مهندس مرتضی مرادی

The replacement of damaged components is not affordable in important structures such as aircraft, ship or gas pipelines. So, the repair of a defective structure is an acceptable process. Composite patches are used to repair the damaged metal and composite structures in different industries, especially the aerospace industry. Assessment of the repaired structure is a challenging topic 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 pulse phase thermography (PPT) approach. Also, the simulation of thermography testing procedure carried out by finite element modeling (FEM). Finally, the results of the experiment and finite element modeling have been compared and good accuracy has been obtained in step heating thermography and PPT algorithm.

In this paper an extensive analysis have been performed on the buckling and post buckling response of unidirectional delaminated composite panels with the different curvatures (zero and 60 degrees of arc’s angle) by means of finite element method. Adjacent plies debonding is simulated by traction–separation law for the geometries containing one and two delaminations through the width and the influence of them on the response of the structure to the compressive loading is investigated. The effect of intact geometry and defective geometry containing delaminations with and without growth capability have been investigated. The complex contribution between nonlinear geometry, material non linearity, and large deformation is considered. Comparing the present results with other literatures in the special case of flat plates, indicates an excellent accuracy. The differences between the global and local buckling response, stable and unstable delamination growth of structures containing one and two delaminations in flat and saddles geometries is compared.