Fiber metal laminates (FML) are a new type of composite developed at the Delft University of Technology. Thin sheets of aluminum are alternated with thin sheets of traditional composite. The first FML was Arall, a combination of aluminum and aramid/epoxy. Although the material showed promise, adoption by the aerospace industry was slow.

In the 1980s, Delft began developing a glass/epoxy FML called Glare. Glare was intended to be an alternative to aluminum in aircraft structures. Early research showed it had benefits over both aluminum and fiberglass composites, especially in fatigue and impact. Development continued over a number of years, and the commercial breakthrough came when Airbus decided to use the material on the A380.

"Fibre Metal Laminates: An Introduction" ("FML:AI") is a monograph that came out of a September 2001 conference on Glare, and includes both technical papers from the sessions and chapters written specifically for the book. Despite the numerous authors, though, the book reads like a unified work.

Glare was intended from the start to be a new aircraft material, and it is evident the developers knew what would be required to achieve certification. Rarely have I seen a book that covers a topic with as much thoroughness as "FML:AI." In fact, it reads more like a handbook than an introduction.

Analysis begins with the Metal Volume Fraction (MVF) method, similar to the rule of mixtures for traditional composites. Once basic material properties are determined, the analysis moves on to stress-strain, blunt notch, stability and fatigue beahvior. Each includes experimental data to supplement the theoretical coverage. Ample references provide the reader with additional sources of information.

After definition of the basic material properties and theories, the book moves on to larger design issues. Case studies show how Glare can be used in specific types of aircraft structures. Analytical methods alone cannot be used on complex structures, so it is shown how to apply the finite element method to Glare structures.

Production methods are just as important as basic properties and analytical methods. A material must be readily formed into real structures or it will never be used, no matter how attractive it seems. Roughly half of "FML:AI" is devoted to such manufacturing topics as machining, forming, joining, inspection and maintenance. These topics are discussed in the context of real aircraft components, not just test panels. Actual pages from the Airbus Structural Repair Manuals (SRM) covering Glare are even shown as examples.

Glare is now an accepted material in the aircraft industry, and its use on the A380 will most likely speed its adoption in other areas. Engineers wanting to learn about this material, whether from a design/analysis or manufacturing viewpoint, won't find a better reference than "FML:AI."

Details: "Fibre Metal Laminates: An Introduction" edited by Ad Vlot and Jan Willem Gunnink, published by Kluwer Academic Publishers, 2001, ISBN 1-4020-0038-3.
Preface; A. Material Properties; B. Methods; C. Design Aspects; D. Production; E. Safety, Maintenance and Inspection