Defect-Independent Multifunctionality Promotion by Single-Walled Carbon Nanotubes in Hierarchical Carbon Fiber/Thermoset Nanocomposites

Abstract

Hierarchically reinforced multifunctional nanocomposites are leading-edge advanced materials. Single-walled carbon nanotubes (SWCNT) are one of their prime additives, exacerbating functional property development at much lower addition than other carbon allotropes. Here, we prove that SWCNT addition at percolation threshold amounts can provide multifunctional performance regardless of their quality. A plasma etching technique was used to induce SWCNT defectiveness (IG/ID ratio drops from 66 to 23). These were used to produce SWCNT/carbon fiber/thermoset nanocomposites with concentrations near percolation levels (0.005 wt%). Multifunctional characterization showed that differences in performance were virtually non-existent. For nanocomposites with additives of different quality, ultimate tensile strength varied between 630 and 645 MPa and flexural strength between 560 and 640 MPa. Both tensile and flexural moduli were within 10% variance. In- and through-plane functional properties, at room and elevated temperature, were also effectively identical. Electrical and thermal conductivity measured up to 150 S cm−1 and 3.7 W(m K)−1, respectively, while thermal capacity and diffusivity were as high as 1.2 J(g K)−1 and 2.7 mm2 s−1. All nanocomposites were thermally stable till ~300°C and microstructural analysis showed no SWCNT-defect connected effects. Thus, SWCNTs may allow relaxation in typical quality parameters during large-scale production, reducing current testing and control requirements and thereby, production costs.