Wood structure
Section of a pine trunk
The structure of a tree trunk with annual rings is basically the same for all trees, but not always as clear as visible here. The pith in the centre is surrounded by a zone of heartwood that is no longer physiologically active (and used to be the sapwood!). A more or less pronounced colouration is produced by the storage of substances. This zone is followed by the sapwood, which is responsible for transporting water into the tree crown. Between the sapwood and the bark is the growth zone, the cambium, which is not visible to the naked eye. Amazingly, wood consists almost entirely of carbon, oxygen and hydrogen. From this, the main components cellulose, hemicellulose and lignin are produced. Macro- and micronutrients make up only a few percent.
Cutting a tree trunk
Already in the sawmill, the tree trunk is prepared for an optimised and maximum wood yield.
Due to its ingenious structure, which is equally a production site, transport and stabilisation system, wood has technical advantages that make it superior to other building materials: low weight with high strength, comparably high elasticity, low thermal conductivity, durability and very good workability. The research work of the wood science departments of the University of Göttingen is aimed at improving the technical properties, increasing durability and combining with other materials, with the primary objectives of a long service life and high utilisation of the raw material wood.
Wood products (construction and furniture sector)
The different properties of different types of wood are taken into account in their use. Roof trusses are often made of coniferous wood because their high elasticity is appropriate there. Trusses, on the other hand, are often made of oak because its stability and durability are important properties.
Musical instruments are often made of wood because wood has very good sound properties.
Breaking wood down into smaller components and reassembling them is an important technique for using wood for other purposes.
For long structural beams, boards are glued together at the ends by finger-jointing to create any length.
Thin wood veneers are glued together to achieve greater dimensional stability. This plays a role especially where dimensional stability is important, such as in the building sector. In addition, larger dimensions of a product can be created (wide boards, long beams).
Wood products (insulation, energy)
There is no waste in the use of wood - neither in the growth of the tree nor in its use. Even small (chips) and tiny parts (wood fibres) are used in the production of chipboard or fibreboard in house and furniture construction. Modern laminate flooring is based on
high-density fibreboard, which can withstand high pressure loads. Medium-density fibreboards are used for furniture construction and low-density fibreboards are used as insulation or packaging material. In combination with other basic materials, new materials such as WPC (Wood Plastic Composite) can be produced.
Waste wood is also used as a source of energy: pressed products such as wood pellets or briquettes or waste wood in special incineration plants form an important part of our energy supply.
Another very important area is paper production, where wood is processed into corresponding paper or cardboard after various pulping processes. Furthermore, wood is used as a basic material or additive in the textile industry (viscose, modal), the chemical (ethylene glycol, turpentine) and pharmaceutical (xylan, lignin, cellulose) industries, but also in the food sector (vanillin).
Wood protection
Wood has an almost unlimited shelf life as long as it remains either constantly dry or constantly wet (bog oak). Fungi and insects are the most important wood-destroying organisms. The durability, i.e. the longevity of the wood, therefore depends on the attack possibilities of these organisms. Moisture, temperature and the presence of oxygen play the decisive role here.
Beetle and butterfly larvae can damage even hard woods such as oak. In seawater, infestation with the shipworm can cause considerable damage to wooden structures or wooden ships. Discolouration by blue stain fungi can often be seen, although there is no impairment of strength.
Wood preservation is usually indispensable for a long-lasting use of the wood. The constructive wood preservation is to be applied with priority, i.e. the wood should not get into an infestation disposition in the first place. For other cases, there are protective coatings or impregnations that help prevent pest infestation.
Wood Science Teaching Collection
Wood - valuable raw material of the past, present and future
Wood is a natural raw material that is formed exclusively by solar energy and natural raw materials.
Wood produces itself: wood only grows on wood. In addition, the individual trees in the forest form a unique ecosystem that significantly increases the quality of our planet with its diverse functions and is also indispensable for human existence today. Wood is certainly one of the oldest raw materials used by man. As a material for fire and for building shelters, it was indispensable. Without this raw material, the development of mankind would not have been possible. Because of its sustainable use, wood will continue to play a decisive role in the future. During tree growth, CO2 is bound and fixed in the wood for the duration of its use and thus removed from the atmosphere. Only during decomposition (in the forest) or combustion is this CO2 released again. With sustainable use, only the growth is used and the system thus remains CO2-neutral.
