Effects of Novel Solvolysis Recycling Processes on Mechanical Properties of Carbon Fibers

• Stephen Wagner, Mechanical Engineering, Syracuse University

• Munetaka Kubota, Center for Composite Materials, University of Delaware

As carbon fiber reinforced polymer composites (CFRP) are being deployed at an accelerated pace, a solution for scrap and end of life recycling of carbon fiber becomes critical. Carbon fiber has a high embodied energy of around 200 MJ/kg due to the need to process at 1000°C after creating a polymer fiber. With an estimated 24000 tons of carbon fiber waste being thrown away, the motivation for recapturing the carbon fiber is clear. Our partners at the National Renewable Energy Laboratory are successfully developing a solvent based method to depolymerize and remove the matrix from epoxy-based CFRPs. However, the damage to the fiber due to the depolymerization process is not understood. In this study, we use a single filament tensile test to characterize the changes in the tensile properties of Toray T700 carbon fibers recycled by this novel process to evaluate whether the process degrades the fibers. These samples, along with as received samples, were tested at a gauge length of 12 mm and the diameters were measured for each individual fiber prior to testing. The strength, strain to failure and modulus were calculated and compared to the manufacturer’s data sheet. The as received fibers showed lower mechanical properties than expected, which could be due to the difficulties separating the individual fibers due to the sizing packages that glue the filaments together, causing some damage during isolation and resulting in strengths lower than expected. The recycled samples showed no signs of degradation as the mechanical properties matched very closely with the data sheet.