Mass-Reduced Lightning Strike Protection in Aircraft Panels
Summary
Lightning strikes pose a threat to aircraft structural integrity as well as the pilots and people aboard aircraft, due to structural damage and electromagnetic interference from the lightning strike. Lightning strike protection (LSP) is a critical requirement in modern aircraft structures, particularly for carbon fiber reinforced polymer (CFRP) composites, which exhibit low electrical conductivity compared to metallic materials. During a lightning strike event, intense localized Joule heating occurs and rapid temperature gradients within the material form. Due to the anisotropic conductivity of CFRP, where carbon fibers are conductive but the polymer matrix is insulating, current flow becomes highly non-uniform, leading to localized hotspots. Delamination, in particular, occurs due to rapid thermal expansion of the matrix and vaporization of entrapped gases, which generate internal pressure between plies and weaken interfacial bonding. To mitigate these effects, conductive pathways must be incorporated into CFRP laminates to safely dissipate electrical energy and prevent catastrophic structural damage. Currently, the aerospace industry relies heavily on expanded copper mesh embedded within composite laminates as the standard solution for LSP. While this approach is effective in distributing current and reducing damage, it introduces significant weight penalties and increases manufacturing complexity. As the demand for lightweight and fuel-efficient aircraft continues to grow, reducing unnecessary structural mass has become a major engineering priority. This is especially relevant in lightning strike Zone 2A regions, where current intensities are lower than direct strike zones but still require sufficient electrical conductivity to prevent localized damage. Recent research has focused on alternative conductive materials, including metallic coatings and conductive veils, as potential replacements for traditional copper mesh systems. These materials aim to provide comparable electrical performance while significantly reducing weight and improving design flexibility. Additionally, coating morphology, thickness, and continuity play a critical role in determining both electrical conductivity and mechanical integrity. Among these alternatives, carbon veils coated with conductive metals such as copper and copper-nickel have emerged as promising candidates for lightweight LSP applications. Therefore, this study aims to evaluate and compare copper-coated carbon veil (CCCV) and nickel-copper-coated carbon veil (NCCCV) as alternatives to copper mesh for lightning strike protection materials for CFRP laminates. By establishing the relationship between coating properties and performance, this project seeks to determine the feasibility of replacing conventional copper mesh for Zone 2A applications with more weight-efficient materials.
Technical Approach/Methodology
Our methodology involves manufacturing three 10” x 10” composite test coupons using three different lightning strike protection (LSP) materials: copper mesh, copper-coated carbon veil (CCCV), and nickel-copper-coated veil (NCCCV). These samples will undergo a series of electrical and mechanical characterization tests, including four-point probe conductivity testing, compressive strength testing, and scanning electron microscopy (SEM). The conductivity measurements will serve as an indicator of potential lightning strike performance, while compression testing will be used to examine the surface morphology and internal microstructural features of the conductive layers.
Based on the conductivity results of the CCCV and NCCCV samples, the higher-performing veil system will be selected for fabrication into a larger 16” x 16” panel alongside a traditional copper mesh panel, which will serve as the industry-standard control. The primary experiment will involve exposing both large panels to a simulated lightning strike current of approximately 100 kA to replicate real aircraft lightning strike conditions.
Post strike evaluation will include CT scanning to measure internal damage depth and delamination volume, optical microscopy to analyze surface damage modes, and compression after impact testing to determine the retained mechanical strength following lightning exposure. Additional SEM analysis will also be performed to examine the integrity of the dielectric veil layer and identify failure mechanisms such as delamination, fiber pullout, matrix cracking, or thermal degradation.
Outcomes
We will produce two 16” by 16” LSP panels, one incorporating the copper mesh, and one incorporating the CCCV that will be subject to a lightning strike test and indicate whether or not CCCV offers any improvement over copper mesh. The goals of the project are to reduce the weight of the overall panels and to improve damage resistance of the panels (measured in compressive strength retained, visible damage area, and length of delaminations).