A Multi-Purpose Sensor for Composite Laminates Based on a Piezo-Electric Film

Abstract

In this study, a multi-purpose sensor for composite laminates is devel oped. The sensor is based on a piezo-electric film. A specialty charge amplifier was devel oped for signal conditioning for long time duration measurements. Experiments were con ducted to show the utility of the sensor for static and dynamic strain measurement. By effectively isolating the piezo film for unidirectional strain, a method was developed to utilize the piezo sensor for general, in-plane strain sensing, regardless of the constitutive properties of the laminate. Non-destructive evaluation in through-transmission and pulse- echo modes were shown to be effective for measuring and quantifying damage in lami nated structures. Using the piezo film as a sensor to detect impact, it was shown that an "event" as well as the onset of damage can be accurately measured. With standard acoustic emission equipment, the piezo film proved to be an effective direct substitution for typical piezo-crystals at a fraction of the cost and weight for acoustic emission monitoring in ad vanced composite laminates. The onset of damage, as well as damage location were ac curately measured. The preliminary results indicate that the sensor is quite versatile, inex pensive and sensitive for a variety of sensing applications in advanced composite laminates. In particular, the electronics needed for signal conditioning are much less elab orate than typical sensors such as strain gages, piezoceramic sensors, thermocouples, etc.