Conductive 3D printed PLA composites: On the interplay of mechanical, electrical and thermal behaviours

Additive manufacturing (AM) techniques represent a real challenge to manufacture novel composites with coupled multifunctional properties. This work focuses on the mechanical, electrical and thermal behaviours of 3D printed polymeric composites of polylactic acid (PLA) filled with carbon black (CB) conductive particles. The incorporation of conductive particles within the polymer matrix allows for programmable conduction paths via the printing process, whose electric properties are intimately coupled to thermo-mechanical processes. In this study, samples were prepared using a fused deposition modelling (FDM) printer, controlling the filament orientation to manufacture three different types: longitudinal (0°); transverse (90°); oblique (±45°) printing orientations. Different types of multifunctional characterisation have been made: (i) electro-thermal tests, evaluating the influence of electrical conductivity on the sample temperature due to Joule’s heating; (ii) thermo-electrical tests, analysing the influence of temperature on the DC resistance of the samples; (iii) mechano-electrical tests, analysing the effect of mechanical deformation on the specimens’ electric resistance. The results show a strong dependence of printing direction on the material properties of 3D printed conductive-PLA and identify strong thermo-electro-mechanical interplays. The results of this work will contribute to the AM progress in functional electro-mechanical components with potential applications in biosensing devices, composite sensors, 3D electrodes and soft robotic industry.