Material characterization of active fiber composites for integral twist-actuated rotor bladeapplication

Abstract

The primary objective of this work was to perform material characterization of theactive fiber composite (AFC) actuator system for the Boeing active material rotor(AMR) blade application. The purpose of the AMR was to demonstrate activevibration control in helicopters through integral twist-actuation of the blade. TheAFCs were a new structural actuator system consisting of piezoceramic fibersembedded in an epoxy matrix and sandwiched between interdigitated electrodes toenhance actuation performance. These conformable actuators were integrateddirectly into the blade spar laminate as active plies within the composite structureto perform structural control. Therefore, extensive electromechanical materialcharacterization was required to evaluate AFCs both as actuators and as structuralcomponents of the blade. The characterization tests designed to extract importantelectromechanical properties under simulated blade operating conditions included nominalactuation tests, stress–strain tests and actuation under tensile load tests. This paperpresents the test results as well as the comprehensive testing procedure developedto evaluate the relevant properties of the AFCs for structural application. Thematerial characterization tests provided an invaluable insight into the behaviorof the AFCs under various electromechanical conditions. The results from thiscomprehensive material characterization of the AFC actuator system supportedthe design and operation of the AMR blades scheduled for wind tunnel tests.