Abstract
Damage significantly influences response of a strain sensor only if it occurs in the proximity of the sensor. Thus, two-dimensional (2D) sensing sheets covering large areas offer reliable early-stage damage detection for structural health monitoring (SHM) applications. This paper presents a scalable sensing sheet design consisting of a dense array of thin-film resistive strain sensors. The sensing sheet is fabricated using flexible printed circuit board (Flex-PCB) manufacturing process which enables low-cost and high-volume sensors that can cover large areas. The lab tests on an aluminum beam showed the sheet has a gauge factor of 2.1 and has a low drift of 1.5 . The field test on a pedestrian bridge showed the sheet is sensitive enough to track strain induced by the bridge’s temperature variations. The strain measured by the sheet had a root-mean-square (RMS) error of 7 compared to a reference strain on the surface, extrapolated from fiber-optic sensors embedded within the bridge structure. The field tests on an existing crack showed that the sensing sheet can track the early-stage damage growth, where it sensed 600 peak strain, whereas the nearby sensors on a damage-free surface did not observe significant strain change.
Highlights
The aging infrastructure of the United States is in dire need of maintenance and repairs
University, we developed a thin-film two-dimensional sensing sheet as one possible two-dimensional sensing system using an array of resistive strain gauges, where commercial resistive sensors were wired one by one to a flexible sheet with metal interconnect traces [34]
This paper presented a scalable resistive strain sensing sheet design that was fabricated with the low-cost, high-volume flexible PCB manufacturing technology
Summary
The aging infrastructure of the United States is in dire need of maintenance and repairs. The fiber optic sensors are typically placed on a straight line (i.e., one dimensional) throughout the structure and enable sensing over very large distances [9,10,11,12] They have a high spatial selectivity and generate a large signal only when the damage is nearby. A nonexhaustive list includes the following: (1) Bioinspired carbon-nanotube-based sensing system, developed by [14] for strain monitoring and impact damage identification. Laboratory tests showcased the strain sensing and damage detection capabilities, and these sensors show promise for long term structural health monitoring applications. (3) A robust and durable sensing skin based on large-area capacitor—called a soft elastomeric capacitor (SEC)—that can measure additive strain on the structure and have been characterized for static as well as dynamic sensing capabilities through laboratory experiments [22,23,24,25,26,27].
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