Distributed fibre optic monitoring of mode I fatigue crack propagation in adhesive bonded joints and comparison with digital image correlation

Lima, R.A.A.; Migliavacca, F.; Martulli, L.M.; Carboni, M.; Bernasconi, A.

doi:10.1016/j.tafmec.2022.103501

Cited by 12 publications

(7 citation statements)

References 63 publications

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“…Moreover, delamination growth occurs at lower loads than the static case, resulting in a lower signal-to-noise ratio (SNR) from a DOFS perspective. Moreover, depending on the laminate characteristics, the strain field in the process zone can be different [32]. Stutz et al show that fiber bridging modifies the expected strain value in the process zone, which affects the damage index used to build POD curves [33].…”

Section: Mapod Concept For Dofssmentioning

confidence: 99%

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A Model-Assisted Probability of Detection Framework for Optical Fiber Sensors

Falcetelli

Yue

Rossi³

et al. 2023

Sensors

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Optical fiber sensors (OFSs) represent an efficient sensing solution in various structural health monitoring (SHM) applications. However, a well-defined methodology is still missing to quantify their damage detection performance, preventing their certification and full deployment in SHM. In a recent study, the authors proposed an experimental methodology to qualify distributed OFSs using the concept of probability of detection (POD). Nevertheless, POD curves require considerable testing, which is often not feasible. This study takes a step forward, presenting a model-assisted POD (MAPOD) approach for the first time applied to distributed OFSs (DOFSs). The new MAPOD framework applied to DOFSs is validated through previous experimental results, considering the mode I delamination monitoring of a double-cantilever beam (DCB) specimen under quasi-static loading conditions. The results show how strain transfer, loading conditions, human factors, interrogator resolution, and noise can alter the damage detection capabilities of DOFSs. This MAPOD approach represents a tool to study the effects of varying environmental and operational conditions on SHM systems based on DOFSs and for the design optimization of the monitoring system.

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Section: Mapod Concept For Dofssmentioning

confidence: 99%

“…Moreover, depending on the laminate characteristics, the strain field in the process zone can be different [ 32 ]. Stutz et al show that fiber bridging modifies the expected strain value in the process zone, which affects the damage index used to build POD curves [ 33 ].…”

Section: Introductionmentioning

confidence: 99%

A Model-Assisted Probability of Detection Framework for Optical Fiber Sensors

Falcetelli

Yue

Rossi³

et al. 2023

Sensors

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“…Therefore, it is important to introduce in‐situ monitoring techniques for damage inspection of adhesively bonded joints due to moisture. Recently, several in‐situ monitoring techniques, such as fiber optic monitoring, X‐ray microtomography, digital image correlation, acoustic emissions, and mechanoluminescence, have been introduced to observe crack propagation in adhesive joints 15–19 . However, until now, there are almost no methods for direct measurement of water penetration in the adhesive layer.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, several in-situ monitoring techniques, such as fiber optic monitoring, X-ray microtomography, digital image correlation, acoustic emissions, and mechanoluminescence, have been introduced to observe crack propagation in adhesive joints. [15][16][17][18][19] However, until now, there are almost no methods for direct measurement of water penetration in the adhesive layer. Degradation due to water absorption is therefore only speculative and insitu monitoring of moisture distribution is essential to discuss what is happening.…”

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confidence: 99%

Experimental measurement of moisture distribution in the adhesive layer using near‐infrared spectroscopy

Han

Sekiguchi

Shimamoto

et al. 2023

J of Applied Polymer Sci

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Adhesive joints are degraded when exposed to moist conditions, making it essential to assess the permeation distance of absorbed moisture. However, monitoring the water penetration in the adhesive layer is challenging because the adhesive layer is sandwiched between the adherends. To overcome this difficulty, we proposed a new monitoring system using fiber-type near-infrared spectroscopy (NIRS), and the moisture distribution at the joint was successfully observed by introducing quartz glass as one side of the substrate. First, the change in the absorbance spectra owing to water absorption by an epoxy adhesive was investigated by immersing epoxy-coated aluminum alloy plates in temperature-controlled water. It was found that the water content can be evaluated by monitoring the change in the peak intensity appearing around 1900-1950 nm. Next, water penetration into the adhesive layer sandwiched between the quartz glass and aluminum alloy was investigated by scanning the surface. The water permeation distance was found to change with temperature. Under the 23 C immersion condition, approximately 2.5 mm of water penetration was observed after 8 weeks. Because the simulation results using Fick's law of diffusion showed similar trends, it was experimentally confirmed that Fickian diffusion dominates the water distribution in the adhesive layer.

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“…Acoustic emissions have also been demonstrated suitable for online monitoring in a laboratory environment [31]. In [32], the authors proposed the shifts in the strain peak measured by distributed fiber optic sensors as features to quantitatively monitor crack growth in double cantilever beam specimens.…”

Section: Introductionmentioning

confidence: 99%

Debonding quantification in adhesive bonded joints by the inverse finite element method

Poloni

Oboe²,

Sbarufatti³

et al. 2023

Smart Mater. Struct.

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In the past two decades, the aerospace industry has massively shifted from Aluminum-made components to Composite Materials such as Carbon Fibre Reinforced Polymers (CFRP), striving for more fuel efficient and lighter aircrafts. Consequently, traditional joints have been replaced by adhesive bonded interfaces, which are also the most common choice to repair damaged components. Although adhesive bonding is the most efficient choice for permanent connections, it is not free of disadvantages: one of the most common failure modes, the debonding of the two laps, is very problematic to detect and predict in practice. Therefore, frequent inspections must be performed to ensure structural safety, increasing maintenance costs, and lessening the availability of the platforms. The development of innovative sensing technologies has allowed for a close monitoring of structural interfaces, and several Structural Health Monitoring techniques have been proposed to monitor adhesive bonded connections. Sensitivity and correlation between measurements and debonding entity has been demonstrated in the literature: nevertheless, hardly any technique has been proposed and quantitively evaluated to estimate the debonding entity independently of the applied loads, such as misalignment-induced torsion, which is a major confounding influence in the traditional backface strain gauge technique. This paper proposes the inverse Finite Element Method (iFEM) as a load and material independent approach to infer the debonding entity from strain measurements in adhesive-bonded joints. Two approaches to estimate the debonding entity with the iFEM are compared on Cracked Leap Shear specimens representative of CFRP repair patches: one is based on anomaly indexes, the other on performing a model selection with multiple iFEM models including different damages. The latter demonstrates satisfactory performances; thus, it is considered a significant scientific advancement in this field.

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Distributed fibre optic monitoring of mode I fatigue crack propagation in adhesive bonded joints and comparison with digital image correlation

Cited by 12 publications

References 63 publications

A Model-Assisted Probability of Detection Framework for Optical Fiber Sensors

A Model-Assisted Probability of Detection Framework for Optical Fiber Sensors

Experimental measurement of moisture distribution in the adhesive layer using near‐infrared spectroscopy

Debonding quantification in adhesive bonded joints by the inverse finite element method

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