A NOVEL APPLICATION OF ULTRASONIC TOMOGRAPHY FOR POROSITY DISTRIBUTION MAPPING IN COMPOSITES

CONVENTIONAL ULTRASONIC NONDESTRUCTIVE EVALUATION IS CAPABLE OF DETECTING POROSITY IN RESIN-MATRIX COMPOSITES, BUT CANNOT EVALUATE THE POROSITY DISTRIBUTION, NOR EVEN EVALUATE RELIABLY THE PROPER POROSITY PERCENTAGE. THIS STUDY IS PROPOSED TO DEVELOP AN ULTRASONIC TOMOGRAPHY TECHNIQUE FOR MAPPING THE POROSITY DISTRIBUTION IN RESINMATRIX COMPOSITES. THE BASIS OF THE PROPOSED APPROACH IS TO USE THE TOMOGRAPHICAL PRINCIPLE TO EXTRACT THE LOCAL PROROSITY LEVEL FROM THE AVERAGE VELOCITY OR ATTENUATION VALUES MEASURED ALONG MANY SETS OF PARALLEL PROPAGATION PATHS. RELIABLE EMPIRICAL RELATIONSHIPS BETWEEN VELOCITY OR ATTENUATION AND POROSITY WILL BE FIRST ESTABLISHED FOR SAMPLES OF UNIFORM POROSITY. THE INVESTIGATION WILL NOT BE RESTRICTED ONLY TO LONGITUDINAL-WAVE NORMAL INCIDENCE, BUT WILL ALSO INCLUDE SHEAR-WAVE AND WAVEGUIDE MODES TO BE EXCITED AT OBLIQUE INCIDENCE. THE DEVELOPED TECHNIQUE WILL THEN BE TESTED ON SAMPLES OF ARBITRARY POROSITY DISTRIBUTION TO DETERMINE ITS TECHNICAL FEASIBILITY. THE FINAL OUTPUT IS EXPECTED TO BE A SPATIAL MAPPING OF THE POROSITY DISTRIBUTION.