A compact tensile tester for carbon nanotube wires

The exceptional stiffness and strength of carbon nanotube (CNT) wires have led to substantial progress in the synthesis of these materials for a broad range of high-performance applications. However, to date, there is a lack of suitable equipment to characterize the mechanical performance of these wires. In this study, a compact and low-cost tensile tester was developed to characterize CNT wires for use in accelerator beam wire scanners. The device combines a stepper-motor actuator, load cell, and a linear potentiometer under Arduino-based control, providing sub-micron displacement precision and milli-Newton digital force resolution. Compliance calibration was carried out using copper and nylon wires, demonstrating the reliability of the measurement system. Initial tensile tests on CNT yarns with diameters between 10 and 50 μm, from multiple commercial suppliers, revealed ultimate tensile strengths of 1-3 GPa and elastic moduli of 120-200 GPa, below manufacturer specifications, corresponding to reductions of ∼50% in strength and up to 60% in modulus depending on the sample. These results highlight challenges related to sample preparation, clamping, and the intrinsic variability of CNT assemblies. Despite these limitations, the instrument enables reproducible testing of fragile filaments and provides a foundation for systematic mechanical evaluation of CNT wires.