Abstract
Composite laminates have some problems, such as damage tolerance and delamination resistance etc. To overcome these problems, reinforcement fiber is distributed in the direction of thickness of composite laminates. This technique improves some properties, but reduces in-plane mechanical properties of plate. Present study focuses on the change of natural frequencies caused by decrease of elastic modulus using some plate theories. Reinforcement fiber was found to make decrease in natural frequencies depending on fiber orientation and vibration mode.
