PMMA birefringence-based optical sensor of load

The results of an investigation of polymethylmetacrylate deformation due to applied high-load utilizing its birefringence are presented in the paper. The sample under the test was placed between two plane polarizers, illuminated by white light and gradually stressed using a machine for fatigue testing of materials. The spectra of transmitted light were measured as function of load and deformation using optical fiber spectral analyzers for visible (VIS) and near infrared (NIR) spectral ranges. The measured spectra were normalized and light intensities for selected wavelengths as function of load and deformation were compared with the dependences according to models describing the stress-induced birefringence of PMMA as function of load and deformation, respectively. A good match between the dependences resulting from the measured data and those calculated according to models implies the models can be used for calculating calibrations curves of PMMA-based sensors of load and/or deformation