Thermographic detection of damaged regions in fiber-reinforced composite materials

The applicability to composite materials of a particular NDI technique, vibrothermography, is studied. With this technique, specimens are excited with a high power, low frequency ultrasonic shaker while the specimen is monitored with an infrared camera. Once temperature patterns are developed, thermograms are photographed from the color display of the infrared camera.

A three dimensional, orthotropic, finite difference heat conduction analysis is performed and written into a computer coding. After an estimate of the heat sources responsible for an experimental thermogram is made, these heat sources along with the material information is fed into the computer coding to produce an analytical temperature pattern. A comparison between the experimental and analytical thermograms may lead to further information concerning the nature of the heat sources. The computer coding is written to handle an eight ply symmetric laminate using one hundred elements per ply in the analysis.

A listing of the computer coding along with a guide to its use, a sample data set, and a sample output are included in the thesis.