Self-Healing Composite Structures

The main thrust of the proposed research is to develop a novel fiber coating system which builds self-healing attributes into fiber reinforced composites. The new fiber coating is a layered composite of piezoelectric and solid electrolyte constituents. The piezoelectric layer generates electric potential in response to fiber stress rise in damaged areas. This potential drives electrochemical processes in the context of the solid electrolyte layer, which transport structural substance towards highly stressed (damaged) areas where they would be electrodeposited to render self-healing effects. The structural substance rendering self-healing effects comprises metallic nanoparticles dispersed within the solid electrolyte layer. The system essentially converts the mechanical energy input of service environment (which concentrates in damaged areas) to electrical energy for driving the self-healing process. Self-healing is an intrinsic attribute of this system, with piezoelectricity providing for both sensing and actuation effects, and concentration of stresses in damaged areas yielding an inherent control of the self-healing phenomenon. We have conducted fundamental theoretical studies to validate the following key hypotheses of our approach: (1) piezoelectricity can generate the potential needed to drive electrolysis phenomena within solid electrolytes; (2) conversion of mechanical to electrical energy by piezoelectric effect can generate the charge needed to transfer structural substance at viable rates; and (3) increased concentration of metal nanoparticles within polymer-based coatings can make meaningful contributions to the mechanical performance of fibers, thereby strengthening damaged areas of fiber composites. Our approach focuses on enhancing the mechanical performance of fibers (in lieu of the matrix) in damaged areas, recognizing the critical contributions of fibers to mechanical performance of composites. The proposed Phase I (and Phase I Option) research will establish an analytical framework for design of self-healing composites, and will experimentally validate the fundamental principles of the approach through establishment of processing methodologies, and design, fabrication and experimental verification of basic self-healing composites embodying our principles. A multi-disciplinary team of top industrial and university researchers with specialties in the fields of composites, piezoelectricity and solid electrolytes has been assembled to conduct the proposed research.