NONDESTRUCTIVE EVALUATION OF MODEL ADHESIVE JOINTS BY PVDF PIEZOELECTRIC FILM SENSORS

Metallized poly(vinylidene fluoride) (PVDF) films can be etched into n ondestructive evaluation (NDE) sensor devices. Since these sensors are relatively inexpensive, thin and lightweight, they can be attached pe rmanently to adhesively bonded joints, laminated composites, and other structures to measure structural integrity. The present study has add ressed techniques to design, attach, and utilize such sensors for adhe sive joint and laminated composite applications. PVDF sensors have bee n successfully used as NDE transducers in pulse-echo, through-transmis sion, and acousto-ultrasonic techniques to monitor curing, and to.dete ct porosity and crack propagation in different model joint geometries. Feasibility of several applications has been demonstrated, although s everal problems remain. The potential of using these techniques for pr actical bonded structures is also suggested.