Ultrasonic polar scans as a possible means of non-destructive testing and characterisation of composite plates

The ability of ultrasound to characterise fibre-reinforced composites is well-known ( 1 - 1 5 ) . Many techniques have been introduced, of which 'time-of-flight' measurements are now wellestablished ( 6 - 1 5 ) . The technique that is introduced here differs from time-of-flight measurements in that it is based on amplitude measurements. A polar scan represents a fingerprint of the mechanical properties of a targeted spot on an investigated material. It is formed by registering the reflected or transmitted sound amplitude as a function of each possible angle of incidence. The present paper reports the ability of ultrasonic polar scans to determine the fibre orientation, the fibre volume fraction, the porosity and to monitor fatigue damage.