Abstract <p>Purpose: Carbon nanotube yarns (CNTYs), composed of twisted nanoscale carbon nanotubes, are promising candidates for high-performance composite materials. However, the tensile strength of a CNTY embedded in a polymer matrix is reduced compared to that observed under atmospheric conditions. This study provides a direct, side-by-side quantification that links the suppression of the self-tightening effect to the strength loss in embedded CNTY. Methods: CNTY statistical strengths in both conditions were assessed through single-yarn tensile and fragmentation tests. Failure behavior was characterized using photoelastic birefringence to identify first-break events, in situ optical tracking of diameter and twist under load, and fractography and transmission electron microscopy near the fracture plane. Results: Embedding reduced the CNTY characteristic strength by approximately 95%, and the failure strain from 6.72 to 0.60%; by contrast, carbon fiber changed little across conditions. Weibull analysis revealed a substantial decrease in both characteristic strength <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$(\sigma_{0} )$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <msub> <mi>σ</mi> <mn>0</mn> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and shape parameter (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$m$</EquationSource> <EquationSource Format="MATHML"><math> <mi>m</mi> </math></EquationSource> </InlineEquation>) values for embedded CNTY. Transmission electron microscopy indicated an outer mixed-phase region and a largely dry CNT core, consistent with partial infiltration and suppressed self-tightening as the proximate cause of the reduced scale and shape parameters. Conclusion: Together, the observations and statistical analysis explain the reductions in Weibull scale and shape for embedded CNTY as consequences of the suppressed self-tightening effect and an observed outer mixed-phase region, motivating the need for yarn-specific models beyond continuous fiber assumptions and informing yarn selection and matrix design to mitigate strength loss in CNTY composites.</p> Graphical abstract <p></p>

Failure behavior of carbon nanotube yarns embedded in polymer matrices

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2025年12月23日

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Redha A. Ramadhan,
Go Yamamoto

摘要

Abstract

Purpose: Carbon nanotube yarns (CNTYs), composed of twisted nanoscale carbon nanotubes, are promising candidates for high-performance composite materials. However, the tensile strength of a CNTY embedded in a polymer matrix is reduced compared to that observed under atmospheric conditions. This study provides a direct, side-by-side quantification that links the suppression of the self-tightening effect to the strength loss in embedded CNTY. Methods: CNTY statistical strengths in both conditions were assessed through single-yarn tensile and fragmentation tests. Failure behavior was characterized using photoelastic birefringence to identify first-break events, in situ optical tracking of diameter and twist under load, and fractography and transmission electron microscopy near the fracture plane. Results: Embedding reduced the CNTY characteristic strength by approximately 95%, and the failure strain from 6.72 to 0.60%; by contrast, carbon fiber changed little across conditions. Weibull analysis revealed a substantial decrease in both characteristic strength $(\sigma_{0} )$ $(σ_{0})$ and shape parameter ( $m$ $m$ ) values for embedded CNTY. Transmission electron microscopy indicated an outer mixed-phase region and a largely dry CNT core, consistent with partial infiltration and suppressed self-tightening as the proximate cause of the reduced scale and shape parameters. Conclusion: Together, the observations and statistical analysis explain the reductions in Weibull scale and shape for embedded CNTY as consequences of the suppressed self-tightening effect and an observed outer mixed-phase region, motivating the need for yarn-specific models beyond continuous fiber assumptions and informing yarn selection and matrix design to mitigate strength loss in CNTY composites.

Graphical abstract