5 - Material and component considerations

Question 1

Compressive strength

Define the material property and give examples

Answer 1

The ability to withstand being crushed or shortened by pushing forces (compression). E.g. surface of a seat when sat on, multi-story car park

Question 2

Tensile strength

Define the material property and give examples

Answer 2

The ability to resist stretching or pulling forces (tension). E.g. suspension bridge cables & climbing ropes, screws

Question 3

Stiffness

Define the material property and give examples

Answer 3

The ability to resist forces that may bend a material. E.g. shelf between two supports, deck of a bridge

Question 4

Hardness

Answer 4

The ability to resist abrasive wear such as scratching, surface indentation or cutting. E.g. drill bits

Question 5

Durability

Answer 5

Ability to withstand wear, damage and weathering.
e.g. outdoor equipment

Question 6

Biodegradable

Answer 6

The ability of a material to break down naturally and decompose by the action of microorganisms. E.g. polylactic acid (PLA), wood

Question 7

Impact resistance / Toughness

Answer 7

Ability to absorb impact force/ shock loading without fracture
Eg. A mallet

Question 8

Plasticity

Answer 8

Ability to be permanently deformed (shaped) and retain the deformed shape

Question 9

Elasticity

Answer 9

Ability to be deformed then return to original shape once force removed.
E.g. Elasticated cuffs in clothing, rubber, nylon

Question 10

Malleability

Answer 10

Ability to withstand deformation by compression without cracking. Increases with temperature. E.g. hammering a metal under heat

Question 11

Ductility

Answer 11

Ability to be drawn out under tension, reducing cross-sectional area without cracking. E.g. stretching a material into a wire

Question 12

Corrosion/ degradation resistance

Answer 12

The ability of a material to withstand environmental attack and decay. E.g. lampost

Question 13

Density

Answer 13

The mass of a material in a standard volume of space
Density = Mass / Volume

Question 14

Strength-to-weight-ratio

Answer 14

Comparing the weight of the structure to the amount of the weight it can support without failing. E.g. titanium, alluminium have high strength-to-weight ratios.

Question 15

Flammability

Answer 15

How a materials burns once ignited and the degree of difficulty required to cause combustion.
e.g. cooking pots should not be flammable

Question 16

Thermal conductivity

Answer 16

• Thermal conductor: allows the transfer of heat energy through the material.
• Thermal insulator: prevents the transfer or heat through the material
• Note: cooking pans should be conductors, but the handles insulators.

Question 17

Electrical conductivity

Answer 17

Electrical conductor: allows the flow of electrical current through the material. Gives very little resistance to the flow of charge
Electrical insulator: does not allow the flow of electrical current through the material.