DETERMINING FIBER VOLUME FRACTION AND POROSITY IN ORTHOTROPIC COMPOSITE LAMINATES

ULTRASONIC NONDESTRUCTIVE TESTING HAS BECOME THE METHOD OF CHOICE FOR THE QUALITY ASSURANCE OF ADVANCED COMPOSITE MATERIALS. THE PROPOSED RESEARCH PROGRAM COVERS THE DEVELOPMENT OF A COMPUTER-BASED NDT METHOD FOR DETERMINING LOCAL FIBER VOLUME FRACTION AND RESIN POROSITY IN PRACTICAL LAMINATED COMPOSITES. THE COMPUTER ALGORITHMS WILL BE BASED ON EARLIER STUDIES THAT HAVE BEEN SUCCESSFUL FOR UNIDIRECTIONALLY REINFORCED COMPOSITES. THEY DEPEND ON SIMULTANEOUS MEASUREMENTS OF TWO ULTRASONIC WAVE VELOCITIES USING IMMERSION TRANSDUCERS. THE SPECIFIC OBJECTIVES OF THE PHASE I STUDY ARE TO DEVELOP A DETAILEDMODEL FOR WAVE PROPAGATION AT OBLIQUE INCIDENCE ANGLES, CHECK THE ANALYTIC MODEL EXPERIMENTALLY, AND MODIFY EXISTING ALGORITHMS FOR FIBER FRACTION AND POROSITY DETERMINATION IN COMPLEX LAMINATES. ADDITIONAL GOALS INCLUDE THE DESIGN AND TESTING OFFIXTURES TO HOLD THE REQUIRED TRANSDUCER ASSEMBLIES AND THE TESTING OF PRACTICAL LAYUPS (WITH SHAPE AND LAMINATION VARIATIONS) TO VERIFY THE PROCEDURE.