Page 322 - Fiber Fracture

304 C. Viney

Abstract

Traditional users of natural fibres achieve effective property control at the length
scale of yams, but are able to exercise only limited intervention at the length scale of
molecules. Advances in biotechnology, and in understanding nature’s processes of self-
assembly, offer the possibility of refining structure and properties at all length scales.
We consider the factors that are especially important to fibre assembly and therefore to
fracture management in this interdisciplinary context. Several desirable consequences
of self-assembly and hierarchical structure are catalogued. Hierarchical structures are
recognised as providing enhanced toughness compared to just a fine structure. The role
of water in ensuring the stability and performance of natural self-assembled fibres is
emphasised, along with its implications for biomimetic materials. Loss of structural
order is shown to be commensurate with retention - even enhancement - of load-
bearing ability in certain cases. The collagen fibres that reinforce composite tissues of
echinoderms are highlighted as a source of several stimulating lessons for materials
engineering. The lessons include dynamic control of fibre strength and stiffness, and
the use of elongated tapered fibres to optimise exploitation of the load camed per unit
volume of fibre.

Keywords

Actin; Collagen; Fibre; Fracture; Hydrophobic bond; Myosin; Nature; Self-assembly;
Silk; Smart composite; Structural hierarchy; Toughness