Abstract
Obtaining the internal stress and strain state of concrete to evaluate the safety and reliability of structures is the important purpose of concrete structural health monitoring. In this paper, a three-dimensional (3D) strain rosette sensor was designed and fabricated using graphene-based piezoresistive composite to measure the strains in concrete structures. The piezoresistive composite was prepared using reduced graphene oxide (RGO) as conductive filler, cellulose nanofiber (CNF) as dispersant and structural skeleton, and waterborne epoxy (WEP) as polymer matrix. The mechanical, electrical, and electromechanical properties of RGO-CNF/WEP composite were tested. The results show that the tensile strength, elastic modulus, and conductivity of the composite are greatly improved by the addition of RGO and CNF. The relative resistance change of composite films demonstrates high sensitivity to mechanical strain with gauge factors of 16-52. Within 4% strain, the piezoresistive properties of composites are stable with good linearity and repeatability. The sensing performance of the 3D strain rosette was tested. The measured strains are close to the actual strains of measure point in concrete, and the error is small. The RGO-CNF/WEP composite has excellent mechanical and piezoresistive properties, which enable the 3D strain rosette to be used as embedded sensor to measure the internal strain of concrete structures accurately.
Highlights
Concrete is the most widely used material in civil engineering
A 3D strain rosette sensor was designed and fabricated using the reduced graphene oxide (RGO)-cellulose nanofiber (CNF)/waterborne epoxy (WEP) composites to obtain the strains in concrete structures
The RGO-CNF/WEP composite was filled in grooves to form six one-dimensional sensing elements
Summary
Concrete is the most widely used material in civil engineering. The service periods of concrete structures are usually several decades or even longer. Owing to the high strength and modulus of RGO and CNF, a cross-linking enhanced network is constructed in the WEP matrix, which significantly improves the mechanical property of the composite. The redundant RGO and CNF agglomerate in the WEP matrix, resulting in stress concentration which would decrease the mechanical property of the composite, affecting the electrical property. The RGO-CNF/WEP composite has good strain sensing property and can be used to structural health monitoring. It can be seen that the films made of the RGO-CNF/WEP composite have good strain sensing performance with high sensitivity, good stability, and large measurement range. It is necessary to develop a new sensor which can measure 3D strain
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