Despite low weight and high strength of composite materials, early failure and their weakness in
vibrational environments are the main obstacles in using them in presence of dynamic loading. Detection
of inter-laminar delamination as one of the most common failures in laminated composites is important
for future life of structure. In this study, the effect of a small size delamination on the modal behavior and
frequency response functions (FRFs) of a composite cylinder is experimentally investigated. Among
usual damage mechanisms, the effect of impact mostly considered as delamination, is increased in four
stages. In each state, modal analysis is implemented and results are compared with those of other states.
Experimental modal analysis shows that small damage doesn’t change natural frequencies. However, raw
data of frequency response functions may leads to damage identification due to the variation of its
features with respect to damage size. To localize damage, the curvature of FRFs are calculated and
compared with those of the healthy cylinder by choosing optimum frequency range.