Carbon Fibre Reinforced Plastics (CFRP)

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atif
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Joined: 30 Jun 2011, 19:14

Carbon Fibre Reinforced Plastics (CFRP)

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Hi Guys,
I am doing a project on CFRP under Tensile Loading conditions. The purpose of this test is to find out the Young's Modulus. I am giving a load of 4KN to a sample of 120mm Long,20mm Wide and 10mm thick and I am getting appox 8 GPA, which is no where near to what I am expecting. From the previous study I found out that the Young's Modulus of CFRP is about 125 GPA but my results are no where near it. I am unable to found any published article or paper which gives the correct Young's modulus of CFRP. It would be highly appreciated for your help.

Many Thanks

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flynfrog
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Joined: 23 Mar 2006, 22:31

Re: Carbon Fibre Reinforced Plastics (CFRP)

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what you are saying is like saying that you want to find the Youngs of metal. There are millions of carbon resin combinations all will be different.

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PlatinumZealot
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Joined: 12 Jun 2008, 03:45

Re: Carbon Fibre Reinforced Plastics (CFRP)

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Atif. I think you will only get a consistent value if you test the actual fibres themselves. But when they fibres are put in the resin they are not aligned perfectly straight so you don't get a direct loading along their axis. So you are testing a carbon fibre spring instead of a carbon fibre.

I think to test the whole composite itself, the fibre + the resin, Is like testing concrete, there are so many combinations there is no standard value for all types.
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speedrcr
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Joined: 13 Jan 2005, 21:58
Location: Greensboro
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Re: Carbon Fibre Reinforced Plastics (CFRP)

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Greetings, a few answers...perhaps.

Regarding the modulus of the coupon. It depends on the stacking sequence of the laminate. If this was a tensile only coupon, with all 0 degree tape plies, using "standard" intermediate modulus graphite, then the stiffness will be around 16-18 Msi. If it is plain weave cloth, then the stiffness will be 8-9 Msi. Now, when you test an actual laminate say [45/0]2s, of cloth, the axial modulus of the laminate will be much lower, in the 6-8 Msi range. Again, it really depends on the material and stacking sequence.

You can find a lot of public information on different graphite material at the following sites. Note that this is from an FAA database which is used in some aircraft certification programs. Your results may differ slightly depending on how the coupons were processed.

http://www.niar.twsu.edu/agate/Documents/default.htm

http://www.niar.twsu.edu/agate/Documents/default.htm

You can also find lamina data from the manufacturer (Toray/Hexcel/Cytect/etc)

One other thing to remember is that matrix (resin) dominated properties will be much more sensitive to the test environment. The temperature and humidity must be controlled in order to get meaningful results. This is less of an issue with the testing you are doing, but once you start testing for strength, the difference can be large ~30% for OHC (open hole compression strength)

Hope this helps.

Erik

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