Vitrimer Composites for Rotorcraft Components

Abstract

Carbon fiber reinforced composites (CFRP) are frequently used in rotorcraft components due to their high strength to weight ratio. Carbon fibers are the principal load carriers whereas polymer matrix provides structural integrity to the CFRP components. Fatigue failure originating in the matrix pose a design constraint on CFRP components. The fatigue failure originates in form of small scale sub-critical cracks which eventually grow into macroscopic cracks/shear localization resulting in eventual failure. Research efforts have been directed at improving fracture and fatigue performance of polymeric matrix by arresting incipient cracks. Thermoset polymers are widely used as matrix material as they posses superior strength due to high crosslinking density. However, since no self-healing mechanism operates in thermosets, damage is irreversibly accumulated over the life cycle of components. A new class of materials called vitrimers provide a novel approach to develop fatigue resistant CFRP. Vitrimers are associative covalent adaptive networks (CAN) which have reversible crosslinking reactions which can be activated by external energy stimulus like heat. As the crosslinked network is reversible, the incipient damage can be 'healed' by application of heat. In this work we explore the self-healing properties of vitrimer fabricated by the reaction of adipic acid and epoxy resin. The vitrimer is initially tested in static tests to probe mechanical properties, followed by fatigue experiments. The vitrimer is then used to make a vitrimeric CFRP (vCFRP) composite and is tested for its static and fatigue performance.