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Densification viscoplastique du bois pour applications à performances structurales

de Crombrugghe de Looringhe, Diego
(2022)

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Details

Supervisors
Pardoen, Thomas ; Jacques, Pascal
Faculty
Ecole polytechnique de Louvain
Degree label
Master [120] : ingénieur civil mécanicien, à finalité spécialisée
Abstract
enToday in Belgium, the forestry sector is facing two main threats to its sustainability ; on the one hand, Belgian forests are increasingly made up of the same dense species, which reduces their resilience and biodiversity. On the other hand, Asian industrial actors are competing with local craftsmen and the latter are more and more deprived of raw material supplies. In order to overcome this problem and to valorize low density wood species, this thesis studies the influence of different parameters during the densification stage of a thermo-hygro-mechanical treatment (THM) on the mechanical properties of wood. The objective of this thesis is to study the influence of temperature, compression ratio, compression speed and compression time on the mechanical properties of common poplar. During the densification process, the pre-treatment and post-treatment steps are kept constant. The densification itself is optimized to maximize the modulus of elasticity and flexural strength as well as the hardness of the wood. Statistical analysis is used to predict the mechanical properties of poplar under untested densification conditions. As a result, an optimal treatment over the range of defined variables was calculated. This is obtained when the wood is densified with a compression ratio of 60.2 % to 140 ◦C at a speed of 4 mm/min for 1800 s. After densification, the modulus of elasticity increases by 132 % to reach 24 GPa, the flexural strength is 169 MPa (+ 92 %) and the hardness has increased fivefold to 21.4 MPa. The work was also able to highlight the influence and interaction between certain variables. Finally, the modulus of elasticity and the modulus of rupture evolve proportionally to the density of the wood while the hardness is rather proportional to the square of the latter.