Resin infusion and resin content

[sorenfdk]

Hi!

I know that when using resin infusion, it's possible to achieve a very low resin content. An experienced builder once told me, that he'd have a hard time getting a resin content much higher than 40%.

But doesn't the resin content depend on the reinforcement type? Can you reach the same low content wíth CSM as with UD?

If anybody has some real-life numbers, please share!

Best regards,
Sorenfdk

[Eric Sponberg]

Yes, the resin content does depend on the types of materials used in the lay-up. 65% resin (35% glass content) content is a upper limit for hand lay-up, and 30% resin content (70% glass content) is the lower limit with resin infusion. If you have resin content lower than 70%, you will very likely have dry areas of fabric with no resin in them at all.

Eric

[sorenfdk]

Thanks for your answer.

Originally Posted by Eric Sponberg

If you have resin content lower than 70%, you will very likely have dry areas of fabric with no resin in them at all.

I guess it should be "...resin content lower than 30%..."

But what I am after, is the typical resin content when using CSM, WR and UD and resin infusion.
In hand lay-up you can achieve a lower resin content with UD than with CSM. Does the same apply to resin infusion?

[lucas adriaanse]

Eric and Soren,

There is a way in between. Using a slow setting resin applying all by hand lay up, putting an extra layer (dry) of glass before laying down your peelply, bleeder and vacuumfoil and then using vacuum to get the surplus of the resin from the hand layed up layers into this last extra layer. The extra layer can later be used to sand down when you start fairing.
Hope you understand what I mean (?)

A safe way to go about it and still have 'vacuumbagged' quality. Infusing is only really better where it concerns emission of fumes while working.

Lucas

[sorenfdk]

Thanks, Lucas, but we're right now negotiating with a customer who wants to use infusion, so I need the numbers for some preliminary work.

BTW: That extra layer would in our case be on the inside of the hull - I guess that's not where you want to do too much fairing...

[Eric Sponberg]

Sorenfdk,

Yes, my mistake, I should have said resin content less than 30%.

There is a good book called "Fiberglass Boat Design and Construction" by Robert Scott. This is available from the Society of Naval Architects and Marine Engineers (www.sname.org). It covers the basic engineering of boats with CSM and WR, showing charts of strength and modulus vs. varying proportions of csm/wr and glass content. Generally, good quality of laminate has about 40-45% glass content for a combination CSM/WR layup. For all WR, you can go higher, to 50 or 60% glass content, and for all CSM it is nealy impossible to get higher than 30% glass content. I am more familiar with talking about glass content rather than resin content, because that is how that book presents the data. Robert Scott was part of the original Gibbs and Cox study on fiberglass laminates in the early 1960s that determined the strengths and moduli of csm/wr laminates. This is the most comprehensive data and engineering guideline for csm/wr laminates.

For resin infusion, 60% glass content is very easy to achieve, with a max at 70%. If you want more precise data, then I suggest contacting Andre Cocquyt at GRPguru.com. Email address is GRPguru@yahoo.com. Andre is this country's resident expert on resin infusion. He produced a video on the different resin infusion processes, and he helps boat builders set up such a process in their plants. He knows everything you need to know about resin infusion.

Eric

[sorenfdk]

Thanks for your advice!

I have Scott's book and several others on the subject, but neither of them seem to have the answer to my question: What is the typical fiber content of CSM/WR/UD when using resin infusion?

I've e-mailed Andre Cocquyt - as a "guru" he must know a lot about this!

[Herman]

Also try and E-mail Arjen Koorevaar at info@polyworx.com. He will probably have some figures at hand.

Eric already gave some numbers, but forgot to specify for which type of fiber this was. Can you still do so, Eric? (probably CSM)

Nicest of all would be a table which would look like this:

Fiber type | High glass content | low glass content

Glass UD, infused | 75% | 60% (just guessing numbers, but I am not way off)
Woven Roving, infused | xx% | xx%
CSM
Knitted
etc.

Factors which also could play a role are: infusion pressure, vacuum pressure, even amount of time the bag has been under pressure before infusion started. (1 hour or one day makes a hell of a difference in permeability, so must have influence on fiber/resin ratio as well)

If there is a great need for it, I could do some tests in our lab. (will take some time, quite hectic here so short before the METS 2004) But if wanted, drop me an E-mail.

[sorenfdk]

Originally Posted by Herman

Nicest of all would be a table which would look like this:

Fiber type | High glass content | low glass content

Glass UD, infused | 75% | 60% (just guessing numbers, but I am not way off)
Woven Roving, infused | xx% | xx%
CSM
Knitted
etc.

Yes indeed - a table like that would be really, really nice! Does anybody have one?

Are you exhibiting at METS? If so, we'll maybe meet - I am there for the first two days.

[Eric Sponberg]

Gentlemen,

Unfortunately, I do not know of any charts that would have laminate results for mat and woven roving plus UDR. But you can figure that out for yourself. You need to know that UDR will have a certain laminate thickness when laminated. Sometimes that information comes from the fiberglass material suppliers, and sometimes you have to do tests yourself. Testing is the most sure way. Also, if you get results from the fiberglass suppliers, they usually specify what the glass content is along with the thickness. Most results are normalized to about 50% glass content. Within small ranges, material properties (strength and modulus) will vary linearly with glass content, say a range of 10-15% or so. Beyond those ranges, new tests have to be done.

The reason that there are no charts of such laminates is because of the infinite variety of layups that you can do. How many mats, how many woven rovings, how much UDR? The more UDR you put in, the stronger and stiffer the laminate will get in the direction of the UDR, but by the same token, the weaker the laminate will get perpendicular to the UDR. This is why testing is so important. And because of the wide variety of layups available to do, that is why testing for tension, compression, flexure, and shear in both the 0 direction and the 90 degree direction are so important.

Also, you cannot assume the mat/woven roving will be one glass content, and the UDR will be another--the laminates don't work that way--the resin will flow to where the voids are, and you cannot guarantee a specific glass content uniformly throughout the layers of the laminate. You have to take the glass content for the whole laminate.

When I engineer a laminate, I have a laminate design program that I use to determine the structural properties of the layup based on the fibers involved, their orientation, and the amount of resin. When I can, I try to get these verified by tests, when the client is willing to pay for it. Unfortunately, a lot of owners and builders don't like to pay for testing, so very little of it gets done, and even when it does get done, designers and builders keep that information proprietary. It is private corporate knowledge.

Some talk occured over the years to try to tabulate the mechanical properties of various types of laminates, but the logistics of doing that are so complicated and so huge, that it would be extremely difficult to do. Who would pay for it? Who would maintain it? And who would assume the liability for numbers that might be wrong? It is just too cumbersome a task. Therefore, you are left on your own to determine the laminate properties yourself, either by appropriate laminate design programs, or by testing, the most assured way.

Eric

[Herman]

We will be exhibiting at the METS, booth 11.080 (Brands Structural Products)

I do understand that different combinations of fiber types will interact, and thus it is very difficult to predict an exact fiber to resin ratio for a given stack of materials. even different types within the same product range will give different results. (for example, rigid or flexible stitching in a stitched multiaxial will already give different numbers)
Also stacking order can cause variations.

However, it is good for the people to have at least some idea of the materials they use, or plan to use.

Gaining the knowledge is good for you, but spreading out the knowledge serves the whole industry. and for us as a trading company it is plain simple: If the industry is OK, we are OK.

I will see what I can do the next couple of weeks. any suggestions?

[sorenfdk]

As I'm no expert when it comes to infusion, I can't come up with any intelligent suggestions (apart from something like the table you mentioned yourself) right now.
But I'll think it over and maybe we get the chance to discuss it at the METS.

[Herman]

I will take some normally used materials, and some heavier products. we supply knitted glass up till 3600 grams / m2

[sorenfdk]

I posted the same question on another website (http://www.eng-tips.com), and today I got this answer:

CSM: 30-50% fiber content by volume
WR: 50-65% fiber content by volume
UD: >70% fiber content by volume

Do these figures look allright? Personally (and without having any experience with resin infusion), I think they may seem a little on the high side.

[Herman]

They seem to be alright for usual calculations, although the WR is a but on the high side. But I have to admit there are various WR's available, some are very dense and fine.

I am only available on the METS 2004 on tuesday and thursday, by the way.