Vibration-Based Structural Health Monitoring of Composite Plates with Integrated Sustainable Micro-Fibre Transducers

Abstract

Composites have gained widespread acceptance in various industries due to their exceptional performance over the last 10 years. In 2024, industries predominantly employ manual and non-destructive testing (NDT) techniques for routine inspection and maintenance. However, a Structural Health Monitoring (SHM) technology that is low in energy consumption, easy to install and applicable to various working conditions could cater better to market demands. To address this, the thesis focuses on the identification, localisation, and quantification of damage through vibration analysis methods based on Frequency Response Functions (FRFs). It also explores potential challenges in the practical application of these methods. The thesis relies on the integral differential method to measure the variation of FRF between the pristine and damaged stages, referred to as the Difference of Response (DoR) index. A series of carbon fibre composite panels with integrated microfibre composite (MFC) sensors arranged in equilateral triangles were fabricated. Through sine swept-frequency vibration testing at three different frequency ranges (10 Hz to 1 kHz, 1 kHz to 3 kHz, and 3 kHz to 5 kHz), the dynamic responses of the sample in both the impact-damaged and pristine stages were recorded in real-time, allowing for mutual comparison. Combined with damage geometrical dimensions measured by thermography imaging technology, a quantification formula is derived through numerical analysis, demonstrating a segmented linear relation between the DoR and damage size governed by power and logarithmic functions. According to the local effect of the damage, the DoR results of each region in the sample were compared, successfully achieving damage localisation in single and multiple damage scenarios. Additionally, experimental results highlight the significant influence of environmental factors on the dynamic behaviours of the structure. This thesis contributes significantly to the realisation of SHM using traditional vibration methods and addresses a longstanding development gap in this field.