Optothermal analysis of polymer composites

Abstract A number of thermographic techniques under optical‐radiation heating are described for the nondestructive evaluation of different kinds of fiber‐filled polymer‐based composites. Shallow delaminations within carbon‐fiber reinforced laminates can be detected by this method under wide‐area surface heating to 5 or 10° above ambient. A number of image‐processing algorithms are described for improving the visibility of subsurface defects. Spot‐heating techniques are presented for the characterization of fiber concentration, distribution, and orientation in carbon or steel fiber‐filled composites. Particular emphasis is given to the possibility of mapping fiber‐orientation properties at gradually deeper layers below the surface. These optothermal techniques appear to be a convenient tool for the inspection of opaque composites in terms of rapidity, lack of sample preparation requirement, and simplicity both in its implementation and in the interpretation of results.