Boeing Simulates Thermal Expansion on EMF Composites

J. Morgan, R. Greegor, P. Ackerman, Q. Le
Boeing, WA, USA

Carbon fiber composites are used extensively throughout the body of modern aircraft, such as the Boeing 787 Dreamliner, because of their exceptional strength and light weight. Expanded metal foil (EMF) is added to the composite structure layup as a protective measure to dissipate the extreme heat and current generated by a lightning strike. Engineers at Boeing Research and Technology (BR&T) are using multiphysics simulation and physical measurements to ensure that protective coatings on the EMF remain intact when subjected to thermal stress arising from the ground-to-air flight cycle. The impact of the EMF design parameters on stress buildup and displacement in each layer of the composite structure layup was evaluated in COMSOL Multiphysics®. Experiments correlated well with simulation results, which confirmed that designs characterized by lower displacements also have a reduced likelihood of crack formation.