Square Pulsed Thermography (SPT) and Digital Speckle Photography (DSP): Non-Destructive Testing (NDT) Techniques Applied to the Defects Detection in Aerospace Materials

The use of composite materials is rapidly increasing in the production of aerospace structures. To match these advanced structures, a modern approach to their inspection and integrity monitoring is required. Composites are by nature inhomogeneous and anisotropic, establishing a good bond before the component enters service is paramount if the structure is to behave as expected by the designer. Constant strength throughout the structures life span requires periodic inspections, so that defects can be detected and eventually repaired at the lowest possible cost. Appropriate testing is needed to verify that the component is effectively bonded and has the required strength without damaging the part in any way. The principal defects that damage these materials are: delaminations, disbonds/unbonds, porosity, and cracks. In our paper, we have focused our attention on a glass fiber composite specimen with fabricated defects typically used for the lining of Agusta 109 LUH and Mc Donnel Douglass helicopters. The damage assessment methodology proposed is an integrated approach between two non-destructive techniques: square heating (SH) thermography and digital speckle photography (DSP). A comparative experimental investigation is discussed herein to evaluate the performance of SH and DSP for the non-destructive testing on this specimen.