Nondestructive cyclic strain evaluation of seismic isolation bearings using Si-69-modified MWCNT/silicone rubber self-sensing composites

Abstract

Conductive elastomer composites are promising for large-deformation sensing and structural health monitoring, but their QNDE application is limited by unstable electromechanical responses, resistance hysteresis, and disordered conductive-pathway rearrangement during cyclic loading. Here, a Si-69-induced siloxane interfacial network regulation strategy was developed for hydroxylated multi-walled carbon nanotube/methyl vinyl silicone rubber (MWCNT-OH/VMQ) composites for cyclic strain evaluation of seismic isolation bearings. Si-69 constructed an in situ Si–O–Si/Si–O–C-rich interfacial layer on MWCNT-OH, forming MOB conductive elastomer composites. The optimized MOB7.5 wt% composite increased tensile strength and elongation at break by approximately 52% and 59.53%, respectively, and achieved an apparent gauge factor of 49.01, a strain-monitoring range of 391.84%, and a dynamic tensile-loading response time of 220 ms. Experimental characterisation and molecular dynamics simulations indicated improved filler dispersion, strengthened filler–matrix coupling, restricted segmental motion, reduced free volume, and increased interfacial binding energy, promoting a more reversible conductive network. A robust AE–CNN–LSTM framework enabled resistance-signal characterisation, strain-history reconstruction, and few-shot calibration. In preliminary bearing-level monitoring, MOB7.5 wt% generated continuous resistance signals under bidirectional compression–shear deformation and showed sensitivity to local strain heterogeneity through bifurcated resistance peaks.