A Closer Look at Composites

  • November 25, 2019
  • Feature
A Closer Look at Composites
A Closer Look at Composites

By Robert Glass, Head of Marketing, Exel Composites

In 1200 A.D., the Mongols invented the first composite bow, combining bamboo, silk, cattle tendons and pine resin to make a tool that was swifter and more powerful than those of their rivals. Since then, composites have transformed the technologies of many industries —although the materials used to manufacture them have evolved. This article examines the progress of composites and their advantages over traditional materials like steel.

Although the method of combining materials has been around for thousands of years, compared to legacy materials such as steel, aluminum and iron, composites are still coming of age. While industries are still awakening to the benefits of composite materials, their physical properties make them an undeniably attractive option. 


Composites 101

Fiberglass composites accelerated from development to mass production during World War II, as alternative materials were needed for lightweight military aircraft. Engineers soon realized that low weight wasn’t the material’s only boon. It was discovered that fiberglass composites were transparent to radio frequencies, and they were used as a replacement for the molded plywood in aircraft radomes.

High strength and low weight remain a winning combination for composites, helping to reduce fuel use, facilitate faster and easier movement of devices such as robotic arms as well as improve topside stability in vessels and offshore structures. Around 0.02 cubic meters of steel weighs approximately 222 kilograms, while the same amount of composite material can weigh up to 70 per cent less.

Another crucial quality of composites is that they do not rust, reducing maintenance requirements. This is especially beneficial for applications prone to corrosion, such as in marine and other offshore environments. This excellent resistance lengthens the lifespan of the material, helping increase profitability for the end user.

Resins play a crucial role in the overall performance of composites. The primary function of resin is to act as a glue that holds a composite’s fibers together and protects them from mechanical and environmental damage. Resins such as polyester (UPE) can be modified to make them flame retardant or self-extinguishing, while we can create specific properties for epoxies (EP) by adapting the hardening process. These modifications add further value to a composite’s properties, allowing it to offer even more benefits.


Industry Expansion

Thanks to its enviable properties, a vast range of industries favors fiberglass. While the body of the 1953 Chevrolet Corvette’s show model was the first time the vehicle was made of reinforced plastic, purely as an expedient to get the job done quickly, the material has withstood the test of time. With doubts expressed over whether the 1954 model should be created using steel, people seemed to be captivated by the idea of a fiberglass plastic body.

Following the original fiberglass model, the Corvette has seen eight different generations of composite bodies. Father of the Corvette, Zora Arkus-Duntov, set the stage for the innovative design with his document titled “Thoughts Pertaining to Youth, Hot Rodders and Chevrolet”. Identifying that Chevrolet needed to overtake Ford’s lead in use by customizers and racers, the evolution of the Corvette continued, including the birth of its first sports edition in 1956.

It’s insulating properties also mean that fiberglass is commonly used in electrical equipment, where non-conductive strength and reliability over long periods of time are required. The design flexibility of fiberglass, for example, makes it a perfect material for high voltage insulators, or used in transformers or electric motors and generators.

Elsewhere, the building and construction sectors have been using composites for over 40 years, beginning with glass reinforced polyester (GRP) cladding panels for buildings in the 1970s. GRP composites are now becoming a more standard material of choice for many small infrastructure projects. As the weight and strength advantages of the material are becoming better known, the materials are being piloted for larger schemes and building projects — including composite bridges and even freestanding carbon fiber roofs.

Perhaps one of the first instances of carbon fibers being used in practice was in Thomas Edison’s lightbulb. The carbonized cotton thread used to create the lightbulb’s filament wasn’t the carbon fiber we know today, but carbon has since been thrust into the spotlight and hailed as a high potential composite material. With five times more strength than steel, and twice as stiff, energy.gov suggests that carbon fiber composites could reduce passenger car weight by 50 per cent, improving fuel efficiency by as much as 35 per cent. The potential is enormous.

If we take a closer look at wind energy, for example, composites play a crucial role in maintaining turbine efficiency. The demand for wind energy is soaring, and this increase brings with it the desire for longer turbine blades to produce more energy. But as blades get longer, we also need to focus on reducing their weight in order to ensure maximum performance.

However, this lighter weight must also be coupled with strong and long-lasting materials. One of the main sources of a turbine’s blade strength comes from a support beam, or spar cap, which runs down the blade. These spar caps have been traditionally made using fiberglass, but manufacturers are turning more towards carbon fiber as it adds stiffness that allows for longer blades.

But carbon fiber is all too often perceived as fiberglass’s more appealing younger sibling. Far less dense than fiberglass and with a higher ultimate tensile strength, carbon fiber is ideal for applications where were every gram of strength or stiffness matters. However, manufacturers should also consider fiberglass’s lower tensile strength and, as a result, greater flexibility. A composites expert, like a member of the team at Exel, will have a sound knowledge of both material’s ideal applications, and should be able to recommend the most suitable material for your desired demands.


Pull It Together

When manufacturing a composite tube to meet specific design considerations, the most common processes used are pultrusion and pull-winding. Pultrusion involves a continuous process of pulling a material through a guide where fibers are placed precisely in relation to the profile’s cross section to ensure a consistent quality.

As the fibers are led through the equipment, they are permeated with resins to lock the fibers in place. Pull-winding is very similar to pultrusion with the exception that fibers can additionally wound around a profile before it enters the heated die. The advantage is in the fiber alignment possibilities in both the crosswise and longitudinal directions that enable a wider range of solutions, and even thinner profile walls, such as those used for tubing.

While these methods are well used in composites manufacturing, the ability to repeatedly produce the desired quality requires an understanding of many factors, such as the choice of reinforcing fiber, the angles at which the fibers are orientated in a profile’s structure and the resins used. This is important both in the manufacturing phase to ensure that the right amount of materials are used and waste is reduced. We also need to make sure that when the products are in use, they provide the desired material properties.

The strength and accuracy of the Mongol’s composite bow made it one of the most feared weapons on Earth, until the invention of effective firearms in the 14th century. By providing lighter weight for increased strength, alongside a multitude of other advantages, composites today are well on their way to becoming a crucial material in several applications. We can’t imagine what the Mongols would have done had they had fiberglass or carbon fiber composite laminates to use rather than silk and pine resin.

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