K.P. Cortés-Guzmán, Z. Demchuk, T. Saito, Y. Jiang, R. Advincula
Oak Ridge National Laboratories,
United States
Keywords: 3D printing, composites, small fiber reinforced composites, carbon fibers, bio-based, additive manufacturing, interfacial adhesion
Summary:
Because of their high mechanical strengths, lightweight, high strength-to-weight ratio, and thermal stability among others, carbon fiber(CF) composite materials are ideal for high-performance applications in industries like aerospace, automotive and sports equipment. However, there are several obstacles to overcome, particularly regarding the CF’s and resin matrix's interfacial interactions. The fiber surface may create empty spaces between the fiber and the resin if the CF’s wettability is poor. This could make the composite more likely to fail and lower its overall mechanical performance. Chemical bonding through surface functionalization of CFs offers a customizable strategy for high interfacial adhesion through chemical bonding and improved wettability of the CF’s. Furthermore, improved compatibility of the composite resin with 3D printing technologies may position the resulting materials in a convenient spot for fast prototyping and production of complex parts for advanced manufacturing. CFs are typically difficult to 3D print using light-mediated polymerization. Their uneven carbon fiber distribution in the resin matrix causes the fibers to precipitate into the vat and further block the light source, which lowers the penetration depth and, consequently, the polymerization. In this work we show that hydrazide functionalized CFs (fCFs) can be effectively 3D printed with a methacrylate resin containing reactive moieties and through chemical bonding between the resin and the fCFs, increase in compressive strengths from 81 MPa in the control sample to 306 MPa in the 3D printed fCFs composite was observed. In contrast to the distinctly noticeable gradient prints produced by pristine CF composites, the fCFs chemical interaction with the resin allowed even distribution of the fibers in the resin, producing uniform composite prints. Improved wettability of the fCFs was demonstrated through SEM, showing no gaps or separations in the interface. Strong polymer composites that take advantage of the design flexibility made possible by 3D printing technology will be possible thanks to this composite design.