What went wrong?

General Composites Discussions Composites Talk
#1

So I wanted to strat my littje carbon project and started with a little practise…

I wanted to make a normal plate, just to find out how it all go with the vacuum etc.

I used a plastic plate, did some resin on it, layed up 3 layers of 200g/m2 carbon fibre (with resin in between each part) did a vacuum bag over it, turned the vacuum on (around -0,7 bar) and left it several hours on.

This morning I unwraped it, but there was no strength in it! The resin in the bucket (left over) was pretty hard. The resin on the product wasn’t sticky or something, but it’s just not strong :frowning: :frowning:

So… got it on the heater for a few hours this day, but when I came home from work, no strenght at all…
The product is nice and shiny from the resin though…

So the big question… What went wrong???

  • Could it be the temparature?? It was about 15 degrees in the garage.

  • The vacuum wasn’t on long enough? was about 3 hours on or so

  • Need to use more layers

  • Combination of the above?

  • Other…

Somebody help??

#2

we need more description

but three layers of anything is going to be really flexible…extremely flexible.

#3

How much layers should I use then?? I have a carbon motorcycle part here (bought that) and that is so extreme thin, you can almost see through it. When I tuch the surface, it feels like metal!

#4

it will be hard but very flexible with 3 layers,the motorbike part no doubt has curves on it,this makes it far more rigid.sounds like you did ok :slight_smile:

#5

also,what resin did you use?? poly or epoxy and what proportion of hardener??

#6

There you have a point… This is a “plain plate” ofcourse…

But… I just heat it up with a paintstripper (gently :slight_smile: ) and now it’s cooled down, it a lot harder :eek:

#7

I use a epoxy. I have 2 brands here, this one goes 1:2, the other is 60:40…

#8

try a curved part,it will be solid as a rock :wink: dont forget to lay the fabric in different direction,like plywood.

#9

didn’t pay any attention to that :eek: :eek: !

Will that make a lot of difference?

#10

it will make a differnce yes :slight_smile: imagine how rigid plywood would be if all plys went in the same direction!

#11

also, I don’t think anyone mentioned above??, what size was your test plate?
A 3x3" square will feel ALOT stronger ie with less flex than a 3’x3’ plate. all other things being equal

#12

Hey Z…have you looked at the new 800 GP bike? Can you guess what it takes to make that replica? Ive got it figured out if you want some ideas for your side of the planet…I thought about giving it a try myself.

#13

That would be nice! Can use all the help I can get…

I know what a job it would be, but that’s the fun, right?

Don’t mind all the work and $$ that go’s in it, but it would be nice if something would actually went right!

It was a plate of aprox. 40cmx40cm.

I tried it again yesterday, using 1 layer of carbon, then 3 layers of the white stuff you can also use with polyester resin and then a layer of carbon. It is twice as thick now, but still missing the strengt…

Can it be the temparature? Should I let it dry on higher temps? (how long under vacuum on what temp??)

I’m willing to start the making of the moulding some place next week, but if I can’t get this simpel carbon thing right, I doubt if I should ever start it…

#14

well Ill tell you this much…with poly resin and 2 layers of carbon and another 6 layers of glass…I can still flatten out a curved part if I stand on it.

I dont know what youre trying to make but if you have problems curing…rais the temps to 150

I made a killer heat box out of some boards and a couple halogen lights…my parts were getting up to 140 after a couple minutes and holding temp.

Hit my email and we can bounce the parts list to make the new 800 gp bike off each other.

xcitebikes@gmail.com

#15

Hi Arnold

I know you from the ZX7-Owners club, my sign on there is Kermit. I’m someway through the carbon learning curve and might have a couple of tips for you.

I’ve found that with the resin I use its not worth bothering trying to make parts if the air temprature is under 60 degrees. It just never seems to fully cure if its cold, even if its placed in a warm enviroment later on.

The resin mixing ratio needs to be absolutely spot on to achieve a full cure. If its not the resin stays kind of ‘soft’ and you don’t get the stiffness. In the end I opted to buy some resin that is mixed by weight and use some digital kitchen scales to make sure my ratios are acurate to the gram. There is also the resin quantity to consider, if you are mixing up tiny amounts then this may not be enough to start the required chemical curing reaction.

Hope this helps

Cheers
Andy

#16

Thanks Kermit,

So it could be my ratio and temp isn’t good… I do look at the ratio ofcourse, but not as scaled as it (probably?) should. Will try it next time

#17

Back again with a second attempt…

Had another shape now (with edges) and vacuumed it.

There also is no “shiny” side on the fender… I first waxed the mold, put a layer of resin in, then the carbon (with resin), then a layer of peel ply and last a layer that sucks up all the resin that came thrue the peel ply. Can it be it sucked too much out of it? How thick should the first layer of resin be and what can I do to keep it that way under vacuum?

#18

Just use some gelcoat and let it B stage. otherwise youll continue having problems…you need the surface coat to be B staged so it cant be sucked thru the peel ply like a wick of oil.

#19

Ok!!

So i put some resin in the mold, let it dry for a while and then continu with the carbon and resin and vacuum?

#20

yeah just let the resin start to harden…it should be sticky but not wet and shouldnt come off on your finger.

When you use resin like that instead of gelcoat its a tricky proposition…youll have to work fast so it doesnt harden all the way up and shrink then crack on you before you get the reinforcement in there and infused.