Materials Science
Science FactThe frame holds your build together. Choosing the right material is about balancing strength, weight, toughness and cost.
Strength vs stiffness vs toughness
Strength is how much force a material handles before breaking. Stiffness is how much it resists bending. Toughness is how much energy it absorbs before cracking. Glass is stiff but not tough; rubber is tough but not stiff.
Strength-to-weight ratio
For things that move or fly, engineers care about strength divided by weight. Titanium is about as strong as steel but 45% lighter. Carbon fiber is even lighter and very stiff, which is why racing bikes and airplanes use it.
Composites
A composite combines two materials to get the best of both. Carbon fiber is thin carbon threads glued in hard plastic resin. Concrete with steel bars inside (rebar) is a composite too!
Nanomaterials
Scientists can now control materials at the nanometer scale, a billionth of a meter. Graphene, a sheet of carbon one atom thick, is incredibly strong. Making perfect nano-materials in big pieces is still very hard.
- Need: strong?
- Need: light?
- Compare strength-to-weight
- Check cost
- Pick material
COOL REAL FACTS
- The Boeing 787 airliner is about 50% composite materials by weight.
- Spider silk is tougher than steel for its weight.
- The SR-71 Blackbird was mostly titanium to survive heat at Mach 3.
SCIENCE FACT vs SCI-FI
Nano-Alloy as a perfect light, unbreakable and self-cooling metal is fiction for now.
TRY IT (SAFELY!)
Fold a sheet of paper into a zig-zag (like cardboard's inside) and test how many coins it holds compared to a flat sheet. Shape adds stiffness!
REAL ENGINEER TIP
Engineers pick the cheapest material that safely does the job, not the fanciest one.
PARTS THAT USE THIS IDEA
LESSON CHECK
Get 2 of 3 right to unlock this lesson's badge progress.