Damage-Reporting Carbon Fiber Epoxy Composites

The ability to detect early damage is of great significance in load bearing composite materials used for high performance applications. Microdamages if left unchecked can grow under subsequent stress, leading to catastrophic structural failure. The sensing of early stage damage via nondestructive methods is therefore critically important for the safe use of these materials. Herein a supramolecular approach to self-diagnosis of early stage damage in a carbon fiber epoxy composite material, via the incorporation of a CB[8] based ternary complex as an additive is reported. The complex comprising a fluorescent probe and a quencher encapsulated by the CB[8] is introduced into the epoxy resin of the composite as a supramolecular crosslinking agent, whose stress-induced dissociation results in the turn on of fluorescence of the probe. In this way, detection of irreversible mechanical strain and fatigue at an early stage is attainable, enabling the assessment of microdamage in the material.