The use of ultrasonic arrays in the field of non-destructive evaluation of composites is a recent technique. This method offers the possibility to achieve fast inspection of components having complex geometries. As compared with the single element transducers, arrays configuration yields more effective detection of defects. However, to achieve adequate imaging by ultrasonic array elements, each element should be excited according to a specific sequence which is called the focal law. At each instant a subset of the array elements is activated and the incident waves are better directed to scattered at the defect. The reflected signals can then be more intensified. In this work, two-dimensional approximation of wave propagation problem was supposed. Array elements with linear geometry and with the elements assumed to be fully coupled with the composite panel were considered. A delamination defect was inserted between the plies of the composite panel at a given depth. The forward model enabling to simulate ultrasonic array data was built by means of the FEM. As each focal position requires a different focal law that fixes a proper protocol of excitation and reception, synthesis of these focal laws was studied. Optimization of signal focalization and reception as function of the delamination extent was achieved.
Optimizing the focal laws of ultrasonic arrays for non-destructive evaluation of composite panels with delamination
