[ckelloug]

Geof et. al,

I hit the library today and pulled ASTM D695 which is the offical test for compressive modulus and strength. This test specifies crushing a .5 x .5 x 2 inch specimen in a press and recording the force. It also specifies doing the test on 5 identical samples. ASTM D695 references this interesting document from the world war II era at NASA http://ntrs.nasa.gov/archive/nasa/ca...1993090554.pdf

I believe that you are suggesting testing a small beam. The equation for deflection at the center of the beam you described is FL^3/(48EI). For a .5 x .5 in. square ASTM specimen has I=h^4/12=.00521.

Unfortunately, the Epoxy Granite composite has different moduli in compression and tension unlike steel so a beam bending test will give you more of an average between the values than the compression value for E/G.

As for yugami's suggestion: If the pressure gage on a press is remotely accurate then that pretty much solves the problem. I was originally thinking from the perspective of how to do the gaging at minimal cost starting from the position of having nothing but a dial indicator.

Measuring the pressure with the gage and the deflection with a dial test indicator and plotting the results would work fine and probably represents the lowest cost home shop solution.

Martin,

You are dead right about the ACME screws as they are the way that the old style presses created their force. I seem to be missing something however because the actual force applied by the press is related to the deflection and young's modulus of the item being squished. Thus crushing a steel bar and then crushing the E/G bar seems unlikely to me to tell you anything about the pressure on the E/G bar.

Hmm. :idea:
If you placed the specimen on a simply supported bar that would deflect by a few thousandths at max force and crushed the whole thing in the press keeping track of the deflection of this member with a dial gage then you'd have a jury rigged strain gage sitting under the specimen and have something although you would want to make damn sure that you measured everything really carefully. The h^4 term in the moment and L^3 term in the deflection mean that the beam is sensitive to conditions.

It seems that without some kind of pressure measurement system, all you can measure is displacement with the acme screws unless you turn them with a torque wrench so you can figure out what the torque was and thus what the current stress is. I think the problem of relating acme screw torque to force is harder than the one we set out to solve but it's probably due to my own limited experience.

Finally, using brunog's numbers for compressive strength from the NIST report, it looks like pressure at failure is about 21ksi leading to about 5000lbf required on the press to fracture the ASTM specimen.

P.S. I learned some other interesting stuff in the library today about small particle reinforcement, but I'll leave everybody in suspense until I have some hard data in a day or two.

[Geof]

Geof et. al,.....

I believe that you are suggesting testing a small beam.....

No. Read through my Post again, then read Martin's Post and my reply to his Post.

I am suggesting a way to use a beam with known properties to calibrate your press.

Rarely does the hydraulic pressure gauge on a press give you any reliable indication of the force exerted by the press.

I am simply describing a way to calibrate the press.

Then you know at what load your sample crumbles.

[ckelloug]

Geof,

Thanks for pointing out my misunderstanding. You're right. Rereading your post and Martin's , If there is no load on an ideal press then an ideal pressure gage would read zero until you contact something because you aren't doing work until you are applying a force. Likewise, you're not doing work on an ideal screw press until you contact something.

As you start to compress the object in the press, increasing pressure or torque will be required to do the work of creating a displacement of the beam. If you correlate the pressure on the gage or the torque on the torque wrench with the displacement in the small test beam, then you know the applied force and that will be true the next time the gage reading or torque wrench has the same reading.

I now see that doing that at enough points would produce a rather serviceable calibration.

That's really cool.

[lgalla]

Cameron quote:
"P.S. I learned some other interesting stuff in the library today about small particle reinforcement, but I'll leave everybody in suspense until I have some hard data in a day or two."
Mork from planet Ork says NA-NU Na-NU.
Nano particulate re-Inforce-Cement?
Cameron Thanks for all the reaserch
Larry

[VoxLimbo]

Can you provide a bibiography with source ranking so we can duplicate your research?

Cameron quote:
"P.S. I learned some other interesting stuff in the library today about small particle reinforcement, but I'll leave everybody in suspense until I have some hard data in a day or two."
Mork from planet Ork says NA-NU Na-NU.
Nano particulate re-Inforce-Cement?
Cameron Thanks for all the reaserch
Larry

[garfieldsimons]

Just bought a used 6" x3 x 4 foot granite surface plate ($50) and could of had 3 more. The second hand market for surface plates is apparently not so good. (Who wants to move 1500 lbs of stone.) I would use these instead of going to the expense of epoxy for any thing big. (Of course I am also a cheap SOB)
Richard

[VoxLimbo]

Just bought a used 6" x3 x 4 foot granite surface plate ($50) and could of had 3 more. The second hand market for surface plates is apparently not so good. (Who wants to move 1500 lbs of stone.) I would use these instead of going to the expense of epoxy for any thing big. (Of course I am also a cheap SOB)
Richard

This raises the question of: How can we dispose of an obsolete polymer concrete system? What is required to break it into small enough pieces to remove from your basement?

Albion.

[lgalla]

Here is a few pics Atenman1 requested.Sorry Calvin for the long delay.
Larry

[walter]

Now that's a speaker system!

[ckelloug]

Here is the info I alluded to yesterday but waited to disclose until I had the price and talked to the company along with the bibliography of sources I've used lately.

The information I found on small particles involved strengthening epoxy with particles much smaller than silica fume aka 20nm particles. The particles are so small that unlike carbon black or silica fume, they <B>DO NOT</B> cause an increase in viscosity!

Nanoparticles provide better fracture toughness, better compressive/tensile modulus by a factor of 100 in some cases, lower shrinkage, lower coefficient of thermal expansion, less heat distortion and better surface finish and abrasion resistance. These SiO2 nanoparticles come wetted in epoxy so there is no problem with mixing or agglomeration.

These SiO2 particles are made by Nanoresins, a spinoff of Hanse-Chemie in Germany. They cost 25$ to 35$ dollars a pound and are added in quantities of no more than 10% by weight. The URL of the company is www.nanoresins.com. I have attached to this post the datasheet sent to me by the leader of the U.S. operation, Dr. Oliver Pyrlik, Technical Sales Director Nanocomposites, hanse chemie USA inc. They have graciously offered me some samples which I may accept when I can deal with them.

I may have confused some people by saying hard data in my last post but what I meant is that I wanted to find the price and talk to the company before raising hopes here. I haven't done any lab work and can't until I stop sitting here posting and go finish building my shop

I am approaching this problem with the idea of working smarter, not harder. I'm thinking that if we design our epoxy mix to use safe additives and admixtures and the smallest practical aggregates for the strength needed then we will likely produce parts with a nicer finish than even the commercially built machines while requiring a minimum of work. Judging by Walter's results from the composite made with just sand, it sounds like it might be reasonably easy to come up with a viable composite without huge aggregates.

<h4>Bibliography of materials I have used in my posts:</h4>

Materials Science and Engineering An Introduction
Third Edition
William D. Callister Jr.
John Wiley & Sons, Inc.
Copyright 1994
ISBN 0-471-58128-3

This is the book whose chapter 17 got me thinking about small particle reinforcement. The technique is still so cutting edge that there is little data 13 years after this book was published.

Introduction to Mechanics of Solids
Egor P. Popov
Prentice Hall
Englewood Cliffs, NJ
Copyright 1968

This book is out of print but a xerox authorized by the publisher surved as the text for most of my engineering mechanics class some years ago. I found a used copy of the book at Powells books in Portland. I've been using chapter 13 to study the process of working out deflections with Lagrangian methods using techniques like Castigliano's Theorem.

ASTM Standard D695
Standard Test Method for Compressive Properties of Rigid Plastics
Annual Book of ASTM Standards 1985 edition

This is the ASTM standard for doing compressive tests of reinforced plastics. I have used it as guidance in my quest for an improvised testing machine to determine the properties of our materials.

Polymer Composites from Nano to Macro Scale
Frederich Klaus
Springer
Copyright 1995
ISBN 0-387-24176-0

This is the book that led me to the above discussion on 20nm sol-gel silica reinforced epoxy as mentioned above. Most of the book is about unrelated things but the 10 or so pages starting from pg 92 were fascinating and said such things like "100 fold increase in modulus" with the introduction of the nano-particles. They pointed out using cure temperatures of up to 200 C. They also listed the use of CAA, Cobalt Acetylacetonate from Sachem Chemicals, and N,N Dimethyl Benzamine as catalysts in addition to the epoxy's normal hardener in the 1% to 1.5% by weight range and indicated approximately 5% strength improvements for the CAA. CAA is even safe!

Marks Standard Handbook for Mechanical Engineers
1987 Edition
McGraw Hill Inc.

I've used this for looking up things like moments and Accepted young's moduli and other misc data for back of the envelope calculations.

[walter]

Thanks Cameron, much appreciated.

I'm working on my own Quartz Formula and I'd be happy to test your nanosand.

Now here's the thing .. I think I've got the "Sand" part covered. I'm all sand. Quartz is 7 on Mohs scale and I fully intend to utilize that.

Now what about the "Epoxy" part? Are we getting the max performance?

Zanite guys advertise their epoxy as "specially-formulated-high-strength-epoxy".

I wonder how high-strength is our epoxy...

Larry?

[ckelloug]

Hi Walter et. al

I called US Composites today and they told me that their low viscosity slow curing epoxy is Reichhold 37-606. Since this is the hardener and the specs are given for an epoxy on page 3 of the data sheet, one would assume that Reichhold 37-140 is the epoxy corresponding to US Composites 63556x series epoxy where I use the x to deisignate the part number changes due to different sized containers.

This epoxy doesn't look like anything special. Data sheet is attached.

[romihs]

Ckelloug,

Thanks for joining this thread. Your input and expertise are invaluable!

Really good information you posted there.

Thanks

Best Regards

Sandi

[eloid]

[QUOTE=ckelloug;288983]Eloid,

I'm the thread's newest participant but the idea is to use epoxy as the matrix to bind granite particles. It's called concrete because it has a matrix with embedded stones but in the discussion on this tread the stones are embedded in epoxy, not portland cement.[/QUOT

I was interested in portant cemment for another other an this project not really related to polymer frames , but was hoping someone has used resin with portland cement.

[romihs]

Ckelloug,

I had published the spec of the resin + hardener I am using, 3 or 4 days back.
I was wondering if you could take a quick look at it and tell me what you think of its properties....
Here is its data sheet. I don't understand the properties if it at all.
I am using the the 294 hardener.

Thanks in advance.

Regards

Sandi

[ckelloug]

Sandi,

I looked at your epoxy the other day but until getting the Reichhold formulation, I wasn't really sure what to compare it to. Comparing the fluxral modulus of yours vs. the Reichhold stuff, your R&G epoxy is 2730MPa while the Reichhold stuff has flexural modulus of 4900MPa. Given all things equal, your epoxy will deflect about 30% more that the stuff Walter et. al are using when formed into a beam. The viscosity of your R&G epoxy is 1600 cps while the epoxy from Reichhold is only 600 cps, (I assume the epoxy is similar to the hardener but may be wrong). An cps (centipoise) is equal to an mPas which is a milli-Pascal second. From wikipedia water is 1 centipoise in viscosity while motor oil is 250 cps in viscosity.

I believe your epoxy is about 3 times as viscous as the stuff from Reichhold and it also seems to be much faster curing. They show the R&G stuff being cured overnight at room temperature and 10h at 70C. The Reichhold data sheet shows theirs being cured overnight at room temperature and 2 hours at 120C or 7 days at room temperature.

A 4 inch square beam 48 inches long made from your epoxy cured according to the data sheet with a 100 lb load placed in the middle would deflect .027 inches while the epoxy Walter is using would deflection .022 inches. This does not reflect the addition of aggregate or particles.

In short, your epoxy is more viscous and faster curing with slightly lower strength than the stuff Walter et. al. are using. There is no reason however that you can't make serviceable parts with it, it may just require different processing to avoid air bubbles, slightly larger members to avoid deflection and perhaps slightly different aggregate design. Unless you are engineering your stuff to really tight tolerances all this is to say the difference probably won't matter except in ease of mixing.

I am very very far from expert at this, but I hope this helps.

[walter]

I am approaching this problem with the idea of working smarter, not harder. I'm thinking that if we design our epoxy mix to use safe additives and admixtures and the smallest practical aggregates for the strength needed then we will likely produce parts with a nicer finish than even the commercially built machines while requiring a minimum of work.

In another words, a home brewed Quartz-Epoxy composite that can rival a commercial unit!

That would certainly push the envelope and introduce new dimensions of performance here on the Zone..

I see two separate solutions:

1. super-low-cost, easy to use E/G filler for weldments/machine bases; ( no problem- we already have that)

2. higher priced option for high performance E/Q machine tools!
(we can have it in 6 months)

I guess that was the original plan, look at the interest (and great feedback) it's getting...

But Are we up to the challenge?
_

[lgalla]

Quote:
This raises the question of: How can we dispose of an obsolete polymer concrete system? What is required to break it into small enough pieces to remove from your basement?Albion
TNT?

[ckelloug]

Friends, (fyffe in particular),

I've finally gotten done a small java applet that solves the deflection at the center of a beam without shear for any of the parameters FL^3/48EI. It's just a nice gui on some trivial algebra. Given Fyffe's spreadsheet for the moment of inertia calculations, one can use this to do the calculations tweaking parameters and seeing what happens. I had planned to add automatic moment of inertia for common shapes and a table of young's modulus's to it but I haven't yet and wanted to see if anybody had feedback.

If you have the latest version of java installed in your web browser, it should work for you. Instructions are to download the zip file and unpack it on your harddrive. Then open Beamer.html in a web browser and barring unfortunate circumstances, the java applet should load and work. I've tested this on Suse Linux 10.2 with firefox 2.0.

Finally, feel free to PM me with comments about how badly I write Java or other comments. I think it's literally the 15th programming language I've had to use in the past year and as a result, I can't seem to find a good way to implement anything in any language now. Why I am learning another programming language while I am on sabbatical is beyond me. . .

:cheers:

[brunog]

Quote:
This raises the question of: How can we dispose of an obsolete polymer concrete system? What is required to break it into small enough pieces to remove from your basement?Albion
TNT?

Sell the house!