Numerical Modeling of Guided Waves in Anisotropic Composites with Application to Air-coupled Ultrasonic Inspection

Abstract

This thesis is about the physics of ultrasonic guided waves in multilayered anisotropic composites. The Stiffness Matrix Method (SMM) is presented, and its implementation into the Dispersion Calculator (DC) is reported. The mode family-specific boundary conditions and characteristic functions as well as the dispersion curve tracing algorithms applied by the DC are discussed. The DC allows the calculation of guided wave dispersion diagrams and mode shapes for laminates containing several hundreds of layers with high efficiency and robustness. A new method of Lamb wave-based non-destructive inspection using an a priori calculated excitation angle map is presented. The Adaptive Slanted Reflection Mode (ASRM) allows the optimal excitation of Lamb waves in CFRP components with varying layups and curvature gradients. The robotic Adaptive End Effector (AEE) enables the in-line adaptation of the Lamb wave excitation angle during the scanning. The ASRM proves superior to the conventional non-adaptive Focused Slanted Reflection Mode (FSRM).