Crack detection and localization in RC beams through smart MWCNT/epoxy strip-like strain sensors

Abstract

In recent years, self-sensing structural materials have drawn enormous attention of scientific community due to their potential to enable continuous monitoring of the integrity of structures. The new paradigm of smart condition-based maintenance advocates the use of next-generation structures completely or partly constituted by self-sensing materials, that is, the structure or part of it also behaves as a sensor. In this context, the remarkable mechanical and electrical properties of multi walled carbon nanotubes (MWCNTs) have fostered an increasing number of applications as fillers for composites with multifunctional properties. Among a wide spectrum of potential applications, the development of skin-type piezoresistive distributed strain sensors shows great promise. Such sensors can be deployed onto large-scale structures, enabling a continuous monitoring of the strain state in the global area of the structure. In this paper, a theoretical study on the potential application of smart MWCNT/epoxy strip-like strain sensors for damage detection/localization/quantification in reinforced concrete (RC) beams is presented. A micromechanics-based finite element model is proposed for the electromechanical analysis of MWCNT/epoxy strips. Furthermore, a damage detection algorithm through model updating approach is introduced. To do so, an Euler-Bernoulli model for beams equipped with a smart MWCNT/epoxy strip is developed. Finally, two numerical case studies are presented including: a 2D concrete beam with multiple prescribed crack-like damages, and a 3D RC beam under four-point flexural conditions with non-prescribed cracking. Results show that the proposed smart strips are capable of exploiting the damage-induced variations in the electrical output to locate and quantify damages for real-time distributed structural health monitoring of RC beam structures.