Mechanics of bonded sensor layers in soft tubes: Suppressing instability and failure for sensing reliability

Abstract

Integrating sensors onto thin-walled tubular structures is of paramount importance for the advancement of smart infrastructures and facilities, enabling real-time detection of mechanical states and environmental conditions. This study systematically investigates the mechanics of bonded sensor layers in suppressing bending-induced ovalization, buckling, and failure in soft, thin-walled tubes, with the goal of enhancing sensing reliability. While significant progress has been made in understanding instability phenomena in tubular structures under mechanical loading, a critical gap remains in characterizing how bonded sensor layers influence deformation and failure mechanisms. To address this, a comprehensive parametric analysis—supported by finite element simulations and experimental validation—was conducted to evaluate the effects of four key parameters: length ratio, thickness ratio, wrapped angle, and relative stiffness. The results reveal that optimized configurations—specifically, length ratios exceeding 0.7, thickness ratios above 1.6, moderate wrapped angles (approximately 2π/3–4π/3), and relative stiffness greater than 0.03—can suppress ovalization to below 25 % in sensor-covered regions, redistribute deformation to uncovered segments, and trigger complex buckling behaviors involving multiple kinks and secondary instabilities. These thresholds mitigate localized strain concentrations, reduce the risk of sensor layer wrinkling or delamination, and preserve measurement fidelity under operational loading. The findings extend classical instability theories to hyperelastic, multilayered systems and provide practical design guidelines for sensor-integrated tubular structures. Applications include smart pipelines and conduits for structural health monitoring and environmental sensing in next-generation infrastructure systems.