Feasibility Study of Microfabrication by Coextrusion (MFCX) Hollow Fibers for Active Composites

Active composites based on a hollow fiber topology have advantages over solid piezoelectric fiber composites in that they require lower voltages for activation and are not limited to electrically non-conductive matrix materials. One critical issue for hollow fiber composites is the fiber aspect ratio (ratio of wall thickness to fiber radius). In this paper analytical and finite element models, which include electric field variations, were developed to determine the “effective d ₃₁ ”of an individual piezoelectric hollow fiber. The effective fiber properties were used to derive a single-row lamina strain/electric field model from classical composite theory. The models were validated with a series of deflection/voltage experiments conducted with hollow piezoelectric fibers fabricated utilizing microfabrication by coextrusion (MFCX) techniques. To determine the feasibility of MFCX hollow fiber composites, the models and experimental results were employed to study the effect of the fiber aspect ratio on a variety of fiber/composite design issues: fiber/lamina performance, fiber strength, matrix material, and electric field effects (incomplete poling and field concentrations).