Morphology, static and fatigue behavior of a natural UD composite: The date palm petiole ‘wood’

Large quantity of date palm wastes annually accumulate in Algeria. We investigate date palm petiole wood (DPPW) and macroscopic fibers from northern and southern Algeria by X-ray tomography, monotonic tension and compression, microscopy analysis, and fatigue tensile tests. DPPW is a unidirectional composite (VF=25%,ρ=210kgm-3) consisting of a fibrovascular ultrastructure (reinforcement) and parenchyma (matrix). Mechanical properties of southern DPPW (E=0.5GPa,σu=6MPa,εu=1.75%) are higher than northern ones because of the dry climatic conditions, its density also is higher. Main failure modes are cell-wall tearing and spheroidal-cell detachment (parenchyma), and pull-out or net fracture (fibers). Stress ratio is the major fatigue parameter, R=0.125 is a limit of endurance for transverse southern DPPW. High mechanical homogeneity of DPPW along that direction reduces the risk for damage development. Thanks to limited density, high fatigue life, and neglectable cost, DPPW is a good candidate for local development of sandwich core.