Materials Technology: Wood, Metals, Structures and Construction

1. Wood

Wood is an abundant natural resource. Its main components are cellulose fibers bound together by lignin, water, resin, acids, salts and pigments. Wood is obtained from trees, and it is transformed into useful products such as sawn or crushed wood, panels and treated boards.

Wood Products and Uses

• Tables, beds and boards
• Battens, laths, sheets and moldings

Physical Properties of Wood

The color, texture and density of wood depend on the presence of salts, pigments and resins, as well as the color and orientation of its fibers.

Types of Wood Panels

MDF, chipboard, plywood, blockboard and veneer are the main wood-based panels.

Difference Between MDF and Chipboard

MDF is made from finely crushed wood fibers, while chipboard is made from wood chips and shavings. Chipboard is not as plastic or hard as MDF.

Tools for Wood Work

Pencil, graduated ruler, compass, scissors, glue and metal ruler are basic drawing tools. Main woodworking tools include the square, punch, marking gauge, saw, plane, chisel, mallet, drill, brace, and sandpaper.

2. Metals

Metals are materials that contain iron and other elements. Ferrous metals are those that contain iron, and their properties depend on the proportion of carbon and other elements added.

Properties of Metallic Materials

Metals conduct heat and electricity, have a characteristic shine, and are ductile and malleable. They can be shaped into sheets and wires without breaking.

Metallurgy and Siderurgy

• Metallurgy studies the properties, uses and processes of obtaining and processing metals.
• Siderurgy applies the same principles specifically to iron and steel.

Common Metals

• Tin plate: steel sheet coated with tin.
• Steel: an alloy of iron and carbon, sometimes with other additives.
• Brass: an alloy of copper and zinc, used for valves and pipes.
• Bronze: an alloy of copper, zinc, nickel and tin, very ductile and easy to work at room temperature.

Main Uses of Copper

Copper is used for roofs, gutters, plumbing and electric cables.

3. Structures

A structure is the set of parts that support, protect and give consistency to a body. A structure must be resistant, stable and maintain its shape.

Causes of Structural Failure

Excess load, fatigue, static stress, fatigue fractures, joint failures and natural disasters can cause structures to fail.

Center of Gravity and Equilibrium

The center of gravity is the imaginary point where the entire weight of a body is considered concentrated. A body is in stable equilibrium when its vertical line passes through the base of support.

Forces in Structures

Loads and forces acting on a structure produce internal stresses. Loads can be dead loads (self-weight) or live loads (occupants and objects), as well as inertial forces.

Types of Stress

• Traction: forces pull the piece apart.
• Compression: forces push the piece together.
• Bending: forces cause the piece to bend.
• Torsion: forces twist the piece.
• Shear: forces cut the piece.

Structural Elements

Pillars are vertical supports that carry the weight of the structure. Beams are horizontal pieces that carry loads and transfer them to the pillars. Arches resist compression. Tie rods are inextensible cables that resist traction. Braces and diagonals form triangles to reinforce the structure.

Triangulation

Triangulation is a technique in which bars form triangles, since a triangle is the only shape that remains rigid without deforming.

4. Building Construction

To build a building, the terrain is first verified, followed by foundation work, construction hoist installation, placement of structural elements, and finishing.

Types of Foundations

Depending on the terrain, shallow foundations are used on firm ground, while deep foundations, such as piles, are used on soft or weak soil.

Building Materials

• Adobe: clay and straw bricks.
• Lime: a white powder that hardens when mixed with water.
• Cement: a mixture of lime, clay and limestone.
• Mortar: a mixture of lime, cement and sand.
• Concrete: a mixture of water, cement and aggregates.
• Masonry: a set of stones or bricks arranged in a formed structure.
• Common stones: marble, granite, copper and slate.

5. Ceramics and Glass

Ceramics are obtained from clay mixed with other materials and then fired. Examples include tiles and bricks. Glass is made from sand mixed with other materials, and its properties include transparency and fragility.