How to calculate total fibre area knowing other parameters

[ebarbero]

I am confused.

In the wizard, I entered the geometry (plain weave, yarn width, yarn spacing, gap, dry fabric thickness, no 10% added).

With Tools > Quick calculate Domain Volume Fraction = 0.477

If I don't select any yarn, Modeller>Assign Yarm Properties shows a window with space for 5 parameters.
If I select one or the 4 yarns, Modeller>Assign Yarm Properties shows a window with the same 5 parameters plus 12 material properties.
Which one should I use if I just want to calculate fibre volume fractions ?

I know the overall fibre volume fraction of the composite obtained from matrix acid digestion test, and the density of the fibre.
I do not know the fibre diameter or number of fibres per tow.
How can I calculate yarn properties, such as total fibre area, to enter in the wizard?

Is total fibre area the area of one tow or yarn? -- of which I have 4 in the domain.

Is Domain Volume Fraction = yarn volume / domain volume ?

Is Yarn Fibre Volume Fraction = fibre volume / yarn volume ?

[louisepb]

Hi,

There is a discussion about which properties are required in order to calculate the volume fraction in the thread here: http://texgen.sourceforge.net/phpBB3/vi ... tion#p6630

If you don't select any yarn then the Yarn Properties will be set for the whole textile. If you select one or more yarns, the properties will be set for those yarns.

Hope that helps,
Louise

[ebarbero]

Oops, I just posted the response in the wrong thread..sorry. here we go again.

I know the overall fibre volume fraction of the composite obtained from matrix acid digestion test, or burn-out test, and the density of the fibre.
I do not know the fibre diameter, number of fibres per tow, total fibre area, nor areal weight [kg/m^2].
All I can do is take the weight of a composite specimen, burn the matrix away and take the weight of the dry fabric (the matrix is gone). That gives me the fiber mass fraction.
The fiber is glass, of which I know the density. The matrix is epoxy, of which I know the density. With that I can convert mass fraction to volume fraction. What fibre volume fraction is this? none that Texgen uses, right?

Anyway, how can I calculate yarn properties, such as total fibre area, to enter in the Texgen wizard?

Is total fibre area the area of one tow or yarn? -- of which I have 4 in the domain.

Is Domain Volume Fraction = yarn volume / domain volume ?

Is Yarn Fibre Volume Fraction = fibre volume / yarn volume ?

[louisepb]

Hi,

The volume fraction that you have calculated should be equivalent to the domain volume fraction calculated by TexGen. This gives the volume fraction for whatever sized domain you have selected for your model, typically a unit cell.

Yes, yarn fibre volume fraction = fibre volume/yarn volume
Domain volume fraction is the volume of fibre in the yarns/domain volume. You therefore have to have yarn fibre data in order to calculate this. Normally you would get this data from the data sheet for the textile. If you don't have this then I can only suggest that you might be able to make an approximation from your burnout tests. If you know the mass of yarn in your sample and could make an approximation of the length of yarn in your sample you could get a fibre area for the yarns.

In the absence of data sheets, you basically need to work out how you can use the data that you have to give the inputs that TexGen uses to calculate volume fraction - as the other post said you need one of: fibre area for the yarn, yarn linear density and fibre density or fibre diameter and number of fibres per yarn.

Hope that helps,
Louise

[ebarbero]

Your response helps a lot, and I think I can use it, approximating the developed length of the yarn, yes, but still have doubts about what exactly is the "domain volume fraction" ?

The wizard calculated DVF 2 ways: quick and slow, without me entering any information about the yarns other than the geometry, and for my example (tg3 file attached) I get the same value DVF=0.477.
I just do Wizard > File > Open Texgen File > T91S1TFAzero.tg3
Then Tools > Calculate Domain Volume Fraction = 0.477

That is why I think that :

domain volume fraction = (yarn volume / domain volume), which is different from (fiber volume / domain volume)

The Wizard knows yarn volume & domain volume because it has the geometry but it does not have TFA.

Further if I select one yarn, or 2 or 3, or 4, then > Tools > Yarn Fibre Volume fraction = 0.0 as expected.

So my question is: what exactly is the "domain volume fraction" ?

[ebarbero]

Upon further trial/error research I have found the following:

1) If you don't ever give the wizard ANY yarn data, neither before selecting any yarn or after selecting yarns, then the Domain Volume Fraction (DVF) calculated by the Wizard using 2 methods is the mesoscale volume fraction defined as

MVF = yarn volume/domain volume (no information about fibers is available).

In my example MVF=0.477, and if you try to get the yarn fibre volume fraction it gives you Vf=0 as expected!
By the way the yarn fiber volume fraction is defined as

Vf = fiber volume / yarn volume

2) If you give the total fiber area (TFA, of one yarn) before selecting any yarn, the FibreAreaValue value is logged on line 3 of the .tg3 file but has NO EFFECT on Wizard's calculation of DVF! you still get the values as in #1 above.

3) If you give TFA after selecting all 4 yarns, regardless of whether you provide it before or not, then the Domain Volume Fraction (DVF) calculated by 2 methods is the overall volume fraction defined as

OVF = fiber volume / domain volume

which coincides with the value one can calculate from acid digestion ASTM standard.
In my case OVF=0.28, and Vf=0.588, biot calculated by the Wizard.

It is worth noting that the values are correct because they satisfy the universal relationship:

OVF = MVF * Vf = 0.477 * 0.588 = 0.28
(see eq. 9.7, pp. 3.11, and Table 9.1 Sample 1, in ISBN: 978-1-138-19680-3)

Maybe we can kindly suggest the developers to fix this issue, but anyway, now I know how to use it.

Thank you so much for all earlier responses that allowed me to reach this conclusion.

[louisepb]

Hi,

I am the developer and wrote these functions!
If you don't give any yarn data then a yarn volume fraction of 1 is assumed and, as you say the domain volume fraction is simply yarn volume/domain volume. You don't seem to have attached your tg3 file but I assume that your textile has constant cross-sections which is why the result will be the same for both calculation methods. The quick always assumes constant cross-section and the other will take into account changing cross-sections along the length of the yarn. (Hence no difference if the cross-section doesn't vary along the length).

If you don't select any yarns but then set the total fibre area this is set for the textile (as shown in the tg3 file) but not for individual yarns. The volume fraction calculations use the values for the yarns. Perhaps it needs changing so that if an overall TFA is set for the textile but none for individual yarns then this will be used for the calculation. I'll think about this.

Best wishes,
Louise

[ebarbero]

However, if you do not give any yarn data, select one or more yarns, then use Tools > Yarn Fiber Volume Fraction > a popup shows Vf=0.0; Should it show Vf=1.0?