Effects of Recycling Processes on Carbon Fiber Strength and Adhesion with PMMA


  • Abigail Conklin, Chemical Engineering, University of Delaware

Faculty Mentor(s)

  • Munetaka Kubota, , University of Delaware


Carbon fibers reinforced composites have high specific strength and stiffness, making them attractive materials for industries such as aerospace, automotive, and energy. The rapid adoption of these materials is resulting in increased scrap and expected end of life parts; therefore, a recycling infrastructure to reclaim and reuse these fibers is necessary. The current recycling process of these composites is limited to grinding and using as filler, though there is ongoing research for pyrolysis/solvolysis for limited fiber reclamation. These approaches can influence the strength and surface chemistry of the fibers due to degradation of the fibers. The objective of this research is to quantify any negative effects of the pyrolysis process to develop a solution which minimizes fiber strength loss and propose approaches to improve fiber/matrix adhesion when redeployed into a composite. This study evaluated as-received Toray T700S carbon fibers, which is widely used in industry, and were compared to recycled fibers under the pyrolysis conditions previously developed in this program. Single fiber tensile tests were conducted to determine the mechanical properties of the carbon fibers before and after pyrolysis. Single fiber pull-out tests were also undertaken to assess the fiber-matrix adhesion properties in a polymethyl methacrylate resin. Significant degradation in tensile properties were observed after the pyrolysis process, but the fiber pullout test did not indicate significant changes to the interfacial shear strength. These results indicate there is potential for improvement in the pyrolysis process to minimize the fiber strength reduction. Further development is necessary to test fiber pullout samples made with the fiber embedded into the resin prior to the polymerization step to better mimic the infusion process and gain insight into the fiber/matrix interactions. Processes to functionalize the surface of the recycled fibers are being developed for application with other resin chemistries.