Composite materials keep forging ahead

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Core materials, such as CorecellTM, PVC foam, PET and balsa, are often used in a composite structure to increase stiffness and reduce weight

By Sian Stimson

Advanced composite materials have made huge advancements over the last 70 years.

In its most basic form, a composite material is one which is composed of at least two elements working together to produce material properties that are different to the properties of those elements on their own. In modern parlance this is generally regarded as ‘advanced composites’, or ‘fibre reinforced plastics’, either in a solid laminate or in a cored sandwich construction.

This typically involves using fibres – glass, carbon, aramid or a combination – together with a thermoset resin (epoxy, vinyl ester or polyester, or a combination) to form a tough, thin “skin”. Structural core materials (foams, balsa, plastic and metallic honeycomb, felts and non-woven fibres) are used to dramatically increase the stiffness of the panel by separating the skins, creating a light, strong, stiff panel with excellent toughness and inherent insulation. Using these materials, it is possible to obtain just about any combination of properties you want. Strength, stiffness, weight, insulation, corrosion resistance, thermal conductivity… the list goes on.

Manufacturers around the world are now using advanced composites to broaden Glass fi bre reinforcement fabric laid up in the mould of a rotary milking platform, manufactured by Waikato Milking Systems in Hamiltonthe design opportunities and improve the performance of the components they make, as well as helping their customers achieve production and cost efficiencies.

Applications for advanced composites are endless and currently include aviation and aerospace, transportation, marine and leisure goods, telecommunications, mining, oil and gas, renewable energy, and architectural designs. In recent times there has been a greater uptake of composites in general industrial applications, due to costs being driven down through improved processes and a better understanding of how to use the materials. This reduces the price gap between composite and metal construction, and making the composite route more viable for applications such as pipe flanges, sewerage tanks, maintenance platforms and robotic arms.

Their military were the first to see the practical use of composites. In the 1940s they were looking to reduce the weight of aircraft, and this coincided with the growth of the polymer industry and the discovery of the high strength properties of glass fibre. Protective GRP housings were introduced for radar antenna; the first aeroplane with a GRP fuselage flew in 1944. In the same year the Allied forces landed in Normandy in GRP-fabricated boats, and composites continued to gain traction within the wider marine industry.

In the 1950s and 1960s, while the use of glass fibre was rapidly expanding, the ‘space race’ led to further composite developments, such as the introduction of carbon fibre as an alternative to glass.

An aramid compound was developed in the mid-60s, leading to the introduction of aramid fibres in the1970s. These new fibres were shown to be five times stronger than steel and were used for bulletproof vests and helmets. Throughout the 1970s and 80s, composites were used in high performance sporting goods, such as carbon fibre tennis rackets and golf clubs, and started to gain popularity amongst a range of commercial applications.

In the 1990s, metal matrix composites were developed further and found applications in rocket nozzles, fuselage, wings and antenna booms. The composites industry also saw the development of ceramic matrix composites – after the introduction of fibres that could deal with the high temperatures required for ceramic sintering, ceramic matrices were now able to be used for components in severe environments such as rocket and jet engines, gas turbines for power plants and heat shields for space vehicles. But the cost of producing metal and ceramic matrix composites has so far prevented them from entering other markets.

In many respects, some aspects of the fibre reinforced plastics industry have settled into a mature phase, exploiting well proven technologies to commercial gain. However, there is still considerable development in materials (for example, natural or recycled fibre and resin) and processes which will open up new applications and opportunities into the future.

Compared to traditional materials such as concrete and metals, composite construction is relatively low weight for any given strength. Low weight is one of the most common reasons for choosing composite materials for a project as it can have a number of positive results.

Advanced composites do not rust or corrode, and properly designed composite parts have a long service life and minimum maintenance requirements compared with most other materials. The parts can be designed to be resistant to abrasion and ultraviolet light exposure, and composite materials are naturally creep and fatigue resistant.

Composites are excellent materials for the construction of complex and freeform shapes, especially cylinders and spheres. When a component has a specific performance requirement such as strength or stiffness or natural frequency, composites are often the only construction option. The range of fibres, resins and core materials available can be used in a myriad of combinations to achieve the required result; in some cases a computational optimisation process, such as finite element analysis, is used to produce numerous iterations, fine-tuning and validating the laminate specification.

Advanced composites have proven themselves in high-end, performance applications, and over the past 15 years have taken big steps towards commoditisation. In addition, as socio-economic factors play an ever important role in all that we do, the end-of-life options for composites will also be a critical factor in them being chosen for new market sectors. The inclusion of bio-composites in specifications, along with proven recycling methods, will no doubt aid this cause.

Sian Stimson is marketing communications executive at Gurit, a global manufacturer and supplier of composite materials, engineering, tooling, parts and systems. Gurit (Asia Pacific) is located in Auckland.

www.gurit.com

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