Thermally conductive composites with hybrid fillers for printing 3D structures

This paper investigates composites with high TC (Thermal Conductivity) for printing complex geometries via AM (Additive Manufacturing). PC (Polycarbonate) served as the matrix with hybrid fillers; h-BN (Hexagonal Boron Nitride), EG (Expanded Graphite), PCFs (Pitch-based Carbon Fibers), and Al (Aluminum Powder) at 10, 20, and 30 wt%. An additional 40 wt% composite was prepared due to the exponential TC increase with filler content. Composites primarily rely on h-BN for its excellent thermal and lubricating properties. A smaller volume of EG is incorporated because, despite its lubricating benefits, its large surface area can lead to increased viscosity. Additionally, Al and PCFs are added in similar, smaller amounts to provide a variety of filler shapes and sizes that contribute to the material's overall TC performance. To evaluate individual filler contributions, composites excluding one filler component were also tested. Printed samples were characterized by laser flash analysis to determine thermal diffusivity and specific heat capacity, from which TC was calculated. • Hybrid filler method was used to create thermally conductive composites for FDM 3D printing. • Filler mixture of boron nitride, expanded graphite, pitch carbon fibers, and aluminum particles was used. • Exponential increase in thermal conductivity (TC) was observed with increasing filler content. • The most conductive composite achieved a TC of 2.477 W m −1 K −1 (at 80.7 °C) when aluminum was removed. • The research identifies key challenges, such as poor printability of high-filler content composites using FFF technology.