Classification of Epoxy Wedges in Glass-Fiber Reinforced Plastics using a Millimeter-Wave Imaging System in W-Band

To determine the mechanical stability of imperfect composite materials it is crucial to classify production faults in terms of shape, depth, and size. Radar-based systems can be used for non-contact and nondestructive measurements of composite materials and provide 3D tomographic images of the components. By using GaAs-based technologies the available bandwidth of 24 GHz in the millimeter-wave regime combined with a low-noise figure enable the detection of low-contrast flaws in glass-fiber reinforced plastics. It is shown that the location of wedges, made of epoxy, inside a glass fiber-reinforced plastic sample can be detected as well as orientation, shape, size, and impact to the adjacent fiber scrims can be determined by evaluating the phase information of the reflected signals.