IBSL Design Technology - Materials Unit Final Pretests

Which type of tree contains considerable resin?

conifer

In which regions do softwoods grow?

temperate

Softwoods like Pine, Spruce, Cedar, and Douglas-Fir grow only in this region: *

temperate

Softwoods grow mainly in...

colder/cooler climates

Hardwood trees reproduce using...

flowers

____________________ trees have needle-shaped or scale-like leaves.

conifer

This material changes from thick fluid to solid when exposed to electric field

electro-rheostatic

This material changes from thick fluid to solid when exposed to magnetic field.

magneto-rheostatic

This material when deformed gives off a small electrical discharge OR When electrical goes through it increases in size (up to 4% change in volume).

piezoelectric

Can be plastically deformed and then will return to their original shape when heated to a higher temperature.

shape memory alloys

This material with a temperature difference creates an electric potential or an electric potential creates a temperature difference.

thermoelectric

What's are the two main ingredients in a composite?

fiber and matrix (or glue)

What is Kevlar (the internal structure...something about "chains & rings")?

linear chains of hydrocarbon rings

Which type of glass breaks into thousands of tiny pieces

toughened

Which type of glass breaks into something that looks like a spiderweb (and stays together)

laminated

Which type of fiber (textile) has the highest strength?

synthetic

What are the 3 natural fibers we studied

wool, cotton, silk

Which type of fiber has the lowest absorbency

synthetic

Does laminated glass provide better UV protection than toughened glass?

yes

Which type of fiber burns and melts?

synthetic

Which type of timber has long continuous ducts for fluid transport?

hardwood

name the three processes for strengthening metals

alloying, work hardening (plastically deforming), and controlling grain size

How does controlling grain size strengthen a metal

Fast cooling gives you small grains. Small grains have more grain boundary area than larger grains (slow cooling). Grain boundaries inhibit (hinder, stop) atom movement.

Explain what is happening internally to a metal's microstructure that allows it to get stronger when permanently deformed.

Work-hardening (plastic deformation) creates internal dislocations in the microstructure. The dislocations inhibit (hinder, stop) atom movement.

What is timber seasoning?

drying out timber after the tree has been cut down.

What is GFRP (carbon fiber)?

Graphite fiber reinforced plastic

How is toughened (tempered) glass manufactured?

flash cooling external surface of a sheet of glass. Internal section of glass stays soft and cools slowly causing internal stresses to develop in the material.

How is Pyrex different than standard glass?

Boron Oxide is added to the silicone dioxide.

The boron oxide added to the silica reduces the _______________________ characteristics (it lowers the CTE) of standard glass.

thermal shock

The lower CTE (of Pyrex) reduces the thermal _____________ caused by temperature gradients, thus making it more resistant to breaking

stress

What is the main ingredient in glass ?

silicon dioxide

What is CTE? 2 parts to this question: Define the acronym and explain what it means for a material.

coefficient of thermal expansion.

This is a quantitative value (a number) that defines the amount of expansion for a material when it sees a temperature change.

Name the two types of plastics we are studying.

thermoplastics and thermosets

What are the two main differences between the 2 types of plastics we are studying (focus on microstructure and recyclability)?

thermoplastics - little or no crosslinks AND can be reheated to form into a new object (recycle)

thermosets - lots of crosslinks AND cannot be reformed into something new (chemical reaction to form these thus cannot heat them up to flow into new mold.

Why is a piezoelectric material smart? When you answer this question it should include a "vice versa".

When deformed gives off a small electrical discharge OR

When electrical goes through it increases in size (up to 4% change in volume).

You need to be able to describe what is happening internally to a plastic when it goes from "no load" to enough of a load to "plastically" deform it. Explain the process here in detail. Once again, the plastic will be unloaded and then a gradual force will be applied until the load exceeds the material's capability

An unloaded plastic consists of a tangle of linear chain molecules (like a bowl of spaghetti). As a load is applied the tangled linear chains begin to straighten out.

If the load is greater than the capability of the plastic material, then the molecular chains would begin to slide over each other and the secondary bonds (many in thermosets, very few in thermoplastics) will weaken/fail. This causes permanent (plastic) deformation.

Why are shape memory alloys smart?

Can be plastically deformed and then will return to their original shape when heated to a higher temperature.

What is plastic reinforced by fine fibers made of glass?

fiberglass

What does it mean if a material has a very low CTE?

he material does not expand/contract very much with temperature changes.

List the 2 main reasons Kevlar is used for ropes in sailing.

Kevlar does not absorb water nor does it stretch.

Give at least one application for the thermoset Urea-Formaldehyde. NOTE: You must know all 4 of them for the test!

i. Glue (adhesive) or

ii. Fire retardant or

iii. Water repellent or

iv. insulation

Give at least one property (characteristics) of Urea-Formaldehyde. NOTE: You must know all 5 of them for the test!

a. Stiff or

b. brittle or

c. Hard or

d. Strong or

e. Good electrical insulator

Which type of fiber has the highest absorbency?

natural

Which type of timber has tracheids for fluid transport?

softwood

After processing, the only way to change a thermoplastic is by cutting and machining. (t/f)

false

Thermosets repeatedly soften when heated and harden when cooled. (t/f)

false

Heat increases the number of crosslinks in a thermoset. (t/f)

true

Alloying decreases ductility. (t/f)

true

In general, plastics come from petrochemicals. (t/f)

true

Superalloys have an oxide layer that encapsulates the material. (t/f)

true

Drawing is a cold-working process. (t/f)

true

Superalloys have a tendency to 'creep'. (t/f)

false

Engineers choose superalloys for mostly low temperature applications. (t/f)

false

Polymers consist of hydrocadmium chains. (t/f)

false

Piezoelectric material decreases in size when an electrical charge goes through it(t/f)

false

Rope is usually made from silk fibers due to their strength. (t/f)

false

Natural fibers are great for clothing worn by surfers due to their low absorbency.

false

These sustain structural change during processing to become permanently insoluble and infusible.

thermosets

Carbon (graphite) reinforced plastic parts begin as:

cloth

The "daub" in the composite wattle-and-daub is the _______________.

clay and sand mixture

A material that is ____ will withstand sudden shocks or blows without fracturing.

tough

the material with the best tensile strength characteristics is...

metal

Which is a physical property of a material (not a mechanical property)?

density

Bendability or crushability (and the ability to be stretched without breaking) is defined by:

ductility

A material that is rated very high for thermal resistivity would be good to use as a fry pan. t/f

false

White glue (Elmer's...polyvinyl acetate) is a thermoset. t/f

false

Which type of plastic would be best for use as a kitchen worktop (counter top)?

thermoset

Urea-Formaldehyde is a _________________.

thermoset

Polyurethane is a _________________.

thermoset

Polypropylene is a _________________.

thermoplastic

Polyethylene is a _________________.

thermoplastic

Acrylonitrile Butadiene Styrene (ABS) is a _________________.

thermoplastic

Polyvinyl Chloride (PVC) is a _________________.

thermoplastic

High Impact Polystyrene (HIPS) is a _________________.

thermoplastic

Melamine Resin (a.k.a. melamine-formaldehyde) is a _________________.

thermoset

Epoxy Resin is a _________________.

thermoset

Polyethylene Terephthalate (PET or PETE ) is a .....

thermoplastic