Conductive surfacing material for composite structures

A method of fabricating a composite structure comprising:

• forming a surfacing material in the form of a tape comprising:
• (a) an electrically conductive layer having two opposite surfaces and a thickness of less than 3 mils and resistivity less than 10 mΩ;
• (b) a resin film formed on at least one surface of the conductive layer, wherein the resin film is formed from a curable composition comprising:
• an epoxy novolac resin having the following chemical structure:
• where n =0 to 5, and R =H or CH3;
• a non-novolac tri-functional or tetra-functional epoxy resin;
• ceramic microspheres;
• a latent amine-based curing agent;
• particulate inorganic fillers;
• and
• a toughening component comprising:
• (i) a pre-react adduct formed by the reaction of an epoxy resin, a bisphenol, and an elastomer and (ii) at least one of a copolymer of polyether sulfone (PES) and polyetherether sulfone (PEES) and core-shell rubber (CSR) particles;
• laying up prepreg tapes in an automated placement process to form a composite structure, each prepreg tape comprising reinforcing fibers impregnated with a matrix resin;
• incorporating the surfacing material into the automated placement process so that the resin film of the surfacing material forms an outermost layer in the final composite structure;
• and
• curing the final composite structure, wherein the cured resin film of the surfacing material exhibits a pencil hardness of 7H to 9H according to ASTM D-3363.