HIGH ACCURACY THERMAL CHARACTERIZATION AND PROCESS IMPROVEMENT FOR 3D-PRINTED CONTINUOUS PITCH CARBON FIBERS

Abstract

This thesis investigates the development of high-thermal conductivity polymer composites through the process improvement of Continuous Pitch-based Carbon Fiber (CPCF) 3D printing. While previous research has identified CPCF as a viable solution for enhancing the thermal performance of 3D-printed parts, significant discrepancies exist between experimental results and theoretical predictions using the parallel model for composites. This research identifies and addresses the factors contributing to these discrepancies. First, a new fiber characterization methodology was established, comparing traditional microscopy with pycnometry to accurately determine the cross-sectional area and volume fraction of K13D2U fiber tows within the composites. Second, a high-accuracy thermal conductivity measurement apparatus was designed, calibrated, and validated. Furthermore, process improvements were implemented in the coating and printing processes to mitigate fiber breakage and maintain tow integrity. The implementation of these optimized processes resulted in the fabrication of a full-scale 3D-printed composite sample. Measurements conducted using a newly developed macro thermal conductivity apparatus demonstrated a significant improvement in thermal performance compared to prior studies, achieving a thermal conductivity of 36.63 W/mK at a volume fraction of 6.42%. While some deviations from the ideal parallel model remain due to inherent discontinuities within the fiber tow, this study contributes a validated framework for the precise fabrication and characterization of high-performance CPCF composites, offering a path forward for thermal management applications in additive manufacturing.