Resin Requirements Calculator

General Composites Discussions Engineering Talk
#1

As many coming from hand layup to infusion, the concept of predetermining exactly how much resin to mix is befuddling. My first infusion I was way too short, and I had to scramble to stop it, only to make way too much, which then later became my first smoking meltdown monster! :wink:

Iā€™ve created a prototype program to calculate resin requirements for infusion. Eventually, Iā€™ll put it up on my website, but for now this is the textural output:

Resin Requirement Calculation:

Area: 437.25 sqIn Target Fabric/Resin Ratio: 60/40

Qty Description Required

2 Carbon Fiber 2x2 Twill (19.7 ozy) 125.59 g
2 Carbon Fiber Plain weave (8.8 ozy) 56.10 g
1 Lantor Soric SF3 (Uptake: 1300 gsm) 366.63 g
1 Process Waste (4 flOz) 125.02 g
==========
Total by Weight: 855.02 g
or 30.16 oz

                 Total by Volume (@ Resin SG:1.1)    777.29 ml
                                                or    27.36 flOz
                                                or     3.42 c

Iā€™ve not fully vetted the calculations and unit conversions yet, but I want to be able to use any routine units of measure as input, and produce practical/useful information. So Iā€™m looking to make sure I cover the units that people most use. (I think I know already, but itā€™s better to ask.) Any input, (even to say thereā€™s something else already), is welcome.

Soon as I get my next mold done Iā€™ll work on getting it online for anyone who cares to play with.

Itā€™s currently at: http://black-lab.com/resin --Still a work in progress!

#2

OK, include the following:

-laminate stack
-fiber weight
-Vf for every material (preferably at various pressures)
-core materials and their resin uptake
-thickness of laminate

And in version 2:
-properties of hand laminate
-properties of infused laminate

Use SI units, as both Europe and NASA use it :). If you really need to, make a switch somewhere to switch to imperial as well.

#3

Thanks Herman. Thatā€™s good advice. (As are the many you give here.) :slight_smile:

I also have an old program I wrote years ago to optimize the cutting of raw stock based on pieces needed. Originally written for plate glass, I donā€™t know if I need to alter it for a ā€œgrainā€ orientation? I probably do. That one will be more involved because itā€™ll need to create a graphic of the layout of the pieces. Perhaps this winter Iā€™ll put that up as well.

#4

Yes, you would need grain orientation, unless you only want to use it for CSM.

#5

Jap,
a correct approach to determine the amount of resin for the infusion process, is to take account of the compressibility of material; from this, fixed the value of pressure applied you obtain than %Vf resulting from that pressure value.Anyway it is not so easy (maybe quite impossible ) to manage such concepts from a practical viewpoint ,but some empirical formulas exist, like those in the file attachedā€¦ā€¦choose your material, ā€œapplyā€ the pressure, obtain the % Vf, obtain the resin amount, compare with your tests
Good luckā€¦.and, of course, let us know !!

#6

sqrt of P: in which unit should P be?

Another factor is that fabrics have different Vf when stacked with other fabrics, CSM, multiaxials, gelcoat or a flat mould.

Anyhow, the error is only very small, so a calculator like I suggested will be reasonably accurate, and will be a real help.

#7

Ahhhā€¦ Now I understand why you mention listing the stack as you do. I do list the layers involved, not in any particular order, and I allow grouping them. (i.e. 2 layers of CF 19.7ozy, 2 layers of CF 8.8ozy, ā€¦) I was thinking more ease of input, but I can deal with that in a different way.

So, I should nix the quantities of layers and deal with each layer, (in order), separately? It looks like Iā€™ll need more information.

BTW, Iā€™m still working out some issues with my mold, so Iā€™ve been doing various corner shots with the stack to get the results I want. I had been guessing on the resin quantities when I do these, but I used the program, (such as it is), and it was pretty spot on. Albeit only ~80 sqIn. :wink: --Itā€™s a lot closer than what I wouldā€™ve guessed the quantity should be. I also added a resin and hardener calculation with the resulting total required, which made it easy. :slight_smile:

#8

That is the whole point. You can get even closer when you know all the variables, but information is lacking, and you are reaching a point where other uncertainties overrule the accuracy of the calculations. (such as guestimated area, resin lines and their resin uptake, etc)

The reason to include the laminate stack as-is, is to be able to later also add the technical data, and arrive at a laminate calculator, not only for infusion, but also for calculating the mechanical properties.

When done in a visual manner, it can really benefit the composite industry.

About all the info is there, Vf / fabric / resin usage / thickness is pretty easy, I have it in Excel.

Also available is a stiffness calculator by Alcan Airex. The 2 combined would already get us pretty far. If I ever get the time I will try and shove them together.

Even nicer would be a website, having an online version of the calculator, and a database system for the different laminates calculated, preferably with the test data of these laminates together with them. (even if it is only a thickness, for verification purposes, but of course preferably the whole lot, including mechanical properties.) There was an initiative in NL, locked up behind a password, but the scale is too small to really work. You need a certain amount of ā€œcritical massā€ to get things rolling. Public domain is the keyword here.

#9

Herman Iā€™m tracking with you. I was expecting at some point to have a table containing common reinforcements/cores, etc.

Itā€™s a bit disgruntling to get good information in leading edge topics like these. Information tied only to product purchase, etc., or even disinformation to include needless products is unfortunate. So, yes, I would only do this Open and free! :wink:

#10

What Resin are you working with

#11

Currently Adtech EL-360. I plan to try Adtech 820/823 next purchase cycle.

#12

Herman,

pressure is in bar

#13

Ok, my friends wings and hermanā€¦ I need to be brutally honest about my understanding of things. Although Iā€™m a gifted programmer, I am very much a newbie when in comes to composites and the technical science behind it. I know little beyond my own basic experiences. I am only one step above the shallow: ā€œOooo, itā€™s carbon fiber!. Yes itā€™s strong, yes I can drive my Mercedes on itā€¦ --But how does it look?ā€. :wink:

I will come to understand the science involved, and Iā€™ll indeed make this calculator, but please donā€™t feel you need to be too careful about insulting my intelligence. Please donā€™t walk on egg-shells on my account. Assume Iā€™m egoless.

That said, some conclusions and questions:

From what I gather, given a pressure Ā§ on the outside of the bag, (atm, or compressed??), I need to take each layer in the stack, determine the %Vf based on the type of composite, (and possibly a factor based on the relationship of whatā€™s on either side of it??), times the surface area to get a per layer resin weight. I currently use an imposed constant of 60% for %Vf. (Which came from some other forum as I recall.)

Am I to understand that %Vf of the stack is primarily due to how much vacuum I pull down on the bag(s), and secondarily, on what reinforcements, and order in which I place them? Am I thinking correctly? Prior to this, I thought 60% was just some magic number, which was the goal, but I didnā€™t know how to affect it. :wink:

  1. P is a constant imposed on all layers equally? (Should be, right?)

  2. What determines the ā€œtype of compositeā€? Weight, weave, manufacturer, type? Is plain weave CF the same as twill 2x2 CF if theyā€™re of the same weight? What about custom weaves, etc.? What about cores, they absorb resin, right? ā€“ Or is that why ā€œwhatā€™s around itā€, is so important?

  3. Meshā€¦ (From the same source as the 60% vf above), they said mesh, (of all types!), has a standard uptake of 700gsm. That sounds like flawed thinking to me.

  4. What different characteristics of resin will affect our calculation? Density? viscosity? I know epoxy is stronger than VE which is stronger than PE, but how does that affect uptake, or doesnā€™t it matter. For mechanical properties, that info will be important and makes sense.

Well, thatā€™s all for now. Itā€™s going to be yet another 103 deg day here today, and two days ago my left kidney decided that itā€™s time to drop a stone! So, instead of spraying Gelcoat over a plug, Iā€™m in bed with a heating pad and meds. :frowning: Bummer.

#14

First pass at a possible UI:

#15

The Vf% is variable depending on pressure and the fiber format. It takes some experience to predict what the Vf will be for certain processes and weaves. The quality and technique used during the infusion also makes a difference.

In my experience the higher the pressure you use the less impacting the weave and orientation is. I see a Vf of 50 to 55% with woven fibers more common with infusion than 60%. 60% is pretty easy with UD and spread-tow carbons.

Here is a spreadsheet that I made that takes into count the density of the fiber and the density of resin. The section at the end of the spreadsheet (called Layup Comparison) is the most applicable. You can also use more than one fiber type within the laminate. You can change the Vf% and see how the thickness changes and the resin volume changes. There is no accommodation for extra resin needed for infusion tubing and such.

Iā€™m not much of spreadsheet writer but it is what it is. At least you can see how the fiber and resin density, and Vf% will change the outcome.

Adam
Whoā€™s had a few kidney stones himself.

#16

Interface looks OK. You will also need a material database. It would be nice to also include the technical properties of the laminate.

What kind of programming languages are you working with?

#17

Came across this calculator if its any help

http://www.saertex.com/materialrechner/rechnere/rechner.php

#18

Hi Guys,

Jap got me started again on a spreadsheet I was working on earlier this year. The idea was to have something that could be used to enter layout data into and then print off the resulting sheet to be used as a parts label. Since I plan on building a boat I was going to use it on all the pre-manufactured bulk heads & etc.

I sent him an earlier version with some admittedly screwed up math - but Iā€™m pretty sure this new version has it all fixed now.
:slight_smile:

I believe Japā€™s version will ultimately be much better since heā€™s planning to include a database with several different materials & etc. But if anyone would like to give my spreadsheet a shot, Iā€™d love to hear back from you!

(The attachment is a zipped up Excel spreadsheet)
There is an Instruction Tab at the bottom, but it should be fairly easy to follow.

#19

PHP for the structure and logic, SQL for the DB, Javascript for managing various parts of the UI. The output will be rendered in HTML5 using CSS3 to define the visuals.

Iā€™ve created the basic beginnings of a materials DB. Iā€™ll add more data columns as I get more enlightened. Currently thereā€™s a ā€œmaterialsā€ table, and a ā€œweightsā€ table.

Iā€™ve added the %Vf algorithm, to individual layers, but didnā€™t get much time to play with it. Programming on pain meds at 2am, does not always lend itself well to good results. Iā€™ll need to check the sanity of things again, but what was output looked to be in the ball park. :slight_smile: I crave better information though.

I was hoping the get much of this knocked out before getting my materials in, but unfortunately Iā€™ve been knocked out, and now my materials are here waiting for me to get productive. No worries, though. :wink:

#20

DallasAB; I looked at your spreadsheet a couple of days ago. I didnā€™t analyze the calculations too heavily, (I honestly wasnā€™t really able at the time to do much), but it made me think about alternative/custom forms of output and the concept of storing these, (for those who may want to), so changes to the data can be made at a later time.

Iā€™m going to finish my part B mold today, (with luck), pop it off tomorrow and add supports, etc. (ā€œAā€ is all done.) Iā€™ll try to do my first infusion with A this weekend. :slight_smile: