Detection and Quantification of Defects in Composite Material by Using Thermal Wave Method

Abstract

This paper explored the results of experimental investigation on carbon fiber reinforced polymer (CFRP) composite sample with thermal wave technique. The thermal wave technique combines the advantages of both conventional thermal wave measurement and thermography using a commercial Infrared camera. The sample comprises the artificial inclusions of foreign material to simulate defects of different shape and size at different depths. Lock-in thermography is employed for the detection of defects. The temperature field of the front surface of sample was observed and analysed at several excitation frequencies ranging from 0.562 Hz down to 0.032 Hz. Four-point methodology was applied to extract the amplitude and phase of thermal wave's harmonic component. The phase images are analyzed to find qualitative and quantitative information about the defects.

Defect detection with thermal imaging and phase shifting methods in lock-in thermography

“…Therefore, experimental artifacts due to environmental reflections, local non-uniform emissivity of the sample surface, air turbulence, etc. are significantly reduced [1,8,9] Phase-Shifting method is a technique used to determine the phase map from a set of thermographic images differing from each other by a known phase value. It is widely used in optical metrology because of its numerous advantages with features such as: speed and accuracy, point by point measurement, less sensitive to surface reflectivity variations and less sensitive to ambient light [1,10,11].…”