NONDESTRUCTIVE EVALUATION OF MODEL ADHESIVE JOINTS BY PVDF PIEZOELECTRIC FILM SENSORS

Metallized poly(vinylidene fluoride) (PVDF) films can be etched into nondestructive evaluation (NDE) sensor devices. Since these sensors are relatively inexpensive, thin and lightweight, they can be attached permanently to adhesively bonded joints, laminated composites, and other structures to measure structural integrity. The present study has addressed techniques to design, attach, and utilize such sensors for adhesive joint and laminated composite applications. PVDF sensors have been successfully used as NDE transducers in pulse-echo, through-transmission, and acousto-ultrasonic techniques to monitor curing, and to.detect porosity and crack propagation in different model joint geometries. Feasibility of several applications has been demonstrated, although several problems remain. The potential of using these techniques for practical bonded structures is also suggested.