Finite element evaluation of the effects of curvature in Lamb waves for composites structural health monitoring

Abstract

This work presents the effect of the high curvature to thickness ratio on the characteristics of Lamb Waves propagating over the skins of composite structures. It is accessed how the curvature on composite skins affects the group velocity of the symmetrical (S0) and asymmetrical (A0) wave modes. It is also accessed the gradient of curvature effect, when the wave propagates from a flat to a curved part on the skin. The results are intended to be used for the improvement of structural health monitoring of wings and wind turbine blades. This is accomplished through dynamic explicit linear finite element method simulations of plates with flat and curved parts made of Eglass-epoxy bidirectional laminate. As the skin structures are often designed to withstand torsional loads, the fibers are aligned with 45 degrees from the leading edge (curved region) throughout the analysis. Several skins with different curvature to thickness ratios are generated and simulated. Results and trends are presented and can be used to improve the algorithms for damage detection on those structures. It is shown that the group velocity of the incoming waves change considerably with the presence of curvature, for both main modes of vibration.

Finite Element Modeling Approaches, Experimentally Assessed, for the Simulation of Guided Wave Propagation in Composites

“…In addition, "optimal frequencies" were identified for each mode, at which, even for high curvatures, the differences in phase velocity were minimal. The authors Santana et al [11] presented the effect of high curvature to thickness ratios on the characteristics of Lamb waves that were propagating over the skins of composite structures. For the curved portion, the S 0 wave mode velocity increased asymptotically with an increase in radius, whereas the A 0 wave mode exhibited an opposite behavior.…”