Large-Area Resistive Strain Sensing Sheet for Structural Health Monitoring

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 μ ϵ / d a y . 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 μ ϵ r m s 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 μ ϵ peak strain, whereas the nearby sensors on a damage-free surface did not observe significant strain change.

Preparation and Characterization of Polypropylene/Carbon Nanotubes (PP/CNTs) Nanocomposites as Potential Strain Gauges for Structural Health Monitoring

“…Even if several authors investigated sensing ability of PP/CNT alone [36][37][38][39][40][41][42], to the best of our knowledge, no studies investigated the possibility to use PP/CNT strain sensors directly embedded in cementitious materials. Several authors proposed the use of sensing skins or sensing elements to be applied on external surfaces of buildings/infrastructures [53][54][55][56][57]. Nevertheless, the application of sensing skins requires specialized technicians and constant maintenance due to durability issues, increasing the cost and delaying the entry into service of the building or the infrastructure.…”

Concentric Array of Printed Strain Sensors for Structural Health Monitoring

“…In this regard, the implementation of the full-Wheatstone-bridge circuit, demonstrated in Figure 4a is very effective in compensating for temperature sensitivity. In terms of the electrical configuration, the sensor demonstrated in this study ( Figure 4b) does not differ from the conventional full-bridge sensors that are commercially available or developed by other researchers [14,17]. It is composed of four resistive sensing elements (R1, R2, R3 and R4).…”

“…Another study showed a sensing sheet incorporating full Wheatstone bridge strain sensors fabricated on a flexible substrate using a photolithography etching process. The sensing sheet was analyzed during a several-hours-long field test on a concrete bridge to measure static strains [17]. Other very promising studies on the development large-area sensing systems includes capacitive sensors [18,19], and sensor arrays incorporating Lead Zirconate Titanate (PZT) piezoelectric sensors [20,21].…”

Practical Evaluation of Printed Strain Sensors Based on Long-Term Static Strain Measurements

“…For example, an array of commercial metal foil strain gauges bonded to a flexible substrate detected and quantified cracks in structural materials [ 13 ]. Further studies presented another type of sensing sheet that incorporated constantan-based (Cu-Ni alloy) strain sensors that were fabricated on a flexible substrate using a photolithography etching process [ 14 ]. The signal stability of the sensing sheet was analyzed in a laboratory test, and the results revealed a 3 drift over two days of analysis.…”