Effects of fiber sizing on fiber matrix interface of Carbon fiber

• Matthew Blair, Mechanical Engineering, University of Delaware

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

Carbon fiber reinforced composites have been rapidly adopted by many industries for a variety of uses. Having this strong fiber matrix interface allows for load-sharing ability between the fibers and the matrix making the material stronger. The rapid adoption of carbon fiber products has led to thousands of pounds of scrap material that tends to end up in landfills. This drastic increase in carbon fiber use has made a sustainable recycling practice a major concern. However, carbon fiber has a similar embodied energy to stainless steel or aluminum but is recycled at a much lower rate. Current recycling methods of pyrolysis and solvolysis are used to remove the matrix that was on the fibers but this can also remove the sizing that was added to the fibers to protect them and increase adhesion with the matrix. Novel processes are being developed by collaborators at the National Renewable Energy Laboratory that have had success with depolymerizing the epoxy matrix but the effects of this process on the fiber-matrix interface are not known. In preparation for this evaluation, the interface strengths between epoxy sized and unsized Toray T700S carbon fiber with a commercial epoxy system Axiom 201UD were evaluated using a fiber pullout test. This set of results showed the commercially sized system had a modest boost in strength. The interface strength of the recycled fiber with the same epoxy system will be evaluated in the coming weeks to understand how the recycling process affects the surface chemistry and the interface strengths.