Piezoceramic hollow fiber active composites.

摘要

The field of active composites is rapidly growing, spanning a broad range of applications including vibration, acoustic, shape, and flow control. Unfortunately, current active composites require high activation voltages and are incompatible with conductive matrices. One potential solution to these issues is a composite based on hollow, radially-poled long piezoelectric fibers. The goal of this research was to develop and characterize this hollow fiber design to improve the state of the art of active composites by enabling the use of conductive matrices, lowering voltage requirements, and maintaining a level of performance and reliability suitable for active composite applications.; One main objective of this research was to physically demonstrate the feasibility of fabricating and activating a long hollow piezoelectric fiber. The Microfabrication by Coextrusion method was employed, producing fibers with excellent geometric and material properties. Modeling the hollow fiber revealed that aspect ratio, a design parameter describing wall thickness, strongly impacts the performance and reliability of the active composite. The effect of aspect ratio on performance was modeled and experimentally validated, yielding effective fiber and lamina piezoelectric properties. For a given matrix material, an optimum aspect ratio was identified which produces the highest lamina strain. Aspect ratio also played an important role in composite reliability, demonstrated through transverse fiber strain modeling, embedding stress modeling, and tensile strain-to-failure testing.; In comparing hollow fiber composites to the current state of the art, their reliability closely matched that of solid fibers, exhibiting an optimum failure mechanism and a high level of fiber/matrix adhesion. The maximum strain of hollow fiber composites is slightly lower than solid fiber composites due to the reduced strain associated with the ‘3-1’ versus the ‘3-3’ mode of piezoelectric actuation. However, this level of strain is achieved at voltage reductions as great as 97% when compared to solid fiber composites. Furthermore, the ability to isolate the inner and outer electrodes was demonstrated through a new electrode pattern, allowing the use of conductive matrices. Therefore, the hollow fiber design has the potential to improve the state of the art of active composites, and the field of smart structures in general.