Bille wrote:................There was a Reason they went with Carbon, it's Better.
How fast does the AC-72 go ? 45kts + ; and they weigh How much ?
I believe they said the AC-72 weighs close to 30,000lbs
overall, I tend to agree with your choice of materials.
But i am having trouble, following the 'analysis'
Hawaiis has followed his intuition and hard work to develop a product that suits him.
You have also followed you intuition and considerable experience with composites to develop an approach that suits you.
However, despite the fact that i support your choice, i find much of the logic and math questionable.
The fiber strength of T-700 is actually quoted as high as 700 ksi (in tension)
In compession the strength drops to 350 ksi. (every tensile load in this beam example will be balanced in compression)
All these fibers need resin to tie the matrix together. A 50% ratio of 10 ksi epoxy (nominal bag process) is going to dilute the 350 ksi to 180 psi net in that particular fiber direction.
Now that you chosen to orient the fibers in an additional 5 directions the max compressive and tensile strength will be reduced even further. < 100ksi ( all because you've attempted to make this stuff isotropic?)
And none of the above addresss the shear strengh between laminates which is effectively limited by the epoxy again at 10ksi.
The benefit of the fibers is you can put them where you need them. They do very little if pointing in the wrong direction. I bet those smart guys on Team Oracle do something like that.
Iso-tropic makes the math easier, but i doubt thats a good enough reason to take a fancy composite layup and turn it into a lump of coal.
Hawaiis has covered a lot of ground on his own and so have you.
Personally the best technical advice i have to offer is:GOOD, FAST, CHEAP.
-Pick any 2
carry on kids.
My advice is to stop discussing strength, start talking STIFFNESS and how to increase it. Start quoting Modulus of elasticity (E) for materials instead of tensile strength which in this case is not terribly relevant,
Making a foil strong enough should not be a challenge go back to grade 12 physics and draw a free body diagram, the loads are laughable. Unless thin high aspect foils are being used.
His piece of wood with a single layer of glass was STRONG enough, it just wasn't STIFF enough
Until the difference between these 2 properties are understood this conversation is not going to be terribly relevant.
Strength, toughness, and stiffness. They are very different properties and not necessarily dependent on each other. through shape, material choice, and fiber orientations, they can all be altered (almost) independently. If you ever want to build something REALLY GOOD out of composites, take the time to understand all three.
Strength - How much can you yank on it until it breaks (Ultimate tensile and compressive strength)
Stiffness - How much does it flex when you yank on it with a given force (Modulus of Elasticity)
toughness - How easily does it break when you jump on it or smash it into something. (drop testing or impact testing ) oftentimes related to the area under the stress strain curve.