Chemistry geniuses needed - Light weight things made strong?

Question

I have to do a PowerPoint Presentation on how light-weight things are made to be so strong.

Basically I am supposed to talk about plastic and fiber glass.

My teacher told me that airplanes are supposed to be light weight, and many of their wings are actually made from plastic. Though plastic is light weight engineers have been able to make it strong enough so that it can be used on planes.

Also I need info on how fiber glass, despite its light weight is so strong.

Can somebody give me some information that they know or useful links of sites that provide such information? I just need to be able to explain it, in a simple manner. Please remember that I am not even in college. How are they able to make such things?

Thanks

Answer 1

Don't forget about aero gel. ~
http://www.jpl.nasa.gov/news/features.cfm?feature=490

Answer 2

It's really the fibers, not the plastic, that are the strong part. The plastic resin is just there to hold the fibers in place and make the parts solid.

Fiberglass is reasonably strong, because glass is pretty strong. Although strong, glass is brittle (means it fails easily if has scratches- doesn't stretch like rubber) but the fibers, embedded in the resin, are protected.

Most high strength aircraft composites are carbon fiber reinforced epoxy. Carbon fibers are strong because the nature of the carbon atom, with 4 electrons available for chemical bonds, makes carbon crystals strong. Carbon fibers are made by heating polyacrylo nitrile (plastic) in a vacuum until all the non carbon atoms burn off. Then the fiber is embedded in special epoxy resins.

Epoxy itself is brittle too so most modern aerospace composite epoxies have modifiers to interrupt crack growth and make the material less brittle.

In design, the fibers are oriented to resist the mechanical loads. Metals are the same, roughly, in all directions, but composites can be tailored.

The wikipedia site is pretty good:

http://en.wikipedia.org/wiki/CFRP


Good luck with your presentation!

Answer 3

You should remember that in some applications, (aeronautics especially), a lighter material is stronger weight for weight than one with a higher tensile strength, (measured 'per Sq. inch`).
Depending on the application, a lighter part of a weaker material can be stronger simply because it allows more cross sectional area for less weight.