Hard: Perfomrance And Charcterisitics Of Materials Flashcards
CFRP and GRP properties? What is CFRP made for?
Can be easily moulded into complex 3d shapes using the lay up methods which allow for monocoque designs to be produced impossible form traditional methods
These materials tend to make products which are light weight and good with toughness and strength throughout the material.
CFRP is often sued for high specification tracing bikes for athlete riders
properties in depth and uses: CFRP, GRP, Tungsten Carbide (need o finish !!!!1
CFRP - lightweight, corrosion resistant tough and hard - sports equipments, tennis racquets
GRP - lightweight, corrosion resistant, tough and hard - boat hulls and kayaks
Tungsten carbide - hard, tough, resistant to hit temps and corrosion resistant - used for cutting tools like drill bits and lathe tools
Aluminium composite boards - lightweight, tough, and good sound insulation - sound proofing in buildings
Concrete - low tensile strength, few surface defects, easy to mould - pathways and buildings
Reinforced concrete - high tensile strength and compressive strength, few surface defects, fire resistant - buildings, grid floors
Fibre cement - lightweight compared to reinforced concrete, hard, tough, fire resistant- bam and bridges
The use of standard stock usage in timer helps saves and keeps material costs down what is the size for rough sawn? The cost for the use of raw material increases with the amount of processing then do it rough sawn is better than planned all round
32mm thick and 50mm thick
What is rough sawn?
Wood that comes directly from seasoning the wood and has rough surfaces produced from the initial conversion. - Come in
What is planned square edge?
PSE wood has only one degree that is planned accurately the rest is rough sawn - this removes about 3mm from he original size
Planned all round
PAR wood is when the sides and edges are all planned straight and level leaving a smooth finish ready to use - the board is about 3mm smaller all round than the original rough sand size
Note: natural wood is only available at the maximum width of the tree. In order of make it wider you would have to join the wood together to make larger sheets. However manufactured boards are different and dont need to be joined together as they can be made wide enough for most applications.
How much natural wood be joined together? And whY?
The wood grains should be facing opposite directions to each other when joint the wood together
- ensure internal forces f the wood do not pull the wood in one direction and the top is joined in equilibrium
What are some of the advantages to using manufactured board?
Available in long and wide board variations
Uniform strength across the board
Difficult to split the board since it has no grain problems
Generally less expensive than solid wood of a similar size
Veneer can applied for aesthetics
What are polymer based sheet material used for? What about their sustainability? Why is it hard to recycle the boards
Used with varying thicknesses for model making to packaging.
Some like cellulose acetate come from a natural source which is biodegradable. whereas some like PP can be recycled
Although it is difficult due to the foam core and outer sheets of card like foam boards which are more likely to be reused than recycled
Polymer sheet based material properties and uses:
Foam board - two layers of card with foam middle core in ranges of thickness - presentation boards
Fluted PP sheets - extruded sheet with flutes or corrugations - light weight and can easily be bent - storage box construction, portfolio cases
Translucent PP sheet - tough polymer sheet, can be scored before producing hinge, virtually impossible to tear - packing products
Styrofoam - dense, closed cell foam, commonly blue - product modelling
LDPE - tough transparent and good chemical resistant - food wrapping
Pastazote foam - tough and flexible - protective packaging
Cellulose acetate - transparent, naturally biodegrade and tough - packaging film
Polylactide - transparent, tough, naturally biodegrade - biodegrade packaging film
What is toxic about wood?
The dust from wood as well as sap can be toxic and a hazard to health to people working with them. This depends on the species of the wood as well so it’s important to consider this when dealing with wood as a designer
Under COSHH hardwood and softwoods have a dust exposure limit of 5mg as they can cause respiratory problems - so to combat this they should ensure that there are ventilation systems and PPE provided for people working with these materials and processes to not exceed the limit
Note timber is strong along the grain than against it, so using a jack plane in line with the wood will but the opposite way not so much and chipping will occur
Most of the wood is converted into sawn and then seconded - removing excess moisture how is this done, explain the two different seasonings:
A-D OAK AIR DRIED: EXTERIOR USE
K-D OAK KILN DRIED: INTERIOR USE
Air seasoning:
An inexpensive method which involves stacking the wood under a shelter away from the rain and allowing the air to circulate the planks slowly remove the excess moisture - used for outdoor products as it is seasoned to the same moisture as the outdoors so less prone to defects
Kiln seasonings:
More expensive and controlled which is very quick and can take a few weeks controlling both the temperature and humidity of the wood and atmosphere in machine
It is initially steamy but then becomes hotter and drier - seasoned to meet indoor conditions and will have lower moisture content that air dried wood
Hat are some advantages of seasoning wood and what happens if we were to place unseasoned wood in a heated room?
Unseasoned wood in a heated room would cause it to twist and warp when drying out and cracks would appear
Advantages include:
Grater immunity from decay and increased resistance to rot
Increased strength and stability
Helps preservatives to penetrate
Makes wood less corrosive metal
As wood is a natural material, it expands and shrinks with changes in humidity (the amount of water present in the atmosphere). To reduce the time taken to season wood to the correct moisture content, trees should be felled in the winter when they grow less, have less sap and therefore contain east moisture The largest amount of shrinkage occurs after the tree is cut down and while it is being seasoned.
Wood shrinks by different amounts in different directions, with almost no shrinkage in the direction of the wood’s grain (lengthwise). Some shrinkage happens radially (perpendicular to the growth rings), with a greater amount of shrinkage occurring tangentially (along the curvature of the growth rings). The ends of the wood tend to lose moisture content more quickly than the core, and sometimes cracks can appear on the plank ends.
Care must be taken when seasoning the wood so that the whole plank will shrink uniformly, and usually once the wood has been fully seasoned, any end cracks will close as the plank is now in equilibrium throughout.
Seasoned wood can also be susceptible to shrinkage due to seasonal changes in the ambient humidity, but this is less of a concern in modern” homes where temperatures are fairly constant due to heating and air conditioning systems.
