Generally speaking, composites don't derive their strength from the resin, but the fabric. The exception is when the composite is loaded in a way that causes inter-laminar tension between the plies. To see this type of loading, take a stack of 15-20 sheets of paper and hold them in the shape of a 90 degree angle. Have the stack compact with no voids. Now open the angle up while holding the vertical and horizontal plies together. You will see voids (gaps) open up in the corner. In this case there is tension between the plies in the corner. Good design practices and proper configuration generally allow us to avoid this type of loading. When there is a tension fitting typ load, it better, for all practical purposes to use a metallic part in those cases.
You've been working on the ribs. The ribs aren't loaded in a way that causes this failure mode so I don't think it would be a big deal. Additionally, looking at the properties the Tg of the proposed substitute is a bit higher, which is good. I suspect that you have a units problem. I don't think there would be as much strength difference as your numbers suggesting. It would make sense that the strength of the resin infusion resin would be 65-73K psi, which would be 434 MPa, which would be much closer to the original material's properties of 313 MPa. They just aren't going to vary by a factor of 5! So, first thing is to check that out – I think there is a mistake. And, if I'm right, which there is about 99.9% chance I am, the new material would be better in every way and so a good substitute. Materials tend to get better and more advanced as time goes on. The Marske article was printed some time ago. It wouldn't be surprising at all to see better material available that when he first wrote it; pultrusions for one, resin for another.
Russell, where do you come up with the nonsense for your posts? Better to keep quiet and be thought a fool...
--- In
This email address is being protected from spambots. You need JavaScript enabled to view it., "Philip Lardner"
wrote:
>
> Ugh... my table didn't turn out as I'd hoped, so let's try again:
>
> Aeropoxy - PR2032/PH3665
>
>
>
> Viscosity (cps=mPa.s.): 925 - 975cps @ 25C
>
> Pot Life : 120mins
>
> Glass Transition Tg : 194F / 90C
>
> Cured Hardness : 87 Shore D
>
> Tensile Strength : 45,870psi (=316MN/m2)
>
>
>
> Easy Composites - IN2-Infusion Resin
>
>
> Viscosity (cps=mPa.s.): 225mPa.s. @ 25C
>
> Pot Life : 80-100mins
>
> Glass Transition Tg : 201-212F / 94-100C
>
> Cured Hardness : 84.5 - 88.5 Shore D
>
> Tensile Strength : 65.5 - 73.5 MN/m2
>
>
> Phil. 