Performance of painted and non-painted non-woven nickel-coated carbon fibers for lightning strike protection of composite aircraft

This study investigates the performance of non-woven nickel-coated carbon fibers with varying sheet resistivity as potential solutions for lightning strike protection of composite aircraft, with a focus on the influence of the paint layer on top of the protection. Carbon/epoxy laminates protected by nickel-coated carbon fibers were subjected to lightning strike tests (modified A-waveform), and the heat transfers in the composite were observed using an infrared camera. The damages were analyzed with C-Scan and CT-Scan, and the retention of mechanical properties in bending was characterized via 4-point bending tests. The sheet resistivity, depth and area of damages, retention of mechanical properties, additional cost and weight were then compared to the expanded copper foil currently used in the aerospace industry, with and without a paint layer. With an additional weight of at most 140g m⁻², nickel-coated carbon fibers are lighter than expanded copper foil (325g m⁻²), while providing 100% of retention of flexural strength after lightning strike, better than the expanded copper foil (90%). However, adding a paint layer decreases the retention of flexural strength to at best 87% when the composite is protected by nickel-coated carbon fibers, but has a very small effect on composites protected by an expanded copper foil.