Dynamic response of composite laminates has received a great deal of attention. One of the most common defects in composite laminates is delamination. The presence of delamination may cause changes to the vibration characteristics of the structure and can be the most damaging failure mode of composite materials. The free vibrations of composite beams with multiple delaminations have extensively studied by Shu and Della [
]. Stepped beams and beams resting on elastic foundation are increasingly used in various fields in structural engineering and their dynamic properties have been investigated by many authors [
]. In the present work the basic ideas of [
] have been extended to the following cases: (i) delaminated composite beams resting on elastic foundation, (ii) delaminated composite beams with piece-wise constant thickness.
The through-width delaminations are parallel to the beam surface and located arbitrarily in both the span-wise and thickness-wise direction. The beam is modeled as consisting of separate component segments each being analysed as an Euler beam. The effect of elastic foundation to the vibration characteristics and mode shape of delaminated beam has been considered. The influence of delamination size and position on the natural frequencies of the stepped beam has been investigated.