Numerical analysis of a smart composite material mechanical component using an embedded long period grating fiber sensor

Abstract

Results obtained by FEM analysis of a smart mechanical part manufactured of reinforced composite materials with embedded long period grating fiber sensors (LPGFS) used for operation monitoring are presented. Fiber smart reinforced composite materials because of their fundamental importance across a broad range of industrial applications, as aerospace industry. The main purpose of the performed numerical analysis consists in final improved design of composite mechanical components providing a feedback useful for further automation of the whole system. The performed numerical analysis is pointing to a correlation of composite material internal mechanical loads applied to LPGFS with the NIR absorption bands peak wavelength shifts. One main idea of the performed numerical analysis relies on the observed fact that a LPGFS embedded inside a composite material undergoes mechanical loads created by the micro scale roughness of the composite fiber network. The effect of this mechanical load consists in bending of the LPGFS. The shifting towards IR and broadening of absorption bands appeared in the LPGFS transmission spectra is modeled according to this observation using the coupled mode approach.

Numerical Simulation Methods Applied at Fiber Grating Sensors Design

“…Consequently, the basics of simulation models are provided. Coupled-mode theory and the transfer matrix methods are the two techniques used for the simulation of FBG and LPG [13,14,17,20,[22][23][24][25][26][27][28]. Thus, the physical mechanism of the grating electric field interaction is given and aims to provide the reader with insight into the operation principles of FBG and LPG.…”

“…In the case of a step index fiber without a grating, the core power confinement factor, Γ, is defined. For uniformity across the core-induced grating, with an induced index change δn co created in core, for the propagation mode, the following relation is defined [13,[21][22][23][24][25][26][27][28]36]:…”

“…Eq. (7) can be rewritten in terms of the propagation constant of the incident beam and the reflected/diffracted light as follows [13,14,[20][21][22][23][24][25][26][27][28]:…”

“…For an improved design of experimental setups dedicated to the above-mentioned applications, it is obvious that, for both FBG and LPG, the principles for understanding and tools for designing fiber gratings are emphasized [11][12][13][14][15][16][17][18][19][20]. The emphasized understanding principles and designing tools are applicable for the wide variety of optical properties that are possible in fiber gratings [19][20][21][22][23][24][25][26][27][28]. There are given examples related to the large number of fiber grating subtypes of both FBG and LPG, considering uniform, apodized, chirped, discrete phase-shifted and superstructure gratings; symmetric and tilted gratings; and cladding-mode and radiation-mode coupling gratings [20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

“…The emphasized understanding principles and designing tools are applicable for the wide variety of optical properties that are possible in fiber gratings [19][20][21][22][23][24][25][26][27][28]. There are given examples related to the large number of fiber grating subtypes of both FBG and LPG, considering uniform, apodized, chirped, discrete phase-shifted and superstructure gratings; symmetric and tilted gratings; and cladding-mode and radiation-mode coupling gratings [20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”