Affiliation:
1. National Institute of Technology, Meghalaya, India
Abstract
Composite materials are often subjected to low velocity impacts which leads to delamination in subsequent layers. Linear ultrasound-based approaches are not accurate enough to detect it properly. The local defect resonance (LDR) based thermosonic is proved to be an efficient candidate for detection of such defects. LDR frequency excitation leads to high amplitude vibration which raises defect temperature drastically, detectable by an infrared camera. In this chapter, a numerical investigation of LDR frequency excited ultrasound thermography is carried out on delaminated carbon fibre reinforced polymer (CFRP) plate. The location and size of the delamination can be easily understood from thermal signature. The temperature gradient variation is found to be high at first and then it decreases due to higher heat conduction rate. The delamination in CFRP plate is detected by standard phased array ultrasound testing (PAUT) using flat bottom hole in aluminium plate as a case study. Delamination detection by PAUT is found to be very time consuming process compared with thermosonic technique.