The Application of Bio-Based Composites in Load-Bearing Structures

A research into the possibilities, properties and the durability of flax fibre reinforced bio-based composites

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Abstract

An increasing environmental concern and a growing interest of environmentally friendly and renewable materials is driving the growth of the bio-based composite sector. From 2010 to 2020, it is expected that the use of natural fibres as a reinforcement in composites will be doubled. Bio-based composites are already widely applied within the automotive and boat industry, as well as product design. Yet, the use of bio-based composites in architecture and building engineering is scarce. Nevertheless, the use of bio-based composites does show potential in the architecture and building engineering industry, having the 3TU bio-based pedestrian bridge project as a recent example which proves the possibilities with bio-based composites. But aside from the benefits of natural fibres as reinforcement in bio-based composites, such as renewability and high technical quality, there are challenges in the use of bio-based materials. One main concern is the long-term durability of bio-based composites, which is particularly important to understand to ensure the safety of load-bearing structures. This thesis studies the potentials and challenges of the use of bio-based composites in load-bearing structures. The major objective of this research is to define the mechanical properties of flax fibre bio-based composites and the effect of weathering on these mechanical properties. The mechanical properties of flax fibre bio-based composites were investigated through a series of mechanical testing, while the effect of weathering on the mechanical performance was researched through an accelerated weathering test. In this weathering test, the flax fibre reinforced bio-based composite has been exposed to ultraviolet light, changing temperatures and moisture. With the results of this research, it can be concluded that natural fibre reinforced composites are suitable for load-bearing structures. However, these experiments have also shown that weathering has a negative impact on the mechanical properties of bio-based composites. After being exposed to 808 hours of accelerated weathering, the tensile strength and the Young’s modules of the tested composites have decreased. Although accelerated weathering tests provide valuable knowledge about the possible weathering characteristics of bio-based composites, the translation to weathering in a real-life situation remains difficult and requires more extensive research.