Boeing simulates thermal expansion in composites with expanded metal foil for lightning protection of aircraft structures

摘要

The Boeing 787 Dreamliner is innovative in that it is comprised of more than 50% carbon fibre-reinforced plastic (CFRP) due to the material's light weight and exceptional strength. Figure 1 shows the extensive use of composite materials throughout the aircraft. Although CFRP composites inherently have many advantages, they cannot mitigate the potentially damaging electromagnetic effects from a lightning strike. To solve this problem, electrically-conductive expanded metal foil (EMF) can be added to the composite structure layup to rapidly dissipate excessive current and heat for lightning protection of CFRP in aircraft. Engineers at Boeing Research and Technology (BR&T) are using multiphysics simulation and physical measurements to investigate the effect of the EMF design parameters on thermal stress and displacement in each layer of the composite structure layup shown at left in Figure 2. Stress accumulates in the protective coating of the composite structure as a result of thermal cycling due to the typical ground-to-air flight cycle. Over time, the protective coating may crack, providing an entrance for moisture and environmental species that can cause corrosion of the EMF, thereby reducing its electrical conductivity and ability to perform its protective function. Contributing to the research effort at BR&T are project lead Jeffrey Morgan from Sealants and Electromagnetic Materials, Associate Technical Fellow Robert Greegor from Applied Physics leading the simulation, Dr. Patrice Ackerman from Sealants and Electromagnetic Materials leading the testing, and Technical Fellow Quynhgiao Le. Through their research, they aim to improve overall thermal stability in the composite structure and therefore reduce the risks and maintenance costs associated with damage to the protective coating.