Continuous Mode Conversion of Lamb Waves in Carbon Fibre Composite Plates—Occurrence and Modelling

Abstract

Recent experimental investigations with scanning laser vibrometer showed irregularities in assumedly undamaged CFRP plates with transiently excited symmetric (S0) and antisymmetric (A0) wave groups. The faster S0- and slower A0- waves occur and move as expected, but arising waves between the primarily excited symmetric and antisymmetric wave groups represent an anomaly in wave behaviour. Since these waves turned out to be A0-waves and extend over an area, they indicate quasi “continuous†mode conversion. The paper includes explanations about why and where this phenomenon occurs. Furthermore, suggestions for the modelling of the “continuous†mode conversion in CFRP plates, using 2D spectral finite elements in the time domain for the plane strain state, are presented.