DEVELOPMENT OF CONDUCTIVE LIGHTWEIGHT NANOFIBER REINFORCED COMPOSITE FOR AIRCRAFT LIGHTNING STRIKE PROTECTION

During the last few decades, application of carbon fiber reinforced polymer (CFRP) composites in aircraft structural elements have been steadily increased. CFRP composites are lightweight, corrosion resistant and possesses better mechanical properties, fatigue resistance and lower thermal expansion. However, they are nearly 2000 times less electrically conductive than previously used aluminum alloys which makes them prone to serious structural damage in the event of a lightning strike. To protect the aircraft, the outer surface is covered with highly conductive metallic jacket which consequently reduces the weight advantage of the CFRP composite. There is a dire need for a lightweight alternative for lightning strike protection which will be just as effective. In this study, electrospun carbon nanofibers were coated with copper to develop a conductive nanofiber network. When it comes to electrical properties, copper and carbon shows complementary characteristics. Copper is better in electrical conductivity and possesses low contact resistance where carbon is very lightweight and have high current carrying capability. Despite having exceptionally high electrical conductivity when tested individually, carbon allotropes show much less conductivity in macro-scale primarily due to high contact resistance. By coating the carbon with copper, carbon-carbon contact was replaced by copper-copper contact, hence reducing the contact resistance. Copper coatings were mostly less than 100 nm in thickness, so it kept the weight gain to a minimum. The study shows significant decrease in sheet resistance in the resultant conductive filler in comparison to the carbon nanofiber mat. Copper coating parameters were successfully optimized to ensure homogeneous coating thickness throughout the structure.