Metallic Coatings for Graphite/Epoxy Composites

Metallic coating systems for graphite/epoxy laminated aircraft structures were developed to provide protection against moisture penetration, electromagnetic interference (EMI), paint strippers and lightning strikes. Foil coatings and pressed powder coatings were evaluated to assess their resistance to these hostile environments. The foil coatings provided a significant reduction in the moisture penetration and the associated strength loss of the laminate after exposure to humidity and humidity-thermal spiking. Techniques were developed for the application of foil coatings to graphite/epoxy laminates. Solid and perforated aluminum foil were applied to cured laminates in a secondary bonding operation. Sulfur dioxide/salt spray testing performed on foil-coated laminates did not indicate a severe corrosion problem.