Is the rule of mixture appropriate for assessing bamboo material properties?: Fid-Bau Portal

Is the rule of mixture appropriate for assessing bamboo material properties?

Akinbade, Yusuf / Harries, Kent A.

Highlights • Behaviour of bamboo is not adequately captured using the rule of mixtures (RoM). • Transverse modulus of rupture is higher than predicted in regions of low fibre volume. • Morphology of failure surface varies through culm wall thickness. • Interfibril cracking observed that affects isotropic fibre assumption. • Modelling supports need for orthotropic bamboo fibre and matrix properties.

Abstract Bamboo is often described as a functionally graded unidirectional fibre-reinforced composite material. As such, the Rule of Mixture (RoM) is often reported as an appropriate method of capturing longitudinal material and mechanical properties. However the dominant failure mode of bamboo is associated with longitudinal splitting of the culm and is therefore affected by transverse material properties. The efficacy of RoM in the longitudinal direction suggests its adoption in the transverse direction. It is concluded that the transverse behaviour of bamboo is not adequately captured using the often-adopted RoM approach. Experimental, morphological and numerical approaches are presented to better understand the reasons for bamboo not behaving as a unidirectional fibre reinforced material as is uniformly described in the literature. The approach has identified possible causes of the deviation of the observed behaviour – all which require further study.