Date of Award

Fall 2023

Document Type

Open Access Thesis


Mechanical Engineering

First Advisor

Austin Downey


Soft elastomeric capacitors (SECs) are emerging as potential low-cost solutions for monitoring cracks and strains in concrete infrastructure, a crucial aspect of structural health monitoring. Effective long-term monitoring of civil infrastructure can reduce the risk of structural failures and potentially reduce the cost and frequency of inspections. However, deploying structural health monitoring (SHM) technologies for bridge monitoring is expensive, especially long-term, due to the density of sensors required to detect, localize, and quantify cracks. Previous research on soft elastomeric capacitors (SEC) has shown their viability for low-cost monitoring of cracks in transportation infrastructure. However, when deployed on concrete for strain monitoring, a structure/sensor capacitive coupling exists that may cause a significant amplification in the signal collected from the SEC sensor. This work provides a detailed experimental study of electrically isolating capacitive sensing skins for concrete structures to reduce the electrically grounded sensor’s structure/sensor capacitive coupling. The study illustrates that using rubber isolators effectively decreases the capacitive coupling between concrete, which inherently has capacitive properties and sensors such as the SEC that utilize capacitance measurements. By investigating rubber isolators, we found that isolation thicknesses between 0.30mm and 0.64mm significantly reduced this capacitive interference, with approximately 0.40mm displaying the optimal response. Secondly, in addressing the challenge of electrical coupling, robust isolation of the SECs from the concrete is done by extending the styrene-block-ethylene-co-butylene-block-styrene matrix of the SECs to include a decoupling layer between the electrode and the concrete instead of a rubber isolator. Experimental results showed this modification lowered the nominal capacitance of the SEC, making them viable for concrete strain monitoring. Comparisons were drawn with conventional resistive strain gauges, emphasizing the modified SECs’ potential. Lastly, the adhesion of SECs onto surfaces is vital for their efficacy. Two adhesion methods were investigated: direct painting with carbon black (CB) and epoxy bonding. Although cost effective and quick, CB posed durability concerns, whereas epoxy bonding offered high adhesion strength, albeit with a more complex application process. Overall, this comprehensive study enlightens the challenges and solutions of deploying SECs on concrete surfaces. It offers insights for their improved performance and broader applicability in civil infrastructure monitoring.


© 2024, Emmanuel Abiodun Ogunniyi