2025 aluminum propeller-blade alloy (toughness vs. 2024)

Composites — well, let me back up. All these materials except ceramics are viable structural materials because they all fall between this little pie-shaped region of elastic-plastic mixed mode. You can get polymers that are plenty ductile. You can get them that are also somewhat brittle — smoky plexiglass is down over here somewhere, and you have to be careful how you design for it, but polycarbonate is way over here. We used to use it as bulletproof glass. So plastics, across the whole field. Aluminum crosses the whole field. The toughest aluminum in the world is an aluminum called 2025. Many of you have heard of 2024 aluminum, the aluminum-copper alloy. 2025 has been around since 1925. It was named right after 2024. It's 15 times tougher than any other aluminum alloy, very low strength. I only know of one application: propeller blades. And you can think about it — wouldn't I like to have toughness in a propeller? Wouldn't I rather have a propeller blade that bends before it breaks and snaps? Yes, it's sort of a critical structure.