Man has been using wood since time immemorial. Fuel, building materials, furniture, musical instruments - products from it accompany us all our lives. In addition, trees are natural calendars and living historical monuments.
There is a whole branch of science - dendrochronology, which allows you to find out the age of the product, as well as in which area the tree from which it was made was cut down. By studying sections of annual rings, you can learn about the nature and atmosphere of ancient times. Advantages and disadvantages, structure, wood as a building material, properties - all these issues deserve attention.
How it works
The properties and characteristics of the material cannot be understood without first studying the structure and composition of wood. The concept itself depends on who uses it. For the average person and builder, this is exclusively a part of the tree under the bark, which can be used in everyday life or in production. For a botanist, the structure of wood and wood is the whole complex, which includes all the elements from the roots to the crown.
Crohn is used in industry slightly, and the branches are used as raw materials for fiberboards and cardboard. The main value is the trunk. The cross-section of the gaze reveals the structure of the wood trunk. The uppermost layer, the cortex, protects living cells from external influences. Between the cortex and the body of the trunk is a layer of living cells - cadmium. In the very center, a core passes through the entire trunk. The loose fabrics of which it consists make it unsuitable for utilitarian needs.
The core of the tree consists mainly of dead cells, resin deposits, dyes and tannins. The core is surrounded by sapwood - the part of the tree that is responsible for conducting water to the leaves from the roots. Accordingly, it has a lot of moisture, it passes water more and is more prone to decay. Not all trees have a pronounced core. In some of them there is no difference between the central and marginal parts of the trunk. Such rocks are called sapwood.
The microscopic structure of wood
Using a microscope, you can study the structure more deeply. Wood is composed entirely of dead cells. Young plant cells are made up of the membrane and the inside — the cytoplasm and nucleus. The basis of a thin transparent membrane is cellulose or fiber. Over time, plant cells undergo metamorphosis and, depending on their function, turn in their mass either into bark (punching) or into wood (lumbering).
Lignin is constantly formed in the cells. It serves as the cause of lumbering. There are two types of wood cells - prosenchymal and parenchymal. The first species is the bulk of the wood, depending on the species - from 85% to 99%. In turn, they are divided by their functions. Conducting cells are responsible for the delivery of nutrients and moisture from the roots to the foliage, mechanical - for the strength and stability of the tree. Parenchymal cells act as a storeroom for a plant. They accumulate nutrients (fats, starches) and give them away as needed in a difficult period.
Conifers
Depending on the type of trees, their structure also varies. Wood species are divided into coniferous and deciduous. The structure of conifers is more simple. The bulk are tracheid cells. The features of conifers include the presence of cells that produce resin. In different species, they can be either randomly scattered or combined into a system of resin passages.
Hardwood
Hardwood trees and their structure are more complex. Wood consists of vessels, librimiform fibers, and parenchymal cells. Since deciduous trees dump foliage in the fall, in winter they need a large supply of food. Hence the greater number of parenchymal cells responsible for the accumulation of nutrients than in conifers. This can be seen in the pronounced core.
The properties
Wood has a number of characteristic properties. Structural features are the reason. The strength of wood is quite high, and among building materials by this indicator it occupies an intermediate position. And given the small specific gravity, it is comparable in this regard with metal. The weak point of wood is that it is an anisotropic material. The ability of resistance to destruction depends on the direction of the force relative to the location of the fibers. The best strength indicators are visible when exposed to the material along the fibers.
Hardness of wood is small, the reason for this is a specific structure. Wood is a porous, flexible material. Beams are able to restore their shape after a short load. But residual deformations, due to prolonged exposure, remain forever. A wooden beam will not be able to restore its shape after a long operation.
The hardness of building materials is determined by what kind of load is needed to press a steel ball with certain dimensions. For the most hard wood species, it is only 1000 N. At the same time, low hardness is one of the main advantages of the material. The tree is easily processed, nails, screws, self-tapping screws are firmly held in it.
The moisture content of wood is determined by the specific moisture content in the pores. In a tree that has just been cut, it reaches 100%. Depending on the purpose, the freshly cut wood is dried to the required levels from 40 to 15%.
Advantages
Wood has a low thermal conductivity. It can be successfully used as a heat insulating material. Easy handling allows you to use a wide range of tools. It is impossible to imagine any orchestra without musical instruments made of wood. The fascinating sounds of the violin are the result of such a property of wood as the ability to resonance. The wood bends easily, a large selection for the manufacture of various bent structures opens up. Also, wooden products are distinguished by good sound-absorbing characteristics. A beautiful surface opens up space for imagination in the design of rooms.
disadvantages
The ability of wood products to absorb loads depends on the direction of application of force. This is due to the anisotropic structure of wood. In addition, the strength characteristics also depend on the proximity to the center of the trunk, humidity, the presence of knots, cracks. This makes it necessary to spend a lot of time on selecting suitable material for work.
Being an organic material, wood is defenseless for insects, mold, fungi. For long-term operation requires expensive chemical treatment. It is worth noting that wooden structures without pre-treatment are easy prey for fire.
