the laminator

[Gionata]

hello to all, I am new to the forum and I wanted to open this discussion that I believe it is useful to the many who like me are not ingenious, but want to try, unpretentious, but only to have some extra ideas, on the dimensions and structural calculation in composite materials.
the request is to bring our experiences on the use of the laminator, an economic but powerful program on the calculation of the mechanical characteristics of a laminate starting from the characteristics of the individual skins.
Is that possible? Does anyone want to help me?
I sharpened today a linear fem program and I would like to put the data that gives me the laminator considering a composite hand impregnated isotropico (to begin with).
Thank you all.

 

[Onda]

Hello,
If you explain what you need, maybe we can help.
laminator is a very simple program, which through the classic lamination theory provides the apparent elastic modules of a laminate in functions of its lamines.
you must then enter the data of the base foil, the lamination sequence, and get the laminate data.
within the software you already find basic material features, with which you can work.
be careful to use congruent measuring units, the system does not control them.
I personally use these units:
thickness mm
elastic module n/mm^2 (mpa)
resistance n/mm^2 (mpa)
I never use expansion coefficients.
If you use the materials of the base library being the elastic modules in pa (n/m^2) you must insert the thickness of the blades in m, so a single skin has thickness of 0.0003m (0.3mm for example) not very comfortable! !
the reverse happens for pascals, where an elastic module is expressed in 10^11.
instead using the mpa and the mm numbers become more manageable.
the thicknesses become with a single decimal, and the elastic modules are in the order of 10^5 (100.000mpa) and therefore it is easier to avoid errors.

 

[Gionata]

Thanks, it's already a good help.
It's simple, but complicated at the same time. For example:
asks you a lot of parameters, my supplier provided me(for carbon) only strength and elastic module.
should resin be considered as distinct material?
how does the orientation of the skin fit?
Do you have to enter the forces applied to the foil?
Thank you very much.

 

[Onda]

if you go to the micromechanics tab you can insert the characteristics of resin, fiber, impregnation percentage.
the program calculates the characteristics of the laminate using the rules of proportions.
I beg you to follow this path, it is, in my opinion, only theoretical.

The best thing would be to have test properties.
Of course this is impossible. you should at least say what type of construction you expect.
prepreg, vacuum, wet, infusion.
What resin do you use? Epoxy? Vinyl?
What's the end of your job? nautical, consumer goods, sports equipment?

If you clarify this information, it's easier to help.

 

[Gionata]

Thank you very much for your help.
I realize limb tutors for people with neuromuscular deficits.
are mainly shell foils that wrap the limb.
are usually isotropic (although some unidirectional along the direction of efforts I put it).
is a hand impregnated laminate and then vacuumed, with the use of epoxy resins of the thickness of about 3mm average.

 

[Onda]

If you send me your mail in mp, I'll send you some references.
wave

 

[Gionata]

Unfortunately, I don't come out.
in the program I sleep a mountain of fields to insert, and I do not understand where and how to insert parameters.
could help photos of the various tables (materials, strenght, layup...) with the values (maybe the ones useful to my case) inserted in the correct way.
Thank you very much.

 

[Gionata]

I bought femdesign and asks me the following parameters to customize the material:
young module (n/mm2)
poissons ratio
expansion coeff.
Mass density.
this in the case of an isotropic material.
Can anyone help me?

 

[gerod]

What's the question?
help you insert values?
you need to know the type of material before.
There are millions of sites on the network where the values you require.

 

[Gionata]

no matter what, I will use the wave table as an indication.
Thank you

 

[listastudio]

I bought femdesign and asks me the following parameters to customize the material:
young module (n/mm2)
poissons ratio
expansion coeff.
Mass density.
this in the case of an isotropic material.
Can anyone help me?

when you open the window of femdesigner materials, go to "use standard material" as in the attached image and next to the "no" option you will find the triangle that opens the library of standard materials loaded with the basic version of femdesigner. Let me know if in the basic course http://www.lista.it/alibre/tutorials.html This point should not be clear. find some other common material in the material database in http://www.femdesigner.it/getting_started.html , the others....just answer them in literature and add them either with the window prompt (in attached figure) or by compiling a file as in the specified material database. Bye!

 

[Gionata]

thank you again, but my problem is that I have to use a hand impregnated carbon laminate, and then everything changes.
There are no preset parameters and I have to find them.
to simplify my life I wanted to consider an isotropic laminate as the skins will be equally distributed. That's why I wanted to use the laminator.

 

[Onda]

you can make a fem considering the homogeneous composite material isotropic, but you must respect some limitations:
laminate must be balanced (with the same amount of fiber at 0 and 90°) and symmetrical with respect to a neutral axis. (The fibers you put outside must be the same as you put inside).
do your laminate with laminator and revenues apparent properties (ex=ey) because balanced. You have no extravagant behavior because symmetrical.
then from laminator take the elastic module, the cutting module and the polka dot coefficient to insert these values into your fem program.
Obviously for more complex laminates (balanced) you need a fem program where you can insert orthotropic materials. I don't know if what you took has this option

 

[Gionata]

perfect, and here we are, and back to the problem bomb, insert the correct parameters in the laminator.
I don't know how and what to insert.
for this first I said I preferred to take the values that kindly wave provided me.

 

[listastudio]

caro gionata, per la parte "the laminator" debbo passare la parola a onda, mentre per costruire il file dei dati del materiale in femdesigner ti allego il template relativo, ciao!

femdesigner material properties template

mechanical

in femdesigner, material properties are specified in simple text files, following the easy-to-understand format shown here. you can edit the material files provided with femdesigner, or you can create your own customized materials to use in your analyses. individual mechanical material files are stored as plain text files (*.txt) in this default location:

c:\program files\femdesigner\femdes\materials\mechanical

*** material properties supplied with femdesigner are for reference only and are generalized values not intended for design. the user must insure that all material property values being used for analysis are accurate for his or her purposes. ***

for the length units specified [in brackets] on line 1, the corresponding material property units are listed [in brackets] following the material property variable below. it is *critical* for accurate analysis that the material properties below are specified in units corresponding to the length units given in line 1.

text following a semicolon ( is comment text, except for line 1, where it is the material id, and will be used as the material label when assigned to a femdesigner part.

e2, g2, phi, and cte2 are used to specify orthotropic material properties.
please see diagram provided in help for a graphical description of orthotropic material properties and orientation.

mechanical material file generalized layout:


material units [m, mm, in] ;<material id=""> (id required - will be
; displayed in femdesigner)
e </material>[Pa, MPa, psi] ;young's modulus for isotropic materials, or
;for direction 1 in orthotropic materials
nu [no units] ;fish's ratio
cte [1/°C, 1/°C, 1/°F] ;coefficient of thermal expansion
rho [kg/m^3, kg/mm^3, lbf/in^3] ;density
t [m, mm, in] ;plate thickness
e2 [Pa, MPa, psi] ;young's modulus in direction 2 for orthotropic
g2 [Pa, MPa, psi] ;shear modulus in direction 2 for orthotropic
phi [degrees] ;angle between direction 1 and global x-axis
cte2 [ 1/°C, 1/°C, 1/°F] ;cte in direction 2
y [Pa, MPa, psi] ;yield stress, tension
uts [Pa, MPa, psi] ; last tensile strength
I [Pa, MPa, psi] ; endurance limit
c [Pa, MPa, psi] ;yield stress, compression

example - aluminum alloy 7075 with a t6 temper:

in ;al 7075-t6
10400000 ;young's modulus (psi)
0.33 ;poisson's ratio
0.000013 ;coefficient of thermal expansion (in/in°f)
0.102 ;density (lbf/in3)
0 ;plate thickness (inches)
0 ;e2 (young's modulus in direction 2, psi)
0 ;g2 (shear modulus in direction 2, psi)
0 ;phi (angle between direction 1 and global x-axis, degrees)
0 ;cte2 (cte in direction 2, in/in°f)
73000 ;yield stress (psi, tension)
83000 ;ultimate tensile strength (psi)
0 ;l (endurance limit, psi)
0 ;yield stress (psi, compression)

 

[Onda]

perfect, and here we are, and back to the problem bomb, insert the correct parameters in the laminator.
I don't know how and what to insert.
for this first I said I preferred to take the values that kindly wave provided me.

I honestly don't understand your problem.
you have the properties of individual blades.
define a laminate, for example:

rc300 @0
uc300@0
xc400@+45
uc300@90
symmetrical

insert data in laminator and revenues the apparent elastic modules.
take this data and enter it into the fem program.
now, if the fem only accepts homogeneous isotropic materials you must have that ex=ey
otherwise you can use an unbalanced laminate, but I recommend you always maintain symmetry, to avoid complex flexional effects that are not easily predictable

 

[Gionata]

My problem is to insert the parameters into the laminator.
there are several cards, one for the characteristics of the material, one for the forces, one for the layups, one called micromechanics.
It is not easy to understand that data enter, with which unit of measurement, with which wording (in the default entries there are other characters beyond numbers for example 1392e + 005).
I'm sorry, I've definitely landed in a bigger business than I am, but at this point it's a matter of principle!

Moreover another problem, if I use a fem that analyzes a solid with its walls thicknesses, how do you reconcile with laminator that already gives you values considering the thickness of the laminate?

 

[Onda]

My problem is to insert the parameters into the laminator.
there are several cards, one for the characteristics of the material, one for the forces, one for the layups, one called micromechanics.
It is not easy to understand that data enter, with which unit of measurement, with which wording (in the default entries there are other characters beyond numbers for example 1392e + 005).
I'm sorry, I've definitely landed in a bigger business than I am, but at this point it's a matter of principle!

in the material characteristics tab you put the material in use.
for example, by inventing me the values of healthy plant: for a unidirectional carbon of 300gr laminated in wet (attention I go to memory and therefore the values are indicative)
e1=ex=110000mpa (module elastic fibre direction)
e2=ey=5000mpa(module elastic normal direction to fibers)
g12=gxy=3000mpa
ni12=nixy=0.3 (adimensional)
cte1=cte2=cme1=cme2=0 (they are thermal and hygroscopic expansion coefficients, to be neglected for analysis that does not take into account these loads)

Steps to Resistance Card (strenght)
xt=1100mpa (traction resistance of fibres)
xc=800mpa (compression resistance direction of fibers)
yt=50mpa (traction resistance normal direction to fibers)
yc=80mpa (traction resistance normal direction to fibers)
s=50mpa (cut resistance in the top, not to be confused with the cut interlaminare ilss)

Steps to the layup tab
set the layer number (always equal because your laminate is always symmetrical!!)
impose symmetric laminate tick
under matid put number 1 because you have only one material, if you have more materials, put the code of the material used see previous cards.
under ply angle insert the angle with which the material is placed regarding the reference direction, expressed in degrees
under thickness insert thickness in mm, having used the modules in mpa that equal to newton/mm^2 in our case about 0.33mm

pass now to the loads card, perhaps the least intuitive of all
your loads are mechanical loads, so the thermal and moisture (humidity, leave them without tipping).
insert forces and moments, not deformations (inserting deformations means imposing a shift to the laminate and going to establish which tension state corresponds to the imposed shift)
Now we need to pay attention to the forces' measuring units.
As we are using mm and mpa as a measuring unit, the forces we have to introduce are in n/mm.
This is because our laminate has a defined thickness and an indefinite width.
I try to explain myself better.
I make a practical example: We imagine we want to study a nearly isotropic carbon strip with 8 layers (0;-45;45;90/sym), 100mm wide. I want to apply a compression load to the 1000n strip (about 100kg).
then the load value to be inserted in the nx will be of (-1000n/100mm)=-10n/mm. (the negative for the compression load).
the same applies to normal loads to the main direction, for cutting ones.
flender moments apply instead in n*mm/mm (for which they are dimensionally n!).

In any case, to insert the properties into a fem program the loads do not serve, as they serve the elastic modules.

to evaluate the resistance of the material, we will make another chapter, because a quite complex speech opens.
You should understand first of all the goals you are looking for with your analysis. .

Moreover another problem, if I use a fem that analyzes a solid with its walls thicknesses, how do you reconcile with laminator that already gives you values considering the thickness of the laminate?

studying composites with solid elements is not trivial. Everything else! !
The first problem is to correctly define property orientation. the second is to correctly represent the thicknesses.
My advice is, leave it alone for the moment.
composites are studied with shells and, in particular cases, with beams.
Then it can happen to make a part with solid elements, but the chances of error are high, you need to be very sure of how you proceed.
to make you understand, composites have a stiffness and resistance out of the low plane. If the composite is in a thin wall, this fact does not create problems. if it is often there are effects out of the shell plane that are to be evaluated. to verify this with solid elements it is necessary to insert the properties in the third direction correctly and to ensure that the orientation of the material follows the curves of the object according to how it is laminated.
I assure you that for a complex piece comes the headache.
shell elements simply neglect stiffness in the third direction. a normal shell load does not crush the shell in its thickness, but deforms flexionally and/or membranely depending on geometry and stiffness.
The only value that is evaluated in the third direction is the iss which is a fundamental value to understand whether the foils remain attached together or unfold among themselves.

 

[Gionata]

Great wave, you're the best.
That's exactly what I needed.
I can ask you two more questions.
- in case you use a bidirectional fabric at 0-90 and +-45 as I insert the layups?
What do you mean?
- if in laminator I insert the skins that carry laminate to the thickness of 1mm, can I draw a solid with thickness of 1mm for analysis?
Thank you very much. I believe that this discussion is useful to many.

 

[Onda]

Great wave, you're the best.
That's exactly what I needed.
I can ask you two more questions.
- in case you use a bidirectional fabric at 0-90 and +-45 as I insert the layups?

Thank you.
insert the lay up in the same way.
ex=ey for a fabric.
0 degrees orientation for a 0/90
45 degrees for a +-45grade biaxial

What do you mean?

I mean the final resistance of the laminate to the stresses that are imposed

- if in laminator I insert the skins that carry laminate to the thickness of 1mm, can I draw a solid with thickness of 1mm for analysis?

You can, I repeat that a laminate should be studied with shell elements.
a mesh of a solid often a mm must have elements comparable to the thickness. I would say max 5 times a lot, so basic element size 5x5x1. becomes a very thick mesh. this is one of the problems to utiilize solid mesh with composite materials

Thank you very much. I believe that this discussion is useful to many.

Please. I hope it's useful to others too