Design Technology: Materials, Properties, Treatments, and Finishes

Vocabulary flashcards covering timbers, manufactured boards, metals and alloys, material properties, defects, metal treatments, and finishes for Design Technology revision.

Hardwood

Timber derived from broad-leaved flowering trees (angiosperms), such as oak and beech; does not necessarily indicate the wood is physically hard.

Softwood

Timber derived from gymnosperm trees, typically needle-leaved conifers (such as pine); does not necessarily indicate the wood is physically soft.

Oak – Properties, Uses, and Disadvantages

Strong, hard, durable, wear-resistant, and has an attractive grain; used for high-end furniture and flooring; disadvantages include being heavy and relatively expensive.

Beech – Properties, Uses, and Disadvantages

Hard, tough, fine-grained, with high impact resistance, and suitable for steam bending; used for chairs and tool handles; disadvantages include being prone to moisture damage without protection.

Pine – Properties, Uses, and Disadvantages

Lightweight, inexpensive, and easy to machine; used for furniture and interior construction; disadvantages include being prone to denting and weakened by knots.

Timber Conversion

The commercial process of cutting a felled tree trunk (log) into usable planks, boards, or structural sections.

Through-and-Through Sawing

A conversion method where a log is cut into successive parallel boards; economical with minimal waste, but produces planks prone to cupping and warping.

Quarter Sawing

A conversion method where growth rings meet the board face at a steep angle ($60\text{--}90^{\circ}$); provides dimensional stability and resists cupping, but is costlier and produces more waste.

Timber Seasoning

The controlled removal of moisture from newly converted wood before use to achieve equilibrium with its intended environment.

Purpose of Seasoning Timber

To improve dimensional stability and reduce shrinkage, warping, splitting, and vulnerability to fungal decay in manufactured products.

Air Seasoning – Method and Characteristics

Boards are stacked outdoors under cover with spacers between them, allowing ambient air circulation to slowly evaporate moisture; low energy use and inexpensive, but slow and dependent on climate.

Kiln Seasoning – Method and Characteristics

Timber is dried in an enclosed chamber with controlled temperature, humidity, and airflow; fast, controlled, and achieves low moisture contents, but requires expensive equipment and high energy.

Knot (Timber Defect)

A hard, dark section of wood formed where an intersecting branch joined the trunk; can weaken structural strength, spoil appearance, and make machining difficult.

Warping

Unwanted distortion in timber (such as bowing, cupping, or twisting) resulting from uneven moisture loss, release of internal stresses, or environmental humidity changes.

Splitting (Timber Defect)

Cracks opening along the longitudinal grain, caused by severe stresses during rapid moisture loss or uneven drying.

Fungal Decay (Timber)

Biological breakdown of wood cell structure by fungi in damp, unventilated conditions ($\text{moisture content} > 20\%$), drastically reducing strength and durability.

Timber Preservatives

Chemical compounds applied via brushing, dipping, or pressure impregnation to safeguard wood against rot, fungal decay, and wood-boring insect attack.

Manufactured Board

An engineered timber sheet material produced by bonding wood veneers, particles, chips, or fibres with adhesive resin under heat and pressure.

Manufactured Boards – General Advantages

Supplied in large standardized sheets, structurally uniform with no natural grain direction or knots, cost-effective, often utilize timber by-products, and exhibit high dimensional stability.

Plywood – Manufacturing Method

Thin rotary-cut wood veneers are stacked with adhesive and bonded under heat and pressure, with adjacent layers arranged so their grain directions run at $90^{\circ}$ to each other.

Plywood – Advantages, Disadvantages, and Uses

Advantages: uniform strength in all directions and high resistance to warping. Disadvantages: exposed edges show layered ply lines; moisture resistance relies on specific adhesive grade. Uses: structural panels, sub-flooring, and furniture.

Plywood – Purpose of Alternating Grain (Cross-Lamination)

Eliminates natural weaknesses along the grain, distributing mechanical strength equally in multiple directions while preventing expansion, contraction, and warping.

Plywood – Water Resistance Limitations

Moisture resistance depends on the adhesive resin and timber grade; standard interior grades delaminate in water, and uncoated veneer edges absorb moisture.

Medium-Density Fibreboard (MDF) – Manufacturing Method

Wood logs and scraps are broken down into fine cellulose fibres, combined with synthetic resin glue, and compressed into flat boards under heat and pressure.

Medium-Density Fibreboard (MDF) – Advantages, Disadvantages, and Uses

Advantages: completely smooth surface, consistent density, machines cleanly, and ideal for painting. Disadvantages: heavy, ordinary grades swell upon water contact, and creates fine dust during cutting. Uses: flat-pack indoor furniture and architectural mouldings.

Chipboard – Manufacturing Method

Coarse wood flakes and particles (sawmill offcuts) are mixed with synthetic resin binder and pressed between heated platens into rigid panels.

Chipboard – Advantages, Disadvantages, and Uses

Advantages: highly economical and utilizes wood waste. Disadvantages: low structural strength, easily damages along edges, poor screw-holding, and swells dramatically when wet. Uses: kitchen worktop substrates and flat-pack furniture.

Hardboard – Manufacturing Method

Exploded wood fibres are compressed under intense heat and hydraulic pressure into thin, dense sheets.

Hardboard – Advantages, Disadvantages, and Uses

Advantages: cheap, smooth on one side, flexible, and lightweight. Disadvantages: low structural stiffness, weak in tension, and disintegrates in damp conditions. Uses: cabinet back panels and drawer bottoms.

Application of Veneer vs. Laminate on Manufactured Boards

Natural wood veneer provides the authentic aesthetic and grain of solid timber; decorative plastic laminate provides a durable, easy-to-clean, scratch- and water-resistant surface.

Timber Surface Preparation – Pre-Finishing Procedure

Sand exclusively parallel to the grain using progressively finer abrasive papers, thoroughly wipe away all dust, and ensure coats dry fully between applications.

Timber Finishes – Paint (Purpose, Benefits, and Limitations)

Provides an opaque, coloured protective barrier against UV radiation and moisture; conceals the underlying grain pattern and can flake or peel over time, needing maintenance.

Timber Finishes – Varnish (Purpose, Benefits, and Limitations)

Forms a hard, clear, transparent coating that enhances and reveals the natural wood grain while offering water and abrasion protection; exterior use requires a UV-rated exterior grade.

Timber Finishes – Oil (Purpose, Benefits, and Limitations)

Penetrates deep into the wood pores to highlight the grain and provide internal water repellency; simple to reapply, but offers low scratch resistance and requires frequent renewal.

Timber Finishes – Wax (Purpose, Benefits, and Limitations)

Buffed on to give a smooth, natural sheen that enriches timber colour; offers minimal barrier protection against liquids, heat, or heavy mechanical wear.

Forest Stewardship Council (FSC) Certification – Purpose

Guarantees that wood or paper products originate from forests harvested in an environmentally responsible, socially beneficial, and economically viable manner.

FSC Timber – Environmental Life-Cycle Considerations

Certification guarantees sustainable forestry only; timber still carries environmental footprints from harvesting machinery, chemical treatments, long-distance haulage, industrial milling, and disposal.

Ferrous Metal

Any metal or alloy that contains iron as its primary constituent (e.g., mild steel, cast iron); most are magnetic and susceptible to rusting.

Non-Ferrous Metal

Any pure metal or alloy that does not contain significant amounts of iron (e.g., aluminium, copper, zinc); non-magnetic and will not rust.

Ferrous Metals – Rusting and Magnetism Exceptions

Properties vary by alloy composition: austenitic stainless steels do not rust due to chromium content and are non-magnetic due to their crystal structure.

Alloy

A metallic substance composed of two or more chemical elements (at least one of which is a metal) combined to achieve enhanced physical or mechanical properties.

Metals – Purpose of Alloying

To tailor engineering properties by introducing different sized atoms that disrupt crystal lattice slip planes, enhancing hardness, tensile strength, corrosion resistance, or castability.

Mild Steel – Properties, Uses, and Disadvantages

Properties: tough, ductile, malleable, and easily welded. Disadvantages: high density and oxidizes (rusts) rapidly without a surface finish. Uses: structural beams, car chassis, and general fabrication.

High-Carbon Steel – Properties, Uses, and Disadvantages

Properties: can be heat-treated to achieve exceptional hardness and wear resistance. Disadvantages: brittle after quenching and difficult to form or weld. Uses: cutting chisels, drill bits, saw blades, and springs.

Stainless Steel – Properties, Uses, and Disadvantages

Properties: highly corrosion-resistant, durable, hygienic, and aesthetically clean. Disadvantages: expensive, work-hardens, and difficult to machine. Uses: surgical instruments, cutlery, sinks, and catering appliances.

Stainless Steel – Corrosion Resistance Mechanism

Contains chromium, which reacts with atmospheric oxygen to create a self-healing, microscopic chromium oxide passive barrier layer.

Aluminium – Properties, Uses, and Disadvantages

Properties: low density ($\approx 2.7\,g/cm^3$), corrosion-resistant via self-passivating oxide film, highly ductile, and thermally/electrically conductive. Disadvantages: lower stiffness and strength than steel, and difficult to weld. Uses: aircraft structures, bicycle frames, and beverage cans.

Copper – Properties, Uses, and Disadvantages

Properties: outstanding electrical and thermal conductivity, non-corrosive, highly ductile, and easily soldered. Disadvantages: expensive and dense. Uses: domestic electrical wiring, printed circuit traces, and plumbing pipework.

Brass – Composition, Properties, and Uses

Composition: alloy of copper and zinc. Properties: low friction, golden appearance, excellent machinability, and corrosion resistance. Uses: plumbing valves, musical instruments, door hinges, and electrical pins.

Bronze – Composition, Properties, and Uses

Composition: alloy of copper and tin. Properties: exceptional resistance to sliding friction wear, resistant to saltwater corrosion, and casts sharp detail. Uses: submerged marine propellers, architectural statuary, and sleeve bearings.

Tensile Strength

The maximum mechanical pulling or stretching stress a material can withstand before necking and fracture occur.

Compressive Strength

The maximum load or stress a material can support under crushing, squeezing, or compaction forces without failing or collapsing.

Toughness

The capacity of a material to absorb kinetic energy and undergo plastic deformation without fracturing or shattering when subjected to sudden shock or impact.

Hardness

The resistance of a material's surface to mechanical penetration, abrasion, scratching, or plastic indentation.

Hardness vs. Toughness

Hardness refers strictly to surface wear and scratch resistance, whereas toughness refers to whole-body impact shock absorption without catastrophic fracture.

Ductility

The property of a material allowing it to undergo permanent plastic tensile deformation without fracture, enabling it to be drawn into elongated fine wires.

Malleability

The property of a material allowing it to be permanently reshaped, hammered, forged, or rolled under compressive force without cracking.

Elasticity

The capacity of a material to return completely to its original dimensions once an applied deforming force is removed, provided its elastic limit has not been exceeded.

Plasticity

The ability of a material to retain a permanently deformed shape without fracture after mechanical stress beyond its yield point is removed.

Brittleness

The characteristic of a material to fracture, crack, or snap suddenly when subjected to stress, exhibiting negligible plastic deformation before breaking.

Stiffness

The mechanical resistance of a component to elastic deflection, bending, or stretching when an external load is applied (quantified by Young's modulus).

Stiffness vs. Strength

Stiffness measures resistance to temporary elastic deflection under load, whereas strength measures the magnitude of stress a material can endure before plastic deformation or rupture occurs.

Durability

The capacity of a material or product to resist wear, fatigue, chemical degradation, and environmental weathering over extended periods in service.

Corrosion Resistance

The ability of a material to resist degradation, oxidation, or dissolution caused by electrochemical reaction with atmospheric gases, moisture, or chemicals.

Thermal Conductivity

The rate at which thermal energy (heat) conducts through the unit thickness of a material per unit area per unit temperature gradient.

Electrical Conductivity

The intrinsic measure of a material's capability to allow the transport of free electric charges (electrons) when subjected to an electric field.

Density

The mass per unit volume of a substance ($\rho = \frac{m}{V}$), determining the relative weight of components with identical geometric dimensions.

Machinability

The relative ease with which a material can be cut, drilled, milled, or turned to achieve a specified surface finish while maintaining acceptable cutting-tool life.

Workability

The ease with which a material can undergo mechanical fabrication processes, including bending, rolling, forging, casting, and stamping.

Annealing – Purpose

A heat treatment used to recrystallize distorted grains, soften work-hardened metals, relieve internal residual stresses, and restore ductility for subsequent shaping.

Carbon Steel Annealing – Method

Heating the steel above its upper critical transformation temperature, soaking at that temperature to equalize internal heat, and allowing it to cool slowly inside the insulated furnace.

Hardening (Steel) – Purpose

A heat treatment performed on medium- and high-carbon steels to produce a fine crystalline structure, dramatically increasing hardness and abrasive wear resistance.

Hardening (Steel) – Method

Heating the steel to a cherry-red critical temperature (approximately $750\text{--}850^{\circ}\text{C}$) and quenching it immediately in water, brine, or oil.

Hardening (Steel) – Limitations and Disadvantages

Significantly increases brittleness, rendering the steel susceptible to catastrophic fracture under impact shock, and risks thermal warping or quenching cracks.

Tempering (Hardened Steel) – Method and Effects

Reheating previously quenched steel to a temperature below its critical point ($200\text{--}300^{\circ}\text{C}$), soaking, and cooling; relieves internal stress, reduces brittleness, and improves toughness with a slight reduction in hardness.

Hardening Followed by Tempering – Rationale for Cutting Tools

Quench-hardening provides an exceptionally hard cutting edge that retains sharpness; subsequent tempering removes extreme brittleness so the tool absorbs cutting impacts without snapping.

Case Hardening – Objective

A metallurgical treatment applied to low-carbon steels to produce a thin, wear-resistant high-carbon surface outer layer while retaining a ductile, shock-absorbing internal core.

Case Hardening – Carburising Method

Heating low-carbon steel in a carbonaceous compound at approximately $900^{\circ}\text{C}$ so carbon diffuses into the outer layer, followed by quenching to harden only the carburised skin.

Case Hardening – Application to Transmission Gears

The hard outer skin resists severe friction, scuffing, and wear on meshing gear teeth, while the shock-resistant ductile inner core withstands cyclic torsional shock loads without fracturing.

Galvanising

Applying a protective zinc coating to fabricated steel components, typically by immersing them into a bath of molten zinc ($\approx 450^{\circ}\text{C}$).

Galvanising – Sacrificial Cathodic Protection Mechanism

Because zinc is more electrochemically reactive than iron, it acts as a sacrificial anode and oxidizes preferentially, protecting exposed underlying steel even if the surface coating is scratched.

Galvanised Steel – Typical Applications

Exterior infrastructural components exposed to weather, including agricultural fencing, motorway crash barriers, outdoor lamp posts, and structural roof trusses.

Anodising – Process and Function

An electrolytic passivation process where aluminium acts as the anode in an acid bath, growing and thickening its protective aluminium oxide layer to enhance corrosion resistance, surface hardness, and dye absorption.

Anodised Aluminium – Typical Applications

Consumer electronic housings (smartphones, laptops), architectural curtain-wall frames, automotive trim, and sporting equipment.

Electroplating – Process

An electrodeposition process in which an electric current passes through an electrolyte solution to deposit dissolved metal ions (e.g., chromium, nickel, gold) onto a conductive cathode workpiece.

Electroplating – Objectives and Benefits

To enhance aesthetic appearance (bright decorative shine), impart corrosion resistance to base metals, lower electrical contact resistance, or improve surface wear resistance.

Powder Coating – Process

Electrostatically charged dry thermoset polymer powder is sprayed onto an electrically grounded metal product, then baked in an oven ($\approx 200^{\circ}\text{C}$) to melt, flow, and cross-link into a uniform skin.

Powder Coating – Advantages and Disadvantages

Advantages: highly uniform, tough, chip-resistant, produces zero volatile organic compounds, and comes in diverse finishes. Disadvantages: requires specialized spray booths and ovens; deep scratches expose base metal to creeping corrosion.

Material Selection – Key Criteria

Mechanical and physical properties, functional performance requirements, aesthetic appearance, raw material and manufacturing costs, availability, product weight, processability, and environmental sustainability.

Exam Technique – Material Selection Justification

Explicitly identify the specific property (e.g., high toughness), link it to the product component, and describe the functional benefit in operating conditions (e.g., absorbs impact shocks without fracturing).

Beech – Suitability for Chisel and Tool Handles

Possesses high mechanical toughness and impact resistance, enabling it to absorb repeated hammer blows and shock vibrations without splitting or shattering.

Aluminium – Suitability for Portable Products

Its exceptionally low density ($\approx 2.7\,g/cm^3$) minimizes the overall mass of the product, maximizing portability and ergonomics for hand-held use while maintaining structural rigidity.

Plywood – Suitability for an Easel Drawing Board

Cross-laminated grain orientation prevents dimensional movement, resisting warping, bowing, and splitting caused by humidity changes, ensuring a flat drawing surface.

Copper – Suitability for Electrical Wiring

High electrical conductivity minimizes resistive energy losses and heat generation, while exceptional ductility allows it to be drawn into flexible, fine gauge wires without cracking.

Stainless Steel – Suitability for Commercial Kitchen Equipment

Exceptional corrosion resistance protects against acidic foods and cleaning chemicals, while a hard, non-porous surface provides hygienic, scratch-resistant, and easily sanitized work areas.

Technique for Comparing Materials in Product Design

Evaluate both materials directly against identical functional product specifications, explain the trade-offs of their physical and mechanical properties, and conclude with a justified selection based on cost and performance.