Youngs modulus of CFRP tank 1

[Zzelk]

Hi
I am trying to calculate the displacement of the top of a 14 m tall CFRP tank.
The manufacturer doesn't tell us what the Young's modulus of the material is. What is a reasonable range of values to assume?

I find conflicting information online. In the ASME-RTP-1 code, table 2A-3, it says it ranges from 0.7x10^6 psi to 1x10^6 psi (4.83 to 6.9 GPa) depending on the nominal thickness. However, I find values online that are 10 times that....
So its not clear.

Any suggestions?

 

[LittleInch]

A Carbon Fibre Reinforced Plastic tank?

If the vendor won't tell you then either test a piece. But why won't he tell you?

This sort if stuff is so vendor dependant you could find any number and you won't be any the wiser.

Or find the two extremes and plug that in to give you a range of values.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[r6155]

displacement for what? wind force or seismic?

Regards

 

[LittleInch]

My guess was for internal pressure.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[r6155]

Table 2A-3 is correct. See ASTM D 638 (my copy is 2008 edit.)

Regards

 

[EdClymer]

Zzelk

CFRP (carbon fibre reinforced plastic) is a combination of carbon fibre and resin - usually an epoxide (epoxy) - to form a laminate ie CFRP.

The Modulus of the laminate depends upon the percentage (by weight) of the fibres in the laminate and (hence) the percentage of resin (ditto).

More fibre and less resin will result in a higher modulus.

Carbon fibre may be combined with other fibres, and be of more than one form, ie woven fabric combined with uniaxial or strongly directional
fibres are common.

The Modulus is usually determined, by tensile testing of a sample (cut from a coupon) made at same time as the structural laminate (and cured
by same means of time and temperature: ie a laminate representing a specific part/point of the final structure. Or, it may be calculated/predicted -
provided the properties of the resin and the fibres making up the laminate at a specific part/point are known.

The original designer would have calculated the required Modulus for the specific application and it would be noted in the design calculations
(or, as we are now asked to call them - mathematical model!)

What displacement are you considering? Due to what - wind, liquid static head, internal or external pressure?

14 m is a tall structure - are you sure it is CFRP, and not glass fibre with black pigmented polyester resin?

Trust this is of some help.

Ed





Ed Clymer
Resinfab & Associates
England

 

[LittleInch]

Would be ingesting to know what asne rtp code is based on then?

How much can it vary in your experience?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdClymer]

I frequently consider that resins (polyester and epoxide) combined with some form of reinforcement (glass, kevlar, carbon etc) is rather like making a cake.

Better ingredients make better cakes: but tend to be more (or much more) expensive.

Using low grade resins, and poor quality reinforcements result in low strength (and Modulus) laminates.

These is now a very wide range of epoxide resins available for lamination (mostly with) carbon fibres, cloths, weaves and now nano tubes. Prices vary widely (but are still about x 3 on cost of kg/kg of polyester). As ingredients vary, so do accelerators, hardeners etc.

Resin manufacturers do make small castings of neat resin and (their choice of) hardener and test them for quality control purposes. Samples are post cured and then tensile tested to establish resin strength and Modulus.

This data is useless on its own, if the properties of a laminate (resin and reinforcement) are required.

As resin manufacturers do not know what reinforcement (or post cure) is to be used, they can't say what
the laminate properties will be. The only way to establish properties, is to make test coupons and from them cut the test pieces and then test.

At the least, the resin only values would be: tensile 70 -110 MPa (10,000 to 16,000 psi) - and for Modulus 2,000 - 4,000 MPa (290,000 to 580,000 psi) and all for non aerospace applications.

There are to many variables to be more precise; and the addition of reinforcement would radically change
the range of properties.

Not only is a 14 m structure (tank) going to be v expensive, but how was it post cured?

As to what Modulus to take for the actual item - quite impossible to say (only the designer would
have this information, and probably a minimum value).

Now if Zzelk could provide more information...

Again, trust this is helpful.

Ed



Ed Clymer
Resinfab & Associates
England