Discipline: Nanoscience or Materials Science
Subcategory: Materials Science
Milan Rede - FAMU-FSU College of Engineering
Co-Author(s): Alamgir Hossain, FAMU-FSU College of Engineering, Tallahassee, FL; , Mehul Tank, FAMU-FSU College of Engineering, Tallahassee, FL; Marissa Dickerson, FAMU-FSU College of Engineering, Tallahassee, FL; Dr. Rebecca Sweat, High Performance Materials Institute, Tallahassee, FL; Dr. Subramanian Ramakrishnan, FAMU-FSU College of Engineering, Tallahassee, FL
Over the past decade, there has been significant interest in the additive manufacturing of thermosetting resin composites. There are issues associated with functionality of the composite, toughness, conductivity, and mechanical properties of the printed structure due to its standard processing techniques. By optimizing the printing parameters via direct ink writing, lightweight composite materials can be engineered with enhanced properties, so they can be used in applications such as electromagnetic shielding materials, heat sinks, and thermal interface materials because they can enhance the thermal coupling between two materials.EPON 862 resin was mixed at varied weight concentrations (10%, 11%, 13%, 15%, 16%, 17%, and 18%) reduced graphene oxide (RGO) fillers along with curing agent, EPIKURE W using the THINKY machine. The rheology of each sample was tested to see the effect of filler concentration on the modulus, viscosity, and yield stress/strain of the samples. Then, the 15 wt% and 18 wt% RGO inks were transferred to a syringe and 3D printed at 10mm/s and 40mm/s. After printing, the samples were cured at 121C for 1 hour and then at 177C for 2 hours. The thermal conductivities and mechanical properties were then measured using LFA (Laser Flash Analysis) and DMA (Dynamic Mechanical Analysis). The thermal conductivities of 15wt% reduced graphene oxide (RGO) samples printed at speeds of 10mm/s and 40mm/s were measured to determine the effect of shear on the thermal conductivity. The thermal conductivity of the samples printed at 10mm/s were ~1.61W/mK at room temperature and 1.29 W/mK at 100C. When printed at 40mm/s were 1.73W/mK at room temperature and 1.41 W/mK at 100C. Additionally, 18wt% GNP samples were printed at 10mm/s and the thermal conductivity was tested to explore the effect of filler concentration on the thermal conductivity of the composite. The thermal conductivity of the samples at 18wt% were ~2.17 W/mK at room temperature and 1.79 W/mK at 100C. The results show as print speed increases, the thermal conductivity increases. This increase is most likely due to the alignment of the particles. DMA results showed an increase in Tg (glass transition temperature) at 40mm/s compared to 10mm/s print speed, due to the alignment of the filler particles reinforcing the strength of the material by restricting the polymer chains at higher temperatures. Further experiments are being done to measure the mechanical properties of the samples and investigate the effect of shear on the tensile strength of the composite. Extrusion-based AM can be used to produce thermoset resin-filler composites with enhanced thermal properties and toughness at loading levels well above the percolation threshold. The design rules for processing novel lightweight composite structures with tailored properties are established. Reference: Haney, R. et al. Printability and Performance of 3D Conductive Graphite Structures. Additive Manufacturing 2021.
Funder Acknowledgement(s): This study is funded by NSF FAMU CREST award #1735968
Faculty Advisor: Dr. Subramanian Ramakrishnan, firstname.lastname@example.org
Role: I prepared the ink samples for the various RGO weight concentrations, I 3D printed the samples, and I did the thermal conductivity and rheology tests.