Although they represent a relatively small segment of the aerospace industry, the lightweight materials offer both enormous untapped potential and formidable challenges to designers and manufacturers.

On an annual basis, the aerospace industry consumes an estimated 700 million lbs. of raw materials including aluminum, composites, glare, steel, titanium and other materials, according to a new market study, called Opportunities for Composites in the Global Aerospace Industry 2007-2026, from global research firm Lucintel. The study further reveals that while composite materials currently represent a relatively small segment of the aerospace industry, “enormous potential exists for composite materials to become a more integral component within the industry in the future.”

Possible advantages of using composites as compared with traditional metals and alloys, according to Desktop Engineering:

• Lighter weight or the possibility to readily create non-uniform weight distributions;
• Higher strength-to-weight ratios and directional strength or stiffness;
• Lower production costs, long-term durability and reduced maintenance requirements;
• The opportunity to design larger, single-piece parts with unusual geometries;
• Corrosion or weather resistance;
• Low thermal conductivity and coefficient of expansion; and
• Non-magnetic, high-dielectric strength.

Weight reduction has been a critical goal since the earliest days of crewed flight, and lightweight composites offer proven benefits over aluminum and steel — benefits such as improved strength and corrosion resistance, in addition to weight reduction.

Desktop Engineering also notes that composites serve well in rockets. “For the primary and secondary structures, as well as integral load-carrying fuel tanks and non-integral tanks — all relatively ‘cool’ surfaces — ordinary organic composites such as graphite-epoxy are sufficient.” However, electrical engineer Pamela J. Waterman writes, “‘hot’ areas, such as the leading edge of the space shuttle or the overall thermal protection system structure require the thermal properties of the more exotic carbon-silicon carbide (C/SiC) composites.”

Moreover, the accuracy of orbiting instruments depends on “skillfully designed and manufactured composite components,” according to High-Performance Composites:

At launch, there are major shock, noise and vibration loads encountered during the two-minute period when the rocket leaves earth’s environment. Once the space structure is in orbit, it is critical that all its components remain in the same relative position to each other despite extreme temperature changes. To accomplish this, designers and manufacturers must take into account a number of factors, including stiffness, thermal gradients and moisture, as well as build and assembly tolerances.

A key in such missions: composites, natch. Their superior strength- and stiffness-to-weight and low coefficient of thermal expansion (CTE) are thought to offer the best-case materials option.

The material is being used toward self-healing aircraft, as well. Cornerstone Research Group (CRG) says its reflexive composites can detect and heal damage in load-bearing airframe structures in less than seven minutes.

According to CRG’s research and development page:

Designed to mimic the human reflex response, reflexive panels will sense structural damage, respond quickly and autonomously to the damage and heal the area while keeping the operator informed of the healing process.

“Reflexive composites will allow aerostructures to regain aerodynamic surfaces after damage, maintain fuel efficiency, and offer more payload capacity to lighter weight composite structures,” CRG claims.

This illustration shows different pictures of a resin-filled hollow fiber self-healing composite. Clockwise from top left: 30μm diameter hollow fibers, time-lapse sequence of healing process, infusion into damage site.
Credit: European Space Agency

Beyond spacecraft, the general aviation community has long been a user of composites technology, especially for small personal-owner aircraft and homebuilt aircraft.

Because composites such as graphite and carbon fiber make an aircraft lighter, aerospace companies today are turning more frequently to them due to increased demand for highly fuel-efficient aircraft, according to High-Performance Composites magazine. “The whole industry seems to be headed in this direction,” Investor’s Business Daily recently said.

All of this having been said, designers and manufacturers of composite space and air structures still face formidable challenges in their composites efforts. But the tools are coming along to overcome these obstacles.

According to Carroll Grant, a contractor/consultant in the aerospace composites industry:

Manufacturing technology advancements have enabled engineers to design composite structures today that were just not feasible to build 15 years ago. Fiber placement machines now are available in much larger sizes, and new delivery heads can run wider materials to achieve better layup rates … In addition, more machine tool companies are getting involved with fiber placement and bringing new innovations to this process. Fiber placement machines soon will be available that can cut and lay down material as fast as 2,400 inches per minute (61m per minute).

Today’s automated tape laying (ATL) machines are faster, more capable of laying complex laminates, and they are available in a wide range of sizes and capabilities, Grant recently wrote at High-Performance Composites: “The big ATL systems that are being used to build the 787 wing skins are the largest composites machine tools ever built for aerospace applications.” (See: King of the Sky: Boeing Dreamliner vs. Airbus A350 XWB and Carbon Fiber is Taking Off… Again)

Moreover, according to NASA Tech Briefs, “specialized CAD-integrated composite engineering software is replacing manual design.” The combination of better fuel efficiency through the use of composite and the high-productivity software for designing with it as well as the rapidly growing experience in assembling aircraft with it, make composite more and more attractive.

“Aluminum is still the material of choice for the aerospace industry and is most widely used because of its light weight and cost-effectiveness. But, in terms of strength, aluminum is not the best choice. Its stiffness is very low compared with composite materials. Composite materials, on the other hand, are comparatively costly, but superior to aluminum in terms of strength and stiffness,” according to High-Performance Composites magazine.

The real question may be which material will cost the most to produce in the future. Since about one-third of the cost of producing aluminum flows from power or energy costs, unless power costs decline, (unlikely) the outlook for the use of aluminum for spacecraft and aircraft isn’t bright. In contrast, although carbon fiber is much in demand, some suppliers are increasing production.

Lucintel CEO Sanjay Mazumdar posits that the global aerospace industry will use $57 billion worth of composites from this year to 2026.

Resources

Opportunities for Composites in the Global Aerospace Market 2007-2026
Lucintel, 2007

Composite Materials Show their Strengths
by Pamela Waterman
Desktop Engineering, June 2007

Composite Materials Show their Strengths
by Pamela J. Waterman
Desktop Engineering, June 2007

Aerospace Market Forecast: What’s in it for Composites?
by Sanjay Mazumdar
High-Performance Composites, March 2005

Carbon Fiber in the Wind
by Ginger Gardiner
High-Performance Composites, July 2007

Composite Structural Design and Manufacturing … the Times Are A-Changin’
by Carroll Grant
High-Performance Composites, July 2007

Designing for Dimensional Stability in Space
by Nancy Pottish
High-Performance Composites, July 2005

Solving Complex Engineering Challenges of Large Composite Aerostructures
by Olivier Guillermain, VISTAGY Inc.
NASA Tech Briefs, Sept. 1, 2006

Defense Contractor Sells Loads of Ammo And Aims for the Stars
Investor’s Business Daily, Aug. 14, 2007

Spacecraft, Heal Thyself
University of Bristol, Department of Aerospace Engineering
European Space Agency, Jan. 20, 2006