Compliant auxetic cementitious composites for piezoresistive sensing

Abstract

Auxetic cementitious cellular composites (ACCCs) exhibit high compressive deformation with recoverable behavior, demonstrating strong potential for self-sensing applications. In this study, compliant piezoresistive ACCCs were engineered to combine auxetic behavior with piezoresistive properties by reinforcing a cementitious matrix with polyvinyl alcohol (PVA) and carbon fibers. Uniaxial compression tests were conducted to evaluate their piezoresistive responses in damage sensing across distinct deformation stages, while Digital Image Correlation (DIC) and Acoustic Emission (AE) techniques were employed to investigate corresponding deformation and damage mechanisms. Cyclic loading tests further assessed the flexible sensing behavior of ACCCs within the recoverable deformation during the auxetic behavior range, with further insights obtained from microscopic analysis and X-ray computed tomography (CT). The piezoresistive sensing behavior of two typical ACCC specimens with different geometries was compared. The results demonstrate that the auxetic behavior promotes high compressive deformation, which can be delineated into four distinct mechanical stages. Each stage corresponds to specific damage mechanisms and exhibits characteristic piezoresistive responses, as reflected by stage-dependent variations in the fractional change in resistance (FCR). This staged behavior effectively extends the sensing range for damage detection. Under cyclic loading, the composites exhibit a reproducible piezoresistive response across an extended self-sensing range, attributable to their substantial recoverable deformation. This behavior highlights their superior strain and stress sensitivity, although residual plastic deformation progressively increases with greater loading amplitude. Given wide availability of cementitious materials, highly deformable ACCCs with piezoresistive strain/stress and damage sensing capabilities offer a cost-effective and sustainable solution for in-situ, real-time structural health monitoring.