Hello,
I dont know how to bond aramid honeycomb 4mm to carbon fiber.
1)First you create the up and down layers and then you glue them to the core?
you lay the cloth up and down to the core and then put it to oven ?
put prepreg layers up and down to the core and put to oven
I am also not sure in what type of aplications a core is adding to the structure…the way i see it it always does good…from body armor to bicycle frame…are there some applications where the use of a core is a waste?
A core like honeycomb gives high stiffness to laminate while it doesnt add much weight. It is only good for parts that need rigidity and doesnt need to be flexible.
And how i bond the layers together with the honeycomb? With what material?
You have 2 pieces so , you brush resin on first plate than put light glass like 48g/m2 then honeycomb then again light glass and upper plate. Once is done you vacuum bag it
If you are using prepregs you may have to use a glue film. But you can lay up the whole thing at once.
Isn the resign that you apply at the fabric layers or the resign that is inside the prepreg enough for the bonding between the layers and the honeycomb ?
It may be enough, but usually the resin content in prepregs is minimal. The bonding of the “dry” honeycomb, or other core materials will need some resin too. If there isn’t enough, the quality of the bond will be affected. Applying an extra glue film, which is basically resin on a light (glass/plastic) scrim, will provide sufficient resin for the bond, withouth starving the fibres. There are gluefilms in different weights, to suit different core materials, and resin ratios of your laminate.
If i dont have a glue film , can i just apply some resign on the honeycomb intead ?
that’s an interesting idea, to use with prepregs I guess?
Every 10 degrees will shorten the cure time by half, roughly . You will probably have at least 45 degrees difference between your room temp and minimal cure temp. So you will need a very, very slow resin to match the curing characteristics of your prepreg, which also needs the minimal Tg to survive the minimal cure temperature.
You’d basicly want the resin mostly liquid or slightly gelling to get a good chemical bond, when the prepreg starts gelling too, the chemical bond is lesser anyway between to different epoxies.
I’d say it is to much trouble for a sub optimal process. Cure seperately and bond together later with laminating resin (like fiberpro explained) is much simpler in most cases, or just vacuum bag the inner layer on(it will create dimples, so not good for cosmetic purposes)
When you don’t need the honeycomb anyway (weight/shear strength), it’s easier to use other cores and process’
Just for an update, and i dont say is the right process ,i tried to lay 2 layers of unidirectional prepreg ( up and down) on a honey comb and a foam core and it seems that it really sticked on .
i didnt use adhesive of any kind - just the prepreg resign.
I dont know how good is the bond … all i know is that i couldnt take it of with my hands…
It is better to use prepreg instead of dry cloth+resin.
We supply nomex honeycomb cores… If you need quotations/samples then email me
neal@cacomposites.com
Our website is neal@cacomposites.com
that kind of bond is probably pretty good. I’m sure if you measure that bond vs one that has film adhesive over the core, the adhesive one would probably be better. Not using adhesive can make the laminate dry but, it varies on materials. We use a fairly low resin volume prepreg, thus we need the adhesive.
I switched from using Nomex Honeycomb to Lantor Soric xf3, which is much more flexible, a solid core material, and does not print when infused (test samples of wet layup showed print)