CSM Grades?

General Composites Discussions Products Talk
#1

I recently began construction of my first mold and I have a couple questions regarding the quality of chopped strand mat. My supplier was at the end of a roll and called to ask if it was OK to send the CSM in two different sections. Since I was going to pull it into small pieces I did not have a problem with it. All of it was 1.5 ounce x 50" wide. The first section of CSM had a tight texture, like a stiff sheet. I was able to tear it into 4" to 5" pieces and wet it out with VER using minimal effort to work out the air pockets. The second section of CSM was very loose and frayed. As I tried to wet it out it turned into blobs and I had a very difficult time getting the air pockets out even tearing it into very small, quarter-sized pieces. It was like trying to use cotton balls to make a mold. So my first question is, are there different grades of 1.5 ounce CSM? Also, is it common to have so much variation from roll to roll or did my supplier simply send me some crappy CSM?

Thanks,
Dennis

#2

Just guessing, but could the second piece be CFM? (continuous filament mat) Looks like CSM but is as the name describes continuous fibres rather than chopped.

#3

Brad1,

You’re absolutely correct. Looks like I know more about using CFM than I wanted. This stuff is probably good for RTM but is no fun to wet out by hand.

Thanks

#4

Is it really CFM? If you pull one fiber out, you will see it is a long fiber. CSM is made of short fibers.

There is a great variation in CSM quality, with some cheaper factorys sometimes spitting out unbelievable junk, with large blobs of fiber on one place, thin spots on the next place, etc. The binder ratio is also a constant factor of concern. Too little binder, and when rolling the mat will roll around your roller instead of impregnating.

#5

What about “powder bound” csm . I haven’t actually used it but it has a different binder.

#6

All of the strands in the first piece were consistently 2" and were straight and stiff. In the second piece, they range from 2" to 4" and about half of them are straight and the other half are curvy or swirled and are very loose.

It’s taking me 3 to 4 times longer to apply it to the mold than the first piece. Unfortunately, the first piece was only about 3 yards long and the second piece is 30 yards long. I doubt I will ever order from this supplier again due to other issues. In the future, though, how do I specify that I want the better quality CSM from any of the other suppliers?

#7

Wow your supplier sent you two different materials. I’d complain unless it’s not a big deal.

#8

I would claim with the seller definately. CFM is unusable crap in hand laminating.

As for CSM:
There is powder bound, which is basicly the industry standard. Good water resistance, good binding. When tearing dust appears, which is the drawback.

emulsion bound (PVAC binder) has worse water resistance (do not use it for boats or other exterior stuff) but impregnates slightly faster. Slightly more “fluffy” but no dust when tearing.

Then there is another funny thing with CSM: Noticed the frayed edge on one side of the roll? Polyester workers like that. It allowes for seamless joints. You can pluck the other end, but that is a lot of work.

Imagine the machine making CSM is 150" wide. Both ends are frayed of the rolls produced. However, the 150" roll is cut in 3x50". The middle roll has both sides cut nice and smooth. This can be a disadvantage when making larger stuff. If you do not specify what you want, sometimes you get sent the middle roll. (they are cheaper).