Investigation on fundamental modes of guided waves propagating in symmetric and nonsymmetric composite laminates

A quasi-isotropic composite laminate is constructed in an attempt to create a structure that behaves like an isotropic plate. Its membrane behavior is similar to that of the isotropic plate while the bending behavior is quite different from the latter. Moreover, the laminae may or may not be arranged symmetrically with respect to the mean plane thereby resulting in a different mechanical response. In this work, guided wave propagation along multiple directions in symmetric and not symmetric quasi-isotropic plates is evaluated. Experimental and numerical results for the fundamental modes A0 and S0 are analyzed for the symmetric and nonsymmetric layups. An eight-node brick type element based on the three-dimensional theory is used in modeling to predict numerically the velocity of wave modes propagating in the graph-ite/epoxy composite plates. Agreement between experimental and numerical approaches is found and interesting dependencies between velocity of propagating modes and laminate stacking sequence are discussed. A final comparison with analytical dispersion curves obtained by the implementation of the global matrix method is discussed.