[TowerTalk] Solid Al vs Solid fiberglass ?

[jimlux]

On 1/22/17 3:06 PM, Jim Thomson wrote:
> Which is stronger,  1 inch  6061-T6  solid rod...... or  1 inch solid fiberglass rod ?
> I know what the tensile + yield  strength is on 6061-T6...... but the typ solid fiberglass rod  gets a bit tricky.
> Extrapolating from metric to queens english, it appears that solid fiberglass rod  has a typ tensile strength
> of  100 ksi, and a yield strength of 88 ksi.     I find this real hard to believe,  but I have zero knowledge of the
> typ solid fiberglass rods sold  for insulators for yagis and ants.
>

I usually assume that structural fiberglass is about the same strength 
as aluminum.  It's more flexible, though.  And it is weaker for certain 
types of loads - if you have pultruded structural shapes (fibers all run 
the long way), then the shear strength crossways is less than lengthways.

This is what I use
http://www.strongwell.com/products/structural-shapes-and-plate/

strength is tensile  30ksi lengthwise, 7ksi crossways,
             compressive 30ksi  lengthwise, 15ksi crossways

modulus is 2.7M psi



> 6061-T6  is typ listed as 48 ksi for tensile , and  39-40 ksi for yield.
>

and the modulus is about 10M psi, so it's about 3 times stiffer than 
aluminum

> I have an application where  I have to either short out the oem 1 inch solid fiberglass rod, or  replace it with solid 1 inch 6061-T6 rod,
> and this is way out on each ele half, like 200 inchs  out from the center...with another 204 inchs of tapered al tubing beyond each insulator.
> If the fiberglass is stronger, I might just short it out with an Al strap.
>
> If I knew the aprx yield strength of the solid fiberglass, then I could plug the numbers into  the  dx eng mech software.
>
> Jim   VE7RF
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