what-are-composites

What are composites?

Composite materials are created by combining two or more base materials. The combination of materials leads to better mechanical properties than the base materials alone. Composites typically consist of a reinforcement (e.g. glass, carbon or aramid fibers) and a matrix (e.g. plastic resin) in which the fibers are embedded. Carbon fiber reinforced plastic (CFRP) is a specific type of composite material in which carbon fibers are used as reinforcement. This combination is considered an example of very high-performance composites.

Types of composites

Composites are classified according to their composition, among other things. There are composites with particles, short fibers and continuous fibers. The choice of type influences the mechanical properties: on the one hand the stiffness (“degree of deformation under a certain load”) and on the other hand the strength (“limit value of the load at which a material fails”).

CFRP bending stiffness

The bending stiffness of CFRP depends largely on the type of fibers. Composites with continuous fibers generally offer the best combination of stiffness and strength. In comparison, composites with particles or short fibers are less stiff and less strong, which makes them less suitable for highly stressed applications.

Typical reinforcing fibers

Common reinforcing fibers include carbon, glass, aramid and natural fibers. Carbon fibers are particularly known for their high mechanical properties in relation to their low density. These are divided into subcategories such as high-strength (HT), intermediate (IM), high-stiffness (HM) and ultra-stiff (UHM).

Typical reinforcing fibers:

⦁ Carbon
⦁ Glass
⦁ Aramid
⦁ Natural fibers

Different categories of carbon fibers:

⦁ High Tension HT (high-tension)
⦁ Intermediate IM (in between)
⦁ High Modulus HM (highly rigid)
⦁ Ultrahigh Modulus UHM (ultra-stiff)

carbon-fiber

Various shapes and lengths:

With reinforcing fibers, a basic distinction is made between “continuous fibers” and “short (chopped) fibers”.
Depending on the application and load condition of the component, continuous fibers in one layer can all be aligned in parallel (uni-directional or UD for short) or woven into a textile fabric. If several UD layers are arranged on top of each other in different orientations (angular alignment), they are also referred to as multi-axial fabrics.
In contrast, chopped fibers are used as short fibers (0.5 to 2mm) in injection molding compounds as reinforcement or as “long fibers (10-50mm) in knitted mats or nonwovens.

A single fiber – also known as a filament – has a diameter of approx. 10 micrometers, which is thinner than a human hair.

CFRP structure and construction

Highly stressed CFRP components are made from several layers of carbon fibers embedded in a plastic matrix. The layer structure can be customized to achieve specific mechanical properties. The fiber orientation in the individual layers plays a decisive role in the performance in a specific load direction.

The principle of laminates and the importance of fiber orientation is shown in the figure below:

The combination of different fiber angles results in different properties of laminates (layered structure of different plies)

Density and mechanical properties of CFRP

The density of CFRP is typically around 1.55 to 1.65 g/cm³ and is therefore significantly lower than that of metals such as steel or aluminum. The stiffness of CFRP is in the range of 50 to 150 GPa, depending on the layer structure, the fiber orientation and the manufacturing process. The tensile strength in the fiber direction is in the range of 1500 to 2000 MPa, which makes CFRP one of the strongest materials available in relation to its low density.

Advantages of composites

Composites, insbesondere CFK, bieten zahlreiche Vorteile:

Light weight due to higher specific strength or stiffness in relation to density (especially with continuous reinforcement)

Possibility of setting an optimal and efficient load-bearing behavior by aligning the fibers (“load-appropriate design”)

No corrosion compared to metals

Excellent resistance to chemicals and harsh environmental conditions

Significantly lower material fatigue under dynamic loads and therefore longer service life possible

Designs made of composites, such as CFRP, often enable a higher degree of integration (fewer individual parts/components).

Applications of composites

Composites are used in a wide range of industries, including aerospace, automotive, motorsport, medicine, energy and sport. CFRP in particular is used in areas where high strength and low weight are required.

Typical industries & market segments

Aviation – aircraft and drone manufacturers
Space travel – rockets, satellites, spacecraft, space telescopes
⦁ Motorsport – Formula 1 and other racing classes including motorcycles
⦁ Automotive – GT vehicles, super sports cars, premium vehicles
⦁ Medical – X-ray transparent products, clinical but lightweight products
⦁ Automation – robotic arms, fast-moving or rotating components
⦁ Oil & gas – pipelines, containers, tanks
⦁ Energy – wind rotor blades, high-pressure tanks (including hydrogen tanks)
⦁ Marine & Yacht – sailing boats, racing yachts, luxury yachts
⦁ Sport & leisure – bicycles, surfboards, tennis & golf rackets, fishing rods

CFK_Platte

Fire protection for composites

Polymers in composites are generally flammable. Additives or special coatings are used to ensure fire protection. The UL 94 standards classify the flame resistance of these materials. Combinations of additives and coatings can be useful for extreme applications.


⦁ Chemical composition: Polymers consist of hydrocarbon chains. They ignite easily in a fire, generating a lot of heat, flames and smoke.
⦁ Different fibers: Synthetic fibers such as glass, carbon or ceramic are flame-retardant, while natural fibers are highly flammable.


Two fire protection strategies:
⦁ Additives in the polymer matrix, such as aluminum hydroxide, reduce flammability.
⦁ Fire protection coatings on the component surface, often intumescent, provide effective protection.


⦁ Availability: There are numerous fire protection additives and resins that have been tested and are suitable for various applications.
⦁ Cost: Fire protection coatings tend to be more expensive, but offer maximum protection in combination with additives.

Connova Group is your partner for composites and CFRP solutions

Connova is your competent partner for innovative solutions in the field of composites and CFRP. With over 35 years of experience and in-depth expertise, we offer customized lightweight solutions for the most demanding applications. From development and prototype production through to series production, we support our customers with state-of-the-art technologies and the highest quality standards.

We cover a wide range of services, including engineering, CNC machining, post-processing and surface finishing. Our focus is on sectors such as aviation, aerospace, motorsport, automotive, industry and medical technology. Whether high-precision structural components, aerodynamic components or ultra-stable solutions for aerospace – we have the expertise to turn your visions into reality.

Benefit from our ISO-certified production, state-of-the-art manufacturing techniques and a holistic approach that guarantees the highest quality and on-time delivery. Let us realize your projects together – contact us for a non-binding consultation!

CNC-Fraesen

CNC milling of CFRP: Innovative and complete solutions

One roof for composites and CNC

We integrate CNC milling services for composites, specializing in CFRP, in a comprehensive manufacturing environment. This enables the precise and efficient machining of hybrid parts and pure composite components.

Complete production chain under one roof

Our vertical production chain covers all steps – from material selection and design to milling and finishing. This guarantees an efficient production line with optimized quality and speed, allowing us to meet complex requirements quickly and precisely.

CNC-Kleinserien

Specialization in CFRP milling

Our expertise in CFRP milling enables us to produce high-precision components that meet specific mechanical requirements while maintaining the structural integrity of the material.

As your full-service CNC partner, we offer not only milling services, but also comprehensive support in the development and production of your projects. Choose us for seamless and efficient implementation of your CFRP and composite projects, all from a single source.

Further questions about composites? Get in touch with us!

 
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