Nondestructive evaluation of fiber composite laminates by thermoelastic emission

The measurement of cyclic adiabatic thermoelastic temperature change was assessed for its effectiveness in analyzing dynamic stress or strain fields on the surface plies of graphite fiber epoxy laminates. The radiometer system used in the study was capable of resolving local stresses that reflected global stress distributions and macroscopic variations in material properties including flaws and damage. The advantages of the thermographic technique were that it was full field and rapid, required little sample preparation, was entirely non-contact, and could cover either a large or small area. Its sensitivity to manufacturing irregularities and to service load damage was demonstrated and compared to that for x-ray radiography.