Materials

Question 1

Hardness

Answer 1

The ability of a material to resist wear

Question 2

Malleability

Answer 2

The ability of a material to be reshaped in all directions without cracking

Question 3

Toughness

Answer 3

Materials resistance to impact

Question 4

Ductility

Answer 4

The ability of a material to change its shape usually by stretching along its length.

Question 5

Calculating stress

Answer 5

Stress(N/m2) =

Applied load/cross-sectional area(CSA)

Question 6

Composites

Answer 6

Materials composed of two or more parts, they can have different physical or chemical properties. eg. (concrete, fibreglass)

Question 7

Smart materials

Answer 7

Materials that have one or more properties that can change by external stimuli, like stress, temperature, moisture, pH, electricity, magnetic energy.

Question 8

Calculating strain

Answer 8

% strain=

change in length/ original length x 100

Question 9

Young’s modulus and calculating

Answer 9

A number which indicates the stiffness of a material. Found by dividing the stress by the strain.

Question 10

2 hardwoods

Name, properties, uses

Answer 10

Oak- hard, tough, strong- furniture, boats, floors

Mahogany- strong, durable, resistance to water- panelling, furniture

Question 11

Softwoods

Answer 11

Scots pine- strong, durable, easy to work- inside work, outside if treated

Cedar- resistant to water and infestation, durable, knot free easy to work- cladding outside of buildings, sauna and steam rooms

Question 12

Manufactured board

Examples, properties, application

Answer 12

MDF (medium density fibreboard). No grain so doesn’t split easily. Used in kitchens, storage units, doors.

Plywood. Thin veneers of wood glued together in opposite directions. Strong and aesthetic. Wall panelling, flooring, furniture.

Question 13

Plastic

Examples, properties, application

Answer 13

PVC. Thermoplastic. Light, rigid, many colours. Doors, pipes, gutters, bottles, shoe soles.

Acrylic. Thermoplastic. Rigid, clear or opaque, easily scratched, easily joined, easily machined.

Phenol Formaldehyde. Thermosetting. Handles for cooking ware, electrical fittings, sockets.

Question 14

Non ferrous metals.

Example, properties, uses

Answer 14

Lead, zinc, brass, copper.
Brass- hard, good conductor, protects itself from corrosion.
Copper. Conductor, malleable, ductile, tough. Electrical wire, roofs, heating pipes

Question 15

Ferrous metal

Examples, properties, uses

Answer 15

Stainless steel. Strong, ductile, prevents corrosion. Cutlery, kitchen stuff

High carbon steel. Strong, hard, wear resistant. Cutting tools, cables.

High tensile steel. Tough and strong. engine parts, gears etc.

Question 16

Discuss use of composites in modern design: Concrete, Fiberglass

Answer 16

Concrete: Used in construction, brick laying, road building etc. Made up of cement, gravel, sand.
Reinforced concrete: Reinforced with Steel Rods to withstand tensile forces. Used in bridge and skyscraper building.

Fiberglass: Strands of glass woven to form a flexible fabric. Material is strong and light. Can be sanded and painted. Used in canoes, cars, surfboards.

Question 17

Smart material examples

Answer 17

Thermochromic materials respond to changes in temperature by changing colour.

Question 18

Vacuum forming

Answer 18

A mould is placed in the machine. The plastic is heated until malleable, soft and flexible. Raise the mould to meet the plastic sheet. Activate the vacuum. The plastic is pulled over the mould. It takes the shape of the mould.

PVC, Acrylic and polystyrene are typically used.
Note: Holes should be drilled in the mold to allow it to come down fully.

Question 19

Compression molding

Answer 19

Plastic placed between two parts of a mould. Pressure and heat are applied till plastic take the shape of the mould.
Used with thermosetting plastics.
Used to make electrical fittings, handles.

Question 20

Blow moulding plastics

Answer 20

Uses air to blow plastic into a solid mould.
PVC, polythene used.
Makes plastic bottles

Question 21

Injection moulding

Answer 21

Plastics are injected into the mould. Material is fed into a heated barrel, mixed and forced into a mould cavity where it cools and hardens in the cavity shape.
Both thermosetting and thermo plastics used.
Makes car body parts, bottle caps, toys etc.