Reformable Vitrimer Patches for Composite Repair: Vitripatch

Composite structures are widespread in Naval systems, and require special repair methods. These repairs are essential to return structures to service, extend their service life, ensure safety for personnel, and mitigate maintenance costs. An added challenge is executing repairs in a non-controlled, contested environment. Composite repair techniques have not changed significantly over time, are slow, and are difficult to implement such that quality can be ensured. Vitrimers have gained attention over the past decade as a potential alternative to conventional thermoset polymers because of possible reformability, recyclability, and reusability. Vitrimers feature a dynamic chemistry with covalent bonds that can be exchanged and rearranged in response to external stimuli, typically heat. We propose to leverage the reformable nature of vitrimers and vitrimer composite materials to develop suitabe composite repairs for Navy structures. Novel process monitoring techniques will be applied to understand process phenomena and to mitigate defects. We aim to demonstrate vitrimer repair patches with (a) mechanical properties comparable to a carbon fiber (CF) epoxy parent structure representative of Navy vehicles, and (b) reformability to conform to and join to parent structures.  The project will determine the feasibility of using vitrimer patches for repairing composite damage on contoured surfaces with a technical approach. In Phase I Base, we will identify suitable prepregs, determine the best method for joining to a CF-epoxy (CFRP) parent structure, and demonstrate reformability. Three technical objectives are identified: (1) Assessing vitrimer prepreg systems for composite repair suitability, (2) Joining vitrimer composite patches to a CFRP parent structure, and (3) demonstrating vitrimer composite reformability on a contoured surface. Upon completion of Phase I Base, a vitrimer repair system will be selected for suitability to composite repairs on a contoured CFRP parent structure. To extend the work to Phase II, the Phase I Option will (1) measure mechanical properties of the vitrimer patch after reforming, (2) expand the vitrimer patches to scarf repairs to increase property levels of joints, and (3) evaluate vitrimer prepreg reformability onto flat scarf angles.