Materials Flashcards
Hardness
The ability of a material to resist wear
Malleability
The ability of a material to be reshaped in all directions without cracking
Toughness
Materials resistance to impact
Ductility
The ability of a material to change its shape usually by stretching along its length.
Calculating stress
Stress(N/m2) =
Applied load/cross-sectional area(CSA)
Composites
Materials composed of two or more parts, they can have different physical or chemical properties. eg. (concrete, fibreglass)
Smart materials
Materials that have one or more properties that can change by external stimuli, like stress, temperature, moisture, pH, electricity, magnetic energy.
Calculating strain
% strain=
change in length/ original length x 100
Young’s modulus and calculating
A number which indicates the stiffness of a material. Found by dividing the stress by the strain.
2 hardwoods
Name, properties, uses
Oak- hard, tough, strong- furniture, boats, floors
Mahogany- strong, durable, resistance to water- panelling, furniture
Softwoods
Scots pine- strong, durable, easy to work- inside work, outside if treated
Cedar- resistant to water and infestation, durable, knot free easy to work- cladding outside of buildings, sauna and steam rooms
Manufactured board
Examples, properties, application
MDF (medium density fibreboard). No grain so doesn’t split easily. Used in kitchens, storage units, doors.
Plywood. Thin veneers of wood glued together in opposite directions. Strong and aesthetic. Wall panelling, flooring, furniture.
Plastic
Examples, properties, application
PVC. Thermoplastic. Light, rigid, many colours. Doors, pipes, gutters, bottles, shoe soles.
Acrylic. Thermoplastic. Rigid, clear or opaque, easily scratched, easily joined, easily machined.
Phenol Formaldehyde. Thermosetting. Handles for cooking ware, electrical fittings, sockets.
Non ferrous metals.
Example, properties, uses
Lead, zinc, brass, copper.
Brass- hard, good conductor, protects itself from corrosion.
Copper. Conductor, malleable, ductile, tough. Electrical wire, roofs, heating pipes
Ferrous metal
Examples, properties, uses
Stainless steel. Strong, ductile, prevents corrosion. Cutlery, kitchen stuff
High carbon steel. Strong, hard, wear resistant. Cutting tools, cables.
High tensile steel. Tough and strong. engine parts, gears etc.
Discuss use of composites in modern design: Concrete, Fiberglass
Concrete: Used in construction, brick laying, road building etc. Made up of cement, gravel, sand.
Reinforced concrete: Reinforced with Steel Rods to withstand tensile forces. Used in bridge and skyscraper building.
Fiberglass: Strands of glass woven to form a flexible fabric. Material is strong and light. Can be sanded and painted. Used in canoes, cars, surfboards.
Smart material examples
Thermochromic materials respond to changes in temperature by changing colour.
Vacuum forming
A mould is placed in the machine. The plastic is heated until malleable, soft and flexible. Raise the mould to meet the plastic sheet. Activate the vacuum. The plastic is pulled over the mould. It takes the shape of the mould.
PVC, Acrylic and polystyrene are typically used.
Note: Holes should be drilled in the mold to allow it to come down fully.
Compression molding
Plastic placed between two parts of a mould. Pressure and heat are applied till plastic take the shape of the mould.
Used with thermosetting plastics.
Used to make electrical fittings, handles.
Blow moulding plastics
Uses air to blow plastic into a solid mould.
PVC, polythene used.
Makes plastic bottles
Injection moulding
Plastics are injected into the mould. Material is fed into a heated barrel, mixed and forced into a mould cavity where it cools and hardens in the cavity shape.
Both thermosetting and thermo plastics used.
Makes car body parts, bottle caps, toys etc.
