Lightning strike protection for composite aircraft structures

Abstract

A composite structure for aircraft having features making it resistant to structural damage when subjected to lightning strikes. Fiber tow is wound over a rotating shaping surface which is a surface of revolution. Spaced bands of tow are laid down in a helical pattern with varying spaces between bands. Some bands are typically wound at an angle of about +45.degree.. By selectively winding in one direction and then the other, a 'basketweave' pattern is obtained. Typically, the tow consists of high strength fibers in a thermosetting or thermoplastic resin matrix wound to a four layer thickness. When cured, the structure has high strength and low weight and is excellent for structures such as aircraft engine cowls. The basketweave pattern gives excellent resistance to peeling and delamination upon being struck by lightning, the types of damage which are likely to occur with the usual hoop or other continuous windings. The resistance to lightning strikes is further increased by winding one or more conductive filaments in a helical pattern, under tension, over the structure before the resin is cured. The conductive filaments serve to dissipate lightning energy over a large area and carry the charges away rapidly without being subject to peeling or separation from the composite structure surface.