ThinKing February 2022: The secret of the accordion for large-scale sandwich composite components



Sometimes, lightweight technology is not just about using the right material in the right place - but also about having the right idea at the right time. In February, the ThinKing will be awarded to an invention that greatly simplifies the production of large-dimension sandwich composite components.

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Compensating pieces made of core material with an accordion effect from Gaugler & Lutz GmbH & Co. KG act like the individual parts of a building kit, with the characteristics of a spring. They are able to compensate for tolerances and, thanks to customised surface treatments and machining and non-cutting production processes, are able to cling tightly to contours on rounded areas.

The Baden-Württemberg State Agency for Lightweight Technology will present the ThinKing for this innovation in February of 2022. Every month, Leichtbau BW GmbH promotes innovative lightweight technology products and services in Baden-Württemberg under this label.

At a glance:

  • Fast: Throughput times for manufacturing large lightweight components made of sandwich composite materials are shortened.
  • Safe: The material kits and the consistent quality they ensure improve process and component safety.
  • Cost reduction: Higher productivity, and potential process optimisations, help lower costs in production.
  • Customised: The material and geometry are flexible, and can be adapted to specific applications.

The ThinKing for February is being awarded to an invention patented by the company Gaugler & Lutz GmbH & Co. KG a few years ago.  This technology, however, has now proven effective as part of the expansion of wind power. “Our invention greatly facilitates and accelerates the production of large sandwich composite components – such as rotor blades for wind turbines – thanks to its accordion effect” says Dominic Lutz, Managing Director of Gaugler & Lutz GmbH & Co. KG.

Anyone who has ever laid a floor understands the problem. At first, the tiles or wood are easy to lay, but once you reach the end of an area, you begin to understand that it just isn’t going to fit. Then you have to start the time-consuming process of measuring, sawing, cutting, and adjusting.

Production employees designing large components – such as rotor blades for wind turbines – face a similar issue with core laminate materials, in order to reinforce them with fibrous outer layers and achieve the desired mechanical properties. Rotor blades are gigantic – frequently longer than 75 meters, and sometimes up to 100 meters long. It is not possible to manufacture the entire sandwich structure at such a large scale. This also applies for the core layer. Because of this, the core laminate material is inserted as a single part in a marked, pre-selected building plan – similar to a puzzle.

Tolerance compensation with core laminate material

Ultimately, due to the mandatory production tolerances for the individual parts and how they add up over the dimension of the component, a gap of several centimetres is often created. This is difficult to bridge. In this case, the core material has to be cut in a time-consuming process, or the gap has to be bonded using resin. Both of these solutions impact quality, and are not ideal.

The solution for manufacturing large sandwich composite parts is the material kit with accordion effect from Gaugler & Lutz. This core laminate material is modified with grooves, so as to achieve a longitudinal stretching effect in one spatial direction. To insert it, the production employee presses the kit together lightly and places it in the gap. Due to the stretching effect, it adjusts to the available space thanks to the spring force of the groove geometry, and fills the space.

Different materials are used for the kits. The available selection is based on the core material used. Synthetic foams made of PVC (polyvinyl chloride) or PET – including recycled material – or renewable raw materials such as balsa wood are possible options. The notches in the material have an application-specific geometry. for example, at a core layer thickness of 15 to 50 millimetres, the grooves of the scoring on the surface must be around two to five millimetres, and the grooves themselves must be spaced about 5 to 20 millimetres from one another.

Optimising production processes

Thanks to the longitudinal expansion effect, manufacturing tolerances at the edges of the component, and the puzzle-like building plan, can be bridged quickly and closed with a perfect fit. Because of this, the invention reduces lead times in component manufacturing, by eliminating rework. It increases process reliability, and thanks to the uniformity of the design, ensures consistently high quality despite different tolerances. What’s more – the smart design of the resin channels in the surface texture makes it possible to control the resin flow downstream, thereby optimising the process.

Expanding design freedom

This method for compensating for tolerances also greatly expands design freedom in developing and manufacturing a sandwich composite component. The ability of the compensating piece to mould to its surroundings is useful not only in edge areas. Instead, the grooves allow the rigid core laminate material to bend along the radius if needed, to take on rounded forms with a tightly conforming contour. This makes it possible to create even complex designs in composite components.

The invention is useful primarily for large-scale sandwich components, and offers characteristics that can be beneficial in many sectors – wind power, ship and boat building, aerospace and aviation, railway and road vehicle construction, or for industrial components.

About Gaugler & Lutz GmbH & Co. KG

Gaugler & Lutz GmbH & Co. KG is an independent, mid-sized company operated by its founders and owners in Aalen-Ebnat. The company is represented worldwide in many different business areas and markets under the Gaugler & Lutz and softX brands. Since 1983, Gaugler & Lutz GmbH & Co. KG has been a reliable partner for dealers and manufacturers of sports, rehabilitation, and recreational products, as a leading provider of core materials and solutions for lightweight and sandwich construction, and a leading processor of foamed plastics and renewable, plant-based raw materials.