Aachen, Germany - Recent years have seen soaring demand for lightweight component construction materials that include aluminum, high-strength steels, magnesium, titanium and, above all, fiber-reinforced plastics (FRPs). FRPs consist of an organic matrix reinforced either with carbon fibers (CFRP) or glass fibers (GFRP). The production of FRP products is currently hindered by long cycle times and low levels of automation – two factors that pose significant obstacles to mass production – and methods are now being sought to produce FRP products more efficiently. The EU project FibreChain and the InProLight project, which is funded by the German Federal Ministry of Education and Research (BMBF), have set themselves the goal of developing various integrated process chains ranging from sophisticated specialist solutions to the mass production of fiber-reinforced thermoplastic composites. Fraunhofer ILT’s primary task within the scope of these projects is to optimize methods of cutting and joining lightweight components.
Structural joining by laser beam welding
Drawing on the characteristics of the raw material, Andreas Rösner and his colleaguesat ILThavedeveloped a method of structurally joining lightweight components, traditionally joined by adhesive bonding or riveting – two comparatively expensive methods that require extensive preliminary work and extended process time. Rösner has overcome these drawbacks by joining the components using a laser with its energy deposited directly into the joining zone, producing complex components consisting of several individual parts. As an extension of this process, the joining of plastics with metal was accomplished in a special two-stage laser process. Rösner first structures the metallic component with a high-brilliance laser beam, and in a second step he heats it by using a diode laser. The softened plastic then penetrates into the structured metal which leads to an excellent mechanical clawing between the joining parts.
Cutting without damaging the edges
In addition to joiningFRPcomponents and producing plastic-metal connections, another step that appears multiple times in the process chain is cutting. As well as cutting the raw material itself, it is also necessary to trim the components and cut out the required holes and sections. One of the key goals of the cutting process is to minimize any damage to the edges of the material. However, conventional laser cutting techniquesoften produce poor results due to the size of the heat affected zone. ILT’s Frank Schneider and his colleagues, therefore, decided to develop a series of new cutting methods, one of which uses an innovative short-pulse CO2laser. By reducing the heat input, they were able to significantly reduce the thermal damage inflicted on the material. The researchers achieve a nearly complete elimination of thermal damages by using a high power ultrashort pulse laser. Even highly sensitive material combinations in aeronautics can be processed economically by these lasers at a performance of up to 500 Watt.
Many potential applications for FRP components
For the first time, these new laser welding and cutting methods will make it possible to automate the production of FRP components to create a production process that is simplified, fast and cost-effective. To demonstrate this new method’s practical feasibility, the Fraunhofer scientists have already successfully applied it to car seat backs made by the company Weber.
Lightweight components are the preferred technology for any application where a reduction in weight offers the opportunity to cut operating costs, from auto and aircraft manufacturing to shipbuilding and spaceflight engineering. Economical and versatile forms of lightweight design are also becoming increasingly popular for highly dynamic machines and civil engineering projects as an alternative to construction with standard components.
ILT’s experts will be attending the JEC Europe 2012 Composites Show from March 27–29 in Paris to showcase a selection of FRP components produced using the new methods they have developed. These will include car seat backs, front-end components and other examples of lightweight construction applications that rely on laser technology.
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