Influence of the Cladding Structure in PMMA mPOFs Mechanical Properties for Strain Sensors Applications

This paper presents a dynamic mechanical analysis of a microstructured polymer optical fiber (mPOF). The fiber material is polymethyl methacrylate, which is widely available commercially. The DMA is made by means of sequential strain cycles produced with an oscillatory load with controlled frequency to obtain the variation of Young's modulus with respect to temperature, frequency, and humidity for mPOFs with two-, three-, and five-ring hexagonal microstructured cladding. Results show that the three different cladding structures have similar Young's modulus on the stress-strain tests performed. Furthermore, the three-ring structure presents the lowest Young's Modulus variation with temperature among the samples tested, whereas the five-ring structure presents a Young's Modulus variation with frequency 25% lower than the two- and three-rings cladding structures. Regarding the humidity sensitivity, the two-ring structure presented a 30% lower Young's Modulus variation for a 25% humidity increase. The results obtained provide guidelines for the cladding structure choice for strain or stress sensors applications when low cross-sensitivity with temperature, humidity, and frequency is desired.