Civil Engineering

Understanding wood

Wood has been used for thousands of years for fuel, as a construction material, and for making tools and weapons, furniture, and paper. It has recently become a feedstock used to make cellophane and other cellulose derivatives, such as cellulose acetate. Today those in the field of woodworking and civil engineering know the essential value of wood. This is why the word wood is a must-discuss term.

understanding wood

In this article, the following about wood will be discussed as the below questions are answered:

  • What is wood?
  • what are the uses of wood?
  • What are the properties of wood?
  • What are the various types of wood?
  • How is wood produced?

Let’s dive in!

Read more: Different types of wood joints and their working

What is wood?

Wood is an organic substance derived from the live tree and has a fibrous, heterogeneous, and anisotropic texture. One of the ancient building materials is wood. Since prehistoric times, wood has been used by humans as a kind of protection and shelter. Owing to the decline of forests due to numerous factors, the difficulty to replace the trees that have been cut down with new trees, or the late development of trees, the value of wood has grown today. In addition to being utilized as a load-bearing or aesthetic material in models and scaffolds, wood is also employed as roof fittings, woodwork, and coating material. In addition, man-made building materials made from by-products of the wood industry, such as woodchips, sawdust, and dust, include chipboard, MDF, and plywood. Lumber is a timber that has been treated and cut into uniform dimensions.

In the stems and roots of trees and other woody plants, wood is a porous and fibrous structural substance. It is an organic substance made of cellulose fibers, which are strong under tension, contained in a lignin matrix, which is resistant to compression. Wood serves a support role in a living tree, allowing woody plants to grow large or to stand up on their own. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere, such as in the roots of trees or shrubs. Additionally, it transfers nutrients and water between the roots, other developing tissues, and leaves.

What are the uses of wood?

The following are common uses of wood:

  • Fuel
  • Pulpwood
  • Construction
  • Engineered products
  • Furniture and utensils
  • Art
  • Sports and recreational equipment
  • Others

 

Fuel

Today, mostly in rural areas of the world, wood is still utilized as fuel, as it has been for a very long time. Because it produces less smoke and burns more slowly than softwood, hardwood is recommended. It’s common to think that a wood stove or fireplace will provide warmth and ambiance to a house.

Read more: Understanding wood finishing

Pulpwood

The term “pulpwood” refers to wood grown exclusively for papermaking.

Construction

Since people first started making huts, houses, and boats, wood has played a significant role in construction. Up until the late 19th century, almost all boats were made of wood, and wood is still frequently used to make boats today. Elm was specifically chosen for this application because, as long as it was kept moist, it resisted rot (it also served as a water pipe before the advent of more modern plumbing).

Lumber is the popular name for wood used for construction in North America. Timber is the term for sawn, usable boards, whereas lumber is typically used to indicate to trees that have been felled elsewhere. Oak was the material of choice for all wood buildings in medieval Europe, including beams, walls, doors, and floors. A larger variety of woods are now employed, and poplar, small-knotted pine, and Douglas fir are frequently used to make solid wood doors.

Engineered products

Construction and industrial applications frequently use engineered wood products, which are bonded building components “designed” for performance criteria particular to the application. To create a stronger, more effective composite structural unit, wood strands, veneers, timber, or other types of wood fiber are glued together to generate glued engineered wood products.

These goods include parallel strand lumber, I-joists, laminated veneer lumber (LVL), and other structural composite lumber (SCL) items. Wood structural panels made of plywood, oriented strand board, and composite panels are also among them. In 1991, around 100 million cubic meters of wood were used for this. Particle boards and fiberboard are predicted to supersede plywood, according to trends.

Furniture and utensils

For chairs and beds, among other furniture items, wood has long been a popular material. Additionally, it is utilized for the handles of utensils like the wooden spoon and pencil as well as tools and cutlery like chopsticks and toothpicks.

Art

For many years, wood has been a popular artistic medium. For millennia, it has been used to carve and create sculptures. Examples include the totem poles made from conifer logs, frequently Western Red Cedar, by indigenous tribes of North America. Other uses of wood in the arts include:

 

Sports and recreational equipment

Numerous sporting equipment categories are currently made of wood or once were. For instance, white willow is the usual material used to make cricket bats. The baseball bats that are allowed to be used in Major League Baseball are typically fashioned of ash wood, hickory, and more recently, maple, even though that wood is a little more delicate. Courts for the National Basketball Association have often been composed of parquetry.

Others

New uses for lignin glue, recyclable food packaging, rubber tire replacements, anti-bacterial medical treatments, and high-strength textiles or composites are some other advancements. New, more sophisticated goods will enter the market as scientists and engineers continue to study and create new procedures to extract different components from wood or to modify wood, such as by adding components to wood. Electronic moisture content monitoring can help improve the protection of next-generation wood.

Read more: Different types of wood finishes and finishing products

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What are the properties of wood?

  • Sensory characteristics
  • Density and specific gravity
  • Mechanical properties
  • Thermal properties
  • Electric properties
  • Acoustic properties
  • Degradation
  • Hygroscopicity
  • Shrinkage and swelling
  • Sensory characteristics

Color, luster, smell, flavor, texture, grain, figure, weight, and hardness of wood are examples of sensory properties. For purposes of identification or other uses, these additional macroscopic features are useful in describing a piece of wood. There are woods in a wide range of colors, although the majority of woods are tones of white and brown. Other colors include yellow, green, red, and practically pure white. Depending on the color differences between the heartwood, sapwood, earlywood, latewood, rays, and resin canals, variations may be visible on a single piece of wood. Bleaching or dyeing, as well as prolonged exposure to the environment, can alter the natural color. Black locusts, honey locusts, and a few tropical species are only a few examples of brilliant woods.

Density and specific gravity

Specific gravity is the ratio of the weight or mass of wood to that of water, while density is the weight or mass of a unit volume of wood. Because 1 cc of water weighs 1 gram, the average density and specific gravity of Douglas fir wood are both 0.45 gram per cubic centimeter (g/cc), respectively, in the metric system of measurement. (One gram per cubic centimeter, or roughly 62.4 pounds per cubic foot, is expressed as weight per unit volume.) Since wood is hygroscopic, the amount of moisture considerably affects both its weight and volume, making determining its density more challenging than for other materials. Weight and volume are calculated at predetermined moisture values to produce similar results.

Hygroscopicity

If in touch with water, wood can absorb it as a liquid or as a vapor from the air. Water is the most significant liquid or gas that wood can absorb, despite this. Wood always includes moisture due to its hygroscopic nature, whether it is a component of the living tree or a material. (The terms water and moisture are used interchangeably here.) Moisture has an impact on all aspects of wood, although it should be highlighted that only moisture found in cell walls is significant; moisture found in cell cavities does little more than add weight.

Read more: Understanding woodworking joints

Shrinkage and swelling

When the moisture level in wood varies below the fiber saturation point, dimensional changes occur. Shrinkage and swelling are caused by moisture gain and loss, respectively. These dimensional changes are anisotropic, meaning they differ in the axial, radial, and tangential directions. Roughly 0.4 percent, 4 percent, and 8 percent, respectively, are the average shrinkage values. Volume loss is around 12%, but there are significant differences between species. These numbers are provided as a percentage of green dimensions and correspond to transformations from the green to oven-dry condition. The cell wall structure is primarily responsible for differential shrinking and swelling in various development orientations.

The orientation of the microfibrils in the layers of the secondary cell wall can be used to explain the variations between axial and the two lateral (radial and tangential) directions, however, it is unclear why these discrepancies exist in radial and tangential directions.

Degradation

Bacteria, fungi, insects, marine borers, as well as environmental, mechanical, chemical, and thermal variables, all contribute to the destruction of wood. The look, structure, or chemical makeup of wood can change due to degradation, which can impact living trees, logs, or products. These changes can range from minor discoloration to irreversible transformations that render wood utterly worthless. As evidenced, for instance, by furniture and other wooden artifacts discovered in perfect condition in the tombs of ancient Egyptian pharaohs, wood can last for hundreds or thousands of years (see Egyptian art). Only under the influence of outside elements does wood deteriorate or get destroyed.

Mechanical properties

The mechanical, or strength, properties of wood are signs of its capacity to withstand external forces that could potentially tend to alter its size and shape. The amount and method of application of these forces, as well as the density and moisture content of the wood, affect the resistance to those forces. In the axial direction, or parallel to the grain, wood’s strength characteristics are noticeably different from those across the grain (in the transverse direction).

The strength of wood in tension and compression (measured in axial and transverse directions), shear, cleavage, hardness, static bending, and shock are some of its mechanical characteristics (impact bending and toughness). Respective tests determine stresses per unit of loaded area (at the elastic limit and maximum load) as well as other strength criteria, including toughness, rupture modulus, and modulus of elasticity (a measure of stiffness). Small, transparent specimens having a cross-section of 2 x 2 cm or 2 x 2 inches are typically used for testing.

Thermal properties

Even though wood expands and contracts with variations in temperature, shrinkage, and swelling brought on by changes in moisture content are much more significant dimensional alterations. Such temperature-related expansion and contraction are typically insignificant and of no practical consequence. Surface checks can only occur at temperatures below 0 °C (32 °F); frost cracks can occur in living trees due to uneven contraction of the outer and inner layers.

Compared to materials like metals, marble, glass, and concrete, wood has a low thermal conductivity (high heat-insulating ability). Light and dry woods are superior insulators because thermal conductivity is highest in the axial direction and increases with density and moisture content.

Read more: Different types of wood finishes and finishing products

Electric properties

Electrical insulation can be found in oven-dried wood. However, when moisture content rises, electric conductivity rises as well, causing saturated wood (wood with the highest moisture content) to behave more like water. It is noteworthy how dramatically electric resistance falls as moisture content rises from 0 to the point at which fibers are saturated. Electric resistance drops by more than a billion times in this range, but only by around 50 times from the fiber saturation point to the highest moisture content. The electric resistance of wood is mostly unaffected by other parameters, such as species and density; variations across species are related to the chemistry of the extractives. The axial resistance is roughly half of the transverse resistance.

The dielectric or poor conductor, properties of wood are also important. Dielectric constant and power factor play a practical role in making electric meters (capacity and radio-frequency power-loss type) for measuring wood’s moisture content, drying wood with electric current (a theoretical possibility, though not currently a reality), and gluing wood with high-frequency electric current. The electric polarization (the appearance of opposite electric charges on opposite sides of a piece) that occurs when mechanical stress is applied causes wood to show the piezoelectric effect. Contrarily, wood experiences mechanical deformation when exposed to an electric field (changes in size).

Acoustic properties

Wood can both create sound (by direct striking) and magnify or deflect sound waves coming from other objects. It is a special material for musical instruments and other acoustic applications because of these factors. The size, density, moisture content, and elastic modulus of the wood all have an impact on the frequency of vibration, which in turn affects the pitch of the sound generated. Higher density and elasticity reduced moisture content, and smaller dimensions all contribute to higher-pitched sounds.

What are the various types of wood?

All types of wood are categorized into the following:

  • Hard
  • Soft
  • Engineered wood

 

Hard

Any tree that doesn’t produce needles or cones is a source of hardwood. These trees are most frequently referred to as deciduous trees or angiosperms in scientific jargon. Trees that produce leaves and seeds are known as hardwoods. Oak, maple, cherry, mahogany, and walnut are examples of common hardwood species. Although several species of hardwood are well renowned for their stunning and distinctive wood grain patterns, hardwood species are not always stronger than softwoods.

Additionally, several timbers are classified as hardwoods but come from non-deciduous trees, such as bamboo and palm. Although technically referred to as monocotyledons, these plants are frequently categorized as hardwoods since they have many of the same traits. Bamboo and palm trees can occasionally be included in the following category of manufactured wood.

Read more: Working of drilling machine on wood & metal

Soft

Conifer trees are used to produce softwoods, such as lumber and wood products. Conifer trees, also known as Gymnosperms, are any trees that have needles and bear cones. Pine, Cedar, Fir, Spruce, and Redwood are a few examples of common softwood trees used in furniture making, carpentry, and other related fields.

Engineered wood

Engineered woods are the third type of wood you might come across. Engineered wood is created rather than occurring naturally in the environment. These boards are typically created from wood that has been modified to have particular characteristics or properties. These goods, also referred to as composite wood, are frequently created using sawmill refuse.

Engineered wood is frequently heated or chemically treated to generate a wood product that can fulfill specific sizes that are challenging to obtain in nature. Plywood, Oriented Strand Board, Medium Density Fiber Board, and Composite Board are a few common examples of engineered woods. Given that it frequently has to be worked with, either by using specialist cutting techniques or putting pieces together to produce a precise size or wood grain patterning, wood veneers can occasionally be categorized as engineered wood.

How is wood produced?

Wood is a component of the system used by plants to store food produced during photosynthesis, transport water and dissolved minerals from the roots to the rest of the plant, and provide mechanical support. Only 3,000 to 4,000 kinds of plants, including herbaceous ones, are thought to generate wood that is appropriate for use as a material, out of the estimated 25,000 to 30,000 species of plants that produce it. Gymnosperms and angiosperms are the two groups that include wood-producing forest trees and other woody plants. Angiosperms, or trees bearing cones, generate temperate and tropical hardwoods like oak, beech, teak, and balsa, whereas gymnosperms, or cone-bearing trees, produce softwoods like pine and spruce. It should be noted that not all situations fall under the distinction between hardwood and softwood. Some hardwoods—e.g., balsa—are softer than some softwoods—e.g., yew.

Wood is a substance with significant economic value. In contrast to coal, ores, and petroleum, which are gradually depleted, it is a renewable resource that can be sustainably maintained. Wood fosters economic growth, creates jobs, and ensures basic subsistence in some nations through its harvesting in forests, transportation, processing in factories, commerce, and consumption. The continuous strong demand for wood and wood products is a sign of its significance.

In terms of weight, wood is consumed much more than other materials. The majority of the world’s Roundwood (log) production is used as fuel, mostly in developing nations. The fastest growth in the production of wood products has been seen in paper and paperboard, and this pattern is anticipated to continue as consumption per person in developing countries catches up to that of industrialized ones. Growing wood use and the ensuing deforestation are caused by a rising global population. The production of an adequate wood supply to meet the predicted need is dubious due to the destruction of many forests, particularly in the tropics. Stopping the loss of forest cover on Earth, boosting the productivity of already-existing forests, establishing extensive reforestation projects and planting nurseries of quickly-growing tree species, recycling paper, and improving wood utilization through research could help solve the wood supply issue and reduce the environmental impact of the lumber industry.

Read more: Types of woodworking hand and portable tools

FAQs

Wood is an organic material with a fibrous, heterogeneous, and anisotropic texture produced from the tree, which is a living organism. Wood is one of the oldest building materials. Humankind uses wood for sheltering and protection purposes since ancient times.

Wood is composed of Cellulose: Cellulose is a polymer (C6H10O5) that can crystallize to form very strong fibers. Cellulose is the primary strengthening material in wood. Lignin: Lignin is also a polymer but is typically in an amorphous form.

Construction of homes and other structures: Wooden houses are still frequently utilized in domestic settings. Additionally, the inside roofing of certain buildings is built of wood. Similar to how the bamboo wood is sometimes used in building construction to support a building until it is sturdy enough to stand on its own.

The main physical properties of wood include color, luster, texture, macro-structure, odor, moisture, shrinkage, internal stresses, swelling, cracking, warping, density, sound – electro – thermal conductivity. Сolor, shine, texture, and macrostructure determine the appearance of wood.

Wood formation is a complex biological process, involving five major developmental steps, including (1) cell division from a secondary meristem called the vascular cambium, (2) cell expansion (cell elongation and radial enlargement), (3) secondary cell wall deposition, (4) programmed cell death, and (5) heartwood

Natural wood means trees, including logs, boles, or slabs, trunks, branches, limbs, and stumps lumber including timber, logs, or slabs, especially when dressed for use.

When was wood first used?

The earliest evidence for woodworking comes from a 1.5-million-year-old Homo erectus site called Peninj in Tanzania.

Examples include ash, beech, birch, mahogany, maple, oak, teak, and walnut. Softwoods typically come from evergreen (coniferous) trees (those that have needles and cones and retain them year-round, also called gymnosperms. Examples include cedar, cypress, fir, pine, spruce, and redwood.

The mechanical properties of wood include strength in tension and compression (as measured in axial and transverse directions), shear, cleavage, hardness, static bending, and shock (impact bending and toughness).

Generally acknowledged as the hardest wood, lignum vitae (Guaiacum sanctum and Guaiacum officinale) measures in at 4,500 pounds-force (lbf) on the Janka scale.

Conclusion

Wood is an organic substance derived from the live tree and has a fibrous, heterogeneous, and anisotropic texture. One of the ancient building materials is wood. Since prehistoric times, wood has been used by humans as a kind of protection and shelter. Wood is used for fuel, pulpwood, construction, engineered products, furniture, utensils, etc.

That is all for this article, where the following questions are being discussed:

  • What is wood?
  • what are the uses of wood?
  • What are the properties of wood?
  • What are the various types of wood?
  • How is wood produced?

I hope you learned a lot from the reading, if so kindly share with others, thanks for reading, and see you around!