Transient response monitoring of a loaded rubber using a circular- shaped optical fibre bend sensor

Abstract

When rubber is subjected to a load, deformation will occur in the form of transverse compression. At a microscopic level, the bond structure in the rubber is transformed from one equilibrium state, corresponding to the unloaded rubber, to another, corresponding to the loaded rubber. As in any transformation process, this takes a certain amount of time called transient response time. This paper presents a simple fibre sensor configuration to experimentally monitor transient response of the loaded rubber bar at a desired point in the rubber at a constant temperature is presented. For this purpose, a coil of polymer optical fibre (POF) with cross-section diameter 10 mm was inserted into a cylindrical rubber rod with cross-section diameter of 3 mm and thickness of 2 cm. Five different loads (2 kg, 2.5 kg, 3 kg, 4 kg and 7 kg) were carefully placed on the cylindrical rubber rod and the resulted change in transmitted light intensity through the fibre sensor was recorded. It was shown that transient response time is load mass dependent which increases with increasing load. Transient response time was also measured as function of depth, it decreases with the increase of the depth, i.e., vertical distance from rubber rod surface. In addition to static loading, transmission curve resulted from dynamic loading was also demonstrated. Based on these results we suggest that smart rubber might be simply formed by sandwiching optical fibre coil into one or more desired points in the rubber bar.