Did My First Infusion With Soric Core.

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#1

Did my first infusion, heck, this is my first composite part ever. :slight_smile: It came out flawless. It is just a test sample for more complex parts that I need to make for a large 28.5" (725mm) mirror diameter telescope project. I just need a starting point as I am new to making CF parts. So this sample serves as a data point for me.

The layup I used is: (all CF)
204 gsm 4HS
3 layers 193 gsm uni (IM7)
810 gsm bi-axial
Soric 4mm
810 gsm bi-axial
3 layers 193 gsm uni (IM7)
204 gsm 4HS

Final thickness is 0.29" (7.36 mm)
Length is 24.25" (616 mm)
Width is 3.188" (81 mm)

Weight, with core, was 278 grams before resin.
Final weight is 383 grams after infusion.
That works out to be approx 46% resin content even with the 4mm soric core. Not too bad considering the Soric has a reputation as a resin sponge.

I have no print-thru on the face thus far. That may be due to the rather substantial amount of CF fabric on each face.

I did simple 3 point bending tests on this sample and find that in bending it is approx equivalent to aluminum of the same moment of inertia. Yet it is 2.5x lighter than that aluminum equivalent. I was hoping that it would be stiffer.

I need stiffer. In telescopes, the stiffness is the limiting consideration. Strength will never be the limiting factor. Stiffness is the ruling factor.

I guess the best way to do this will be by using thicker core material. What other core options do I have that work with infusion? I was thinking about trying Balsa, Divinycell H80, or Polyisocyanurate Foam, because they are available and on sale at Fiberglast. Would they work for infusion with some holes drilled and small channels cut in the faces? Any other suggestions would be welcome. Many of the parts to come are going to be complex and will need to have moulds created. Some parts I may need to use Soric for due to itā€™s ability to conform to a contour, others will be OK with a core that is just flat.

Any suggestions on changing my layup to gain stiffness? I understand uni will be the stiffest, and that is why I used 3 layers in the long axis, which is the axis that I was seeking to make the stiffest. I added the biaxial to give the sample some resistance to twisting, and the 4hs was just cosmetic on the surface. I can get intermediate modulus CF at a reasonable price, but going to a high modulus CF is just too expensive.

Thank you for your time and suggestions.

#2

very nice work. Looks good.

If you need stiffer, then you could use sandwhich construction. A thicker core will create much greatter stiffness. you could go with honeycomb core if your part will allow? What is the shape of the final part? Honeycomb and foam have limitations in how they curve. They can be machined into shape.

Or you can use carbon fiber stiffeners

I have a small test piece that was made using some very small stiffener plys on a thin skin laminate, and they make the piece amazingly rigid in one direction but flexible in the other. This material has many amazing properties.

Also you can use higher modulus materials. Switch to a unidirectional for lower resin content.

Havenā€™t you posted pictures of a recent project? I thought I remember seeing a sweet carbon telescope but, I dontā€™ know if it was yours?

#3

You will also find that adding shape (curvature) will increase the stiffness quite a bit

#4

Thank you for your response sammymatik.

 I am already using a core, the Soric.  I understand that using a thicker core is one way to increased stiffness. I was just looking for any tips that may help. I want to stay away from honeycomb and prefer to infuse entire sandwich all at once.  I am thinking of infusing a foam core with Soric (2mm) on each side of the core between the foam and carbon fiber.  That will add a little weight due to the Soric resin absorbtion, but it would allow infusion on cores that are normally not infusable, because the Soric acts like a flow media.

Yes, stiffeners are great. But at this point I would like to just incorporate them into the laminate and not secondary bond unless it is the only way.

Final part shapes are not fully developed yet. I have modeled the telescope in Autodesk Inventor, but that was with aluminum. CF is a different world and needs much redesign to make it work out. The final product will be an open truss assembly and not just a tube. It will probably be a hybrid of aluminum and CF, but I would like to use the CF wherever possible.

There are many parts of rather varied design. I did not post that telescope a few years ago. That was someone else. I have looked for high modulus CF, but the few sources I found provided it in narrow tapes and it was silly expensive.

#5

I see.

Yes the soric is great stuff. Theyā€™re are a few different varites to use as well. different thicknesses and it works great as an inter-laminar core/flow media. I remember doing some test panels a while back and it seemed that the version i used had a very low resin absorption; especially compared to some of the foams we were using.

Yes design for composites is much different. Iā€™ve also been working with 3d printing to try to make some structures without using molds and applying the carbon directly to the printed components. This way I can add geometry, like those stiffeners, with no secondary bonding. The printed ā€˜coreā€™ could be left in place or washed out depending on application. Iā€™m trying to apply some ideas to quadcopters at the moment, but it could be used in many applications.

Your project sounds interesting. Iā€™d say prepreg could make things easier but, itā€™s expensive and has itā€™s own caveats.

Can you show a picture of your design? Or is this a trade secret?

I havenā€™t had to find high modulus dry fiber, but surely it must be available.

something like this: http://www.hexcel.com/Resources/DataSheets/Carbon-Fiber-Data-Sheets/HM63_Aero.pdf

#6

I put together a quick and dirty mock up of the telescope to give myself some sense of size. I already have the optics for it, just waiting for a structure. I was going to use steel/aluminum as I have a machine shop and CNC/fabricating experience, but the properties of CF are way more desirable for a telescope. The low CTE combined with the excellent specific modulus make it very desirable. This is just a personal project, so there is no trade secretā€¦:slight_smile:
To give you a sense of size, the pink foam center ā€œringā€ is 39" (1 meter) across the flats.
I will post more pics as the project progresses.
Prepreg would be great, but the cost and handling issues put it out of reach.

#7

Look pretty cool, good luck!

#8

High modulus dry fibres are not a problem, you can get them.
For the sandwich material, take a look at 3DCore.

#9

Have you looked on Solar Composites for the high modulus fabric? They used to have it, though I canā€™t remember the price or its properties. Theyā€™re generally always quite well priced though.

#10

That looks pretty cool.

The CTE of carbon is definitely an advantage, especially when you go out in winter time and itā€™s freezing. Not to mention lugging around a big metal structure can get unwieldy.

That Design might lend well to some of the ideas Iā€™m working on. Iā€™m trying to develop a way to make similar types of truss like structures. I need to do more testing but my printer is currently under constructionā€¦ with a baby itā€™s hard to get anything done on my projects. :frowning:

Did you model this in cad already? How do the optics mount?

Looks like itā€™ll be an awesome piece when itā€™s finished!

#11

The best I could find at Soller was Hexcel IM7, which nowadays is called an intermediate modulus at 40 msi (276 GPa). I have purchased some IM7 Uni fabric from Composite Envisions and it is on sale for half the price of Soller. I think Composite Envisions purchased it surplus or from a company that went out of business. I might grab some more IM7 uni while they still have it.
Google has not taken me to any other sources that sell small quantities.

#12

I hear you about the baby. I first dreamed about building this project 20 years ago and then 4 kids came alongā€¦My youngest is now 7, so I am seeing a bit more time.

Here is the only all CF truss telescope that I know of. Other companies usually use CF just for the truss connecting tubes.
http://www.dreamscopes.com/pages/projects-04/newt-astro-16-ota-photos2.htm

My telescope will me more like this, but all CF where possible.
http://www.alluna-optics.com/products-newtonian-telescopes.html

Working on the CAD model. CF makes you rethink how everything has to be designed. As for the optics, they mount on a 18 point floatation cell. Google will provide you with some images.

Here is a picture of the back of my mirror. The 18 points are where it mounts. The mirror was cast by Dream Cellular out of borosilicate, then sent off to a master optician.
The front surface of the mirror is parabolic to an accuracy of several millionths of an inch. It cost me over $10k to have that surface produced. (ouch!)

#13

Looks like a great project! I I just skipped through the previous posts but also, what resin are you using? What was the cure schedule?

Also, I assume stiffness is axial stiffness primarily axially along the length of the telescope?
I would drop the heavy bi-axial for a start if it was me. I would also use a less absorbent core and maybe double the thickness. That should give you good stiffness characteristics.

#14

Fascinatingā€¦

this one looks particularly interesting to me from a manufacturing stand point. by using this sort of design it would be very economical to manufacture and with a cored structure it could be quite rigid indeed. Looks like the flotation sell is fastened to the bottom panel, but itā€™s hard to tell from the images. Itā€™s also hard to tell what sort of core, if any, is in this truss.

So youā€™re design looks to be more similar to the 2nd link. Youā€™d prefer to use tubing? Will the telescope be an assembly of smaller parts that are bonded or fastened together or one large monolithic piece?

Iā€™m curious to see what your design looks like in cad and how you are going to approach manufacturing it. Doing wet layup or infusion would be tricky on a shape like this. Again, prepreg allows for very complex parts with great control. I do have lots of prepreg, including himod uni, if you wanted to think about going down that route. Seems like something that will have a $10k mirror, would have an equally expensive body. I donā€™t know what these actually sell for; iā€™m sure theyā€™re not cheap.

and as for the kidsā€¦ 7 years before the kids leveled outā€¦ noooo! hahaha. i got 6 more to go then. :wink: Still I try to get a little done when I can. My new 3d printer is almost built, just down to wiring and calibration. Hopefully soon cause I have some ideas that I need to be working on.

Thanks for sharing your project, looking forward to see your progress.

#15

In looking at their website, they have some interesting info including videos on testing and test data
http://www.dreamscopes.com/pages/2010/composites_01.htm

also it appears that they make tubes with 1" core in making their tubes, which is a great way to increase stiffness. But it appears that they use ultra hi mod carbon in their parts as well.

also they give a price of $33kā€¦ http://www.dreamscopes.com/pages/projects-04/newt-astro-16.htm

#16

It is definitely cored. See pic below.

It has to be bonded, at least for me anyway. It would be way beyond my capability and means to make it monolithic.
The image below is what I am playing with. The splice plates are yellow to show where they are. All the main ā€œringā€ pieces can be quartered as they are all the same. I figured using secondary bonding with splice plates to create the entire rings for the top, center and bottom. I am working on figuring out what works and what is stiff enough, along with how to fabricate the parts to make it all work out.

Prepreg would be ideal. I just donā€™t think that it is in the cards. There is very little selection of prepreg available in small quantities.
Do you have a source for prepreg in small quantities?

Oh, and the optician cost $10k for his mirror work. The cast borosilicate mirror blank with machine work was almost another $10k. Add in the secondary mirror, the corrector lens and the mirror coatings and I am into the optics for about $30k.

Here is a commercial scope the size of mine that costs $200k:

These are popular with universities and other large institutions.

I need to get mine finished for FAR less because my money tree has died. :slight_smile:

My truss tube setup will be virtually identical.

#17

Unfortunately, that 16" telescope price does not scale linearly. It is an exponential price increase as the size gets larger.