Laser Finishing of composites opens up efficiency potentials

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The benefits of laser-based technologies include high flexibility and non-contact, wear-free finishing. In addition to this, the introduction of energy precisely tailored to the given application makes it possible to also finish materials sensitive to temperature. COMPOSITES EUROPE in Stuttgart from 6 to 8 November will also show which laser finishing processes are suited for fibre composites.

Global market for laser technology has almost doubled in ten years

Posting 7.4% growth the global market for laser systems for material finishing reached sales worth EUR 11.4 billion in 2016. This is the result of a study by Swiss consultancy Optech Consulting. According to this study, laser systems for macro-processing, cutting, welding, marking and for generative manufacturing processes account for a 75% market share while 25% are accounted for by laser systems for micro processing in the electronics industry.

This means – by experts’ accounts – that the global market for laser technology has nearly doubled over ten years. In 2006 the total sales still stood at EUR 6.1 billion. Since their decline to EUR 3.8 billion in 2009 the industry has developed dynamically posting stable growth rates to reach the current record high. The growth drivers primarily come from Asia – especially China and Japan – while demand in Europe and North America hardly changed against the previous year.

 

2016 also saw the world market for laser sources for material processing post a 6.0% plus reaching a volume of EUR 3.0 billion. According to the study, fibre lasers account for a 40% market share followed by gas lasers (including CO2 and excimer lasers) that total 35% as well as solid state and diode lasers at 25%. Posting a 15% increase to EUR 1.2 billion, fibre lasers enjoyed a particularly significant boom. Experts see the rising number of applications in cutting, welding, marking and generative manufacturing processes as the principal reason for this.

Laser transmission welding reliably joins fibre composites

Photonic processes are also becoming increasingly attractive for finishing composites because mechanical processes often cause delamination (layers becoming undone) due to the associated stress and strain. In contrast with this, laser processing of fibre-reinforced plastics allows the matrix material to be finished selectively and at high speeds while producing more complex geometries at the same time.

Initial laser applications are currently being studied by scientists and industry or are already being put into practice. Laser transmission welding, for example, reliably joins fibre-reinforced plastics. With this laser-based surface treatment composites can be prepared for bonding and repairs. Furthermore, CFRP and GRP can be laser cut and drilled precisely and reproducibly.

Automated laser processes prolong the useful life of CFRP car body parts

The Laser Zentrum Hannover (LZH) plays a prominent role in the research of efficient applications for laser-based processes for finishing fibre composites. Here scientists run numerous projects with industry partners to study applications-specific photonic technologies.

As part of the “HolQueSt 3D” project initiated with Volkswagen AG, Jenoptik Automatisierungstechnik GmbH, Trumpf Laser GmbH, Invent GmbH, KMS Automation GmbH as well as the Technical University of Clausthal, laser processes for the automatic trimming, drilling and repair of three-dimensional automotive parts with curved surfaces are being developed. Parts were chamfered for preparing the repair in a short process cycle. Then the chamfered holes were closed again with custom-fit patches – an important step to significantly prolonging the life cycle of CFRP body parts.

Higher geometric resolution thanks to new fibre orientation measuring device

With a view to re-working aircraft parts from composites more efficiently the LZH has started the composite project “ReWork” together with Invent GmbH, OWITA GmbH and Precitec Optronik GmbH. It aims to develop a safe process for thin-wall, complex CRFP components. Here innovative systems technology comprising a laser, scanner, low-coherence interferometry system, and control software, is designed to establish individual process parameters in line with the component properties. Furthermore, the further development of laser processes is centre stage in order to fulfil the specific requirements of frequently thin-wall and complex components.

Moreover, the scientists from Hanover have joined forces with Apodius GmbH to combine a novel device for measuring fibre layer orientation with an innovative, laser-based repair process to make FRP components more durable and eco-efficient. The new fibre orientation measuring device makes possible a higher geometric resolution than mechanical measuring processes. Due to the speed of image recognition the data can be analysed in real time thereby fulfilling the basic requirements for controlling the chamfering and scarf joining process.

Removal of foreign fibres by photonic technologies

However, there is much more that photonic technologies can do. The Saxon Textile Research Institute (STFI) in Chemnitz has developed a laser-based process for removing foreign fibres from carbon-fibre recyclates and has produced promising results. The pure carbon fibre materials obtained through this process were first subjected to textile-related physical tests and then studied as to their suitability for textile processing. The results showed that the laser did not cause any significant changes in strength and/or e-modulus. The production of non-woven fabrics from radiated materials did not pose any problems either.

So as to assess possible downstream applications the scientists finally produced sample boards from radiated and non-radiated material and subjected them to tensile and bending tests. The test showed that the laser-treated material displayed comparable properties to non-radiated material. Bending strength and the flexural modulus of elasticity could even be increased by up to 30%. The researchers therefore concluded that, as a rule, laser technology is suited for removing foreign fibres from carbon-fibre recyclates.