Natural fibres, which are composed principally of a combination of cellulose, hemicellulose and lignin, can be derived from leaf (e.g. sisal), bast (e.g. flax, hemp), seed (e.g. cotton) and fruit (e.g. coir) but also from other sources such as chicken feathers. Natural fibres offer  a number of advantages over existing synthetic fibres (e.g. carbon and aramid fibres). From an environmental perspective, natural fibres are biodegradable and are carbon positive since they absorb more carbon dioxide than they produce. In addition, they are non-irritating and tend to be non-abrasive with the latter property resulting in reduced wear on tooling and manufacturing equipment. Fibre producing crops are also easy to grow, cheaper than synthetic fibres and provide one solution to the over-production of food crops in Europe. 

Natural fibres also possess a number of advantages in terms of specific material properties.  For light-weighting purposes, substitution of synthetic fibres with natural fibres can reduce the weight of a composite by up to 40% thereby offering substantial gains in fuel efficiency for the automotive, transport and aerospace sectors [1,2].   Improvements in flexural strength, stiffness and ductility can be achieved through the substitution of natural fibres [1].   In terms of overall strength properties, however, synthetic fibres still perform better than natural fibres although some natural fibres can approach the tensile modulus of E glass.  They also are preferential to synthetic fibres in automotive crash scenarios because the broken fibres have less of a sharp edge that can cause injury.

1. G. Marsh, “Next Step for Automotive Materials”, Materials Today, 36-43, April 2003.

2. J. Nickel and U. Riedel, “Activities in Biocomposites”, Materials Today, 44-48, April 2003.