Hi everyone,
I made this flat panel a week ago on 11/16/11 and it had stayed flat up till this morning, now it is warped.
lay up is lantor soric core and a layer of carbon/kevlar on each side with infusion epoxy. demolded after 24 hrs (as suggested by the manufacturer ) no post cure.
the panel was a 12" by 17" before I cut it to the current shape 3 days ago.
what do you guys think is the problem and how can it be fixed? post cure? the choice of fabric?
I just noticed that the fabric on the back side is not very straight, you can clearly see it in the 3rd pic, could that be the problem?
I had used the same resin and soric core but with carbon fiber cloth and none of them warped before, the only difference is I never cut the other panels to any shape.
The warping of the fabric might have something to do with it or it could be a effect of the warpage. What was your layup?
lay up is lantor soric core and a layer of carbon/kevlar on each side with infusion epoxy.
what is the warpage effect?
I think the problem is the aramid/kevlar. The coefficent of thermal expansion of kevlar is different to the carbon. And is your layup symmetric?
Have you dryed the aramid? Aramid is hygroscopic, that may also cause problems.
Try to let it cure at 60° in the mould for 48 hours.
And cut the fabric into shape before infusion, espacially when working with aramid/kevlar/dynema…
ddcompound what do you mean by drying? I did let the lay up stay under vac for an hour before adding resin. I used adtech 820 but I cant find any info for post curing. has anybody used this epoxy before? here is the link for tech sheet.
http://www.adtechplastics.com/ADTECH_TECH_SHEETS/Marine%20Products/820%20Series%20Tech.pdf
One hour under vacuum should be enough if your vac level was below 20mbar.
Try post curing for 6 hours at 60° and 6 hours at 80° with a heating of max 20°/h
ok… couple of questions…is Tg and HDT the same? (never-mind this question, i figured it out http://www.ides.com/property_descriptions/ISO75.asp and http://www.ides.com/property_descriptions/ASTMD648.asp)
and also At the bottom of the page I found this…(see the pic)
so should it be post cured at 65C for 4 hours?
Flat panel, few layers, sheared fabric, = warped plate. No way around it. Could be due to the CF/Kev mix, depends on the fabric balance. Else…flat panels are hard to keep straight, unless VERY thick. Even a 24 layer 0/-45/90/45 is hard to keep flat.
Glass transition temperature and heat deflection temperature are not the same thing although they’re related by the mechanics of polymers. In the most basic sense they’re two ways of measuring how “soft” polymers get under temperature. Posted this answer so people coming to this thread at a later time could read it.
What I meant earlier was the fibers curving could be the cause of the warping. Or the warping could be causing the fibers to curve.