The contribution of numerical models to Lamb wave driven NDT processes – part I: model building

Abstract

Components made of fibre-reinforced polymers (FRP) may suffer from various types of damages, such as cracks or delamination. In order to monitor the structures’ material condition, non destructive testing (NDT) methods have emerged – among them, the use of ultrasonic waves. Inter alia, research focused on Lamb waves (LW), which offer promising conditions for NDT processes. However, prior implementation in a specific production environment, practitioners are faced with many open questions such as excitation frequencies to be used or which mode to select for defect identification. Therefore, the study aimed at demonstrating how a finite element analysis (FEA) can assist the experimental design of an LW driven NDT process. For that, a numerical model was developed, capable of computing LW propagations in an exemplary component: Stringer-stiffened C-FRP panels. The study was divided into two parts: In this part, all information regarding the model building is presented and principal functionality demonstrated. In the second part, the FEA is validated and then used to perform parameter studies, highlighting important conditions for practical application. The results of the present paper showed that stiffeners provoke varying interactions with LW modes – effects that increase wave field complexity but do not limit defect identification within or behind the stringer.