New Sensor for Detecting Defects in Lightweight Structures

"Defect Defender," a sensor developed by the Laboratory for Machine Tools and Production Engineering at RWTH Aachen (WZL), measures the geometry and fiber orientation of carbon-fiber reinforced plastic surfaces in 3D.

Light and strong at the same time – this is what designers want from a material that can be used to manufacture energy-efficient components. Lightweight components made of carbon-fiber reinforced plastic possess these characteristics. They consist of two components: high-quality carbon fibers and a plastic matrix into which these fibers are embedded. This composite provides a unique potential for lightweight construction for numerous applications, such as in the aeronautics and space industry or automotive manufacturing.  

While carbon-fiber reinforced plastics are becoming increasingly important, the level of automation in the manufacturing processes is still very low, and material costs are high. Currently, most components made of composites are manufactured manually or using partially automated processes. This requires both a lot of time as well as being expensive.

In order to be more efficient, it will be essential to detect deviations during the layering process and to correct them automatically. Not least, this will also prevent that defective parts get into the processing chain.  "This is where we are using our sensor," explained Andre Duffe. Together with his colleague, Christoph Mersmann, he was watching a robotic arm making its programmed passes over a semi-finished carbon-fiber component to be used for covering an airplane turbine. On the high-tech system, it says "Defect Defender." This new sensor can measure the 3D geometry and the 3D fiber orientation of carbon-fiber composite surfaces.

The two employees of the Department for Metrology and Quality Management at the Laboratory for Machine Tools and Production Engineering (WZL) are watching all this on a large monitor showing the rotating turbine shell. "What is particularly essential for composite components is 3D fiber orientation because they can only absorb the loads affecting the component in the direction of their orientation," explained Christoph Mersmann.

Since the beginning of the lightweight component trend, the Lab’s image processing team around Dr.-Ing. Robert Schmitt has been researching new approaches for automating composite material production.  "Our research approach is to improve the process by integrating  suitable measuring technology into the process. With our new sensor, the Defect Defender, we are looking to creating a universally applicable sensor solution that can be used both for detecting defects as well as automating processes," said Schmitt.

In a next step, the researchers want to make the sensor even lighter and more convenient. A portable 3D tracking system will be used to ensure that 3D data can be captured fast and during production even from large components and if there is no robotic arm available.  "There is much left to be done. But the first industry partners have already used our sensor successfully, and of course, that’s motivating," the two engineers confirmed.