Influence of hornification on the physical and flexural properties of Moso bamboo

This work aims to investigate experimentally the improvements on the physical and flexural properties of Moso bamboo species (Phyllostachys pubescens) associated to the hornification phenomenon, widely used as a treatment in wood pulps or paper to reduce porosity, absorption capacity and water retention of the fibers, as well as to increase their stiffness. To accomplish this task, bamboo samples subjected up to ten wetting and drying cycles had their flexural characteristics such as stiffness, strength, neutral axis, deflection at failure and through-thickness shear modulus compared with untreated samples. The moisture content was monitored during cycles and image analysis was performed to determine the distribution of vascular bundles throughout the wall thickness of the culm's cross-section. The experimental program showed a reduction in water retention capacity of bamboo and in the deflection at failure, as well as an increment in the modulus of elasticity up to 70% after treatment. The tests also reveal a major influence of shear deformation on the overall deflection and appropriate strain measurement techniques must be used for a more accurate moduli determination. Finally, a simplified micromechanical approach was used along with fiber content distribution to estimate the influence of hornification on the moduli under compression and tension of the constituents. (C) 2020 Elsevier Ltd. All rights reserved.