GM is going aluminum

Passin Thru wrote:
YOu can't buff the tailgate, CA will give you a ticket for blinding someone following you. Stupid law but that's why they have quilted aluminum doors on Great Dane Trailers.
Wes Tausend, Why do they use Titanium on airplanes if it isn't stronger and lighter than steel? I sure broke a lot of drill bits adn screwdriver bits on titanium. Also, I read an arcticle thant said Carbon Fiber was corrosive to any metal it touched due to dissimilar metal corrosion. The use of carbon-fiber composites with steel structures requires a thorough understanding of the phenomenon of galvanic corrosion. In theory, as long as two materials have not
contacted each other, a corrosion cell will not initiate. However,
in case of direct contact between carbon fibers and steel
in the presence of an electrolyte, the wet corrosion cell could
accelerate the corrosion of steel and create possible blistering
and subsequent delamination or debonding.
Probably why they don't use carbon fiber in vehicles that run down roads we salt and use calcium chloride on.

Titanium isn't quite as strong as some high strength steels, but it is stronger than aluminum. But you right, it is considered lighter for the strength it has. But not as much as one might think for practical purposes, depending on how it is used. That is what I meant by "sort of" in my post above. Also, I admit I was mostly thinking of steel vs aluminum as I mis-spoke. Titanium is mostly used on fighter jets because it is resistant to heat from air friction. It is used on just a few other items where composite, steel or aluminum won't do.

Below is a partial (crooked) chart of Specific Strength (strength per density).
Stainless steel is at 254 whereas Titanium is at 288. They are fairly close together, as opposed to stronger Balsa which is at 521, or weaker aluminum which is only at 214. Aluminum is stiffer than steel per weight which is why it makes good panels and this probably related to the lower Fatigue Limit, making less durable frames.

...................................Material.....................Density...........Specific Strength
.....................................Strength.................(g/cm³)...............(kN·m/kg)
......................................(MPa)
Magnesium........................275_________1.74____________158
Aluminium.........................600__________2.80____________214
Stainless steel.................2000_________7.86____________254
Titanium...........................1300_________4.51____________288
Bainite.............................2500_________7.87____________321
Balsa (axial load)...............73__________0.14____________521
Scifer steel wire.............5500__________7.87____________706
carbon-epoxy compo.....1240_________1.58____________785
spider silk......................1400__________1.31___________1069
Silicon carbide fiber.....3440__________3.16___________1088
Glass fiber....................3400___________2.60___________1307
1 ?m iron whiskers......14000__________7.87___________1800
Carbon fiber (AS4).......4300__________1.75____________2457
Kevlar.............................3620__________1.44____________2514
Carbon nanotube.........62000_________.037-1.34________46268
Colossal carbon tube.....6900___________.116__________59483

Note that the strange Scifer Steel wire has an unusually high tensile strength.
"The scifer wire is said to be composed of 97 percent steel, 2.9 percent silicon and manganese and 0.1 percent carbon. The material is available for 43 cents per kilogram."
It appears to only work this way as a thin thread however.

Carbon fiber is electrically conductive and, unisolated, it can react with metals (especially aluminum), not a lot different than the carbon anode in a zinc-carbon battery. OTOH, a carbon body makes a better ground plane for an antenna than fiberglass. Most Corvettes have a metal plate under the rear deck for this reason. But some do have other carbon body panels. Wonder if they're eroding?

Wes
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