UCLA

The objective of this research is to develop an improved nondestructive evaluation (NDE) technique to inspect composite aircraft and aerospace structures. This work presents an efficient and versatile numerical modeling tool to aid in the design of cost-effective non-destructive evaluation technologies. The global-local method, which combines finite element discretization and Lamb wave modal expansion is used. An extension to the traditional global local method is made to couple the source problem with the scattering problems to deal with a surface source generating Lamb waves that interact with defects in multilayered structures. The modeling tool is first validated against analytical solution and the finite element method. Since the relationship between ultrasonic signal change and the nature of defects is complex, the efficient modeling tool is used to create a library of many damage inspection scenarios for FML and stiffened composites. The waveforms associated to the different damage cases are then used to establish a set of damage indices for damage characterization.