Defect-caused alteration of a composite unit modal parameters

This paper presents research on diagnostic parameters for monitoring conditions of a light aircraft engine blade made of composite materials (CM) in flight. This study covers the modal parameters investigation of the blades in the frequency range of 30-60 Hz. Using the Doppler Effect the vibration response between the used blades and a new blade was compared. The used blades demonstrated a fourfold increase in amplitude of resonant vibration in the first bending mode. The amplitude growth of the first bending mode resonant vibration can be used as a diagnostic sign of emerging defects. The ease of amplitude and frequency analysis of a blade resonant vibration in flight conditions will allow researchers to develop an express-control device for technical condition analysis of CM blades while in air.