This application note explains how SWCNT-enabled conductive networks in polymer composites convert strain and damage into resistance change for in-situ structural feedback.
SWCNT enables self-sensing polymer composites by forming a sparse conductive network where strain shifts nanotube spacing and contacts, changing tunneling/contact resistance and producing a resistance signal correlated to deformation and damage.
SWCNT is used when the composite must remain polymer-dominant mechanically while still supporting a conductive pathway at low filler loading. High aspect ratio lowers the percolation threshold, and the measurable signal is often dominated by junction resistance rather than bulk filler resistivity.
Non-Applicability: If the process window cannot achieve stable dispersion (e.g., viscosity limits prevent adequate shear/mixing), SWCNT networks remain discontinuous and self-sensing becomes noise-dominant.
Unknown/Unverified: Long-term gauge stability (baseline drift + hysteresis) under combined humidity and thermal cycling is formulation-specific and not universally predictable from loading alone.
Activation Boundary: Below the effective percolation point, the composite remains insulating and strain response is typically not measurable; in practice, self-sensing usually requires bulk resistivity below about 1e8 to 1e9 ohm-cm (target dependent).
A common failure sensitivity is re-bundling or agglomeration, which localizes current paths and destabilizes resistance under cyclic loading.
Mechanisms summarized here follow established CNT/polymer literature on electrical percolation and piezoresistive sensing: junction-dominated conduction near threshold, tunneling/contact modulation under strain, and topology-driven signal amplification during damage evolution.
Last Updated: 2026-01-21