Complete MMME1029 Lecture 2

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2. What are the main classifications of materials?
> Metals, glass and ceramics, plastics, elastomers,
> Metals, glass and ceramics, ~~plastics, elastomers,~~ polymers, composites, and semiconductors
3. [There are] Few Iron Age artefacts left. Why?
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2. What material properties were mentioned in the second slide set?
> Young's modulus, specific heat, coefficient of thermal expansion
# Lecture 2
## Metals
- Ductile (yields before fracture)
- High UFS (Ultimate Fracture Stress) in tension and compression
- Hard
- Tough
- High melting point
- High electric and thermal conductivity
## Ceramics and Glasses
- Brittle --- elastic to failure, no yield
- Hard (harder than metals)
- Low UFS under tension
- High UFS under compression
- Not tough
- High melting points
- Do not burn as oxide ceramics are already oxides
- Chemically resistant
- Poor thermal and electric conductivity
- Wide range of magnetic and dielectric behaviours
## Polymers
- Organic---as in organic chemistry (i.e. carbon based)
- Ductile
- Low UFS in tension and compression
- Not hard
- Reasonably tough
- Low threshold temperature to charring and combustion in air or pure oxygen
- Low electrical and thermal conductivity
- There are some electrically conductive polymers
## Composites
- Composed of 2 or more materials on any scale from atomic to mm scale to produce properties that
cannot be obtained in a single material
- Larger scale mixes of materials may be called 'multimaterial'
- Material propertes depends on what its made of
## Organic vs Inorganic Materials
- Organic materials are carbon based
- From chemistry, organic compounds are ones with a C-H bond
- Inorganic compounds do not contain the C-H bond
## Crystalline vs Non-Crystalline Materials
- Most things are crystalline
- Ice
- Sugar
- Salt
- Metals
- Ceramics
- Glasses are non-crystalline
## Material Density
$$\rho = \frac m v$$
- Density if quoted at STP (standard temperature and pressure---$298$ K and $1.013\times 10^5$ Pa)
- Metals, ceramics, and glasses are high density materials
- Polymers are low density
- Composites span a wide range of density as it depends on the materials it is composed of
e.g. composites with a metal matrix will have a much higher density than those with a polymer
matrix
## Material Melting Points
- Measured at standard pressure and in an intert atmosphere (e.g. with Nitrogen, Argon, etc)
- Diamond and graphite will survive up to 4000 \textdegree{}C in an inert atmosphere but would
burn at around 1000 \textdegree{}C in oxygen
- High melting points -> high chemical bond strength
## Material Corrosion
- It's not just metals that corrode
- Polymers
- UV degradation
- Water absorption can occur in degraded polymers
- Glass
- Leaching
- Sodium ions can leave the glass when covered in water. If the water stays, the high pH water
can damage the class
## Self Quiz
### Consolidation Questions 1
1.
i. Metal
ii. Titanium
2.
i. Polymer
ii. Polyester
3.
i. Ceramic
ii. Alumino-silicate
4.
i. Composite
ii. GFRP or CFRP
5.
i. Metal
ii. Aluiminium alloy
6.
i. Metal
ii. Aluiminium alloy
7.
i. Polymer
ii. Acrylic
8.
i. Ceramimc
ii. Glass
9.
i. Composite
ii. Concrete
### Consolidation Questions 2
> ~~C~~ B