Structural health monitoring of composite structures with distributed fibre optic sensing
File(s)
Author(s)
Li, Yingwu
Type
Thesis
Abstract
The utilization of Carbon fibre reinforced polymers (CFRP) in aircraft structures has increased due to their advantageous properties, including being lightweight, strong, and cost-effective. However, CFRP materials are more complex than aluminium alloys and are susceptible to damage issues such as delamination, debonding, and matrix cracking, making structural health monitoring (SHM) essential. Strain measurement is a critical SHM technique as it detects structural damage by measuring changes in strain distribution. One effective sensor for strain measurement in CFRP is the single mode fibre that can be interrogated using the optical frequency domain reflectometer technique, which provides high spatial accuracy and continuous high-precision sensing.
At present, limited research has been conducted on the analysis of measurement accuracy in the presence of complex environmental conditions, such as thermal and vibration variations. Moreover, SMFs are sensitive to both mechanical and thermal loads. Therefore, this thesis focuses on fundamental research at first, including improving the sensitivity of strain measurements, calibration of strain measurement accuracy, and consistency of strain measurement on different structures.
Upon obtaining an accurate strain distribution based on fundamental research mentioned above, the next step of this thesis focuses on damage detection and shape sensing of CFRP shells using the inverse finite element method. The detection of damage is achieved by detecting sudden changes in the strain field under loading. In addition, a widely applicable and high-accuracy shape sensing scheme based on distributed fibre optic sensing has been proposed in this thesis. This scheme combines a block-based strain acquisition method with strain extrapolation based on single image super resolution algorithms to obtain displacement fields with high accuracy and high spatial resolution.
The research objectives are geared towards enhancing the SHM of CFRP structures using distributed fibre optic sensing, which improves their performance and durability in aerospace applications.
At present, limited research has been conducted on the analysis of measurement accuracy in the presence of complex environmental conditions, such as thermal and vibration variations. Moreover, SMFs are sensitive to both mechanical and thermal loads. Therefore, this thesis focuses on fundamental research at first, including improving the sensitivity of strain measurements, calibration of strain measurement accuracy, and consistency of strain measurement on different structures.
Upon obtaining an accurate strain distribution based on fundamental research mentioned above, the next step of this thesis focuses on damage detection and shape sensing of CFRP shells using the inverse finite element method. The detection of damage is achieved by detecting sudden changes in the strain field under loading. In addition, a widely applicable and high-accuracy shape sensing scheme based on distributed fibre optic sensing has been proposed in this thesis. This scheme combines a block-based strain acquisition method with strain extrapolation based on single image super resolution algorithms to obtain displacement fields with high accuracy and high spatial resolution.
The research objectives are geared towards enhancing the SHM of CFRP structures using distributed fibre optic sensing, which improves their performance and durability in aerospace applications.
Version
Open Access
Date Issued
2023-10
Date Awarded
2024-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Sharif Khodaei, Zahra
Sponsor
Imperial College London
Engineering and Physical Sciences Research Council
Grant Number
EP/R513052/1
Publisher Department
Aeronautics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)