Sensing and Acutuation of Composite Piezoelectric Materials for Smart Joint Applications

Abstract

Piezoelectric materials have the ability to provide desired transformation from mechanical to electrical energy and vice versa. When a mechanical force is applied to the piezoelectric material an electrical voltage is generated and when an electrical voltage is applied to the piezoelectric material it gets strained or mechanically deformed. Owing to these characteristics piezoelectric materials can be used as a sensor, an actuator, as well as a power generation unit. The high brittleness property of the original piezoelectric material is one of the major constraints in using them in engineering applications. In order to overcome this difficulty the composite piezoelectric materials were developed. The piezoelectric fiber material is flexible and can sustain large deformation without being damaged, and is compatible with the composite structures processing procedure; which makes it an ideal material to be used as an embedded sensor, power harvesting device, and a force actuator within the composite structures. The smart joint can be designed to have the piezoelectric materials embedded in them, wherein the piezoelectric materials can detect the various loads that act on the composite joint and could provide the required counter-balancing force to the externally applied input excitation forces acting on the joint; and thereby could reduce or even eliminate the effects of stress concentrations at the composite joint. High stress concentrations are one of the principal causes of structural failures as it may cause unexpected high stresses exceeding stress level caused by design loads. In this work our main objectives are to study the sensing and force generation capabilities of various commercially available composite piezoelectric configurations through series of experimentations; and to compare their performances in order to use them in the smart joint applications; and eventually, to reduce the detrimental effects of stress concentrations in the structures. Firstly, the sensing capabilities of these piezoelectric materials were investigated at various input frequencies and amplitudes of the vibration loads. Secondly, the tensile and bending force generation capabilities of these piezoelectric materials were inspected with respect to various input excitation voltages. The results of these experiments confirm that the voltage signals generated from these materials are proportional to the amplitudes of mechanical movement, with good response to high frequencies, even at micrometer deformation domain; but the force generation is relatively low under the input conditions investigated.