Government/Military Trends
October 2004
Interview with Adam Quilter
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Adam Quilter heads the Strength Analysis Group at the Engineering Sciences Data Unit, or ESDU, a division of IHS located in London, England.
Q: What is ESDU?
ESDU began in 1940 as the Technical Department of the Royal Aeronautical Society. At the time there was a need for concise aeronautical design information for use by designers from non-aeronautical backgrounds. This information was compiled by the Technical Department in the form of ‘Data Sheets’ (now ‘Data Items’). In time, it was realized that these Data Sheets could hold commercial value — engineers and designers in industry often do not have the time and/or the resources to evaluate all available information on a subject — and ESDU evolved.
Engineers at ESDU focus on a specific topic of interest, collecting all information available from industrial, governmental, academic, and sometimes unpublished sources. The information is sifted and evaluated to produce a Data Item.
The most important part of the production of a Data Item is the validation process. Throughout its development, each Data Item is monitored and guided by technical committees consisting of independent experts from industry, governmental institutions, and academia
Q: What are the most promising composites for aerospace use?
As with metallic materials, there are many composite materials, each with strengths and weaknesses that determine suitability for a particular application. The strengths and weaknesses of composite materials for a particular structural component have to be considered carefully. In aerospace weight tends to be the primary factor. Composites may offer significant benefits in this area, but cost, ease and expense of design, fabrication, assembly, maintenance and repair, and resistance to fatigue are all extremely important. Other factors, such as resistance to corrosion, and, particularly in space applications, the ability to tolerate extremes of temperature, can be highly significant.
Q: Is the increasing use of composites likely to make obsolescence worse?
The short answer is that I really don’t know. One has only to browse the literature to see that widespread- and multi-site-fatigue damage are subjects of considerable interest at the moment. Solutions are being sought, found, or developed. Whether there will be a similar problem in the future with composite materials is difficult to predict.
Q: What are the issues regarding fatigue and damage tolerance with composites?
Generally, fatigue characteristics of composite materials tend to be fairly good; GLARE (glass-fibre-reinforced aluminum alloy), for example, offers very good fatigue resistance. Some composite materials suffer ill effects over time from moisture ingress. Delamination is sometimes a problem. Problems can also arise with impact damage. Significant impact damage to a metallic component, such as the leading edge of a wing, tends to be fairly visible as a dent. In a composite, more significant damage is often internal and, after an impact, the surface of the element might appear only slightly damaged or completely intact, giving little or no indication of deeper problems.
Q: What is the tipping point for composite use, particularly in commercial aviation?
The tipping point passed many years ago: the primary structures of rudders, fins, tail-planes and large parts of fuselage of commercial aircraft have all been made of composite materials.
The remaining landmark is the use of composite materials for the primary structure of the entire wing of a transport aircraft.