Thermal imaging of composites

Active thermal imaging techniques and their applications to composite mater ials are reviewed. The techniques included are transient thermography, scan ning 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 mod elling results for carbon fibre-reinforced plastic are used to show how the resolution of subsurface features depends on their size and depth and on t he anisotropy in thermal materials properties common in such composites. Fo r 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 th e potential of these techniques for the imaging of composite materials.