Having been prevalent in the aerospace industry for many years, fiber-reinforced materials are now being used in numerous other sectors, such as automotive construction, medical engineering, and building construction. As a result, the demand for materials and processing methods is also growing fast.
|Exposed fiber structure. (Courtesy: Fraunhofer ILT, Aachen, Germany)|
The high-quality mechanical characteristics of fiber-reinforced components stem from a load-adapted composition of polymer matrix and fibers. To remove the matrix material close to the surface, the Fraunhofer Institute for Laser Technology (ILT; Aachen, Germany) developed a method that allows the outer layers of the surrounding polymer matrix to be removed without damaging the underlying fibers.
|CFRP components, whose coatings have been removed by laser. (Courtesy: Fraunhofer ILT, Aachen, Germany)|
Using ultrafast laser radiation, the matrix material—which usually consists of epoxy resin—can be processed with local and depth-selective ablation, and can even be removed completely. An adapted process control allows the surface to be processed in such a way that the adjacent fibers do not suffer any damage. By local and selective adjustment of laser power and beam guidance, complex geometries and 3D components can be processed with the laser, explains Christian Hördemann, a scientist at Fraunhofer ILT. This ability to process surfaces without disturbing load-oriented processed fibers is especially interesting for the aerospace industry, he says.
|Laser-pretreated and subsequently metalized 3D CFRP component. (Courtesy: Fraunhofer ILT, Aachen, Germany)|
A possible application for the new method is preparing a solid joint between composite materials and adjacent components. In a subsequent step, heterogeneous plastics can be sprayed directly onto the exposed fiber structure, where they surround the fibers and can be mated in a form-closed joint. The method is also suitable for subsequent work steps using adhesion. For certain applications, carbon fiber-reinforced plastics (CFRPs) and other plastic components must be coated with conductive layers. Working together with the Fraunhofer Institute for Surface Engineering and Thin Films (IST), the researchers developed the method so that plastic components can be supplied with a well-bonded copper layer without using toxic Cr(VI) chemicals.
Direct metalization is also possible, as the method can be used for highly loaded antenna bodies and for chrome plating of decorative lightweight components.
For more information, please visit www.ilt.fraunhofer.de/en.