Some materials are considered very strong, yet they are also very brittle. To me this sounds a bit counterintuitive so please explain to me how a material like carbon fiber for example, is considered strong but yet breaks easily.
In: Engineering
Roughly the “strength” refers to how much force is required to deform the substance. So stronger substances require higher forces to change their shape.
“Brittle” refers to what happens to the substance as it approaches and crosses that threshold. Brittle substances simply break, where as malleable substances will bend or deform without breaking.
Consider a spaghetti noodle cooked vs uncooked:
You can put a book on an uncooked spaghetti noodle and it will be unaffected. Put it on a cooked spaghetti noodle and it goes squish.
But bend an uncooked spaghetti noodle even slightly and it will snap. You can bend a cooked spaghetti noodle all day and it is fine.
This is always confusing for most people. I think it is a problem of semantics. People refer to HARD materials as strong and RESISTENT materials as strong, too.
There’s an old expression in engineering: if you do not bend, then you break [instead].
A thing that is “brittle” chooses to break. It may take a lot of force, but it breaks with minimal bending then legally it is “brittle”.
Stone is strong, but doesn’t bend. It’ll break into pieces if you stress it too much. Cardboard isn’t that strong, but it just bends when the force becomes too strong and stays… sorta intact…
These terms have very strict definitions in material science. You’re quite wrong about carbon fibre, it doesn’t break easily.
What you’re talking about is the fact that it splinters when it does break. This seems to have given you the incorrect impression that a material that splinters does so easily. The way a material fails does not necessarily dictate it’s strength.
When steel fails, is plastically deforms (bends, dents etc) in most cases. Steel with high-carbon content or that has been heat treated can fracture instead of deform.
The method of failure is dictated by the molecular structure of the material. A strong material will withstand greater force before permanently changing shape. Once the forces exceed the yield strength, it will fail. How the failure happens doesn’t change the amount of force needed to deform it.
Take concrete: you can put a building onto a column not even a meter across. But you can whack that same column into pieces with a sledgehammer.
Now take rubber. It will just squish and roll over if you try to put pressure on it. If you try to sledgehammer it, you’ll just receive your hammer back in your face though.
> please explain to me how a material like carbon fiber for example, is considered strong but yet breaks easily.
You put 100kg force on a metal pole and it bends.
You put 200kg force on a carbon fiber pole and it shatters.
The carbon fiber pole is technically twice as strong, but the metal pole has failed more gradually by bending.
“Strong means something, but its not the olny property”
Hard things resist scratches and cuts.
Tough things resist sudden impacts.
Strong things resist getting stretched or squished.
Glass is both hard, and strong, but its not tough.
Rubber is tough but not hard or strong
Steel is a mix of all three but not really that great at any of them.
Different materials are a mix of each
It’s common to think of strong and brittle as opposites, but they are not.
Brittle doesn’t mean it “breaks easily”. Brittle just means that when you put enough force to exceed the strength of a material, the material breaks instead of bending.
The opposite of brittle is flexible or malleable.
Glass is brittle but weak. Carbon fiber is brittle but incredibly strong — 5 times stronger than steel by weight.
Tin is a metal, it is malleable but weak. Steel is malleable but strong.
In material science, strength refers to how much stress a material can take before failing, while brittleness refers to how little a material deforms before fracture. For the most part, they are independent properties.
A material that is strong yet brittle would be able to withstand a lot of stress, but would fracture quite readily when it reached its limit.
Latest Answers