Comparison of heating protocols for detection of disbonds in lap joints

A thermographic technique is presented which is shown to be effective for disbond detection in lap-joint samples. The study of various heating protocols shows that shorter heating times allow the greatest contrast in smaller disbonds; the optimum heating technique for this case is periodic heating. In order to compare the different heating protocols, contrast is defined as a function of the moments of the histograms for the bonded region and unbonded regions of the reduced thermal images. A comparison of the bonded-unbonded contrast for different heating times establishes the parameters which maximize disbond detection probability.