Tensile properties of recycled carbon fibers subjected to superheated steam treatment under various conditions

A new treatment condition involving superheated steam (SHS) was proposed to achieve optimal carbon fiber recovery with a minimal decrease in fiber strength. Unidirectional carbon fiber reinforced sheets were exposed to SHS at 650 degrees C for 1 h with the addition of N-2 or CO2 as process gas. The recovery was assessed based on mass change and using thermogravimetry and differential scanning calorimetry. The results showed that the addition of N-2 efficiently suppressed the decrease in fiber strength and achieved optimal recovery. Weibull parameters indicated that lower strength fibers tended to present a narrower strength distribution. The observation of fracture surfaces and oblique sections indicated that the presence of intrinsic defects and corrosion of surface crystallites under the oxidative condition are responsible for the deterioration of and the changes in the distribution of strength.