Design project of a low-cost data acquisition system for electromechanical testing of smart materials

Abstract

This thesis aims to develop a low-cost data acquisition system to record electrical resistance and deformation data in self-sensing smart cement specimens. Subsequently, the developed system must be tested with cyclic load tests, a text file must be generated with the data obtained and said data must be analysed to extract conclusions about the performance of the system and the piezoresistive "smartness" of the materials. The most interesting application of this thesis is to implement the system designed in an intelligent cement for Structural Health Monitoring applications, where a structure can be continuously monitored to detect deformations and possible failures before they happen. For this reason, the research on this thesis’s state of the art has focused on the current applications of smart cement, current SHM systems and research about low-cost solutions. To achieve the thesis goals, fluent communication has been established between the thesis director and the author, both by exchanging emails and face-to-face meetings. In addition, face-to-face sessions have been held in the Resistance of Materials laboratory, such as preparing the test specimens and testing the data acquisition system at different points in the thesis. The results show that the developed system can record electrical resistance and deformation data and generate text files for its processing. The analysis of the obtained data also illustrates the linear relationship between the fractional change in the electrical resistance and the deformation, allowing in this way to characterize the specimens with their gauge factor and thus determine their "smartness”. To sum up, it can be established that this thesis manages to develop a low-cost system for the acquisition of reliable and replicable data and, due to its linear relationship, the cement can be considered "self-sensing" since the application of a load is translated into a change into the electrical resistance, eliminating in this way the need for off-the-shelf strain sensors in SHM systems.