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Browsing by Author "Santos, Beatriz Varela"

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  • Piezoresistive Sensing for Structural Health Monitoring: A Practical Application in Adhesive Joints
    Publication . Santos, Beatriz Varela; Silva, Abílio Manuel Pereira da; Pereira, João Pedro Nunes
    Composites play a significant role in various industries. However, the use of mechanical systems such as bolts and rivets introduces damages that can compromise the structural health of the composite. As a result, adhesive bonding is increasingly becoming a viable technique for assembling composite structures. Despite offering advantages, such as mass reduction and uniform distribution of forces, the feasibility of adhesive joints is not fully established, and it is crucial to improve the monitoring capability of structures where adhesion is used. This study aims to contribute to advancing knowledge by suggesting the development of multifunctional adhesives, incorporating carbon nanotubes (CNTs) into epoxy-based nanocomposites, simultaneously enhancing their mechanical strength and piezoresistive sensory response. Throughout this work, multifunctional adhesives were applied in practical scenarios of structural health monitoring (SHM), especially in single-lap joints. The research involves the electromechanical study of bulk adhesive samples with varied percentages of CNT loading (0.25 wt.% and 0.50 wt.%) in an epoxy matrix and adhesive joints of single-lap configuration. Experimental results reveal that adhesives with 0.50 wt.% of CNTs exhibit superior mechanical properties and better sensing capabilities during bending tests, demonstrating a higher gauge factor (GF) of 5.2. However, for single-lap joints, the sensitivity is slightly reduced, with a GF of 0.77. In tensile tests for single-lap joints, the GF is 1.27, highlighting that different loadings and damages result in distinct piezoresistive measurements. With the mentioned GF it was possible to monitor different ranges of deformation and detect cyclic loadings of up to 100 cycles, with almost negligible hysteresis. The functionalization of adhesives has proved its effectiveness in developing multifunctional materials with mechanical and piezoresistive sensory capabilities.
    2024-02-19Master thesis Open access Show more