Course Reflection
AK47
hacker_ch.4.pptxMaterials & Materials Processing
Chapter 4 Hacker
ETSC 101 Chapter 4 Hacker
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Types of Materials
Natural
Organic
Inorganic
Synthetic
Mixed
ETSC 101 Chapter 4 Hacker
Organic means it came from something that was alive and it is a carbon based molecular structures.
Inorganic means it occurs in nature but not from something that was alive, like a rock .
Synthetics are human-made. You have rubber, and then you have synthetic rubber. You have vitamins but then you also have synthetic vitamins that you can get from a Flintstones gummy. Also plastics are great examples. They are produced from molecular engineering and playing around in the chemistry lab.
Mixed is exactly as it implies: A mixture of synthetic and natural materials. Plywood, paper, clothes are great examples.
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The Four Major Groups
Woods (nature’s composite)
Metals (primarily metallic-bonded atoms)
Plastics (primarily covalent molecules)
Ceramics (primarily ionic compounds)
ETSC 101 Chapter 4 Hacker
I say primarily because there are always exceptions.
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ETSC 101 Chapter 4 Hacker
Ionic bonds are formed by metals and nonmetals. Electrons stolen.
Covalent with two nonmetals. Electrons shared.
Metallic with two metals. Electrons homeless.
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Most Important Fact in Materials:
The structure of a material drives its properties!
Therefore if you know something about the structure, you can say something about its properties.
ETSC 101 Chapter 4 Hacker
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Ceramics
Ionic Bonds
Structure characterized by…
Crystalline structure (Except for glass)
Very strong bonds
Properties
High hardness, brittleness and melting point
Great insulators but can be rearranged in structure to exhibit conducting properties
Low weight/low density
ETSC 101 Chapter 4 Hacker
The ionic bonds and crystalline structure caused by the polar nature of the ionic bonds makes many ceramics very hard and strong. Even the non-crystalline ceramics are very hard and strong because the non-crystallinity is caused by a contaminant molecule such as boron or sodium as in the picture and prevents movement of the compound. That is why only diamond can scratch glass.
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Metals
Metallic bonds
Structure characterized by…
Sea of electrons. Bond strength between ionic and covalent.
Electron sea allows metallic atoms to slide past each other easily.
Crystalline structure.
Properties
High strength and ductility.
Very thermally and electrically conductive.
High Density
ETSC 101 Chapter 4 Hacker
Ductility refers to the materials ability to deform without fracturing.
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Plastics
Covalent Bonds
Structure characterized by…
Long polymer chains
Secondary bonding between chains.
Properties
Low strength but very ductile
Insulators of heat/electricity
Melted very easily if thermoplastic
Can’t be melted if thermoset
ETSC 101 Chapter 4 Hacker
Thermosets incorporate rigorous crosslinking between chains that require a very high energy input to break the bonds, an energy that is higher than the molecular bonds between each monomer of the polymer chain. This results in the thermoset decomposing before it can melt. Not so with thermoplastics! There is no crosslinking so the chains break down way before the decomposition energy input.
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Woods
Polymer composite
Other polymers are plastics, rubbers, and adhesives.
Structure characterized by…
Fiber length
Wall thickness
Compactness of fibers
Properties
Strength -> More dense
Lightweight -> Hollow cellulose tubes/less dense
ETSC 101 Chapter 4 Hacker
Wood is a composite: cellulose fibers strong against pulling in a matrix of lignin strong against pushing.
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Composites
A Reinforcement and a matrix that retain their properties, just like wood.
Reinforcement
Usually a fiber or particulate.
Matrix
Usually a resin, or poured material such as ceramic or metal.
Processing
Laminate or fiber/particulate-infused molds.
ETSC 101 Chapter 4 Hacker
Composites are as old as the stone age with mud and straw bricks but engineered composites began enjoying widespread use in the 30’s.
Woods are used to make stronger wood composites or cheaper wood composites
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Material Properties
Physical
Density
Phase
Mechanical
Tension/Compression/Shear
Toughness
Impact Resistance
Hardness
Brittleness/Ductility
Electrical
Conductivity/Resistivity
Magnetic
Dia-, Para-, Ferro-
Thermal
Conductivity
Expansion Coefficient
Optical
Absorptivity/Reflectivity
Refraction
Transmittance
Acoustic
Speed of sound
ETSC 101 Chapter 4 Hacker
This is all a question of energy when it boils down to it.
Energy comes in many different forms, but can be summarized into kinetic, potential, and transferred (heat and work).
Kinetic is the movement of mass, potential is the attraction of masses to other masses, and transferred is the energy transferred from mass to mass
It all starts from the sun and trickles down to us through many conversions with associated losses.
Properties express a materials ability to absorb and store, transmit, or reflect energy.
There’s many more types of energies then listed and therefore properties, but we will just cover these listed.
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What We Care About
Physical
Is it light/heavy enough?
How do I store/use it?
Mechanical
Will it break?
Will it deform?
Electrical
Can it conduct/insulate electricity?
Will it shock me or short out?
Magnetic
Will it repel/attract other magnets?
Will it introduce magnetic waves that interfere with other things?
Thermal
Will it get too hot?
Will it heat/cool the room?
Optical
Will I be able to see through it?
Will it actually be a mirror or a pair of glasses?
Acoustic
Will it keep noise out?
Will it sound good?
ETSC 101 Chapter 4 Hacker
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And the Bigger Question…
Will it perform its intended functions? (Meet specifications)
ETSC 101 Chapter 4 Hacker
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Dealing with Constraints
After seeing which materials can be used to allow our design solution to meet specifications, constraints have to be dealt with such as…
Processing and manufacturing
Cost constraints
Environmental
Safety
Availability
ETSC 101 Chapter 4 Hacker
Processing/Manufacturing on next slide
But the more is done, the more money it cost, the more labor it cost, the more equipment time, etc.
We also have to be good to the environment as we’ve been discussing, therefore cars that run on nuclear energy may not be a good idea…YET!
We can’t have anyone dying from our design solutions either, the materials have to be safe. Think of asbestos and how we use to use it all the time.
It would be nice to be able to make our product out of Einsteinium because it sounds cool, but its only produced as a byproduct when a hydrogen bomb goes off so not too available.
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Processing and Manufacturing
Mass Change
Machining
Phase Change
Casting (Metals)
Molding (Plastics)
3D Printing
Structure Change
Heat Treatment
Deformation
Extrusion/Drawing/Rolling
Forging/Pressing
Consolidation
Welding/Brazing/Soldering
Fastening/Assembly
Sintering
Coating
ETSC 101 Chapter 4 Hacker
It would be nice if we could just pull material out of the ground, snap our fingers, and it magically become the design solution that we need, but things don’t work like that. Materials have to be processed to get a desired outcome, and there are only so many ways to process materials.
Metals are most likely to experience all of the processing categories because they take so much, but are rigid enough in structure to be able to handle it.
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