Unit 4 Flashcards
Piezoelectricity meaning
The ability to release an electric charge when deformed. When an electric current is passed through a piezoelectric material its volume will increase or it will vibrate.
Magneto-rheostatic & Electro-rheostatic meaning
Electro-rheostatic (ER) and magneto-rheostatic (MR) materials are fluids that can undergo dramatic changes in their viscosity.
viscosity meaning
the state of being thick, sticky, and semi-fluid in consistency, due to internal friction
what are MR fluids used for?
use in car shock absorbers, damping washing machine vibration, prosthetic limbs, exercise equipment and surface polishing of machine parts.
what are ER fluids used for?
use in clutches and valves, as well as engine mounts designed to reduce noise and vibration in vehicles.
Thermoelectricity meaning
Thermoelectricity is, at its simplest, electricity produced directly from heat. It involves the joining of two dissimilar conductors that, when heated, produce a direct current.
What is thermoelectricity used for?
used in remote areas and space probes to power radio transmitters and receivers.
Photochromicity meaning
Photochromicity refers to a material that can described as having a reversible change of colour when exposed to light.
How does photochromicity work?
A chemical either on the surface of the lens or embedded within the glass reacts to ultraviolet light, which causes it to change form and therefore its light absorption spectra.
Example of photochromicity?
One of the most popular applications is for colour-changing sunglass lenses, which can darken as the sun brightens.
Shape memory Alloys meaning
have a pseudo-elastic property that allows them body to return to its original shape after deforming. Their shape changing property can be stimulated by either a change in temperature or the application of an electrical current. When the load is released, the body returns to its original shape.
What are SMAs used for?
- The frames of some eyeglasses use SMAs to create a flexible frame
- Medical devices such as Nitinol stents use SMAs to repair damaged blood vessels. to allow a thin device to be inserted into a vein. As the device heats up because of the body heat, it changes shape and keeps the blood vessel open.
modern plastics are derived from?
-derived from non-renewable petroleum resource, such as crude oil, coal or natural gas.
All plastics are a type of ___?
polymer
What determines the physical and mechanical properties of plastic?
the different types of bonds.
Which plastics are made from biomass?
PLA and Bioplastic
what is biomass?
plant or animal material used as fuel to produce electricity or heat.
plastic production’s impact on our environment?
The social, environmental, and economic impacts of plastic production and disposal are of increasing concern for our global community.
Which plastic can be reheated and molded?
Thermoplastics
Characteristics of thermoplastics
low production cost
easily injected into a mold
low stiffness, making them ideal for uses requiring flexibility
can be reshaped after heating
Types of thermoplastics?
- PP (Polypropylene)
- PE (Polyethylene)
- HIPS (High Impact Polystyrene)
- ABS
- PVC (Polyvinyl Chloride)
Properties and applications of polypropylene?
Polymer resin
Low cost
Stiff
Production Process: Injection molding
Application:bottles such as cleaning materials
Properties and applications of Polyethylene?
- Available in a variety of density levels (low, medium, high)
- Density determines properties:
LDPE: low cost, translucent
HDPE: Flexible, transparent to opaque, low temperature toughness, waterproof, Very common
Applications: plastic bags, water bottles
Properties and applications of High Impact Polystyrene?
Easy to machine and shape
Low cost
impact resistant
Applications: Lunch trays
Properties and applications of ABS?
Low cost
heat resistant
dimensional stability
Applications: lego bricks, keyboards
Properties and applications of Polyvinyl Chloride?
High hardness; Can be flexible when exposed to a plasticizer
Applications: Pipes, windows
plasticizer meaning?
a substance (typically a solvent) added to a synthetic resin to produce or promote plasticity and flexibility and to reduce brittleness.
Thermoplastics have a ____ chain
Linear
Thermosetting plastics have a ____ chain
Cross-linked
What are thermosetting plastics?
linear chain molecules with strong primary bonds between adjacent polymer chains. Gives a rigid 3D structure.
Characteristics of thermosets?
high stiffness
higher strength than thermoplastics
cannot be reheated and re-moulded – it will usually char and burn
Types of Thermosets?
- Polyurethane
- Urea-formaldehyde
- Epoxy Resin
Properties and application of polyurethane?
Very effective electrical insulator
High tensile and compressive strength
easily bonded
flexible
applications: glove coatings, rubber boots, wheels, shoe soles, varnish
Properties and application of Urea-formaldehyde?
High heat distortion temperature
high tensile strength
applications: decorative laminates, textiles, paper, foundry sand molds, wrinkle-resistant fabrics, cotton blends, rayon, corduroy, etc.
Properties and application of Epoxy Resin?
Resistant to chemicals and water
Adhesive form can bond to metal.
High mechanical strength
Applications:used in the construction of vehicles, snowboards, aircrafts and bicycles and adhesive purposes
Is plastic recyclable?
Plastic is recyclable, however the degree to which it can be recycled depends on the type, economic factors, logistics, and technology.
As it is a non-renewable resource, it is quite valuable. However, its low cost combined with a throwaway society and poor collection mean that much plastic ends up in the environment.
How is plastic recycled?
Plastic needs to be separated by type in order for it to be recycled. Mixing different types of plastics, or allowing contaminants can reduce the overall quality of the recycled plastic.
Disposal of thermosets and thermoplastics
Thermoplastics are easier to recycle than thermoset plastics. In many cases, Thermoset plastics are sent to the landfill or incineration (destruction of something).
Strategies when it comes to the use of plastic
Designing for Disassembly strategies can include the labelling of plastic parts with the type of plastic to ensure proper recycling.
Light-weighting or reducing the amount of material required in a product and its packaging
Promoting and using recycled plastics can encourage user acceptance of the unique aesthetic properties.
Selecting other materials when appropriate (glass, metal, or wood)
What are bioplastics?
Bioplastics are plastic materials produced from renewable biomass sources, such as vegetable fats and oils, corn starch, straw, woodchips, sawdust, recycled food waste, etc.
Applications: bags for compost, agricultural foils, horticultural products, nursery products, toys and textiles. They are also often used for disposable cups, salad bowls, plates, clingfilm and food containers.
Disposal of bioplastics
Plant based polymers are able to fully compost at the end of their useful life
What are composite materials?
A MIXTURE COMPOSED OF TWO OR MORE MATERIALS WITH ONE ACTING AS THE MATRIX (GLUE) THE OTHER ACTS AS A REINFORCEMENT (FIBRES/SHEET/PARTICLES).
characteristics of composites?
It takes the form of fibres/sheets/particles (reinforcement) in a matrix (glue).
The fibres/sheets/particles can be made from textiles, glass, plastics, wood and carbon.
The matrix can be made from thermoplastics, thermosetting plastics, ceramics (e.g. concrete), metals.
It is made via the process of weaving, moulding, pultrusion or lamination
Composition and structure of composites
- concrete
- engineered wood-also called composite wood, man-made wood, or manufactured board.
- fiberglass
- carbon
- laminated veneer lumber
- kevlar
composition of concrete?
water, Portland cement, and aggregates (gravel etc)
composition of engineered wood
Gluing sheets (veneer), particles or stands of wood together.
composition of fiberglass
stands of glass, formed into a matt and then covered in resin (polymer/thermoset plastic).
composition of carbon
reinforced plastic – carbon fibres formed into a matt (see above image) then covered in resin
composition of LVL
uses multiple layers of thin wood assembled with adhesives
composition of kevlar
para-aramid synthetic fiber covered in a resin
Advantages of composites
Excellent strength-to-weight and stiffness-to-weight
Laminate patterns and ply buildup in a part can be tailored to give the required mechanical properties in various directions.
It is easier to achieve smooth aerodynamic profiles for drag reduction.
Complex double-curvature parts with a smooth surface finish can be made in one manufacturing operation.
Composites offer excellent resistance to corrosion, chemical attack, and outdoor weathering;
disAdvantages of composites
- Composites are more brittle than wrought metals and thus are more easily damaged
- Repair introduces new problems, for the following reasons:
Materials require refrigerated transport and storage and have limited shelf lives. .
Hot curing is necessary in many cases, requiring special equipment. Curing either hot or cold takes time.
Repair at the original cure temperature requires tooling and pressure
design context of concrete
skyscrapers, bridges, sidewalks, highways, houses and dams.