Methods for Assessment of Composite Aerospace Structures

In this paper results of detection and localization of artificially initiated delaminations in small carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymers (GFRP) samples were presented. The first method was electromechanical impedance method (EMI). In the research real part of electrical impedance (resistance) was measured. Delamination in CFRP sample caused frequency shift of certain resonance frequencies visible in resistance characteristic. The second method was based on scanning laser vibrometry. It is a noncontact technique that allows to measure vibration of structure excited by piezoelectric transducer. During research standing waves (vibration-based method) and propagating waves (guided waves-based method) were registered for CFRP sample. In the vibration-based method, the frequency shifts of certain resonance frequencies were analyzed. In guided waves-based technique, the interaction of elastic waves with delamination can be seen in the RMS energy map. The third method is based on terahertz spectroscopy. Equipment utilizes an electromagnetic radiation in the terahertz range (0.1-3 THz). During research time signals as well as sets of time signals creating B-scans and C-scans were analysed. The obtained results showed that the THz spectroscopy technique can detect and visualize delamination between the GFRP layers.