The selection and use of materials is a matter of weighing up advantages and disadvantages in search of the optimum – because every material has its own individual properties such as density, rigidity or tensile strength. The stable, massive, strong materials usually show one handicap: their enormous masses. Heavy weights can only be moved with great effort. And low-weight materials often lack the necessary resilience. This is exactly where CFC comes into play.
What is CFC?
Carbon fiber composite (CFC) or carbon fiber reinforced plastic (CFRP) is a composite material consisting of carbon fibers as reinforcing layers embedded in a polymer matrix. The polymer matrix usually consists of a thermoset such as epoxy resin or thermoplastics. The matrix is used for shaping and fiber protection, forms the surface and ensures good load distribution. Desired mechanical properties can be set individually with the choice of fibers and their arrangement. This makes CFC a high-tech material that is irreplaceable in lightweight construction today.
CFC: Outstanding properties
Composite materials consist of different materials that are connected at the micro level, so that new, desired properties arise macroscopically. CFC is an anisotropic material: its strength and rigidity are significantly higher in the direction of the fibers than perpendicular to the direction of the fibers. With several fiber layers in different fiber directions, the mechanical properties can be perfectly configured to suit the respective application.
The material density depends on the fiber used, the matrix material and the fiber volume fraction. For most CFC materials it is around 1.5 g/cm³. Elasticity and strength values also differ depending on the fiber configuration. The same applies to the coefficient of thermal expansion, since the carbon fiber expands significantly less than the polymer matrix material when heated.
In addition to the individual and outstanding mechanical properties, CFC has other advantages that make it a highly interesting material for a wide variety of industries:
• Machinability • Good cushioning properties • Low water absorption • High abrasion resistance • Excellent gliding properties • High chemical resistance • Operating temperatures over 200°C depending on the matrix material • …
CFC in use
Due to the high weight-specific strength and rigidity, CFC is a common material in aviation, vehicle construction, wind energy, sports equipment and much more. CFC has long been established in general mechanical engineering when it comes to saving weight while maintaining rigidity. With the appropriate design, CFC components can be significantly lighter than components made of steel or aluminum. Less mass means higher dynamics. At BUSCH Microsystems we use this advantage of CFC for the highly demanding dynamics of our precision machines.
We adapt the components made of the composite material ideally to the specifications required by our customers. Components are individually designed according to the loads and dynamics that occur, so we can ensure the maximum efficiency of the application.
CFC meets granite
BUSCH Microsystems relies on hybrid machine structures: While granite is used for the base, highly dynamically stressed parts are made of CFC. BUSCH systems are used in ultra-precise processes; therefore, the challenge with CFC is to achieve the necessary precision. Our experienced production team has found a way to process the quality of the evenness just as precisely as with granite – and with this accuracy a whole new dimension of precision and dynamics is possible.
CFC, granite and steel in comparison
At around 1.5 g/cm³, the density of CFC is almost half that of granite (approx. 2.9 g/cm³) and even more than five times lower than that of steel (approx. 7.9 g/cm³). With the same load and dynamics, however, the design and cross-section of the components made of these three materials is always different, so that the weight saving must be considered relative to the respective component.
By using CFC at BUSCH Microsystems, weight savings of approx. 40% compared to granite and up to 70% compared to steel, based on the respective component weight, can be achieved. This makes CFC the ideal material for our precision systems in terms of dynamics. While we were able to achieve speeds of 1.5 m/s and accelerations of up to 10 m/s² on machines with moving components made of granite, CFC enables us to increase the dynamics to up to 5 m/s and 50 m/s².
Exactly this dynamic was required for a customer project in an XY gantry system. This made the use of CFC absolutely necessary. The traverse used in the system weighs almost 36 kg. Without optimization work and with the same structure, a granite traverse would have weighed around 250 kg – about seven times as much. With an evenness of less than 5 µm, the surface of the CFC truss is just as precise as that of a granite truss. This allows us to guarantee the highest precision with maximum dynamics.
In the video you can see one of our hybrid systems made of granite and CFC in motion: