Properties of natural fibre composites for structural engineering applications

Since the last two decades, many researchers have refocused on using natural fibres, as reinforcements for cementitious and polymer based structural materials. The use of natural fibres for structural applications is not modern. Long before a century ago people in many small towns in China and Korea already mixed straws with mud to build walls in villages. However, at that time there was no systematic way to study the fundamental mechanism and interpret how natural fibres strengthen structures and what processes should be adopted to maximize the performance of natural materials. Currently, nevertheless natural fibre reinforced polymer (NFRP) composites have been widely used in automotive and building industries, it is still a room to promote them to high-level structural applications like primary structural components of aerospace and maritime structures. It is difficult to evaluate the quality of natural fibres, which generally extracted from the nature, and thus it is challenging to develop a generic formula to predict the structural and mechanical properties of NFRP composites. Hydrophilic and hydrophobic properties of natural fibres and polymers, respectively, cause poor bonding interaction at interface. Traditional shear-lag model was popularly used to study the stress transfer mechanism between fibre and matrix of advanced composites. However, such model is not applicable to NFRP composites due to the imperfect shape of nature fibres along their longitudinal direction and irregular shape of fibres' cross section. In this paper, analysis on different aspects in related to the use of natural fibres for real life engineering applications is given. Basic analytical models focusing on the stress transferability in composites are also discussed to provide an insight for researchers and engineers to understand the design and requirements of using natural fibres for structural applications in the future.