ABSTRACT
Since the advent of laminated fiber reinforced composite materials about four decades ago, their applications in the load bearing structures have been wide spread especially in aerospace systems. The next notable evolution in aerospace systems requires advanced and enabling structures that are lighter, more reliable, less expensive, survivable, and satisfy the multifunctional design goals. New materials are needed to satisfy these competing and demanding requirements. Recent advances in nanocomposites have shown promise of fulfilling these multifunctional roles. A polymer reinforced with only a few percent of electrically conductive nanofibers can make them electrically conductive and hence, suitable for several applications. Two notable examples are space bus structures and aircraft structures. The space structures require the capability to discharge electrostatic potentials, should provide sufficient conductivity for electrostatic painting, and should shield from the radio frequency interference. Current
carbon based polymeric composites suffer from low electrical conductivity leading to low attenuation of high frequency electromagnetic radiation and higher susceptibility to electrostatic discharge (ESD) induced damage. Therefore, space structures made from conventional polymeric composites require additional labor intensive manufacturing steps to provide the electrical ground path, which increase mass and add extra costs in the space structures [1-3]. Thus, conductive nanocomposites are extremely useful for space applications not only to provide electromagnetic interference (EMI) and ESD protection but also due to their light weight and high strength/stiffness. Further, nonconductive composite materials offer little or no protection against lightning strikes when used in aircraft structures [4, 5]. Lightning strikes break fibers and disintegrate the resin that holds the fibers and lamina together. The current state of the art lightning protection method involves metallic meshes (or other devices) which are co-cured with conventional polymeric composites [6]. This prevents concentrated damage from the lightning strike by dispersing it around the airframe. However, metallic meshes increase weight and may corrode over time. Further, they do not fully protect the composite, and are hard to repair. Therefore, conductive nanocomposites are also extremely desirable for aircraft structures to provide protection against the lighting strike.
