Fruehwald-Koenig, K.1); Heister, L.2): Macro- and Micromechanical Behavior of Oil Palm Wood (Elaeis guineensis JACQ.): Tensile, Compression and Bending Properties

Abstract

Abstract Being monocotyledons, palms show distinct differences in anatomical structure compared to common wood species. Oil palm wood can be seen as a unidirectional long-fiber-reinforced bio-composite, if vascular bundles are considered reinforcements (fibers) and parenchymatous ground tissue the matrix. The elastomechanical properties in bending (fm, Em), compression parallel (fc,0) and perpendicular (fc,90) and tension parallel (ft,0, Et,0) and perpendicular (ft,90) directions to the vascular bundles of small-size test specimen show a much higher exponential increase in density, following power law relationships, than common wood species and a significant gradient over both trunk height and cross section. The rule-of-mixture cannot be confirmed for ft,0 and Et,0, because the concentration of vascular bundles, as well as the share of fibers within the bundles, is greater in the periphery of the stem than in the central tissue. Furthermore, the cell wall properties themselves are not constant; cell wall thickening is more pronounced in the peripheral than in the central tissue and more in the bottom of the trunk than near the top. The “fibers” of the composite material are not homogeneous nor regularly spaced, which leads to exponents > 1 of the power law relationship. Different from common wood species, the compression strength of oil palm wood exceeds the tensile strength: fc,0 : fm : ft,0 are 2.2 : 3.3…1.7 : 1. The performance indices for minimum weight design by Ashby et al. (1995) are comparable to that for coconut and date palm.