An engineering approach to understand senile coconut palms as foundation for biomimetic applications
- Format
- DoctoralThesis
- Status
- publishedVersion
- Description
The present study ?is based not on what we can extract from nature, but on what we can learn from her, to strive innovation inspired by nature? (Benyus, 2002). Specifically, the research that constitutes this thesis aims at understanding, from an engineering perspective, the form-structure-function relationship of one monocot plant species, the coconut palm (Cocos nucifera L). Superior to woody plants (i.e. hardwoods and softwoods), coconut palms are able to withstand extreme conditions (e.g. hurricanes, tornadoes) without significant failure. Previous studies have shown that the internal structure of coconut palm stems significantly differs from hardwoods and softwoods, and even other palm species, likely influencing the mechanical performance of the palm. Yet, there is currently an absence of fundamental knowledge about the underlying principles and effects produced by the form and structure on the mechanical function of the palm (i.e. functional design). The present investigation contributes to partially address this issue by investigating the biomaterial form-structure-function relationship at the integral and macroscopic levels of hierarchical structure. The present research commenced approximately 3.5 years ago with the scientific and technical support of the Department of Agriculture, Fisheries and Forestry (DAFF), Queensland Government, Australia. The study comprised three major phases. The first phase aimed at defining, quantifying and analysing the coconut palm morphology (form) and hierarchical structure at the integral level (stem structure) and macroscopic level (tissue structure) in terms of such factors as radius, fibrovascular bundle orientation and density distribution. To achieve this purpose, more than 40 senile coconut palms (estimated to be greater than 80 years old) from the Pacific islands of Fiji and Samoa were analysed. The second phase aimed at quantifying and characterising the entire set of mechanical properties within the stem green tissue of senile coconut palms (referred to as cocowood in this study). Compressive and shear tests were carried out to fulfil this purpose. The investigated mechanical properties included: the modulus of elasticity and compressive modulus of rupture in the three loading directions (longitudinal, radial and tangential); the modulus of rigidity in the three mutually perpendicular planes of symmetry, including the longitudinal-radial (LR), radial-tangential (RT), and tangential-longitudinal (TL) planes; the Poisson?s ratios in several directions, and the shear capacity in the LT plane. Furthermore, this part of the study analysed the relationships between the measured mechanical properties and related physical properties, such as basic density and moisture content. From the analysis of the cocowood biomechanical performance under progressive wind loadings, a critical wind speed of 23 m/s was determined. At this wind speed, the cocowood stem tissue started experiencing failure, and the maximum height of the palm was reduced by 12.68%. The characteristic coconut palm stem showed a remarkable bending capacity during extreme wind conditions (e.g. maximum studied wind speed of 60 m/s), which allowed the palm stem to significantly reduce the wind surface and, therefore, the bending moments. The fundamental understanding advanced from this study has far-reaching implications for enhancing wood materials from a biomimetic perspective. Further, the study provides concept generators to improve current fibre-reinforced composites and engineered wood products (EWPs), such as spirally laminated hollow veneer based composite (VBC) poles.
- Publication Year
- 2015
- Language
- eng
- Topic
- PLANT BIOLOGY
MATERIAL MECHANICS
SENILE COCONUT PALMS
STRUCTURAL ANALYSIS AND COMPUTATIONAL MODELLING
- Repository
- Repositorio SENESCYT
- Rights
- openAccess
- License