Experimental Testing Towards the Regulatory Inclusion of Sustainable Composite Materials

Abstract Polymer-matrix composites are omnipresent in recreational and high-performance small craft structures, whose design is governed by regulations such as ISO 12215-5:2019. However, such regulations only provide default mechanical properties for glass, aramid and carbon fibre because a rigorous characterization of the mechanical properties of sustainable materials remains lacking. In this work, we consider sustainability as a reduced overall environmental impact and embodied energy over the entire life cycle of a yacht. Consequently, this paper undertakes the mechanical testing of sustainable composite materials, namely: flax, hemp, bamboo, basalt, diolen, innegra and recycled carbon fibre, and reports the results of experiments conducted in line with ISO 178:2019 for flexion, ISO 527-4:2023 for tension, and ISO 14126:2023 for compression, to ascertain the necessary mechanical properties for regulatory composite design. Particular attention is paid to the quantification of the experimental uncertainty to ensure safe and reliable properties are provided, as required for regulatory adoption. Here, we show that several sustainable fibres would enable lighter laminates for equal strength with fibreglass and that the mechanical properties of sustainable composites can be accurately quantified to support inclusion in future rules and regulations. These findings provide novel insights into the mechanical properties of a range of candidate sustainable composite materials for recreational and high-performance yacht structures, in order to guide future research and focus on the most promising options. As such, it is envisaged these results will support the wider adoption of environmentally friendly fibres for composite applications and may inform future rules and regulations. Keywords sustainable composites; sustainable fibre; polymer-matrix composite; small craft structures; ISO 12215-5