carbonfiber- reinforced polymer (CFRP) laminates, used for micro-mechanical engineering applications where high strength-to-weight and high stiffness-to-weight ratios are required, to prevent structural distortions induced by the absorption of water vapour and water in liquid phase (hygroscopic behaviour). The films are made up of two layers: the inner layer was deposited from a mixture of hexamethyldisiloxane (HMDSO) as monomer, O2 and Ar in conditions of high monomer fragmentation to confer the material barrier properties against moisture absorption while the most superficial layer was deposited from the same monomer and feed gases in conditions of low monomer fragmentation to confer the material hydrophobic properties against the absorption of water during machining operations. Three films, made up of the same barrier layer and of three different hydrophobic layers have been grown to choose the one which best fulfils impermeability, hydrophobicity, wear and scratch resistance.