Fatigue of Fiber Metal Laminates

Fiber-metal laminates were developed as a family of hybrid materials that consist of bonded thin metal sheets and fibers embedded in adhesive, i.e. rubber-thoughened epoxy (Fig 1). This laminated layout creates a material with excellent fatigue, impact, and damage tolerance characteristics, and a low density (Vogelesang and Gunnink 1986, Vlot et al. 1999). The bondlines act as barriers against corosion of the metallic sheets, and the metal layers protect the fiber/epoxy layers from picking up moisture. The laminate has an inherent high burn-through resistance as well as good damping and insulation properties. The material; like monolithic aluminium, these sheets can be machined and formed into products. The laminate can also be cured in an autoclave into a complete structure: large, curved panels with co-cured doublers and stiffening elements. The so-called "splicing concept" makes a larger panel size possible compared to conventional aluminium structures, with consequent reduced assembly costs. The possible 20% weight reduction was the prime reason behind the development of these materials for aircraft structures.