A method of aerobic depolymerization of fiber-reinforced polymer (FRP) composites using sustainable reagents and conditions. A cured matrix is digested into soluble monomers and oligomers by catalytic aerobic oxidation. Carbon fibers are removed for re-use, then the remaining material is treated and valuable monomers are isolated. The isolated monomers can be converted back into resin precursors for re-use. The method solves the problem created because the typically irreversible cure reaction impedes recycling and re-use of FRP composites.