Quality Control of Composite parts by robot guided Terahertz imaging

In this work a new approach for in-line quality inspection of drilling holes in glass reinforced fibre composites (GFRP) is presented. The method relies on Terahertz radiation and its large penetration depth in non-conductive materials. By applying THz reflection imaging, 3D information such as interfaces or defects within the sample can be obtained. As a starting point, a laboratory setup based on an industrial THz time-domain spectrometer (TDS) in combination with linear stages for the sample manipulation is built. A software for measurement automatization and data acquisition is developed. Based on measurements performed on drilled GFRP plates, an algorithm highlighting possible defects within the measurement data is developed. The results correlate very well with x-ray tomography (XCT) measurements. Finally, the THz-TDS system is transferred onto an industrial robot and the THz signal synchronized with the position of the robot’s head, expanding the flexibility of the method regarding the applicability to a wide variety of specimen geometries.