Aerospace Composite Solutions: A Comprehensive Guide

Composites refer to materials made by combining two or more distinct substances to create a material with better properties. These materials are designed to offer specific benefits:

• High strength
• Reduced weight
• Stronger durability

These three characteristics are crucial for applications in the aerospace industry.

Nowadays, composites have become essential in modern aerospace engineering due to their ability to replace traditionally used metal materials. Previously aluminium and steel were dominant in aircraft manufacturing, but now composites offer significant advantages. Their lightweight properties – are one of the most important advantages, as it directly impacts fuel efficiency and performance. Aircraft made with composite materials weigh less, leading to lower fuel consumption and reduced operating costs.

For example, materials like PEEK (a high-performance thermoplastic) can be up to 70% lighter than traditional metals while maintaining similar strength and stiffness. This weight reduction leads to significant fuel savings.

In addition to being lightweight, aerospace composites are also incredibly strong, with some composites like carbon fibre-reinforced polymers (CFRP) providing a higher strength-to-weight ratio than many metals. This makes composites ideal for use in critical structural components such as wings, fuselage sections, and tail structures. The durability of composites also makes them more resistant to corrosion compared to metals, leading to fewer maintenance requirements and a longer service life for aircraft.

Main Types of Aerospace Composites

Carbon Fibre Reinforced Polymers (CFRP)

Carbon fibre-reinforced polymers (CFRP) are among the most widely used composites in aerospace. They are composed of carbon fibres embedded in a polymer matrix, typically epoxy or high-performance thermoplastics such as PAEK (polyaryletherketone), providing exceptional strength and low weight. CFRP is used in critical structural components like wings and fuselage sections because it can handle high loads while significantly reducing the overall weight of the aircraft. For example, CFRP materials are up to 70% lighter than metals such as steel, yet they offer superior stiffness and strength, making them indispensable in modern aerospace design.

Additionally, CFRP is frequently used in engine components, where it helps to withstand high mechanical stresses while reducing the overall mass of the engine.

Glass Fibre Composites

Glass fibre composites, which combine glass fibres with a polymer matrix, are another popular choice in aerospace. Although they are heavier than carbon fibre composites, they offer a good balance between cost and performance. These composites are often used in less critical parts, such as interior components and fairings, where the priority is not maximum weight reduction but rather durability and cost-efficiency​. The affordability of glass fibre composites makes them a practical option for applications where cost considerations are significant.

Aramid (Kevlar) Composites

Aramid fibres, known by the trade name Kevlar, are known for their impact resistance and toughness. In aerospace applications, Kevlar composites are used in parts that are prone to high impact or need enhanced protection, such as reinforced panels in fuselage sections or protective layers around vulnerable areas of the aircraft​. These composites not only provide superior impact resistance but also contribute to overall weight reduction, helping to minimise the aircraft's total mass without compromising safety.

Hybrid Composites

Hybrid composites combine different fibres, such as carbon and aramid, within a single matrix to tailor the material properties for specific applications. For instance, hybrid composites can provide the high stiffness of carbon fibre along with the impact resistance of Kevlar, making them ideal for components that need a balance between strength, durability, and impact protection. A practical example of hybrid composite use is in aircraft brackets and connectors, where the material’s combined properties allow for lightweight designs that can withstand mechanical stress​. Hybrid composites are also gaining traction in more specialised applications like tubing and cable conduits, where precise properties are required for optimal performance​.

Benefits of Composites in Aerospace

Extended Component Lifespan and Reduced Maintenance

A major benefit of using aerospace composites is their ability to extend the lifespan of aircraft components. Composites with PEEK (poly-ether-ether-ketone) offer high resistance to wear and fatigue, which means they can endure long-term usage under harsh conditions without the need for frequent replacement. This durability directly reduces the downtime required for maintenance.

For example, composites are less susceptible to stress fractures and fatigue damage, especially when compared to metals. By reducing the frequency of part replacements and associated labour, airlines can save on both maintenance time and costs, particularly for critical components like brackets, insulation systems, and fasteners.

Improved Design Flexibility

Another key advantage of composites is the flexibility they offer in aircraft design. Unlike metals, which have more rigid structural limitations, composites can be moulded into complex shapes, enabling innovative aerodynamic designs. This is particularly useful for parts with intricate geometries, such as engine cowlings and wing tips, where composite materials can provide improved aerodynamics without compromising strength. This ability to create complex, lightweight shapes helps enhance the overall performance of aircraft by reducing drag and improving fuel efficiency without adding extra weight.

Resistance to Extreme Environments

Composites, especially advanced materials like carbon fibre reinforced polymers (CFRP) and PEEK, are known for their resistance to extreme environmental factors, such as exposure to high levels of heat, moisture, and aggressive chemicals. These materials maintain their structural integrity even under conditions that would degrade traditional materials like aluminium, steel or thermosets. This resilience is particularly beneficial for components exposed to high temperatures and pressure, such as those in the engines or landing gear. By maintaining their properties over extended periods, composites ensure the reliability of aerospace systems in challenging environments.

Manufacturing and Processing of Aerospace Composites

The manufacturing and processing of aerospace composites are critical steps in ensuring that these materials meet the high-performance demands of modern aircraft. Unlike traditional materials like metals, composites require advanced production techniques that allow for the creation of lightweight, strong, and durable components.

These processes involve precision and often use automation to ensure consistency and efficiency at scale. By employing modern methods, aerospace manufacturers can produce complex shapes and structures that are both lighter and stronger than their metallic counterparts.

One of the most innovative processes used in aerospace composite manufacturing is hybrid over-moulding, which allows for the integration of multiple material types within a single component.

Hybrid Over-moulding

Hybrid over-moulding is a process that combines different composite materials to optimise performance and functionality in a single part. In this method, a continuous fibre-reinforced composite substrate, such as LMPAEK(™) polymer, is overmoulded with a short fibre-reinforced polymer like PEEK. This approach allows for a combination of properties — high strength and stiffness from the fibre-reinforced substrate, and flexibility or additional features from the overmoulded polymer​.

One of the major advantages of hybrid overmoulding is the ability to create highly functional parts with reduced weight. For example, components produced through this process are up to 70% lighter than their metallic counterpart. The technique also enables complex geometries, such as reinforcing ribs or clips, to be integrated directly into the part during the moulding process. This eliminates the need for secondary processes, such as assembly or fastening, which can save both time and costs.

Hybrid overmoulding is particularly useful in the production of structural brackets, fasteners, and connectors, where a balance between strength and weight is critical. Moreover, the process is highly efficient, with cycle times under 10 minutes, making it suitable for large-scale production. The ability to customise and fine-tune material properties during manufacturing makes hybrid over-moulding an attractive option for aerospace engineers looking to push the boundaries of design and performance.

Automation in Composite Manufacturing

Automation plays a crucial role in the manufacturing of aerospace composites, particularly for increasing production efficiency and ensuring the consistency of high-performance components.

Two widely used methods in automated composite lay-up are automated tape laying (ATL) and automated fiber placement (AFP).

Automated tape laying (ATL) is where layers of composite materials are precisely placed and tack welded to create tailored preforms for various aerospace parts. The ATL process allows for accurate control over the material placement, reducing waste and enhancing the structural integrity of the final part.

Automated fiber placement (AFP) is a similar process but uses multiple narrow tows of composite material rather than wide tapes. This provides greater flexibility in fiber orientation, making it well-suited for manufacturing complex shapes with intricate curves. AFP enables optimized structural performance and is particularly beneficial for high-performance aerospace applications where precise fiber alignment is critical.

Automated tape laying involves the precise placement and bonding of composite tapes to create tailored preforms for various aerospace parts. This process allows for accurate control over material placement, reducing waste and enhancing the structural integrity of the final component. Similarly, AFP follows a comparable approach but offers greater flexibility by allowing fibers to be placed in multiple directions, making it particularly useful for complex, contoured surfaces.

In automated tape laying, composite tapes are laid down in precise patterns using robotic systems. These tapes are then welded together using ultrasonic spot welding, which not only secures the layers but also ensures that the part remains strong and lightweight. This process is particularly useful for producing large, complex shapes like wing panels, where traditional manufacturing methods would be time-consuming or inefficient.

Another benefit of automation in composite manufacturing is the reduction in cycle times. With the use of advanced robotic systems, production times for composite parts can be shortened significantly, allowing manufacturers to meet the high demand for aerospace components. For instance, parts that would take hours to produce manually can be manufactured in just minutes using automated processes. This level of efficiency is critical in the aerospace industry, where production volumes and deadlines are often tight.

Furthermore, automation helps ensure the repeatability and accuracy of complex parts, reducing the margin for error and minimising defects. This is essential for maintaining the high safety standards required in the aerospace sector, as any deviation in part quality could lead to performance issues or safety concerns.

Composite Materials in Aerospace Industry: Challenges and Considerations

Cost of Production and Adoption

While aerospace composites offer numerous benefits, one of the key challenges is the initial high cost of production. Manufacturing composite parts requires specialised moulds and fixtures, which represent a significant upfront investment. This can be a deterrent for companies producing low volumes of parts, however, for businesses with high production volumes, these costs can be spread across more units, making composites more economically viable over time.

Some materials can be expensive to manufacture due to the advanced processes and precision required. For example, creating high-performance composite parts often involves specialised equipment, such as automated tape-laying machines and high-temperature moulding systems, which increase production costs. These high upfront costs can be a barrier to adoption, especially for smaller manufacturers or companies new to the use of composites​.

However, the long-term savings from using composites often outweigh the initial investment. Aerospace components made from composites are significantly lighter than their metal counterparts, leading to reduced fuel consumption and lower operational costs over the aircraft's lifespan.

For instance, the use of PEEK in place of metal can lead to weight savings of up to 70%, which, could translate into millions in fuel savings per year for large fleets​. Additionally, composites require less maintenance due to their resistance to corrosion and wear, further lowering long-term costs. These factors make composites a worthwhile investment, particularly for major aerospace manufacturers looking to reduce their environmental impact and improve fuel efficiency.

Material Testing and Certification

Another significant challenge in the adoption of aerospace composites is the rigorous testing and certification required to ensure that these materials meet the strict safety and performance standards of the aviation industry. Composite materials must undergo extensive testing to verify their strength, durability, and resistance to environmental factors such as heat, pressure, and chemicals​.

Victrex has been instrumental in the development of standardised databases to support the certification process for thermoplastic composites. For example, Victrex has worked on creating an allowable database for its PEEK and PAEK materials, which helps manufacturers understand how these materials perform under different conditions​. By standardising material performance data, this initiative accelerates the certification process, allowing aerospace manufacturers to adopt new composite technologies more quickly and with greater confidence.

Additionally, the development of such databases is critical for reducing the risks associated with introducing new materials into aerospace applications. With a well-documented performance history, manufacturers and regulatory bodies can rely on consistent, validated data when approving composite materials for use in aircraft.

Conclusion

As the aerospace industry continues to evolve, the use of advanced composites like PEEK and hybrid materials will play an increasingly important role in shaping the future of aviation. While the initial costs and certification processes present challenges, the long-term benefits of improved performance, weight reduction, and fuel savings make composites a vital component of modern aerospace engineering.

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