Effect of natural weathering on water absorption and pore size distribution in thermally modified wood determined by nuclear magnetic resonance

Funder: Teollisuusneuvos Heikki Väänänen's FundFunder: International Thermowood AssociationFunder: Quantum Institute, University of OuluAbstractThermally modified wood (TMW) is widely used in outdoor applications due to its advanced properties towards weathering stresses. Although the structure changes of TMW from weather factors have been reported, investigation of the quantitative analysis of water states and cell wall structure of TMW after weathering is limited. In this work, the amount of bound water, fiber saturation point (FSP), cell wall pores, and free water distribution of thermally modified Scots pine, Norway spruce, and European ash were measured before and after a 2-year natural weathering via NMR relaxometry, cryoporometry, and magnetic resonance imaging. The results show that weathering increased T2 relaxation time of lumens, indicating the degradation of tracheids and vessels, especially in TMW compared to unmodified wood. The amounts of bound water, FSP value, and cell wall pores were increased after weathering; however, an increase in thermal modification intensity resulted in lower FSP and limited the increase in number of pores. In summary, TMW showed better performance than unmodified wood after weathering.</jats:p

Effect of natural weathering on water absorption and pore size distribution in thermally modified wood determined by nuclear magnetic resonance

Funder: Teollisuusneuvos Heikki Väänänen's FundFunder: International Thermowood AssociationFunder: Quantum Institute, University of OuluAbstractThermally modified wood (TMW) is widely used in outdoor applications due to its advanced properties towards weathering stresses. Although the structure changes of TMW from weather factors have been reported, investigation of the quantitative analysis of water states and cell wall structure of TMW after weathering is limited. In this work, the amount of bound water, fiber saturation point (FSP), cell wall pores, and free water distribution of thermally modified Scots pine, Norway spruce, and European ash were measured before and after a 2-year natural weathering via NMR relaxometry, cryoporometry, and magnetic resonance imaging. The results show that weathering increased T2 relaxation time of lumens, indicating the degradation of tracheids and vessels, especially in TMW compared to unmodified wood. The amounts of bound water, FSP value, and cell wall pores were increased after weathering; however, an increase in thermal modification intensity resulted in lower FSP and limited the increase in number of pores. In summary, TMW showed better performance than unmodified wood after weathering.</jats:p

Mechanical behaviour of phenolic coated Finnish birch plywood with simulated service damage

This paper investigates the mechanical behaviour of Finnish birch ($\textit{Betula pendula}$ and $\textit{Betula pubescens}$) plywood commonly used in road freight trailer decking. A series of tests have been performed to characterize the mechanical performance of the material and the effect of in-service damage that is likely to occur when the material is used in this application. Moisture damage, indentation damage, and abrasive wear are all recreated in the laboratory and the severity of each is assessed. In particular, the effect of indentation damage on flexural properties is compared against the effect of moisture damage. It is found that while indentation damage can often appear more severe during a visual inspection, it generally has a lesser effect on flexural stiffness and strength compared to moisture damage. While the effect of moisture damage on flexural properties is well documented, the effect of indentation damage is previously less well understood. Both indentation damage and moisture damage significantly increase variance in flexural stiffness, but not flexural strength. This work provides a practical insight into whether damaged road freight trailer decking can still withstand in-service loadings. It also provides a benchmark for the performance of novel deck systems such as composite sandwich panels and glass-fibre pultrusions.Centre for Sustainable Road Freight; Engineering and Physical Sciences Research Council [Grant ID: EP/K00915X/1