Electrical properties of 3D printed continuous carbon fibre composites made using the FDM process

Fused deposition modelling (FDM) is an additive manufacturing process for the 3D printing of continuous fibre-thermoplastic composite laminates. The electrical conductivity of continuous carbon fibre (CF)-nylon filaments and laminates printed with a Markforged MarkTwo® FDM machine is experimentally investigated. The axial electrical conductivity of single filaments measured before, during and following the FDM process reveal a large reduction (∼40%) due mostly to breakage of carbon fibres. The electrical conductivity of 3D printed laminates made by the layer-by-layer deposition of the single filaments were determined in the longitudinal, transverse and through-thickness directions, and compared to the electrical properties of a hot moulded composite with a near-equivalent carbon fibre content. The longitudinal conductivity of the 3D printed laminate was only ∼50% that of the hot moulded composite, and this was due mostly to fibre breakages caused by the FDM process. However, the transverse and through-thickness electrical conductivities of the 3D printed laminate were higher (∼13 times and ∼3 times, respectively) than the hot moulded composite due to higher fibre waviness causing increased fibre-to-fibre contact which aids the flow of electrical current in these two directions.