Wood and engineered wood with improved properties for structures

To improve the quality of wood products, researchers in this project studied how the optimisation of materials in nature could be transferred to technological applications (bionics). To this end, they applied nanotechnology, polymer chemistry and scale-independent modelling. The main focus of the work was on the chemical modification of wood using in situ polymerisation as well as scale-up of the process. In addition to their experimental investigations, the researchers modelled the properties of modified materials to enable design of specific property profiles in future.

The advantages of wood as a building material are its light weight, excellent mechanical properties and the ease with which it can be processed. Yet wood also swells and shrinks, is often only moderately durable and catches fire easily.

The project aimed at increasing the reliability of wood as a building material. In this context, the researchers attempted to change the cell walls in a way that would reduce their capacity to absorb water. Wood thus treated was expected to swell and shrink less and to be more durable in the long term.
The researchers modelled the changes in the cell walls and the fibre surfaces at the nano- and microlevel to define decisive parameters for the property profiles and to optimise individual process steps.

The resulting in situ polymerisation in the wood structure gives rise to new possibilities for developing functional wood-based materials. For example, specifically modifying veneers to improve their property profiles is of practical interest, and will favour their use in the decorative industry for the interior design of automobiles, yachts, aircraft etc. The insights gained in this project could help make wood and wood-fibre-based materials more reliable and more widely used in the building sector. As a result, wood stands to gain added economic significance as a renewable resource.

In situ polymerisation makes wood more dimensionally stable. The modular approach also enables wood to be actuated through changes in temperature and targeted alteration of its hygroscopicity (binding of moisture). Modifications of veneers were scaled up using an experimental reactor. Investigations into the properties of the veneers were conducted. A hierarchical multiscale model was implemented and tested using generic modification approaches for spruce. The most significant changes in the mechanical properties were evident in a preliminary parametric study for shear components.

Improved wood materials for structures