Evaluation of elastic constants in composite laminates with guided wave tomography

Ratassepp, Madis; Tallinna Tehnikaulikool; Estonia

Ratassepp, M.; Tallinn University of Technology; Estonia
Rao, J.; Nanyang Technological University; Singapore
Yu, X.; Nanyang Technological University; Singapore
Fan, Z.; Nanyang Technological University; Singapore

ID: ECNDT-0597-2018
Download: PDF
Session: Composite General 2
Room: G1
Date: 2018-06-11
Time: 16:20 - 16:40

Post-impact structural performance of a laminated composite is a concern for aerospace and other advanced industries. Low-velocity impact may cause barely visible but considerable internal damage in structures, which is difficult to detect. To identify and accurately characterize such localized damages, efficient non-destructive evaluation methods are required. In this study, the potential of guided wave tomography to quantify the changes in material properties of a quasi-isotropic composite with a stiffness defect is investigated. The method reconstructs the velocities of guided waves by the inversion of ultrasonic signals captured by a transducer array around the inspection area. The resulting velocity maps are then converted to specific elastic constant maps by the material dependent dispersion characteristics of selected guided modes. The reconstruction is based on a full-waveform inversion algorithm and was implemented on the data obtained from finite element simulations. The sensitivity analysis showed that the Lamb mode A0 is suitable for the determination of effective in-plane Young’s modulus and out-of-plane shear modulus. The reconstruction of these parameters can be decoupled by considering varying sensitivity of the velocity depending on material properties at different frequencies. Numerical results on a localized defect with reduced elastic constants illustrate the interest of this strategy.