Pleats

General Composites Discussions Composites Talk
#21

I can’t absolutely prove it, but i think polystyrene is effected by higher temperatures. I tried brushing some epoxy over polystyrene and it disolved the surface of the foam. The epoxy actually ate into the foam to a depth of about 3/16 inch. The outdoor temperature at the time was 103-108F degrees. I only brushed i’d say a 10 mil thick coating of epoxy.

Back to the original topic… So say you are infusing a part that is 1 ft wide x 2.5 ft long. You would want your resin lines on the short ends or the long ends of the rectangle? Not in the corners opposite each other?

#22

The part is actually a semi-circle one inch thick. It’s actually a puzzling part to infuse. Well for me anyways. I think what I’m going to do is put the resin line mid way on the straight side and loop the vacuum around the radius. This way the resin will flow from one point outwards in all directions towards the vacuum. I’m going to trim the flow media short of the edge and leave a good resin break (just peel ply) between the edge of the part and the vacuum line. That should slow down any runaway resin before the part is fully infused.

We’ll see how it goes. Next test in a week or so. Waiting for supplies.

#23

I think it depends on how well your resin flows through your material. Say if it flowed easily along the long axis of the rectangle, then you’re fine.

If the resin doesn’t make it all the way, then you can flow along the short axis. Or stage the resin feed lines to flow when the previous one stops.

Or feed from the center and have vacuum all around the perimeter, or the opposite.

With these two ways, you’ll have to find a method of avoiding the lines imprinting on the center of your part. Baznos made is own infusion jackets to combat this IIRC.

#24

The resin moves really well with the flow media, top and bottom. Last time I was afraid that with all the pressure of the vacuum the bottom would get starved, it didn’t. The biaxial fabrics flow really well. I’m going to try to do both sides at once again this time. I think it’ll work!

If it was a circle I’d drill holes in the foam and feed from the center outwards. This is sort of the same thing but with half the circle missing! lol

#25

No, it is a chemicial reaction. Try taking a PS foam cup and pour acetone into it. Watch what happens…

Same thing happens with a PS foam cup and PER resin. I would go over that in class, show them and purposally leave some PS foam cups in the cups cabinet for those not listening and watch them make a mess. Then they have to clean it up…:rolleyes:

Generally, PS foam wil not melt by using Epoxy resins but…?

With the PUR foam you are getting FastRR, you will notice a big difference!:eek::cool:

#26

Ok, more accurate update on the glass/epoxy thickness. As it turns out, measured with a digital micrometer, the glass/epoxy is 1.8mm thick which is about 0.070" or somewhere inbetween 4 and 5/64ths thick. I’m thinking that’s too thin which would mean too little resin left in the skin. The fabric was 1708 biaxial. Thoughts?

Update: Found some technical info on that fabric. http://www.wetconcepts.com/KnittedFabrics.pdf
I should be about 0.040" so that test piece was resin rich! Go figure. Next piece will be better!

#27

cool on the PUR foam, I plan on making a plug/part for my bike with it. A new solo seat cowl… the one i messed up on the first try:o I didn’t have your guys’ knowledge back then.

sorry for the thread jacking.

Now back to the infused part pictured above. How come a lot of guys, all i think, only use resin flow medium on a portion of the part being infused? Would too much flow medium cause the resin to not be absorbed into all the reinforcement material? So then my question moves on to: Why use any flow medium at all?

Gotta learn somehow lol.

#28

I’ve given a lot of thought to the same questions you have on the flow media. I ran it over the complete part last time which probably wasn’t necessary but I wanted to ensure it got totally infused. The biaxial fabrics flow (so I’ve been told) really well and it’s not necessary to use flow media over the entire part. Just enough to get it moving in the directions you want it to go. Thicker fabric stacks could possibly suffer from resin starvation w/o the flow media or just flow so poorly they never completely infuse. Experience I guess is the key to knowing how the resin will flow through various materials.

#29

Attempted the second infusion today. Failure and success.

Success: Got a perfect bag. Had to chase some leaks with gorilla snot and acoustical sealant but managed. I picked up a couple of “Spy Ears” off of e-Bay. They’re kids toys that magnify sounds so kids can play spy stuff I guess but ya know? they worked great! For $2 plus shipping I thought I’d give 'em a try. E-Bay item #120149832296

Failure: The stupid semi-circle is a nightmare to infuse. I thought I was being smart setting up the perimeter vacuum and infusing the resin from a central point. Well sh*t! The epoxy immediately ran around the part to the vacuum outlet! As you can see from the pics it followed the minor bridging along the edges. This left a huge void in the part.

Success: We fell into Plan “B” after a half hour when it became apparent the remainder of the part wasn’t going to infuse. We clamped off the resin feed and relocated it to the center of the void. This was easier than I thought it would be and it worked. After the void was about 80% complete we sealed off the inlet and let the vacuum take over. I don’t know if there’s a void on the bottom but I’m assuming there is. That’d be cool then I can try a mini-infusion on the void there like you’d do on a repair.

Success: I used only a small semi-circle of flow media, enough to get the resin up and under the part. That worked well and the biaxial fabric flowed just fine on it’s own. I also provided a resin break of just peel ply between the part and the vacuum outlet which is probably the only thing that saved our bacon this time. We used about half the resin we did last time and I don’t think there’s more than an ounce or two in the resin trap.

No more semi-circles for me! I don’t know enough yet about how the epoxy flows through the stack. Well I know more than I did two weeks ago! I’ll demold the part tomorrow and we’ll see how we did.

#30

It popped out slick as sh…

Well. The toughtest part was getting the butyl tape off the mold. That Polymer Composites mold release wax works extremely well. Better than the stuff I had for the first test.

Note to self: Flow Media goes “Over Top” of the peelply! Don’t let me forget that!

The flow media is now a permanent part of this part. :o Good thing it’s not a critical part for a paying customer. Guess I was in a bit of a rush to get the job done. Anyhow, the part is still serviceable for the intended purpose.

With no peelply on the bottom the part is smooth as glass! The downside is without the flow media the part was starved in a kidney shaped pattern. I sort of expected that. That’ll provide an opportunity to do a “spot infusion”.

I’ll have the cut outs tomorrow so we can see the and measure the thickness of the glass/epoxy.

Better than the first but still not perfect. Good thing I only have 1 sump hole to cover! No more semi-circles!

Now all I have to do is learn how to use a HVLP paint gun!

#31

Well so the next chapter in this saga has played out. I tried to do a spot infusion of the void in the part. Yeah ok…

The fresh f/g part was porous and it was near impossible to hold a vacuum on it. The pumps still runnin’. The resin moved well through the part with the peelply and infusion media in the correct order. The resin flowed really well till about half way then it started to race along the creases in the bag and along the very edge of the flow media. Sheez. I stole DT’s trick of making up little diapers of bleeder to suck up the excess. No resin in the vacuum line this time.

We’ll see how it turns out tomorrow.

Do you know what to do with excessl epoxy when you’ve mixed up too much? I do!

Knock the cup off of the table and coat the floor with it! :eek:

#32

Well now you’re gonna have to coat the entire floor just to get it to look even! Just kidding, I love the documentation you’re doing, learning a lot from it.

#33

Thnx Rez

I learned a couple other interesting lil’ tidbits about epoxy today.

[ol]
[li]You can’t comb partially catalyzed epoxy from your hair
[/li][li]Make sure you wipe up all the spilled epoxy before you put your tools back down in it
[/li][li]Don’t just cover the spot where the epoxy spilled with a chunk of old carpet
[/li][li]Advise the Admiral where you spilled the epoxy so she doesn’t walk through it!
[/li][li]Check the back of your hands for uncured epoxy before you wipe your forehead with them!
[/li][/ol]

Oh this is fun! :eek:

#34

:D:D… we all learn from our experinces or at lest SHOULD! :stuck_out_tongue:

Some days, it is just better to go for a drive in the car instead!

#35

Oh I’ll learn eventually. You only gotta hit me over head the five or six times before I figure it out!

I also learned no more grinding fiberglass in the basement. scratch scratch scratch :frowning:

Well not finished yet. Once I get these HVLP sprayers figured out and tuned I’ll paint them. Also going to dowel them together so they’ll stay put. That should keep the cat toys and tools out of the sump!

#36

To prevent the itch’s from machined (or just handling) fiberglass:

Get baby powder and powder up big boy! It plugs the pores and prevent the glass fibers to get in.

Also, shower in cold water as hot opens the pores and the glass gets in deeper!

#37

Now ya tell me! Toooooooo late! lol

Thnx Werks. I think I read that somewhere on here before. Does barrier cream work? Trouble with working outside is the crap blows everywhere. I might make a fume hood to work on small parts and vent it outside. It gets to -30 degs C here in the winter so outdoor projects are out of the question.

#38

Knotty, I can’t quite make out your writing on the infusing part, I’m just curious what the times are that you outlined and documented by sharpie?

#39

I flipped it and added some text to make it easier to see. Think we started in 3 min intervals and got to about a half hour before I bailed and relocated the resin line.

#40

thanks thats great