Importance of wood, composition, properties, features and structure. Wood is what?

Man has been using wood since time immemorial. Fuel, building materials, furniture, musical instruments - products from it accompany us all life. 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, and also in what area the tree from which it was made was cut down . Studying sections of annual rings, you can learn about nature and the atmosphere of ancient times. Advantages and disadvantages, structure, wood as a building material, properties - all these questions deserve attention.

How everything works

The properties and characteristics of the material can not be understood without first having studied the structure and composition of the wood. The very concept depends on who uses it. For an ordinary person and a builder, this is only part of the tree under the bark, which can be used in everyday life or production. For the botanist, the structure of wood and wood is the whole complex, which includes all elements from the roots to the crown.

Crown in industry is used slightly, and branches are used as raw material for fibreboard and board. The main significance is the trunk. On the cross-section, the structure of the tree trunk opens. The uppermost layer is the core, it protects living cells from external influences. Between the bark and the body of the trunk there is a layer of living cells - cadmium. In the center, the core passes through the entire trunk. The loose fabrics of which it is made make it unsuitable for utilitarian purposes.

The core of the tree consists mainly of dead cells, resin deposits, coloring and tannins. The core surrounds the sapwood - the part of the tree that is responsible for holding the water to the leaves from the roots. Accordingly, it has a lot of moisture, it passes more water and is more prone to rot. Not all trees have a distinct core. In some of them there is no difference between the central and marginal part of the trunk. Such breeds are called sapwood.

Microscopic structure of wood

Using a microscope, you can go deeper into the structure. Wood consists of a whole of dead cells. Young plant cells consist of a membrane and an inner part - the cytoplasm and nucleus. The basis of a thin transparent membrane is cellulose or fiber. With the passage of time, plant cells undergo metamorphosis and, depending on the incorporated function, transform into their mass either into the bark (corking) or into wood (lignification).

In cells, lignin is constantly formed. He is the cause of lignification. Separate two types of tree cells - prochenchymal and parenchymal. The first species is the bulk of the wood, depending on the breed - from 85% to 99%. In turn, they are divided by their functions. Conductive 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 function as a pantry for the plant. They accumulate nutrients (fats, starches) and give them as needed in a difficult period.

Softwoods

Depending on the type of trees, their structure differs. Wood species are divided into coniferous and deciduous. The structure of conifers is much simpler. The main mass is formed by tracheid cells. The characteristics of coniferous species include the presence of cells that produce resin. In different species, they can be either chaotically scattered, or combined into a system of resin courses.

Hardwoods

Harder trees and their structure are more complex. Wood consists of vessels, fibers of the librium and parenchymal cells. Since deciduous trees shed foliage in autumn, in winter they need a large supply of food. Hence, more parenchymal cells responsible for the accumulation of nutrients than in conifers. This can be seen from a pronounced core.

Properties

A number of characteristic properties have wood. Features of the structure of the cause. Strength of wood is quite high, and among the building materials for this indicator, it occupies an intermediate position. And given the small specific weight, it is comparable in this regard with the metal. The weak point of wood is that it is an anisotropic material. The ability to resist to failure depends on the direction of the force relative to the location of the fibers. The best strengths are visible when exposed to the material along the fibers.

Hardness of wood is small, the reason for this - a specific structure. Wood is a porous, flexible material. The beams are able to recover their shape after a short load. But residual deformations, due to prolonged exposure, remain forever. A wooden beam can not recover its shape after a long operation.

The hardness of building materials is determined by what kind of load is required to force the steel ball into certain dimensions. For the hardest types of wood, it is only 1000 N. At the same time, low hardness is one of the main advantages of the material. The tree is easy to process, nails, screws, self-tapping screws are firmly held in it.

The moisture content of the wood is determined by the specific moisture content in the pores. In the newly felled tree it reaches 100%. Depending on the purpose, freshly chopped wood is dried to the required values of 40 to 15%.

Advantages

Wood has a small value of thermal conductivity. It can be successfully applied as a heat-insulating material. Simplicity in processing allows using a wide range of tools. It is impossible to imagine any orchestra without musical instruments made of wood. The charming sounds of a violin are the result of such a property of wood as the ability to resonate. Wood easily bends, there is a great choice for the manufacture of various bent designs. Also, wooden products have good sound-absorbing characteristics. A beautiful surface opens up space for imagination when designing rooms.

disadvantages

The ability of wooden products to perceive loads depends on the direction of application of force. This is due to the anisotropic structure of the 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 spending a lot of time selecting the right material for work.

As an organic material, wood is defenseless for insects, mold, fungi. For long-term operation, expensive chemical treatment is required. It is worth noting that wooden structures without pre-treatment - easy prey for fire.

Wood processing

In general, there are three types of wood processing:

• The most common is the mechanical method. The tree is sawed, cut, split.
• During the chemical-mechanical treatment, the material is subjected to intermediate preparation. Chips, chips are mixed with a binder and heated. A chemical polymerization reaction takes place, and materials such as plywood, particle boards, fibrolite are obtained at the outlet.
• In the chemical treatment, wood is exposed to acids, alkalis, salts, and subjected to heating. Among the products of such treatment can be called charcoal, rosin, gum, tannins, cellulose.

Trees are older than a man for hundreds of millions of years. All ever existing civilizations are based on the use of wood. Books, furniture, musical instruments - all this is possible due to this unique natural material.