Figure 8

Wave vector (left) and dispersion (right) curves for an angle-ply composite plate. Longitudinal (\(k_L\)), shear (\(k_S\)) and bending (\(k_B\)) curves are depicted in purple, black and red colour, respectively. Squares and circles denote wave numbers of incoming and outgoing waves, respectively. Furthermore, green squares and circles represent parts of the shear wave vector and dispersion curves that exhibit negative group velocity behaviour. The wave vector curves are plotted for a fixed frequency \(f=3000\) Hz, whereas the dispersion curves are plotted for a fixed wave number component \(k_x=5 \, \text {m}^{-1}\).