Thermal imaging of composites.

Active thermal imaging techniques and their applications to composite materials are reviewed. The techniques included are transient thermography, scanning thermal microscopy and scanning thermal probe microscopy. The factors that affect the images produced by both pulsed and periodic forms of active heating are considered. For pulsed heating, experimental and numerical modelling results for carbon fibre-reinforced plastic are used to show how the resolution of subsurface features depends on their size and depth and on the anisotropy in thermal materials properties common in such composites. For periodic heating, thermal wave characteristics are introduced to show how the resolution of subsurface features also depends on modulation frequency and focal spot radius. Examples are given of the applications of scanning thermal microscopy and scanning thermal probe microscopy that illustrate the potential of these techniques for the imaging of composite materials.