Propeller generates the traction force required for self-rotation,
which is necessary for airplane flight. At the same time, propeller is
subjected to periodic disturbance of pressure and generates aerodynamic
forces and moments that cause vibrations on propeller
blade. These forces and torques may show their effect in different
ways and can cause strain due to torsion and stretching. Propeller
respond to different excitation forces depends on its natural frequency,
vibration reduction and blade stiffness [30]. Propeller
blades are flexing in the direction of the aircraft flight due to the
pulling force effect. The thrust force moves the aircraft in the direction
of flight and also opposes the centrifugal force. The most influential
force affecting the blades is the centrifugal force. It affects
the blades by stretching them from the hub to the blades tip. The
torque effect results in bending the blades towards the back, opposite
to the direction of the propeller rotation [30].