Maintenance, monitoring and damage detection of civil infrastructures are important to ensure safety. Civil structures have a long lifespan and without regular and sufficient maintenance, there is a risk of failure.
Structural health monitoring (SHM) can become an important factor to avoid such failure, not least related to large-scale structures. Several evaluation strategies exist and research in the field is ongoing.
Pulse-echo, dynamic response and acoustic emission are some of the strategies proposed for SHM. Due to technical or cost constraints, these methods can often only be applied temporarily and in localized areas and are difficult to implement for large-scale structures.
At present, the monitoring is still predominantly done by visual inspection, which is often costly and time consuming while also very dependant on the judgment of the inspector.
PolyPower material for structural health monitoring
Researchers from Massachusetts Institute of Technology, USA and University of Potsdam, Germany have joined forces to investigate if the PolyPower DEAP material is suitable as sensor for SHM.
The PolyPower material functions as a capacitance sensor and was selected because of the corrugated surface of the material, which combines a stretchable polymer material with stretchable electrodes. In addition, the material is commercially available at low cost.
For the experiments, different sensor configurations (both in terms of differential sensor geometries and sensor patterns) were tested. The tests were carried out on both small-scale and scaled-up concrete specimens.
The setups were used to first verify the measurement principles and then to show if the principle would hold under realistic settings being able to locate cracks.
Test of PolyPower material demonstrated promising performance
SHM using sensors based on PolyPower DEAP material based sensor seems to be achievable, both performance and cost wise. The results from the test showed promising performance for the sensor material with high correlation with the loss of stiffness in the specimens.
The tests demonstrated that the sensor material is capable of detecting cracks. Furthermore, by organising sensor patches on a sensor sheet it was possible to locate a crack.
The conclusion from the researchers is that with the PolyPower material, monitoring systems become “a promising easy to apply, low-cost application for large surfaces, compared to existing sensor types” (Laflamme et. al, 2010).
This case story is based on the published article on this research topic: Laflamme, S. et al; Soft capacitive sensor for structural health monitoring of large-scale systems; Structural Control and Health monitoring (2010). If you have any questions, feel free to contact Simon Laflamme: laflamme@mit.edu