Tensile Strength of Carbon Fibers Reclaimed from CF/Epoxy Composite Using Subcritical Water and Supercritical Methanol

Abstract

Carbon-fiber reinforced epoxy was decomposed using subcritical water and supercritical methanol to reclaim carbon fibers. The tensile strength of the reclaimed carbon fibers was measured. Then SEM observation, XPS, and Raman spectral analysis were conducted to elucidate the change of tensile strength caused by decomposition. The tensile strength decreased by 6% in the case of decomposition with supercritical methanol, and by 12~17% with subcritical water. The surfaces of reclaimed carbon fibers were resin-free. Decomposition did not affect the fiber surface and fracture surface morphology. Subsequent XPS analysis revealed that functional groups of the carbon fiber surface had been removed. Raman spectral analysis showed decreased graphitization of the carbon fiber surface. These results imply that the fracture toughness of the carbon fiber surface decreased because of breakage of carbon-carbon bonds in the carbon fibers as a result of decomposition.