Thermal Conductivity of Additively Manufactured Chopped Fiber Composite Materials

ABSTRACT Thermal properties of additively manufactured composite materials are not as commonly studied as mechanical properties, dismissing processing considerations and potential applications. This study investigates the thermal conductivity of chopped composite PA6‐carbon fiber materials. Thermal conductivity was assessed for rectangular infill samples of increasing infill density. The effects of heat flow direction on thermal conductivity in longitudinal and transverse directions with respect to the infill pattern geometry were also analyzed. A thermal conductivity technique based on ASTM standard D5470 was developed to evaluate non‐isotropic sample conductivity. Transverse heat flow samples of infill between 10% and 77% demonstrated a positive linear relationship between infill density and conductivity due to proportional increases in channels extending from the hot to cold surfaces. Longitudinal samples between 10% and 92% demonstrated a power law increase in conductivity due to more complex changes in geometry and heat flow around air cavities. The orientation of the chopped carbon fibers compared to the direction of system heat flow exhibited significant influence, with greater alignment facilitating higher effective thermal conductivity. At high and solid infill densities, rules of mixtures principles are not representative of sample conductivities because of the fiber orientation with respect to heat flow.