Abstract

Structural health monitoring (SHM) of composite materials is critical for ensuring the reliability and longevity of high-performance engineering systems. This review comprehensively examines the advancements, challenges, and applications of flat optical fibre sensors (FOFS) for real-time strain monitoring in composite structures. Traditional electrical strain gauges and piezoelectric sensors face limitations in multiplexing, electromagnetic interference (EMI), and integration within composite layups. In contrast, FOFS offer unique advantages, including high spatial resolution, compatibility with composite manufacturing processes, and immunity to EMI. This paper analyses the working principles of FOFS, their fabrication techniques, integration methodologies, and signal interrogation systems. Case studies from aerospace, civil engineering, and renewable energy sectors underscore their practical efficacy. Challenges such as signal attenuation, temperature cross-sensitivity, and long-term durability are critically evaluated. The review concludes with future directions, including nanotechnology-enhanced sensors and machine learning-driven data analytics.