Electrolytic deposition of PZT on carbon fibers for fabricating multifunctionalcomposites

Abstract

Piezoelectric fiber composites (PFCs) have been developed in order to overcome the fragilenature of monolithic piezoelectric materials by embedding piezoceramic inclusions into apolymer matrix. The flexible nature of the polymer matrix protects the piezoelectric fiberfrom damage or fracture under mechanical loading and allows the composites to be easilyconformed to curved surfaces for use in many applications. Although PFCs have manyuseful properties, they still suffer from several drawbacks, namely the requiredseparate electrodes make it impossible to embed the composites into the hoststructure, and the relatively low tensile modulus of the piezoelectric inclusion meansthat it contributes little to structural properties. To resolve the inadequaciesof current PFCs, a novel active structural fiber (ASF) was developed that canbe embedded into a composite structure to perform sensing and actuation, andprovide load bearing functionality. The concept and feasibility of this ASF hasbeen validated by coating a silicon carbide (SiC) fiber with a barium titanate (BaTiO3) shell using electrophoresis deposition techniques. However, lead based ceramics react withSiC fiber during high temperature sintering and thus the use of these highly coupledpiezoceramics requires alternative deposition approaches. This paper will introduce anew ASF fabricated by coating a single carbon fiber with a concentric PZT (PbZr0.52Ti0.48O3) shell using electrolytic deposition (ELD). ELD quickly and uniformly coats the fiber and,since the PZT precursor has a low crystallization temperature, the carbon fiber is notexposed to high sintering temperatures which typically degrade the in-plane materialproperties of the fiber and composite. Carbon fiber has been widely used in industry andstudied in academia due to its excellent mechanical properties, while PZT has beenextensively used for sensing or actuation because of its high piezoelectric coupling. Crystalstructures of the PZT before and after annealing are characterized by means of x-raydiffraction, and a pure perovskite structure of the PZT after annealing is shown.