GUIDED-WAVES IN MULTILAYERED PLATES FOR INTERNAL DEFECT DETECTION

In this paper, stress and displacement fields inside a multilayered pl ate are analytically computed. For the theoretical modeling, individua l layers of the multilayered plate are assumed to be elastic and homog eneous, but anisotropic. These theoretical computations are then exper imentally verified in a qualitative manner. Experimental investigation s are carried out on a ceramic composite plate that has 12 plies of fi bers going in 0 degrees and 90 degrees directions, [0,90](3s). The inc ident angles and frequencies of the ultrasonic signal for generating d ifferent Lamb wave modes in this plate are obtained experimentally as well as from the theory. Displacement and stress fields inside the pla te for some of these Lamb nodes are then computed. Computation of stre ss and displacement fields inside the plate is useful for studying the internal damage. Internal stress distribution varies significantly fr om one Lamb mode to another. Hence, different Lamb modes should detect defects in different layers of the plate. The Lamb mode that produces maximum stress in a specific layer should be most sensitive for detec ting defects in that layer. This is observed experimentally as well.