Procedures developed for self-repair of polymer matrix composite materials

An investigation was made into the feasibility of developing polymer matrix composites which have the ability to self-repair internal cracks due to mechanical loading. It focused on the cracking of hollow repair fibers dispersed in a matrix and the subsequent timed release of repair chemicals which result in the sealing of matrix cracks, the restoration of strength in damaged areas and the ability to retard crack propagation. These materials, capable of passive, smart self-repair, consist of several parts: (1) an agent of internal deterioration such as dynamic loading which induces cracking; (2) a stimulus to release the repairing chemical such as the cracking of a fiber; (3) a fiber; (4) a repair chemical monomer carried inside the fiber either a part polymer or a monomer; and (5) a method of hardening the chemical in the matrix in the case of crosslinking polymers or a method of drying the matrix in the case of a monomer. It was found that cracking of the repair fiber and subsequent release of the repair chemicals could be achieved. Release of chemicals into cracks was observed using optical microscopy. Impact fracture and bend tests were performed and revealed the ability of this system to fill and repair cracks, restore strength and retard crack growth. This work was accomplished by Natural Process Design. These results were positive.