spectra vs kevlar?

[sigurd]

So, I have compared the data we have collected so far about the fiber properties. Not much to go after, might as well throw a dice for column and one for row.
Are they talking about UTS (stress to failure) and tensile modulus of elasticity everybody?
Surprising that carbon has lower yield strength by an order of magnitude than S-glass.

Originally Posted by sigurd

So, I have compared the data we have collected so far about the fiber properties. Not much to go after, might as well throw a dice for column and one for row.
Are they talking about UTS (stress to failure) and tensile modulus of elasticity everybody?
Surprising that carbon has lower yield strength by an order of magnitude than S-glass.

Nice collection.Save money, you can throw the same dice for both decisions!!!
UTS, ultimate tensile stress, is stress to failure yes. Whereas modulus of elasticity, is the E- modul. The ability to carry loads of bending and compression.
PS what was it, you´re going to build?
Attachment: this laminate maybe what you want:
you know, there are coming 1 or two more, FINISHED!
Regards
Richard

[sigurd]

uh, think it was a boat...
looks like a nice program..
wonder why you put the carbon on the outside.. would it not be more vulnerable than glass?
biaxial 0' is the same as +-45' fiber direction right?

Originally Posted by sigurd

uh, think it was a boat... 1.
looks like a nice program.. 2.
wonder why you put the carbon on the outside.. would it not be more vulnerable than glass? 3.
biaxial 0' is the same as +-45' fiber direction right? 4.

Hello Sigurd,

1. no, really? And which sort of?
2. Yes it is
3. I see the laminate as a sandwich (just this example), so, hardest layer outside. And it made the most homogen layup. See graph above.
4. No, +- 45° is Bidiagonal. I used 0° Unidir. There are either +45°, or -45° Unidir., or Bidiagonal. available too. Example:

UNIDIREKTIONAL - GELEGE 0°
Unidirektional E-Glas Gelege 0°
BIDIREKTIONAL - GELEGE 0°90°
BIDIAGONAL - GELEGE ±45°
BIDIAGONAL - KOMPLEX - GELEGE ±45° + CSM
TRIAXIAL - GELEGE 0°±45°
QUADRAXIAL - GELEGE 0°±45°90°

If you would tell me wich sort of layup you are thinking of, I could run the calc. for you. To make it a reliable calculation, choose the material from R&G please, the program does not work with other products.

Regards
Richard

[sigurd]

I used 0° Unidir.

The pdf you sent says 90' bidirectional 310gsm glass. I figured it was +-45' because the graphs shows the best shear modulus in those directions?
It would also be more intuitive to me to put the glass in the same way as the sprectra, not the carbon, because of the compression strength.

I am going for a corecell laminate, at least for the most part.
I had figured that moduli and strength in tension and compression would be the limiting characteristics.
Looking at wikipedia, elastic modulus can be one of several moduli. I assume the one in the graphs, and the several tables above, are young's modulus: describing tensile elasticity. But you say it is for bending and compression.
The problem with R&G is they don't have wood veneer.
One could substitute corecell with their airex.
I think this should be a good place to start: The degrees signify fiber orientation. Outside first:
0' 600gsm wood
+-45' 150gsm dyneema plain weave (I haven't seen any dyneema in their webshop but you obviously have it in the program)
90' 100gsm carbon uni
4mm A600
45' 75gsm carbon uni
-45' 75gsm carbon uni
0',90' 150 gsm dyneema plain weave

A kiteboat. 6m long.

Originally Posted by sigurd

The pdf you sent says 90' bidirectional 310gsm glass.

A kiteboat. 6m long.

Hello Sigurd I´ll check that and try to calculate the layup, but have no data about the veneer at hand, can you provide some?

Regards
Richard

[sigurd]

Look at the last line in the table. It is snipped from http://www.fpl.fs.fed.us/documnts/fp...tr113/ch04.pdf
Thickness is 0.6mm.
I made the program work in excel.
A windsurf board with 0.6mm pine surface: http://www.star-board.com/viewpage.php?page_id=16

Originally Posted by sigurd

Look at the last line in the table. It is snipped from http://www.fpl.fs.fed.us/documnts/fp...tr113/ch04.pdf
Thickness is 0.6mm.
I made the program work in excel. Nice !
A windsurf board with 0.6mm pine surface: http://www.star-board.com/viewpage.php?page_id=16

Thanks, I have former source (the mech. properties of wood) on my Laptop, but had forgotten.
I wait in suspense what sort of layup you are going to design. Let me know here.

Regards
Richard

[sigurd]

I have come upon a great information well: http://www.sailboat-technology.com/l...e_articles.php
Currently reading the one about impact strength.
I think their conclusion about carbon being best in impact is rather surprising, although I am not well schooled on the subject. Later in the paper they seem to come to a different conclusion. I guess it depends on what is the first thing to fail, core or fiber. I bet with the harder cores like balsa, carbon will do relatively better on impact whereas the tougher fibers like S-glass may do better with corecell or airex?
I had wondered about replacing the 90' carbon with a somewhat heavier S-glass (or maybe h-glass), to match the elongation of the +-45' spectra and thus get a higher yield strength, and possibly better impact strength, but it supposedly fatigues more than carbon - has to be kept below 20% of yield vs carbon 60%. More on that in the link.
Just made some test strips with a yellow foam I have, not sure what it is, seems brittle.
May be ready for destruction tomorrow.
This here is 0' ipe, 90' 100gsm carbon, other side 0' 100gsm carbon and 90' makore.

Originally Posted by sigurd

Just made some test strips with a yellow foam I have, not sure what it is, seems brittle.
May be ready for destruction tomorrow.
This here is 0' ipe, 90' 100gsm carbon, other side 0' 100gsm carbon and 90' makore.

Let´s see what happens.
Why did you choose to lay the wood at 90° ?

[sigurd]

The first testing will be 3 point bending, a little, then turn sample, bend again, repeat until one of the sides fail. The 90' wood is because I did not want to help the 0' carbon on that side, to be more fair to the 0' ipe.
Outside of the impact testing it will have no effect I think.
I am pretty sure the ipe will fail in buckling before anything else - the 90' carbon under it is quite uneven.

I also made one with only 0' ipe and 0' makore on the other side.
And one with 0' 100gsm carbon one side and 0'/90' 4x100gsm plain weave glass on the other - 90' makore on both outsides.

edited glass weight.

understood.........
Regards
Richard

[sigurd]

I am sitting here destroying some pieces of laminate. Edit: now they are all trashed.

It is hand layed up epoxy and cured over night over an oven. The shopping bag stuck to the surfaces so is not a release film.
The test apparatus is a fine calibrated human made by Mom and Dad.
I can hear the core getting torn or its microbubbles collapsing with only a small deflection. Hope the corecell is a lot better. If anybody has any idea what this yellow foam could be please tell.

The glass is ridicolously soft even at 400gsm. Comparable to 230 gsm makore on denting resistance (protecting the core). I can press the laminate into the core with the thumb. The ipe can also be depressed but it is more difficult. The makore I can break by pushing it into the core but not the other two.

The wood/carbon samples can easily be pierced with a flathead screwdriver. It is "almost" not possible with the glass/wood and I can not do it with the plasma/wood except by aligning the driver so it slides between the uni fibers.

sample)

1) 0' 430gsm ipe, core, 0' 230gsm makore
seemed equally stiff either way.
makore buckled into the core.
tried to break it the other way afterwards, just got delam on the makore (tension) side. the samples are very short, and using only half the length of it (it was broken remember) would make this failure mode more likely.
thin layer of core left on the makore.

2) 90' 230gsm makore, 0' 100gsm carbon, core, 90' 100gsm carbon, 0' 430gsm ipe
seemed equally stiff either way. seemed to start buckling like 3) on both sides but I moved my thumbs apart to not excacerbate the buckling. ipe broke then in tension. Likely tensile properties of veneer is hugely affected by grain runout and other stuff. Afterwards, tried to break it the other way but got delam just like on 3)

3) 90' 230gsm makore, 0' 100gsm carbon, core, 0'/90' 4x100gsm glass plain weave, 90' 230gsm makore
seemed equally stiff each direction. Tried to avoid buckling by applying soft pressure over wide area with thumbs. Core sheared (?) and delaminated, not sure which came first.it just cracked, skins intact, the crack is in the middle between the thumbs and the fingers on the upper side of the sample. The delam is on the tension side.

4) 0' 230gsm makore, 0' 200gsm carbon, core, 0' 200gsm carbon, 0' 230gsm makore
delam/core shear

5) 0' 230gsm makore, 0' 200gsm carbon, core, 0' 200gsm plasma (enhanced spectra from puget sound rope), 0' 230gsm makore
delam/core shear

Originally Posted by sigurd

The test apparatus is a fine calibrated human made by Mom and Dad.
I doubt that! especially the ..fine...
I can hear the core getting torn or its microbubbles collapsing with only a small deflection. Hope the corecell is a lot better. If anybody has any idea what this yellow foam could be please tell.

most PU foam used in the construction industry is yellow with a brownish touch. Just rubbish.

If it´s simple assembly foam you used, you can assume to get much better results with corecell.
I wait until the test results are final.
R.
R.

[sigurd]

I'm pretty much done with them, there are only shrapnel left.
Both the ipe and the spectra results are encouraging except for the ipe tensile strength. I wanted to be able to relate it to carbon for strength in compression and tension (assumed I would need about 5-10 times heavier wood than carbon) as they should have a similar strain to failure (at least some species).
Now, the ipe will mostly be loaded on compression, being on the outside.
For the more global longitudal tensile loads, it is not so important whether the strength is on the inside or outside of the core, so the inner 0'/90' spectra will help (again, if I can get it). Also the bilge will get some more stuff on the outside of the core which can be longitudal.

Since I mostly got core failure the experiment was not hugely successful but it helped build a little bit of intuition regarding the materials.