14 Questions
What are the tracheids held together by in timber?
Lignin
What is a downside of using timber as a resource?
It can damage fragile ecosystems when removed
What is the typical ratio of aggregate to sand to cement in concrete?
4:2:1
What is the purpose of the cement in concrete?
To act as a binder
What is a characteristic of fibre-reinforced polymers?
They have improved rigidity and impact resistance
What is an example of a fibre-reinforced polymer?
Glass fibre in polyester resin
Why is concrete a stronger material than cement alone?
Because the aggregate and sand add strength
What is a natural composite mentioned in the passage?
Timber
What is the primary reason for selecting materials with biocompatibility in bio-engineered products?
To prevent adverse reactions with the body
What property of stainless steel makes it a suitable material for bio-engineered products?
formation of a thin oxide layer
What is the primary advantage of titanium in bio-engineered products?
Excellent corrosion resistance
Why are conventional steels not suitable for bio-engineered products?
They are prone to corrosion and weaken over time
What is the primary application of titanium in bio-engineered products?
All of the above
Why are materials like stainless steel and titanium preferred in bio-engineered products?
They resist corrosion and are biocompatible
Study Notes
Timber
- Composed of cellulose fibre, tracheids, and lignin, a natural resin
- Excellent specific strength, but prone to weather damage and pest attacks
- Renewable resource, but many hardwoods are difficult to replace once felled
- Removal can harm fragile ecosystems
Concrete
- Composite of cement, sand, and aggregate
- Sand fills gaps between aggregate particles, cement acts as binder
- Portland cement is a man-made ceramic that reacts with water and sets to a hard, brittle solid
- Stronger and more efficient than cement alone for large structures and paths
- Typical composition: 4 parts aggregate, 2 parts sand, 1 part cement
Fibre Reinforced Polymers
- Polymers with added fibre for improved rigidity and impact resistance
- Examples: glass and carbon fibre in polyester or epoxy resins
- Widely used, with extensive applications in aeronautical fields
Bio-Engineered Materials
- Stainless steels, aluminium alloys, and tungsten alloys are commonly used in bio-engineered products.
- Polymers and ceramics are also important, especially for internal use.
Importance of Biocompatibility
- Biocompatibility is crucial when designing devices that are implanted or in contact with the skin.
- Materials must not react with the body and must remain inert to ensure product integrity and health.
Stainless Steels
- Advantages: creates a stable, thin oxide layer that resists corrosion when exposed to atmosphere or body fluids.
- Conventional steels are prone to corrosion, weakening the material and causing infection or rejection by the body.
Titanium
- Derived from minerals rutile and ilmenite (oxide layers).
- Properties: lightweight, excellent corrosion resistance, high strength-to-weight ratio, and good high-temperature properties.
- Corrosion resistance is provided by an adherent TiO2 film stable until 535°C.
- Uses: hip joints, bone screws, knee joints, bone plates, dental implants, and pacemaker cases.
- Machining properties are comparable to stainless steel.
Explore the characteristics and properties of timber and concrete, two common building materials, including their composition, strengths, and weaknesses.
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