Composites are becoming an increasingly popular alternative to traditional manufacturing and building materials in the aerospace, automotive and architectural sectors.
Fuel economy regulations, environmental concerns, and an industry-wide move toward “light-weighting” (that is, designing and building cars, planes and other vehicles to weigh as little as possible) have all contributed to the popularity of composite materials.
A composite is created by combining “two materials with different physical and chemical properties,” explains British organization TWI Ltd. The end result is a composite that is often stronger than the base materials used to create it, adds TWI.
Composites can either be synthetic or natural. For thousands of years builders have used traditional techniques of blending straw and mud to create natural composite bricks. Concrete (cement, sand, gravel, and water mixed) is arguably the most common composite material on the planet.
A list of other popular composites compiled by TWI includes:
• plywood (thin layers of wood glued together for added strength)
• fiberglass (glass fiber blended with plastic)
• carbon fiber reinforced polymer (carbon fiber set in plastic)
• engineered wood (particles or strands of wood blended with adhesives or other materials)
• reinforced concrete (concrete with embedded steel bars for added strength)
Something for everyone
In addition to being strong, composites are often lighter, which accounts for much of their appeal. “While composites are lighter they can also be stronger than other materials, for example, reinforced carbon-fiber can be up to five times stronger than 1020 grade steel and only one fifth of the weight, making it perfect for structural purposes,” says TWI.
“Composite materials offer good vibrational dampening and low coefficient of thermal expansion… Composites are resistant to fatigue [and] have proven resistance to temperature extremes, corrosion and wear, especially in industrial settings, where these properties do much to reduce product lifecycle costs,” says a March 14, 2016 article in CompositesWorld magazine.
There’s more: composites “provide design fabrication flexibility that can significantly decrease the number of parts needed for specific applications – which translates into a finished product that requires less raw material, fewer joints and fasteners and shorter assembly time.”
Building – where it began
As mentioned, composites have been used in architecture for millennia. In addition to creating bricks from mud and straw, people in early times blended wood and clay to build structures.
More advanced composite materials have been used in a number of contemporary projects. “The 1990s saw the first all-composites pedestrian bridge installed in Aberfeldy, Scotland; the first FRP (fiber-reinforced polymer) concrete bridge deck built in McKinleyville, West Virginia; and the first all-composites vehicular bridge deck in Russell, Kansas,” says CompositesLab, a resource established by the American Composites Manufacturers Association (ACMA).
At present, “FRP composites systems are used in thousands of installations around the world to strengthen or seismically upgrade reinforced concrete or masonry structures ranging from buildings and parking garages to transportation structures such as bridge columns and decks,” adds CompositesLab.
In Germany composite use for building purposes takes another step forward with researchers at Technical University, Dresden currently constructing “the world’s first building made entirely from carbon fiber-reinforced concrete,” according to a June 12, 2020 article in CompositesWorld.
Foundations for the two-storey, 220 square-meter “Carbonhaus” demonstration project were poured in March. Construction was supposed to wrap up next year, though that timeline might be delayed because of Covid-19. Once completed, Carbonhaus will offer rooms for academic classes, labs, and presentations.
“The goal of this project is to show and demonstrate with a real structure that carbon-reinforced concrete is usable and practical,” says CompositesWorld.
Composites hit the highway
The automotive sector, for its part, helped pioneer the use of synthetic composites. In 1907, a chemist in the United States named Leo Hendrik Baekeland produced the world’s first totally synthetic plastic. He named this substance Bakelite. Car companies took note and Rolls Royce began using Bakelite for gearshift knobs and junction boxes. Bakelite became familiar everywhere in countless other products, from radios to airplane propellers and telephones.
General Motors was another early adopter. While developing the Chevrolet Corvette sports car, GM elected to use composites to save money on tooling costs. When the Corvette debuted in 1953, it featured fiberglass body panels – quite an innovation for the time. Over the decades, General Motors continued to experiment, taking advantage of new composite materials and processing techniques. The eighth generation Chevrolet Corvette, revealed in July 2019, boasts a high level of composites, just like its predecessors.
Other carmakers have also embraced lightweight composites. During the mid-1970s, American gas prices skyrocketed after the Organization of the Petroleum Exporting Countries (OPEC) launched an oil embargo. Following this harrowing experience the U.S. federal government legislated regulations to boost fuel efficiency in new cars and trucks. To meet these standards, U.S. auto makers began building less bulky cars and fitted them with more fuel-efficient engines. Given that composites frequently weigh less than equivalent traditional manufacturing materials, they became central in the move towards lighter vehicles.
“The prevailing narrative among the composites community for the past decade is that the ‘vehicle of the future’ will be multi-material – some combination of steel, aluminum and composites in the body panels and structure,” says a November 22, 2019 CompositesWorld article.
Aerospace firms have been equally bullish about using composites for light-weighting purposes.
“Rising fuel costs, environmental regulations and an increase in airline traffic have helped drive the increasing use of composite materials in the aerospace industry. Composites are used in military, business and commercial aircraft of all sizes, including spacecraft,” says CompositesLab.
As mentioned, composites are tough as well as light – a vital requirement for materials utilized in aerospace. At any height, mechanical failure is a no-no.
“Composites offer several advantages over the aluminum alloys typically used in small aircraft construction. They are lower in weight and resist corrosion, but at the same time have excellent fatigue strength and stiffness. Because manufacturers can mold them into sculpted shapes, composites also offer greater design flexibility and have the potential for better aero-elastic tailoring of flying surfaces,” notes CompositesLab.
These benefits were appreciated during World War II, when huge amounts of composite materials were used in the construction of aircraft and boats for the military. By reducing their weight, the range of such military craft could be extended. Durable and strong, composites were an obvious choice in this early exercise in light-weighting.
During the 1940s, eccentric aircraft-manufacturer Howard Hughes used composites in his mammoth, eight-engine H-4 Hercules flying boat. Dubbed “the Spruce Goose,” the plane was “manufactured with a composite construction technique before carbon-fiber technology was invented,” says a December 1, 2016 article on the Aircraft Owners and Pilots Association (AOPA) website. The aircraft’s 160-foot long wing spar was “built up with 150 wafer-thin layers of Wisconsin birch,” adds the article.
While the Spruce Goose was a dud, other efforts to utilize composite materials in aircraft were more successful.
In late 2009, for example, the composite-equipped 787 Dreamliner passenger jet from The Boeing Corporation of Chicago successfully performed its first flight. The 787 Dreamliner was “50 percent composite by weight and 100 percent composites on its aerodynamic surfaces,” reports the March 14, 2016 edition of CompositesWorld.
After the 787 Dreamliner went into production, Boeing rival Airbus of Toulouse, France released its own composite-built aircraft. Over half of the Airbus A350 XWB passenger jet, which was first delivered in 2015, consisted of composite material. Airbus also utilized composites in the A380 passenger jet and a military transport plane.
Virgin Galactic is eager to waft passengers to much greater heights than Airbus or Boeing can manage. The company is working on a passenger craft capable of spaceflight. On May 1 of this year, Virgin announced that its fledgling project, SpaceShipTwo, completed a successful debut test-flight in New Mexico.
If all goes to plan, the craft will offer passengers zero-gravity spaceflights. As if this weren’t sufficiently cutting-edge, the futuristic vessel also boasts a unique “all-carbon fiber-composite structure,” notes a May 4, 2020 article in CompositesWorld.
Other space vehicles have also benefited from composites. The heat shield on the Parker Solar Probe, a robotic spacecraft recently launched by NASA to investigate the sun, is “made of two panels of super-heated carbon-carbon composite sandwiching a lightweight 4.5 inch-thick carbon foam core,” says a NASA press release from July 5, 2018. The heat shield weighs only 160 pounds but can withstand temperatures of nearly 2,500°F, adds NASA.
Of course, the advent of 3D printing has opened new vistas in the world of composites. “The rise of 3D printing in the 2010s brought manufacturing into homes and small businesses, allowing users to bring to life on a desktop any item they can dream up with a CAD program. Composites companies are jumping into the field by 3D printing items with reinforced fibers. Discontinuous strands of carbon fiber or fiberglass are most frequently used to reinforce plastics in 3D printing processes across every market sector, including automotive, aerospace, tooling, medicine and infrastructure,” notes CompositesLab.
Given such developments, it’s almost certain that composites will continue to grow in popularity as more companies see the value in making things with non-traditional materials.
“Composites are the material of the future. They solve problems, raise performance levels and enable the development of new innovations,” is CompositesLab’s summary.