Advanced Ultrasonic Testing and post-processing for detection of sustainable composites


Carbon-fibre reinforced composites (CFRP) and glass-fibre reinforced composites (GFRP) has seen widespread usage in various industries, from aerospace to utilities. With the 'The green shift' and sustainability movement gaining momentum, there is an increased pressure for sustainable / natural materials to be used. Natural materials such as flax fibre can be used as a replacement for glass fibres. With the expectation that these composites will see increased usage, there is a need to develop inspection technologies. 

In this paper, single element immersion ultrasonic testing is used to inspect the flax fibre composites. The initial step involved inspection optimisation to obtain ideal input parameters. The raw results had no clear detection of the seeded delamination (using Teflon sheets). An advanced post-processing technique used for fibre waviness detection in CFRP was applied to the data. This post-processing technique included frequency analysis, phase analysis and amplitude analysis. The three types of data were separated from the raw data and visualised using a C-scan. Using this post-processing method, the seeded delamination could be detected. 

As a follow-up, more samples of various thicknesses and varying values of fibre waviness were fabricated to understand the limitation of inspection of flax fibres composites. This was achieved by having different thicknesses of Teflon sheets. The aim is to eventually have an inspection technique for a natural composite. 
This inspection technique and post-processing techniques has the potential to be applied onto the composite fabrication process, to aid in the manufacturing, optimisation, and validation process.
