Reversing fatigue in carbon-fiber reinforced vitrimer composites

Despite decades of research, fatigue remains the primary culprit for catastrophic failure in carbon-fiber reinforced polymeric (CFRP) composites. Existing approaches to combat fatigue are usually based on nano-scale additives that slow the growth of cracks in the polymer. While this prolongs fatigue-life, it cannot avert eventual failure since crack growth is being slowed and not reversed. Other approaches have explored self-healing polymers that release a curing agent to repair local damage. However, this approach also fails to tackle fatigue, since once the curing agent is released, it gets consumed and cannot be re-used. To addresses the irreversibility of fatigue, we report here a vitrimeric system, for which reversal of fatigue damage can be achieved repeatedly, by heating the material to above its topology freezing transition temperature. This enables intermittent healing of fatigue-induced damage, as it accumulates in the vitrimer matrix. Using this approach, we show that fatigue failure in vitrimers and in carbon-fiber reinforced vitrimers (vCFRP) can be postponed indefinitely. Such vCFRPs could open the door to future materials, in which natural aging and fatigue processes can be periodically reversed, so as to guarantee safe and reliable long-term operation.