Flaw Detection in Composite Materials Using Infra-Red Thermography by the Method of External Heating

Abstract

A non-destructive technique for the detection of air-filled voids and foreign bodies within glass/polyester composite material is described. The technique involves the use of infra-red thermography with an external radiative source to excite temperature differences at the surface of the body. A low-intensity heat source is used to avoid large overall temperature rises which might damage the composite and some care is taken to ensure a uniform heat distribution. Results are presented that show the detection of air-filled voids at depths up to 9 mm. A qualitative measure of defect depth can be derived from the test results. A one-dimensional heat conduction model is presented and shown to reproduce the qualitative nature of the measurements in terms of defect depth and type.