Functionalized polymer matrix and/or reinforcement materials that are capable of a thermoreversible Diels-Alder reaction are useful for making composite materials. Also disclosed is a composite material which includes one or both of functionalized reinforcement materials and functionalized polymer matrix materials, as well as a method for repairing a composite material including the step of thermally treating the composite material at a temperature sufficient to react a functionality on one of the reinforcement material and the polymer matrix material with another functionality via a Diels-Alder reaction. A method of making a composite material including functionalizing one or both of a reinforcing material and a polymer matrix material with a first reactive group, providing a second reactive group capable of undergoing a Diels-Alder reaction with the first reactive group and reacting the first and second reactive groups to form a composite material, is also described.