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Title: Vibration-based structural health monitoring of composite laminates
Author: Yang, Chen
ISNI:       0000 0004 6498 2867
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2017
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Over the past three decades, carbon-fibre reinforced plastics (CFRP) and glass fibre-reinforced plastics (GFRP) have been increasingly used in modern engineering designs to make composite laminated structures. This increase is due to their attractive mechanical performances and their stable physical and chemical properties. However, these composites are subjected to distinctive failure modes which are different from those of metallic alloys. These failure modes include delamination, matrix cracking and fibre breakage. Therefore, structural health monitoring (SHM) of composite laminated structures during the operational phase has become increasingly important. This thesis presents the development of vibration-based SHM approaches. A non-contact fibre optic sensor is developed for modal testing and structural health monitoring of composite laminate structures. Signal processing methods are used on the acquired modal data to produce a new damage index. The main investigations and contributions of the thesis are summarised as follows,1) A delamination detection method using additional mass loading and modal frequencies is numerically and experimentally studied. The study shows that the interaction between local inertia and delaminations affects the vibration characteristics of composite laminated beams for delaminations located at different depths. 2) A two-step delamination producing technique through mechanical pull-up is proposed and experimentally validated for composite laminated plates. The proposed technique overcomes the inadequate performance of PTFE inserts approach and shows the ability to produce both near surface and far surface delaminations at inaccessible regions from the boundaries. 3) A delamination detection approach using wavelet coefficients of the multiple-mode modal frequency curve for beam-like structures is developed. The method does not require the knowledge of the intact state nor the use of artificial noise filtering procedures.4) The proposed intact-free wavelet coefficients of modal frequency surface are further applied to two-dimensional composite laminate plate-like structures. In conjunction with the wavelet-based edge detection method in imaging processing, the proposed method shows the satisfactory performance in delamination identification and localisation for laminate plates.5) A cost-effective non-contact fibre optic displacement sensor is developed based on the theoretical model. The parameters of the sensor are calibrated following standard procedures. The sensor shows satisfactory performance in structural modal testing. 6) The application of the developed fibre optic sensor in structural health monitoring for composite laminate structures is demonstrated by experiments and its performance is compared with that of commercial sensors.
Supervisor: Oyadiji, Sunday ; Ji, Tianjian Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available