Committee Members:
Dr. Meisha Shofner, MSE
Dr. John Reynolds, SoCB, MSE
Dr. W. Jud Ready, GTRI, MSE
Dr. Blair Brettmann, ChBE, MSE
Dr. H. Jerry Qi, ME
Processing Approaches to Realize Electrically Conductive Surface-Localized Nanocomposites
Summary: Electrically conductive polymer materials can greatly increase the range of applications for polymers, particularly in challenging environments such as space, where static charging and thermal build-up can be significant. Electrical conductivity can be introduced through conductive polymers or composite structures made with electrically conductive fillers, typically nanoparticles. While progress has been made in developing conductive polymer systems suitable for space applications, nanocomposite structures are still a primary interest in the space and aerospace community. Unfortunately, many blended nanocomposite systems face processing challenges related to poor particle dispersion and increased melt viscosity which impose limits on particle loading levels, electrical percolation, and mechanical properties of the blended material.
Surface-localized nanocomposites (SLNCs) formed by melt infiltration are a path to creating highly loaded, mechanically robust, electrically conductive, fully integrated composite surfaces without affecting the properties of the bulk substrate. Prior works on SLNCs made with carbon nanotube mats primarily focused on the surface energy properties of the final processed nanocomposite surface and do not include a thorough analysis of the process-structure relationship with respect to particle chemistry, matrix microstructure, or critical thermal transitions of the substrate. In this work, will focus on the development a process-structure-property relationship for SLNCs with respect to critical thermal transitions and nanoparticle chemical functionality for lightly functionalized chemically modified reduced graphene oxide (CMrGO). It will evaluate the suitability of these SLNC materials for use as flexible, durable conductors in the space environment including evaluation of electrical properties under strain and abrasive wear in the presence of lunar dust. It will also examine how light particle functionalization and high loadings in SLNCs affect matrix-particle interaction dynamics and the resultant matrix microstructure using thermal analysis tools. Finally, developments from planar SLNC structures will be transferred to cylindrical filament surfaces for fused filament fabrication (FFF) to support the development of functional materials for in-space manufacturing (ISM). In-space manufacturing is critical to the success of long-duration space missions and robust, well-understood electrically conductive polymer filaments for FFF will increase the impact of ISM on mission safety and feasibility by broadening the application areas of printed plastic components. In this portion of the work will include measuring the impact of highly loaded layer-to-layer interfaces on the development of 3D conductive network structures and the overall mechanical properties of printed components. Finally, melt rheology will be used to measure the effects of small weight fractions of CMrGO-polymer blends as a model for thermoplastic recycling of printed SLNC components back into blended feedstock for circularity in ISM operations.