Morteza Moradi - MSc, Iran University of Science and Technology;
Mir Saeed Safizadeh - Associate professor, Iran University of Science and Technology;

Composite patches are used to repair of the damaged metal and composite structures in different industries. Assessment of the repaired structure is challenging in order to ensure the restoration. The thermography technique is one of the most powerful non-destructive testing methods that is used to survey the repaired structures. In the present study, the defects of the de-bonding type between the based aluminum structure and the carbon/epoxy patch made by 4 layers with layup configuration [04] have been investigated by step heating thermography method. Defects locate close to the patch edges because it is more likely that debond onset in a repaired structure at edges in practice. Furthermore, detection of the edge defects is more difficult than the middle defects because of edge effects. The step heating thermography results have been processed by using principle component analysis (PCA) approach and increased contrast. Finally, the results of the experiment and simulation are compared and good accuracy has been obtained in step heating thermography and PCA algorithm

Thermography, Composite patches, Disbond, Finite element modeling, principle component Analysis