Stress-Strain Curve of Structural Epoxy (type IV) 1

[khinz]

I've searched for over an hour in the internet for the stress-strain curve of type iv structural epoxy and can't find this. Anyone knows where to get them? I need them asap.

I need to know the portion in the curve where young's modulus (hooke's law) apply and what tests they did to derive the modulus of elasticity of such epoxy. Thanks.

 

[dhengr]

If anyone answers this OP, they ought to get their a$$ kicked.
khinz... call the supplier of the epoxy for this info.

 

[khinz]

The supplier of the epoxy said they only have data on the following:

2 part Structural Epoxy resin and hardener with polyamide with the following characteristics:
Compressive Strength Minimum 8,000-11,000 psi
Compressive Strength Maximum 11,000-12,000 psi
Tensile Strength 3,000 - 5,000 psi
Flexural Strenth 6,000-9,000 psi
Bond Strength (Slant Shear Test) 3,000-5,000 psi

They said they don't have the technology to measure the very micro strains and stress relationship since no one asks for the information. They only do the above tests. That is why I'm asking others if they have encounter an actual curve and this can only be done by high technology laboratory that not even the suppliers and factory have accessed to.

Therefore let those who know the answer not fear dhengr and give the information, lol

 

[Ron]

dhengr...can't resist reiterating your comment. Right on.

khinz...you obviously don't have the experience to be interpreting such spurious data off the internet. Each manufacturer's epoxy has proprietary formulation so there are few, if any, generalizations that can be made. dhengr is exactly correct. If the manufacturer can't give you that information then that should tell you a lot...unreliable info.

 

[IRstuff]

One generalization that you can make is that if the manufacturer does not have the data, run for the nearest exit. As in the case of two massive Space Shuttle disasters, just because a product or process has never failed, it does not mean that it can't or won't fail in a catastrophic fashion.

TTFN
faq731-376

Need help writing a question or understanding a reply? forum1529

 

[khinz]

Compressive strength tests of their products in the form of epoxy cubes are done and strength can reach up to 8,000 psi. But for a cylinder the height of 8 inches or 200mm. A strain of 0.0005 would be only 0.1mm and we don't have the machine to measure that micro strain versus stress in that accuracy. Where can they do tests like this as I can send the epoxy cubes to them? They said I'm the only person asking for stress-strain curve. But then maybe it needs technology not far from the Large Hadron Collider particle accelerator to determine it. Even SIKA doesn't have any stress-strain curve of their structural epoxy! Only compressive tests, tensile strength test, flexure strength and bond shear slant tests.

 

[Ron]

khinz...you are confusing yourself. The 0.0005 in/in of strain was the limiting factor used in your example in another post. That is not the strain one would expect in an epoxy stress-strain curve. You will get a lot more strain movement than you are projecting.

Any university with an engineering department likely could do the test for you. Many commercial labs in the US can do that test; however, I don't know the capability of the labs in your area.

 

[BAretired]

I agree with Ron. It should be possible to obtain stress vs. strain curves for the epoxy material.

Another important property would be resistance to elevated temperatures.

BA

 

[BAretired]

Is this the Sika product you are using?

BA

 

[msquared48]

I would not only consider elevated temperature onditions, but also colder environs with varying humidity also for both.

Mike McCann
MMC Engineering

 

[khinz]

Ron, I'm not limiting it to 0.0005 in/in of strain in epoxy. The reason I use 0.0005 is it's the elastic limit of concrete. Above 0.0005. Concrete is no longer elastic but plastic (permanent deformation). I'm assuming uniform strain for a cylinder with say half of concrete and half of epoxy fused together and compressed at a strain of 0.0005.I know epoxy elastic strain can go more than 0.0005, up to how large, I don't know.. that is the reason I'm interested in the stress strain curve of the epoxy to see its elastic range. Also BaRetired showed that in column with epoxy filling, there is bending moment induced so for every area of the layer, there is different strain of both epoxy and concrete with the compression edge the largest strain and the other side maybe in tension depending on the moment.

If you or anyone know of good laboratory in the U.S. and their web sites which can do any stress-strain curve for any material. Let me know. I'll send sample of the epoxy cube via DHL courier to them and make them produce the curve of the sample. The manufacturer is not interested in doing that because they said nobody asks for the curve except me. Most simply ask for the compressive strength rating and none asks for the modulus.

 

[Ron]

khinz...there are numerous labs that can do this. The following come to mind:

Wiss, Janney and Elstner in Chicago, Illinois, USA
R.J. Kenney in Boston, Massachusetts, USA
Simpson, Gumpertz and Heger in Boston, Massachusetts, USA
AMEC in Atlanta, Georgia, USA
exp Global, Brampton, Ontario, Canada

I have worked with each in some respect and all are professional, competent and capable. I'm sure there are numerous others who can do this and some of those listed have multiple offices with laboratory capability in various parts of the US, Canada and internationally.

 

[dicksewerrat]

Microlab in Denver, Colorado and Boyle consulting in Charlotte, NC. Haven't you ever seen third party tests? You never use the supplier tests,if they are done inhouse. If you really want to use this stuff, have the supplier set up the testing with a third party lab and have the LAB send you the results.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[BAretired]

Looking again at the Sikadur AG Grout, there are substantial differences in compressive strength between 15^oC (59^oF.) and 25^oC. (77^oF.) with higher values at the higher temperature. Who knows what happens at elevated temperatures which could be expected in a fire?

The Modulus of Elasticity is reported as 22GPa (3.2x10¹² psi). But 22GPa is 22,000MPa which is 3.19*10⁶ psi so something seems haywire with the reported numbers.

I agree with Richard. Independent tests are required to determine the properties of the fill material in the existing columns. Alternatively, it should be removed and a proper repair carried out.

BA

 

[khinz]

BA, the structural engineer told me he will only authorize any replacement of the epoxy after he sees the stress-strain curve because he believes that something with compressive strength of 11,000 psi should have large modulus and said the concrete relationship E=57,000 (sqrt(fc)) may hold for epoxy. So it will be weeks before I got the stress-strain curve of the sample to be sent to one of Ron's laboratory and he deciding what to do.

Meanwhile, the structural engineer said the reasons I must not worry about the short term effect of the epoxy is because the service load of the column can be taken merely by the bars in the column. The following illustrates the point.

Loads taken the column:

Dead load = 683 Kn
Superimposed Dead Load = 277.64 Kn
Live Load = 403.84

The Live Load has the load combination including earthquake and wind already.. something higher than even 1.4 DL + 1.7 LL, so the total of 683 + 277.64 + 403.84 = 1364 Kn includes all load combination already. Now the column has continuous bars from foundation to 2nd floor concrete roof with the following specs:

20 pc of 20mm bars = 20 x 314 mm^2 = 6280 mm^2 = 0.006280 m^2
fy=60,000 psi or 414 MPA so fy(As)= 414 MPA x 0.006280 = 2600 Kn. So the bars
alone are enough to take double the actual service load of 1364 Kn. Of course he is not saying bars are sufficient but with concrete around the bars and stirrups spaced at 80mm apart. Buckle won't occur and the column is very strong.

In other words, he overdesigns the building to take care of unexpected problems like this. You agree the bars are very strong??

After receiving the stress-strain curve and looking at the modulus.. that's when he would consider further repair plans and authorize the contractor to do it. Meanwhile. All I have to do is wait for the tests if I can successfully transfer the epoxy cube to one of the international labs.

 

[BAretired]

khinz,
I see no reason to make any hasty decisions. If remedial measures can still be carried out after receipt of the test results then by all means wait for the test results, but if in the meantime, more load is added to the affected columns then the cost of repair will increase.

Please let us know the test results when you get them. And the best of luck with your project.

BA

 

[Ron]

E=57000(sqrt(f'c)) is an empirical relationship and is only valid for concrete. It has nothing to do with epoxy and should not be used as a relationship for epoxy. Most epoxies will have a modulus of about 1/10 to 1/5 that of concrete. The engineer is correct that the rebar will hold the concrete in the interim until test results are obtained...obviously it hasn't fallen yet.