Built-in fiber-optic mechanophotoluminescent sensor of complex deformed state for monitoring vibrations of polymer composite structures

A mathematical model of an embedded fiber-optic mechanical (elastic) photoluminescent (MFL) sensor of a complex stressed-deformed state for monitoring vibrations of polymer composite structures has been developed. The sensor includes one or more light guides doped with many spherical MFL nanoparticles (uniformly distributed over the volume of the light guide) of the "core/shell" type. The latter is an elastomechanoluminescent (EML) core with a photoluminescent (FL) shell. Here the EML effect is the light output of the material with its elastic (non-destructive) deformations. The FL-shell of each capsulated particle transforms the informative "internal" ML-radiation of the core into an "external" informative FL-light flux within the light guide. The resulting value of the FL-light flux from all particles is recorded at the output of each light guide. An additional function of the shell is the localization (within the boundaries of each particle) of the information glow of the EML-core, which, as a result, improves the spatial resolution of the sensor to diagnose significantly heterogeneous (along the length of the sensor) deformation fields. The MFL-sensor is designed to diagnose the components of the harmonic macrodeformation amplitude tensor of the local composite region under consideration, i.e. the vicinity of the built-in sensor based on the measurement results of informative photoluminescent FL-light fluxes at the outputs from the light guides of the sensor. Control and adjustment of the output (in the working end "input/output" of the sensor) and recorded informative FL-light fluxes is carried out by using a variable input control light flux, in particular, the same for all light guides of the sensor. It was found that in case of using the single "quartz/MFL particle" light guide (pressure sensor), the desired "spectrum" of pressure amplitudes (the density function of the distribution of amplitude values along the longitudinal axis of the sensor) is a solution of the Fredholm integral equation of the 1st kind based on the results of measurements (at the output from the light guide) of the informative resulting FL-light flux as a function of the control incoming (ML) light flux flow. The results of the numerical modeling are obtained for the dependence of the light FL flux value on the control ML flux for cases of uniform and non-uniform (but with a "uniform" spectrum) distributions of the diagnosed pressure amplitude value along the sensor length.