Direct Copper Metallization of Carbon Fiber-Reinforced Thermoplastic Polymers for Lightning Strike Protection Using Low-Pressure Cold Spray

Abstract

Metallizing polymer composite via cold spray is an attractive process for producing lightning strike protection (LSP) in composite-based aircraft. However, direct deposition of copper, the most common conductive metal, on carbon fiber-reinforced thermoplastic polymers (CFRTP) remains challenging due to the severe polymer erosion and carbon fiber fracture induced by cold-sprayed multi-particle impact. In this work, the copper direct deposition window was explored by varying copper particle size and operating gas temperature, which are primary parameters determining particle impact energy. Following this, a lightning strike test was performed to evaluate the protective effectiveness of the deposited copper coating in reducing damage to the underlying CFRTP substrate. It was revealed that fine copper particles approximately 5 µm in diameter are effective for direct deposition due to their minimal induction of polymer erosion. Sufficient heating of the particle spray area above the glass transition temperature promoted continuous coating formation. The lightning strike tests demonstrated that the cold-sprayed copper coating effectively protects the underlying CFRTP by acting as a major electric current path and a sacrificial protective layer. These findings highlight the promising potential of cold spray as a new LSP technology for polymer composite aircraft.