Self-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.
A magnetic resonance is an image obtained by means of an imaging test that uses magnets and radio waves to create body images, however, in some images it's difficult to recognize organs or foreign agents present in the body. With these Bessel filters the objective is to significantly increase the resolution of magnetic resonance images taken to make them much clearer in order to detect anomalies and diagnose the illness. As it's known, Bessel filters appear to solve the Schrödinger equation for a particle enclosed in a cylinder and affect the image distorting the colors and contours of it, therein lies the effectiveness of these filters, since the clear outline shows more defined and easy to recognize abnormalities inside the body.
The civil structures during their useful life are subjected to different loads (environmental and mechanical), that cause progressively deterioration and that consequently requires maintenance efforts to keep them safe and operative. In this work, a novel alternative is proposed based in the development of a smart material with multifunctional characteristics that allow the Structural Health Monitoring (SHM)without requiring external sensors. This was possible by developing cement matrix compounds with the addition of carbon nanotubes. The manufacturing of this material began with an experimental design (DOE) that allowed to determine the mixturestype with which the sensor was manufactured, additionally repeatability and reproducibility was guaranteed. To measure the piezoresistive behavior of the samples, we used an INSTRON 5582 universal testing machine, a data acquisition equipment to obtain the variation in voltage and Micron Optics SM130 optical sensing interrogator for measuring deformations. Once the rheological and mechanical behavior of the material were characterized, mechanical tests of the material were carried out without exceeding the maximum deformations of the material in order to acquire data on the resistive behavior of the structure and find the gauge factor. The results of this development offer a part of the solution to the growing needs in the field of civil engineering against the early warning of damages caused by both natural phenomena and human causes (use of inappropriate materials, wrong calculations, overloads).
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