Static micromechanical measurements of the flexural modulus and strength of micrometre-diameter single fibres using deflecting microcantilever techniques.

The mechanical properties of natural and man-made fibres ultimately govern the robustness of products. Examples range from textiles to composite materials for mechanical parts in emerging technological applications. An accurate determination of the mechanical properties of microscopic single fibres is therefore important. Today, macroscopic mechanical techniques, such as tensile testing, are commonly employed to obtain this information. However, a relatively high dispersion of results is often encountered due to a relatively long sample size. As an alternative to tensile methods, we demonstrate here micromechanical techniques to accurately measure the flexural modulus and strength of micrometre-sized diameter fibres without the need of force sensing. To demonstrate our ideas, we use the example of single natural fibres (Linum Usitatissimum). The flexural modulus of the single fibres is first accurately measured in the low deflection regime of an inclined bending cantilever in an original setup. The flexural strength of the single fibres is then measured in the high deflection regime of a bending cantilever. Interestingly, the novel measurements have allowed the authors to quantify the flexural strength of two different failure modes in flax fibre, enabling a contribution to plant mechanics.