Damage Detection of Mechanical Fastened Composite Laminates by Electric Resistance Change Method

Laminated composite plates have low delamination resistance. Since delamination crack creation is a difficult problem for visual inspection, delamination causes low reliability for primary structure of laminated composites. To improve this low reliability, identifications of delamination cracks in-service are required. The present study employs an electric-resistance change method in an attempt to identify internal delaminations experimentally. In our previous paper, a two-prove method was adopted for the electric resistance change measurements because of the simplicity. Instead, the present paper adopts multiple-prove method for the measurements of electric resistance changes. Electric current is charged from the different electrodes to measure the voltage changes. The measurements of electric voltage change at multiple points are robust against electric resistance change at the electrodes, and the method is similar to the four-probe method for high precision measurements of electric resistance change. In the present study, high precise measurement system of electric voltage change is developed, and the electric voltage measurement method is adopted for identifications of embedded delamination location and size. As a result, the improved electric resistance change method is shown to be effective for the identifications of embedded delamination cracks of graphite/epoxy laminated composites.

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Toward Structural Health Monitoring of Civil Structures Based on Self-Sensing Concrete Nanocomposites: A Validation in a Reinforced-Concrete Beam

International Journal of Concrete Structures and Materials ◽

10.1186/s40069-020-00451-8 ◽

2021 ◽

Vol 15 (1) ◽

Author(s):

Diego L. Castañeda-Saldarriaga ◽

Joham Alvarez-Montoya ◽

Vladimir Martínez-Tejada ◽

Julián Sierra-Pérez

Keyword(s):

Reinforced Concrete ◽

Damage Detection ◽

Direct Current ◽

Health Monitoring ◽

Electrical Resistance ◽

Concrete Beam ◽

Reinforced Concrete Beam ◽

Structural Member ◽

Rc Beam ◽

Electric Resistance

AbstractSelf-sensing concrete materials, also known as smart concretes, are emerging as a promising technological development for the construction industry, where novel materials with the capability of providing information about the structural integrity while operating as a structural material are required. Despite progress in the field, there are issues related to the integration of these composites in full-scale structural members that need to be addressed before broad practical implementations. This article reports the manufacturing and multipurpose experimental characterization of a cement-based matrix (CBM) composite with carbon nanotube (CNT) inclusions and its integration inside a representative structural member. Methodologies based on current–voltage (I–V) curves, direct current (DC), and biphasic direct current (BDC) were used to study and characterize the electric resistance of the CNT/CBM composite. Their self-sensing behavior was studied using a compression test, while electric resistance measures were taken. To evaluate the damage detection capability, a CNT/CBM parallelepiped was embedded into a reinforced-concrete beam (RC beam) and tested under three-point bending. Principal finding includes the validation of the material’s piezoresistivity behavior and its suitability to be used as strain sensor. Also, test results showed that manufactured composites exhibit an Ohmic response. The embedded CNT/CBM material exhibited a dominant linear proportionality between electrical resistance values, load magnitude, and strain changes into the RC beam. Finally, a change in the global stiffness (associated with a damage occurrence on the beam) was successfully self-sensed using the manufactured sensor by means of the variation in the electrical resistance. These results demonstrate the potential of CNT/CBM composites to be used in real-world structural health monitoring (SHM) applications for damage detection by identifying changes in stiffness of the monitored structural member.

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A Study on Thermal and Electrical Conductivities of Ethylene-Butene Copolymer Composites with Carbon Fibers

International Polymer Processing ◽

10.1515/ipp-2020-4003 ◽

2021 ◽

Vol 36 (4) ◽

pp. 417-422

Author(s):

Y. Hamid ◽

P. Svoboda

Keyword(s):

Mechanical Properties ◽

Thermal Conductivity ◽

Carbon Fiber ◽

Electric Conductivity ◽

Carbon Fibers ◽

Mechanical Strain ◽

Electric Resistance ◽

Resistance Change ◽

Electrical Conductivities ◽

Fiber Sample

Abstract Ethylene-butene copolymer (EBC)/carbon-fiber (CF) composites can be utilized as an electromechanical material due to their ability to change electric resistance with mechanical strain. The electro-mechanical properties and thermal conductivity of ethylene butene copolymer (EBC) composites with carbon fibers were studied. Carbon fibers were introduced to EBC with various concentrations (5 to 25 wt%). The results showed that carbon fibers’ addition to EBC improves the electric conductivity up to 10 times. Increasing the load up to 2.9 MPa will raise the electric resistance change by 4 500% for a 25% fiber sample. It is also noted that the EBC/CF composites’ electric resistance underwent a dramatic increase in raising the strain. For example, the resistance change was around 13 times higher at 15% strain compared to 5% strain. The thermal conductivity tests showed that the addition of carbon fibers increases the thermal conductivity by 40%, from 0.19 to 0.27 Wm–1K–1.

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