Laboratory Results of a Real-Time SHM Integrated System on a P180 Full-Scale Wing-Box Section

Abstract

The final objective of the study herein reported is the preliminary evaluation of the capability of an original, real-time SHM system applied to a full-scale wing-box section as a significant aircraft component, during an experimental campaign carried out at the Piaggio Lab in Villanova D'Albenga, Italy. In previous works, the authors have shown that such a system could be applied to composite beams, to reveal damage along the bonding line between a longitudinal stiffening element and the cap. Utilizing a suitable scaling process, such work has then been exported to more complex components, in order to confirm the outcomes that were already achieved, and, possibly, expanding the considerations that should drive the project towards an actual implementation of the proposed architecture. Relevant topics dealt with in this publication concern the application of the structural health monitoring system to different temperature ranges, by taking advantage of a climatic room operating at the Piaggio sites, and the contemporary use of several algorithms for real-time elaborations. Besides the real-time characteristics already introduced and discussed previously, such further steps are essential for applying the proposed architecture on board an aircraft, and to increase reliability aspects by accessing the possibility of comparing different information derived from different sources. The activities herein reported have been carried out within the Italian segment of the RESUME project, a joint co-operation between the Ministry of Defense of Israel and the Ministry of Defense of Italy.

Keywords: composite structures; damage characterization; real-time processing; sensors; smart devices; structural health monitoring.

Figure 1

General view of a small composite wing-box demonstrator.

Figure 2

Wing-box section from which the test article has been taken.

Figure 3

Actual test configuration: (a) left picture reports the climatic chamber specifically designed to host the test rig; and (b) right picture reports the bending actuator installed on the test article, while the compression actuator is detached.

Figure 4

Load direction in compression and bending configuration.

Figure 5

Thermal scan of the wing-box under thermal conditioning—test @ 70 °C.

Figure 6

Optical fibers and damage locations—sketch. Embedded optical fibers are shown in light green and coded according the letters A, B, C, and D, while the qualitative positions of the FBG arrays are reported in the tallow oval. Damage locations are presented as blue parallelograms, and their numbering is reported in white digits.

Figure 7

Schematic layout of the additional fibers installed on the wing-box, bottom panel, with the associated code; namely, 03 and 04 for the rear spar; and 01, 02, and 05 for the front spar. For the sake of clarity, a synthetic scheme of the flaws and fiber positions is reported, for both the spars, top and bottom. These same schematics are used to describe the results, in the last part of the paper.

Figure 8

Hardware setup.

Figure 9

Block diagram of the experimental set-up.

Figure 10

Screenshot of the SHM module running in real-time mode. Red box indicates the channel (arr1 and arr2) with the corresponding bar plot and the readout (damage detected at sensor number 2).

Figure 11

Strain distribution in the function of the increasing bending load each curve characterized by a different color. For an embedded FBG sensors array, along the front spar; (a) the incremental strain at room temperature; and (b) the incremental strain at high temperature.

Figure 12

Cumulative damage index under bending: red line sensor A; black line sensor B; TL as the dashed blue line; (a) the cumulative damage index at room temperature; (b) the cumulative damage index at high temperature.

Figure 13

Strain distribution in the function of the increasing compression load each curve characterized by a different color. For FBG sensors embedded array, along the front spar; (a) the incremental strain at room temperature; (b) the incremental strain at high temperature.

Figure 14

Cumulative damage index under compression: red line sensor A; black line sensor B; TL as the dashed blue line; (a) the cumulative damage index at room temperature; (b) the cumulative damage index at high temperature.

Figure 15

Strain distribution in the function of the increasing bending load each curve characterized by a different color. For FBG sensors embedded array, along the rear spar; (a) the incremental strain at room temperature; (b) the incremental strain at high temperature.

Figure 16

Cumulative damage index under bending: red line sensor C; black line sensor D; TL as the dashed blue line; (a) the cumulative damage index at room temperature; (b) the cumulative damage index at high temperature.

Figure 17

Strain distribution in the function of the increasing compression load each curve characterized by a different color. For FBG sensors embedded array, along the rear spar; (a) the incremental strain at room temperature; (b) the incremental strain at high temperature.

Figure 18

Cumulative damage index under compression: red line sensor C; black line sensor D; TL as the dashed blue line; (a) the cumulative damage index at room temperature; (b) the cumulative damage index at high temperature.

Figure 19

Strain distribution in the function of the increasing bending load each curve characterized by a different color. For FBG sensors bonded array, along the front spar; (a) the incremental strain at room temperature; (b) the incremental strain at high temperature.

Figure 20

Cumulative damage index under bending: black line fiber 01; red line fiber 02; blue line fiber 05; TL as the dashed green line; (a) the cumulative damage index at room temperature; (b) the cumulative damage index at high temperature.

Figure 21

Strain distribution in the function of the increasing bending load each curve characterized by a different color. For FBG sensors bonded array, along the rear spar; (a) the incremental strain at room temperature; (b) the incremental strain at high temperature.

Figure 22

Damage index under bending: red line fiber 03; black line fiber 04, TL as the dashed green line; (a) the cumulative damage index at room temperature; (b) the cumulative damage index at high temperature.

Figure 23

Main results for damage detection by fibers A and B. The black color refers to the position of the damage.

Figure 24

Main results for damage detection by fibers C and D. The black color refers to the position of the damage.

Figure 25

Main results for damage detection by fiber 02. The black color refers to the position of the damage. The arrow indicate the fiber under test.

Figure 26

Main results for damage detection by fiber 05. The black color refers to the position of the damage. The arrow indicate the fiber under test.

Figure 27

Main results for damage detection by fiber 03. The black color refers to the position of the damage. The arrow indicate the fiber under test.

Figure 28

Main results for damage detection by fiber 04. The black color refers to the position of the damage. The arrow indicate the fiber under test.