The potential of thermal nonlinear effects in composite materials was investigated for nondestructive testing. Second harmonic generation in thermal-wave fields has attracted much attention in recent years for the non-destructive evaluation of solid structures. Even though not the only source, the presence of a defect can result in a strong nonlinear signature, which could enhance the detectability of photothermal methods. The following experimental survey trails several theoretical analyses on the subject, mostly for homogeneous isotropic samples. As composite material structures exhibit often thermo-mechanical nonlinearities originating from the polymer matrix, they appeared to be ideal candidates to exploit the potential of nonlinear photothermal radiometry. In this work, a theoretical model that was recently developed is used to estimate the generated overtones that originate from the most common cause of failure of composites, the delamination. Moreover, the theory is experimentally validated using IR photothermal radiometry by modelling the oscillation of the size of the delamination by means of a piezoelectric transducer.
展开▼
