Topic 4 - pt.2 test knowledge Flashcards

1
Q

physical properties

A
  • mass = amount of matter contained within a specific material
  • weight
  • hardness = resistance of a material to penetration or scratching (affected by strength and plasticity of mat.)
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2
Q

mechanical properties

A
  • tensile strength = ability of a material to withstand pulling forces (important for ropes, cables, etc)
  • compressive strength = capacity of a material or structure to withstand forces trying to reduce size
  • toughness = ability of a material to resist cracking (a material’s resistance to fracture when stressed)
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3
Q

aesthetic characteristics

A
  • taste
  • smell
  • appearance
  • texture
  • colour
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4
Q

composite

A

reinforcing (strands, particles, poles) + matrix (e.g. glue)
- an example is concrete: poles are placed (reinforcing) to shape the structure and concrete is poured in the middle (matrix)

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5
Q

timber general knowledge

A

Man-made: plywood, MDF, particle boards (all composites)
- limited recycling so not sustainable
- more even
- can be as big as you want

Natura: oak, pine, beech
- looks natural (grew like that & a certain size)
- more sustainable and recyclable
- can shrink due to temp & moisture
- splitting, cupping, warping, bowing

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6
Q

metals

A

Ferrous: iron, steel
- contains iron –> rusts & magnetic

Non-ferrous: copper, gold, silver, aluminum
- doesn’t contain iron so doesn’t rust
- not magnetic

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7
Q

plastic

A

Thermoplastics: PET, PP, PS
- once set it can be reset/changed bc there are no cross-links (chains can move freely when heated)
- physical structure / molecular structure
- can be recycled

Thermosets: polyester, epoxy resin, urea-formaldehyde
- once set it can’t be reset or changed
- chemical structure = strands that hold it together (cross-links)
- limited recycling

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8
Q

metal crystals

A
  • smaller crystals = harder but more brittle (grains packed closer) + cracks move easily across metal
  • larger crystals = softer, more malleable metal + cracks take longer to cross the metal
  • more dense = more brittle
  • grain boundaries are weak spots
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9
Q

heat treatments

A

Annealing: heating metal to high temps & then cooling slowly –> large crystals form
- malleable & softer
Quenching: heating metals to moderate temp and cooling them quickly
- small crystals form –> harder but more brittle
Tempering: reheating quenched metal but to a much lower temp –> reduces brittleness but keeps hardness
- gets the best of both annealing and quenching
- more impact resistant

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10
Q

alloys

A
  • mixture of metals
  • e.g. brass = copper + zinc
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11
Q

textiles

A

Natural: cotton, wool, silk
- fibre –> stands –> weaved into longer strands –> yarn –> big sheets of fabric
- very ductile

Synthetic: polyester, nylon, lycro
- plastic (oil based)
- not sustainable

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12
Q

toughened/tempered glass

A
  • heat treated to make it tougher
  • shatters into small pieces
  • used for car glass, furniture
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13
Q

seasoning of timber

A

Seasoning of timber:
- Air Seasoning (natural) –> no expensive equip. needed, small labour cost, env. friendly bc little energy used BUT takes longer than Kiln, large area needed
- Kiln Seasoning –> kills insects, requires little stacking space, dries quickly BUT expensive, requires supervision by skilled operator, uses lots of energy, gives weaker timber

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14
Q

why straws are hard

A

Straws need to resist deformation when force is applied, especially if someone bites or squeezes them slightly. A straw that is too soft can easily deform, blocking the flow of liquid or making it uncomfortable to use.

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15
Q

finishes - timber

A
  • aesthetics: to improve the natural beauty of material
  • function: to protect it from environmental impact, heat, moisture
  • finished timber needs to be sanded with abrasive paper
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