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Monday, June 1, 2009

What Composites Mean for You

By John Persinos

The adoption of composites represents a revolution in aircraft manufacturing — a change as significant as the switch from wood to aluminum in the 1920s. However, the maintenance, repair and overhaul (MRO) sector is still grappling with how this historic trend will change conventional ways of doing business.

What do composites mean for mechanics and MRO procedures? These issues were discussed in my latest podcast interview: Why The Increasing Use of Composites Makes Training More Vital. In this podcast, I interviewed Michael Hoke, president of Abaris Training Inc., based in Reno, Nev. This podcast was recorded and archived on Aviation Today; you can access and listen to it for free at www.aviationtoday.com/podcasts/

Abaris conducts "hands-on" training classes in advanced composite aircraft structural materials, such as carbon fiber, Kevlar, and fiberglass. The company offers 17 different classes in manufacturing and repairing composite components. Most of Abaris’ classes are geared for the A&Ps and other technicians who physically undertake the work with their own hands, or for their supervisors. Below is an excerpt of my 15-minute interview with Mike:

Q: Explain to us how the use of composites is increasingly pervasive in the aviation and aerospace sectors. The Boeing 787 is a "game changing" aircraft that’s all composite and it exemplifies this watershed in the industry. Quantify for us how the use of this high-tech material is spreading, and what it means for aviation players of all types.

Hoke: There is no question that the use of modern high-performance composites is rapidly spreading throughout the industry. The primary reason is not weight savings, which many people think. While saving weight is indeed possible in well-designed composite structures, other advantages often are the deciding factor.

The ability to create complex one-piece shapes with multiple compound curves while maintaining a very smooth aerodynamic surface, with no rivet heads or seams, is a significant benefit. Lack of corrosion is another, leading to real reductions in maintenance costs, especially in transport category aircraft as they age.

Composites aren’t necessarily a silver bullet, are they? What are the pros and cons of using them?

You’re absolutely right. Like anything else in engineering, composites have both advantages and disadvantages, and there are areas in which metals are a better choice. I have already discussed some of the advantages, so I will address some of the disadvantages.

From an engineering strength point of view, composite laminates tend to not do very well in compression loading, compared to metals. While they certainly can bear compression loads, the potential for weight savings largely disappears when compared to metallic structures.

Considering all of these trends that you just fleshed out for us, what are the implications for training?

Composites are not inherently difficult to build or to repair. However, the techniques used and the skills needed are often quite different than those for metallic structures. Many more adhesively bonded repairs, rather than mechanically fastened repairs, are used on thinner composite laminates, for example. The "riveted doubler" technique used on so many aluminum structures is usually not applicable on composites, except on thick solid laminates, and will in fact seriously compromise a thinner composite structure and create a potentially dangerous situation.

When it comes to composites, what qualities set effective training apart from ineffective training?

One of the areas that help to make our training effective is our ability to keep the students interested and enthusiastic about the training.

This whole area of advanced composite materials training is quite technical, and has the potential to be deadly dull and boring in the wrong hands. We all know people who might be technical experts in a given area, but would put a classroom of students asleep in about five minutes. So while of course I hire technical experts as instructors, I also am very cognizant of their personalities as teachers. They absolutely can’t be boring and dull, and their personalities are a very large part of our success.

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