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One of the key parameters monitored in structural health monitoring applications is strain. In this work an extrinsic plastic optical fiber (POF) sensor developed previously has been optimised to increase its strain sensitivity. The extrinsic POF sensor basic design used here and previously comprises of two fiber units. As the distance of separatio...
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... Intensity-based optical fiber sensors with conventional light emitter and detector system offers a low-cost technique for health monitoring (the sensing unit and the data acquisition unit for collecting voltage input may cost less than USD 500). Several intensity-based optical fiber sensors for monitoring strain and cracks have been demonstrated [55][56][57][58]. For applications involving concrete structure monitoring the key consideration is that the sensor should have high strain sensitivity. ...
... For applications involving concrete structure monitoring the key consideration is that the sensor should have high strain sensitivity. Hence, lens-based plastic optical fiber (LPOF) sensor, which is a low-cost intensity-based plastic optical fiber strain sensor [58] can be used for corrosion monitoring. The plastic optical fiber sensor offers several advantages with regard to cost, strain sensitivity, construction and customisability (as the mechanical parts of the sensor are 3D printed). ...
... In the previous work [58], the sensing principle and its performance under quasi-static and dynamic loading was demonstrated. It was shown that the sensor has 5-6 times higher strain sensitivity compared to strain sensor developed by [57]. ...
Corrosion of reinforcement in concrete is one of the major causes for deterioration of concrete structures. This work presents an approach in the monitoring of concrete structures for damage induced by corrosion of steel in concrete using a lens-based plastic optical fiber (LPOF) strain sensor. The optical fiber sensor offers the advantage of being light weight, small in size, low-cost, immune to electromagnetic interference and it does not pose any spark hazard. The intensity-based optical fiber sensor used in this work consists of an emitter fiber, a ball lens, a receiving fiber and a light detector system. The light from the emitter fiber converges to focal point using the ball lens, before it enters the receiver fiber. A change in distance between the ball lens and the receiver fiber would lead to a change in the light intensity transmitted. The intensity change is correlated to the relative distance using a suitable calibration curve. Following the calibration of the sensor, it was used to monitor response of concrete members subjected to flexural loading. Subsequently, the sensor was tested for its ability to monitor corrosion of steel in concrete using an accelerated corrosion test set-up. The sensor shows promising results for detection of corrosion. The test results were used for identification of the corrosion propagation phase, which can be used for predicting the remaining service life of the structures. The optical fiber sensor strain readings were then correlated to the corrosion penetration depth to estimate the extent of damage during the corrosion of rebar. The test results show that it is possible to monitor concrete structures for damage due to flexural loading and corrosion of rebar using an intensity-based LPOF strain sensor.
Airglow discharge plasma (ADP) was used to modify the surface properties of zein film, and the influence of plasma dosage was investigated by controlling treating time (from 0s to 120s). Fourier transform infrared spectrophotometry (FT-IR) results indicated that the ADP treatment partly destroyed the acylamino groups of zein film, and the X-ray photoelectron spectrometer (XPS) analysis proved that oxygen was introduced into the matrix of zein films during ADP treatment, with the content enhanced from 14.29% to 18.45%. The microstructure of zein film exhibited a more robust surface with longer treating time, corresponding to the X-ray diffraction (XRD) results that the crystal structure of zein film was destructed under ADP treatment. The contact angle changed from 78.3° ± 2.3° to 62.1° ± 1.7° under ADP treatment, representing higher wettability. Mechanical properties also showed desirable changes under ADP treatment, with the tensile strength increased from 12.25 ± 1.23 MPa to 18.12 ± 0.68 MPa. ADP treatment could be a promising approach to modify the surface properties of protein films.
