FEATURE: AEROSPACE
CFRP MACHINING TAXIS FOR TAKE-OFF
Tim Gillett investigates the process of laser machining composite materials for the aerospace industry
The day after I was asked to investigate laser machining in the aerospace industry, my father gave me a collection of animal skulls he’d been amassing over the years. Among them was the skull of a sparrow
hawk, which had met its maker after flying into a glass conservatory while chasing a pigeon. Picking up the skull, it struck me immediately that it weighed almost nothing – which, of course, is a quality that is essential when it comes to the concept of flight. Whether you are considering a raptor weighing 200g, or an aircraft weighing 200 tonnes, the ratio between weight and strength is crucial. In two three-year research projects,
the Laser Zentrum Hannover (LZH) – sponsored by the German Federal Ministry of Education and Research and the German Federal Ministry for Economic Affairs and Energy – is aiming to further develop the laser machining of lightweight composites for series production in the aircraft industry. Their focus is on designing an efficient system and a process technique that meets the demands of aviation. The use of composites in aerospace is not a new thing – it’s already decades old, in fact – but these days as much as 50 per cent of a modern aircraft can be made from carbon-fibre reinforced plastic (CFRP). It’s extremely light, durable, and strong – but
18 LASER SYSTEMS EUROPE SUMMER 2019
there have long been difficulties around the process of machining the material.
Material challenges Hagen Dittmar, who works in the production and systems department at LZH, explained that there are specific issues in machining a non-homogenous material such as CFRP: ‘Unlike a metal, for example, CFRP is made up of two chief components – fibres and plastic – with completely different properties (carbon fibre is very strong, whereas the plastic, which acts as the matrix material and forms the actual shape of the specific product, is very weak). Carbon fibre produces a large amount of wear on traditional tooling, which is one of the drivers towards laser machining.’
The LZH project ReWork, set to end in June, is looking at the process of reworking CFRP components that have either been damaged in use or those that suffered faults in the original production process – the procedure is the same in either case. Dittmar said: ‘Using near-infrared lasers, the machining process effectively removes material layer by layer to eliminate the damage or fault. If we are working on parts of
Left: Laser-drilled holes in an aircraft component made of CFRP; Right: Repair preparation of a CFRP aircraft component through layer-by-layer laser removal of the damaged material areas
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