W. Bai et Bs. Wong, Evaluation of defects in composite plates under convective environments using lock-in thermography, MEAS SCI T, 12(2), 2001, pp. 142-150
Lock-in thermography is a technique which is increasingly being used for th
e evaluation of subsurface defects in composite materials such as carbon-fi
bre-reinforced polymers (CFRPs) in aircraft structures. Most CFRP structure
s have a finite thickness and non-destructive inspection is performed in a
natural ambient environment. In this paper, a photothermal model is develop
ed in order to investigate the behaviour of thermal waves in homogeneous pl
ates and layered plates with finite thicknesses under convective conditions
. The model is then utilized to predict the phase differences produced by m
ulti-layer subsurface defects and optimum inspection parameters. The theore
tical results are compared with the experimental results. The detectivity o
f lock-in thermography for CFRP is also presented in this paper.