Measurements of stress-optic coefficient and Young's modulus in PMMA fibers drawn under different conditions

Abstract

We have systematically measured the differential stress-optic coefficient, ΔC, and Young's modulus, E, in a number of PMMA fibers drawn with different stress, ranging from 2 up to 27 MPa. Effect of temperature annealing on those parameters was also investigated. ΔC was determined in transverse illumination by measuring the dependence of birefringence on additional axial stress applied to the fiber. Our results show that ΔC in PMMA fibers has a negative sign and ranges from -4.5 to -1.5×10-12 Pa -1 depending on the drawing stress. Increase of the drawing stress results in greater initial fiber birefringence and lower ΔC. The dependence of ΔC and initial birefringence upon drawing stress is nonlinear and gradually saturates for higher drawing stress. Moreover, we find that ΔC is linearly proportional to initial fiber birefringence and that annealing the fiber has no impact on the slope of this dependence. On the other hand, no clear dependence was observed between the fiber drawing stress and the Young's modulus of the fibers as measured using microscopic digital image correlation with the fibers tensioned using an Instron tension tester.

Determination of the radial profile of the photoelastic coefficient of polymer optical fibers

“…Moreover, the values measured in the two singlemode fibers are clearly much smaller than in the multimode fiber. This finding can be explained by the strong dependence of the photoelastic constant of a polymer fiber on the fabrication and production process [22]. Note that we obtain identical results for different lengths of fiber taken from the same fabrication batch.…”

Annealing effects on strain and stress sensitivity of polymer optical fibre based sensors

“…Polymer optical fibres (POF) offer greater elasticity 2 and higher failure strain 3 . The lower Young's modulus of polymer materials 2,4 renders POFBG sensors more sensitive to strain 5 , stress 6 , pressure 7 and acoustic wave detection 8 . The large negative thermo-optic coefficient of polymer compared with the small positive thermo-optic coefficient of glass [9][10][11] can also offer to POFBG sensors enhanced sensitivity to temperature variations 12,13 .…”

Strain Sensitivity Control of an In-Series Silica and Polymer FBG

“…The result is a consequence of the difference in length, cross-sectional area and Young’s modulus of the fibers involved. In fact, silica fibers have a Young’s modulus of about 70 GPa [ 6 ], while PMMA-based POFs are commonly found to have 3.2 GPa [ 5 ]. This difference results in unequal strain distributions on each fiber section, which is higher in PMMA fibers and lower in silica ones.…”

“…The gap between the fibers was adjusted to its minimum in order to avoid the formation of Fabry Perot cavities that could deteriorate the reflection signal of both the silica and polymer FBGs. To set the resin, a handheld UV source (Opticure LED 200, from Norland Products, Inc.), with a wavelength of 365 nm and a fluence of 2.5 W/cm 2 , was used to illuminate the region for 10 s. It is worth noting that the resin employed was chosen due to its optimum adhesion to polymer and silica materials, offering a Young’s modulus of ~2.5 GPa [ 19 ], which is close to the value found in PMMA fibers [ 5 ]. One feature of the fiber connection employed in this work is related to the induced coupling loss between the silica fiber and the mPOF.…”

“…POFs can offer key advantages over the traditional silica fiber. Among these advantages is their lower Young’s modulus ( E ), which, for the most popular fiber material, polymethylmethacrylate (PMMA), is around 3.2 GPa [ 5 ], while silica fibers can reach values of 70 GPa [ 6 ]. This property allows POFs to monitor soft materials, a capacity that the stiffer silica fiber does not have.…”