Nanocomposites for Additive Manufacturing: Interplay Between Matrix <scp>MFI</scp> and <scp>CNT</scp> Aspect Ratio on the Electromagnetic and Toughening Mechanisms

ABSTRACT Acrylonitrile–butadiene–styrene (ABS) is a benchmark polymer for fused filament fabrication (FFF), but its dielectric transparency restricts its use in electromagnetic compatibility (EMC). Incorporating multi‐walled carbon nanotubes (MWCNTs) overcomes this limitation, enabling electromagnetically active nanocomposites. This study utilizes a design of experiments (DOE) to evaluate the interplay between matrix melt flow index (MFI) and carbon nanotube (CNT) aspect ratio on nanocomposites prepared via melt extrusion and processed by injection molding (IM) and FFF. Results demonstrate that a lower‐MFI matrix slightly enhances electrical conductivity and shielding due to improved dispersive mixing. Crucially, lower‐aspect ratio CNT significantly outperform higher‐aspect ratio variants due to superior dispersion and distribution within the matrix. Furthermore, structural comparisons revealed a unique mechanical advantage for 3D printing. While FFF specimens exhibited expected reductions in elastic modulus and tensile strength due to intrinsic porosity, they demonstrated a notable increase in impact toughness. These periodic inter‐raster voids act as toughening mechanisms, effectively mitigating the embrittlement associated with high CNT loadings, validating FFF as a method to tailor multifunctional, impact‐resistant ABS nanocomposites for high‐performance EMC.