The research objective of this award is to study a new form of autonomous material that senses the presence of damage and use stimulus to not only heal the material but to toughen it against the propagation of damage. This objective will be accomplished through the synthesis of light activated shape memory polymers that incorporate cinnamic moieties, which are able to undergo efficient photoreversible cycloaddition reactions when exposed to alternating wavelengths of light. This reversible reaction will be used to actively cleave and reform covalent crosslinks to mitigate the propagation of damage though local modulus changes at the crack tip, achieve shape recovery for crack closure and to ultimately reform crosslinks across the crack face to recover the strength of the material. A fiber optic network will be employed to detect and signal the presence of damage while providing a mechanism to deliver stimulus directly to the crack tip. The shape memory effect will provide a means to recover the plastic strain induced at the crack front thus returning the material to its original geometry, relaxing built up stresses and bringing the crack faces into intimate contact to allow healing of the damage.
The broader impacts of this award focus on the bridging of structural health monitoring and autonomous systems that can react to heal damage in a controlled and repeatable manner. This includes the design of sensor systems and signal conditioning hardware in coordination with the host structure rather than the ad hoc deployment currently used. Furthermore, this research will impact the current state in photoresponsive polymers allowing their integration into a range of new applications. The goal of the education component is to use the concept of biologically inspired systems and smart materials to demonstrate the multidisciplinary character of modern engineering and to stimulate the educational growth of students.
