Innovative Photonic Sensors for Safety and Security, Part II: Aerospace and Submarine Applications

Abstract

The employability of photonics technology in the modern era's highly demanding and sophisticated domain of aerospace and submarines has been an appealing challenge for the scientific communities. In this paper, we review our main results achieved so far on the use of optical fiber sensors for safety and security in innovative aerospace and submarine applications. In particular, recent results of in-field applications of optical fiber sensors in aircraft monitoring, from a weight and balance analysis to vehicle Structural Health Monitoring (SHM) and Landing Gear (LG) monitoring, are presented and discussed. Moreover, underwater fiber-optic hydrophones are presented from the design to marine application.

Keywords: aerospace structure monitoring; distributed sensing; fiber bragg gratings; optical fiber sensors; submarine monitoring.

Figure 1

Block scheme representing the proposed solution.

Figure 2

Picture of the test piece, highlighting the interested area.

Figure 3

Block scheme regarding the measurement setup with (in table) info on the instrumentation employed.

Figure 4

Representation of FBG sensor positioning during the measurements.

Figure 5

Temperature measurement through 4 FBG sensors (a); same temperature obtained through thermal imager after 25 s in the middle of the interested area (b); heat mapping of the thermal imager temperature measurement with highlighted temperature deviation at left, right, and center of the interested area (c).

Figure 6

(a) Schematic representation of the mock-up structure; (b) drawing of the metal plate; and (c) pvc support. Adapted from Ref. [57].

Figure 7

Experimental setup. Adapted from Ref. [57].

Figure 8

(a) FBG sensor responses during the calibration tests and (b) calibration curves of the three FBG strain. Adapted from Ref. [57].

Figure 9

(a) FBG sensor responses during the tests along x-axis and (b) estimated weights. Adapted from Ref. [57].

Figure 10

Map of the stress in static arrangement for (a) MLG and (b) NLG. (Reprinted/adapted with permission from Ref. [68]).

Figure 11

FBGs (white) and conventional strain gauges (black) integrated on the (a) main and (b) nose landing gear; (c) pictures of the experimental setup. (Reprinted/adapted with permission from Ref. [68]).

Figure 12

Optical and electrical strain gauges sensorgrams installed on the Nose Landing gear. Reproduced with permission from ref. [68] (the figure is released under a Copyright Clearance Center’s RightsLink^® service).

Figure 13

(a) Calibration curves of the sensors integrated on the NLG, as determined by 2 identical (step-by-step) experiments; (b) enlargement in the interval 0–6 kN; and (c) True force vs. Calculated one during the validating test performed using the NLG. Reproduced with permission from ref. [68] (the figure is released under a Copyright Clearance Center’s RightsLink^® service).

Figure 14

(a) Path of the optical fiber employed during the ground test (blue line), electrical strain gauges (green circles) and artificial delaminations (red patches); and (b) Strain profiles acquired by the optical fiber sensor for an applied load of 348 N.

Figure 15

(a) Schematic view of the composite panel and optical fiber deployment; and (b) picture of the composite panel used for the tests.

Figure 16

(a) Temperature evolution as acquired by the TC, the BOFDA sensor, and the FBG in the same position of the plate; and (b) temperature distribution as acquired by the BOFDA sensor in one instant of the heating phase.

Figure 17

(a) Scheme of the arrangement of FBG sensors along Y-array and C-array, (b) spectra of the FBGs in the two arrays, (c–e) photos of the real item with the sensors (Adapted from Ref. [89]).

Figure 18

Time response of all FBG sensors in different test sections: (a) test A, (b) test B, and (c) test C. (Adapted from Ref. [89]).

Figure 19

FBG Surface strain profile vs. time: (a) strain profile along y-axis; and (b) strain profile along c-axis (Adapted from Ref. [89]).

Figure 20

Experimental test setup for the vibration tests.

Figure 21

FBG installation of composite drag link.

Figure 22

Details of the FBG sensors installed on the body (a) and on the fork (b) of the landing gear during the drop tests.

Figure 23

Acceleration spectrum during the vibration tests.

Figure 24

Strain history during sine sweep test.

Figure 25

(a) Transversal and (b) lateral side view of the composite mandrel hydrophone. (c) 3D radial displacement pertaining to the FOH under 1 Pa static pressure. Reproduced with permission from ref. [120] (the figure is released under a Copyright Clearance Center’s RightsLink^® service).

Figure 26

(a) Schematic of the experimental setup. The instrumented water tank is large 11 m × 5 m with a depth of 7 m. (b) Experimental Responsivity in dB of FOH hydrophone in a range from 3 kHz to 25 kHz in two different characterization tests. (c) Directivity of the FOH at 5 kHz, 10 kHz, and 15 kHz. Reproduced with permission from ref. [120] (the figure is released under a Copyright Clearance Center’s RightsLink^® service).

Figure 27

(a) Schematization of FOH in array configuration (sensitive hydrophones are labeled with “S”, reference hydrophones with “R”), (b) FOH array, and (c) Experimental responsivity in dB of FOH array. Reproduced with permission from ref. [120] (the figure is released under a Copyright Clearance Center’s RightsLink^® service).