CAPS

Fraunhofer Cluster of Excellence Advanced Photon Sources (CAPS)

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New generation of ultrashort pulsed lasers and their application

Ultra-short pulsed lasers promise amazing possibilities. However, the technology has so far been limited by low laser power. The Fraunhofer-Gesellschaft has founded the Cluster of Excellence Advanced Photon Sources CAPS in 2018 to solve this restriction. Under the leadership of the two Fraunhofer Institutes for Laser Technology ILT in Aachen and the Applied Optics and Precision Engineering IOF in Jena, the participating research groups concentrate on developing laser sources and process technology for outputs of up to 20 kW. The goal is international technological leadership in laser systems that achieve the highest performance with ultra-short pulses (USP) and research into their potential applications. The new systems are to exceed all previous USP lasers by an order of one magnitude in average laser power. At the same time, the necessary system technology and possible applications in industry and research are being developed.

The Cluster of Excellence Advanced Photon Sources CAPS is designed to research not only beam sources but also process technology and applications. Partners from research and industry are invited to participate. The cluster acts as a "virtual institute" in which experts from the 13 Fraunhofer Institutes FEP, IAF, IIS, IKTS, IMWS, ISE, ISIT, ITWM, IWM, IWS, IZI as well as ILT and IOF offer their focused expertise.

We conduct research in these application areas

FRP Processing

USP laser processes for high-performance processing of fiber-reinforced plastics for lightweight applications in multi-material design (CAPS FRP Processing)

Test part cut with ultrashort pulse laser and textured on the surface.
© Fraunhofer IWS
Test part cut with ultrashort pulse laser and textured on the surface.

Economical and automated manufacturing processes of FRP for use in lightweight applications

The use of modern materials, such as fiber-reinforced plastic composites (FRP), enables weight savings due to the excellent stiffness-to-mass ratio, reduces the consumption of fossil raw materials and reduces exhaust emissions from e.g. motor vehicles. The operating range of electric vehicles is increased, making them more attractive.
 

Production and further processing of pultruded fiber composite components

The transition from conventional materials to new lightweight materials is being inhibited due to manufacturing challenges that have not yet been solved. The properties and machinability of composites differ significantly from metals, so established metalworking manufacturing processes must be replaced by technologies adapted to the challenges of the new materials. For large-scale production, there is a need for economical, automatable manufacturing processes for machining (e.g. cutting) as well as for the production of reliable multi-material components, which firmly connect metallic elements with FRP components.
 

Technology gap

For multi-material components that also contain metal components, there is currently no satisfactory separation process. For the joining of FRP and metal components, load introduction elements are often integrated into fiber composite components. This can be done, for example, by additive processes. Bonding strength of the supplemented material are insufficient without surface pretreatment of the interface. Laser-based pretreatment in the form of selective fiber exposure or defined structuring of the FRP has shown promise in preliminary studies in combination with plastic injection molding and thermal spraying. However, the process speeds achieved to date are too low.

In the pultrusion process, metallic layers can also be integrated directly into the composite part. This improves the crash behavior of components and enables the subsequent use of conventional fasteners (screws, rivets). A prerequisite, however, is a strong material/form-fit connection in the interface between metal and FRP. Currently, the metal inserts are pretreated in a complex process involving powder coating or a subsequent, additional patching process. Here, too, a laser-based pretreatment process of the metal integrated into the process chain would be an attractive alternative to ensure the required bond strength between the metal layer and the pultruded component.
 

Use of USP lasers

As an alternative to mechanical processing, quasi-cold material removal with ultra-short pulse lasers offers the potential to overcome existing challenges, e.g., surface pretreatment of pultruded components for subsequent printing of tethering elements or integration of a laser-structured steel strip into pultruded components. The laser power available with the CAPS sources also opens up the possibility of multiplying the still too low process speeds for structuring but also for efficient cutting of metal-reinforced pultruded components.

The stated goal of this project is to significantly increase the marketability of hybrid materials and associated manufacturing processes, thereby revealing the potential of very high average power USP lasers for these applications.