ABSTRACT
Composite materials are widely used in aeronautical, marine and automotive
industries, because of their excellent mechanical properties, low density and ease of
manufacture .However, composite laminates are susceptible to delaminations, which
may not be visible externally, but can substantially affect the performance of the
structure. Vibration testing, in particular delamination detection, in the composite
structures is an active research area. D'Alembert principle is used to determine the
theoretical natural frequency of laminated orthotropic composite plate. The present
free vibration experimental study of simply supported square laminated plates is
based on the comparison between natural frequencies of healthy and delaminated
composite plates. The test square plates made of hand lay up 8 layers E-glass
woven fibre and epoxy resin are used here. The present paper discusses the
observations made on the measured natural frequencies of vibration testing from
both the healthy and the delaminated square simply supported plates. The possibility
of the delamination detection by vibration testing is also introduced. The effects of
delamination area on the natural frequencies of the plate are presented. The
delamination in composite laminates has considerable effect on the natural
frequencies of the plate.