Section properties of palm petioles. Part 1: The influence of section shape on the flexural and torsional properties of selected palm petioles

Shape factors have been used to calculate the shape efficiency of palm leaf petiole sections in order to understand how palms compensate for the torsional and bending forces they are subjected to by their environment. The part of the palm leaf that is similar in form to the leaf stalk (petiole) in dicot leaves will be referred to as a petiole in this paper, whilst recognising that it is probably not an exact homologue. Wind and rain on the blade generate combined flexural and torsion loads on the petiole and a question arises as to how the section properties of the petiole deal with this loading. By isolating the shape from the size of the sections through the use of shape factors, the effects of the petiole section shape can be analysed on its own. Thus microstructural and material factors become a separate issue and will be discussed in a later paper. Cross section profiles from seven palm petioles are modelled, independent of their sizes, in order to calculate and plot the flexural and torsional coupling efficiencies for comparison with other plants and typical engineering cross sections.