Self-Healing Composite Structures

The proposed Phase II project will develop and fully characterize self-healing composite materials and selected structural components embodying the principles validated in Phase I research, and will establish criteria for selection of self-healing composites in new applications. Strengthening of damage zones to mitigate catastrophic failure is accomplished in the new composite through dynamic redistribution of structural substance. This process relies on functional (piezoelectric and solid electrolyte) constituents which are introduced, in the primary system configuration, as a hybrid fiber coating. The self-healing phenomenon involves electrolytic transport of structural substance within solid electrolyte towards the damage zone where its deposition yields strengthening effects. This process is guided by piezo-induced potential gradient, which reflects on local stress rise in the vicinity of damage zone. The piezoelectric effect converts the mechanical energy concentrated in damage zone into the electrical energy needed to drive the self-healing process. In short, the self-healing phenomenon makes constructive use of the otherwise destructive strain energy concentrated in damage zone for mitigation of catastrophic damage growth. The Phase I research validated: (i) the viability of electrolytic mass transport in solid electrolytes to render strengthening effects; (ii) the ability of piezo-induced potential and charge to guide and drive electrolytic transport of mass in solid electrolytes; and (iii) the potential to integrate the piezoelectric and solid electrolyte constituents rendering self-healing effects in the context of a hybrid coating system. The following objectives will be accomplished in the proposed Phase II project: (i) development and thorough characterization of nano-structured piezoelectric and solid electrolyte fiber coatings which complement distinctly high functional qualities (greatly benefiting the rate and extent of self-healing) with desirable thermo-mechanical attributes; (ii) development of theoretical models for integrated design of composites for both self-healing and thermo-mechanical performance requirements; (iii) design, processing and thorough characterization of self-healing composite materials; (iv) design, manufacturing and experimental evaluation (of the self-healing attributes and airworthiness) of selected helicopter components (tail cone and elevator); and (v) development of selection criteria for self-healing composites based on application-specific cost/benefit analyses. A multi-disciplinary team of top industrial and university researchers with specialties in composites, piezoelectricity, solid electrolytes, aerospace structural systems and nano-scale processing has been assembled to conduct the proposed research.