PROBING COMPRESSIVE BEHAVIOUR AND FAILURE IN SINGLE FIBRE CARBON FIBER COMPOSITES: IN-DEPTH ANALYSIS USING IN SITU LASER RAMAN SPECTROSCOPY

Compressive failure of fibres in unidirectional composites is often characterised by microbuckling and the formation of kink bands. Developing insight into the behaviour of reinforcing fibre and the fibre-matrix interface before, during, and after failure is crucial for enhancing compressive performance. Direct mechanical testing of single fibres is limited due to scale considerations, necessitating alternative approaches, additionally, characterising interfacial behaviour in compressive loading lacks a direct quantitative method.

In this study, Raman spectroscopy is utilised as a non-contact method for characterising micromechanical behaviour and interfacial responses during compressive loading. In situ laser Raman spectroscopy is employed to investigate compressive stress-strain behaviour of single fibres as well as generate spatially resolved stress maps of single carbon fibres under compression. Two experimental setups are discussed: a four-point bending setup for static Raman analysis and a uniaxial compression setup for stress map generation. High-resolution Raman stress maps, scanning electron microscopy, and confocal laser scanning microscopy are used to examine the evolution of failure of high modulus carbon
fibres. This research contributes to a deeper understanding of compressive performance in carbon fibre composites, crucial for advancing their design and future applications