10. Sep 2026
Carbon fibre makes 3D-printed TPU stronger and conductive
Researchers have developed carbon-fibre-reinforced thermoplastic polyurethane (TPU) filaments for fused filament fabrication (FFF), achieving substantial increases in stiffness and strength as well as electrical conductivity.
The researchers produced composites containing between 5 and 20 wt% carbon fibre (CF) using a powder-based process in which TPU and micron-sized CF powders were dry blended before extrusion into 1.75 mm filament.
The work was reported by researchers led by Nauman Maqsood in the Journal of Materials Research and Technology. The base material was BASF Elastollan EOS TPU 1301 powder.
The resulting filaments were successfully printed at all four CF concentrations using a Prusa i3 MK3S FFF printer.
Adding 20 wt% CF increased tensile strength from 9.13 MPa for unfilled TPU to 15.72 MPa, an increase of around 72%. Young's modulus increased from 118.78 MPa to 301.84 MPa, while hardness rose more modestly to 93.5 Shore A.
The researchers said the relatively small increase in hardness indicated that the composites retained their flexible elastomeric character despite the substantial increase in stiffness.
Carbon fibre also transformed the electrical properties of the material. The researchers observed a percolation threshold between 5 and 10 wt% CF, after which interconnected conductive pathways formed through the TPU matrix. Electrical conductivity reached approximately 12 S/m at 20 wt% CF.
Thermal stability also improved, with the onset decomposition temperature increasing by around 14°C at the highest CF loading. Modelling predicted that effective thermal conductivity could rise from 0.25 W/mK for the TPU to approximately 0.48 W/mK at 20 wt% CF.
However, increasing the amount of carbon fibre produced a trade-off in print quality. SEM analysis showed increasingly pronounced gaps between deposited beads at 15 and 20 wt% CF, while average surface roughness increased from 3.62 μm for unfilled TPU to 36.20 μm at 20 wt% CF.
The researchers attributed this partly to the increased melt viscosity caused by the rigid carbon-fibre phase, which reduced the ability of adjacent TPU beads to coalesce during printing.
Preliminary testing also showed a piezoresistive response, in which electrical resistance changed when the material was strained. The researchers said this combination of flexibility, reinforcement and electrical functionality could make the composites suitable for strain sensors, wearable electronics, soft robotics and antistatic components.
The paper, “Carbon-enhanced thermoplastic polyurethane composites for FFF: Filament extrusion, microstructure, printed-part quality, multifunctional performance, and preliminary piezoresistive response”, appears in volume 44 of the Journal of Materials Research and Technology, September–October 2026.