1. Forces and Materials

2. Compression and tension
Some materials are strong when squeezed (compression)
Some are strong when pulled (tension)
Compressive strength = how much compression a material can handle before failing
Tensile strength = how much tension a material can handle before breaking

3. Concrete Concrete is a combination of two materials: cement and
aggregate.
Cement is a powder made of a variety of materials (usually clay and limestone). When cement is mixed with water a chemical reaction called occurs that causes the cement to harden.
Aggregate is a mixture of sand and gravel rock.
Concrete alone is not as strong as concrete with rebar or a mesh. Adding steel to concrete makes reinforced concrete which is stronger

4. Concrete Advantages to using concrete:
Concrete is extremely strong in compression and therefore has a high compressive strength.
Concrete is inexpensive compared to steel.
Using forms, concrete can be made into practically any shape.
Disadvantages to using concrete:
Concrete is a brittle material and shows very little yielding before cracking or breaking
Concrete is very weak when a tension force is applied to it and therefore has a very low tensile strength.

5. Steel Steel is created from purified iron ore.
Iron ore is a rock that contains a high concentration of iron. Common iron ores include hematite (Fe2O3), magnetite (Fe3O4), limonite (Fe2O3), and siderite (FeCO3). All iron ores contain iron combined with oxygen. To make iron from iron ore, the oxygen must be removed.
One way to accomplish this is by using a blast furnace.

6. Steel Advantages to using steel:
Steel is very strong in both tension and compression and therefore has high compressive and tensile strengths.
Steel is a ductile material and can handle large strains before breaking or failing.
Steel is usually assembled relatively quickly.
Disadvantages to using steel:
Steel is expensive compared to concrete and wood.
Steel can rust when exposed to some environmental conditions making it weaker.
Steel is a heavy material and so beams can’t be too long without support.

7. Reacting to stress and strain
The modulus of elasticity indicates the stiffness of a material. 
Stress is the load divided by the materials it’s acting on
Strain is how much stretching or pressing is on each unit length of the material.
The end points of these curves represent failure. The concrete curve shows a steady increase in strain and stress before it ruptures. Concrete fails with little or no warning; thus, it is considered a brittle material. Just before steel breaks, it experiences a reduction in stress while strain increases. This is seen on the steel curve as the negative sloping section of the curve. When steel fails, it presents some type of warning, typically in the form of large deflections; thus, steel is considered a ductile material.

8. Wood Advantages to wood Wood is relatively inexpensive and easy to get
Wood looks good
Relatively light weight
Good tensile strength
Renewable
Disadvantages to wood
Subject to decay or rot so you have to treat it
Not ductile (not easy to bend)

9. Plastic Advantages of plastic Light weight Inexpensive Waterproof
Lasts a long time
Disadvantages
low heat resistance
poor ductility (bending and stretching)
Hard to make your own shapes

10. Particle board
Particleboard is a widely used material in the building industry. It is created by placing wood chips, fibers or even small scraps of wood under intense pressure with glue.
Advantages to particle board
Very inexpensive and easy to make
Renewable, uses up scraps
Comes in many different kinds
Disadvantages to particle board
Breaks easily
Not ductile (not easy to bend)
Will absorb moisture and swell