Hello!

I am making a rather complex model where making a mould is extremely difficult, and not necessary because it is a one time only. 
There fore, I wonder if it is possible to make the the core out of some kind of polyurethane, and proceed to wrap it in pre-preg and then cure it as usual? Does anyone have any experience on this topic? 
Would the polyurethane handle the heat?
Would it bend or deform under vacuum? (The construction is about 40mm wide at thinnest and about 600mm long)

Best Regards, 
Anders

Polyurethanes will inhibit the cure of epoxies at high temperatures unfortunately. 

PU will inhibit the cure even at relatively low temperatures.  By far the better choice would be an Epoxy Tooling block such as our EB700


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

it would help if you can explain a bit more about what you are trying to achieve? Does it need to be prepreg that you are using? Could you make the core from a cheaper foam material and then skin it using dry fibre and the XCR resin system?

Im doing some work on using 3d printed parts as the sacrificial core but the PLA material isnt able to cope with even a 65degree cure. I would have a look into other materials as the guys above say the PU block will inhibit the cure

Tooling board would work, but it wouldn't be lightweight at all, especially the EB700 tooling board as it is a 700kg/M3 density - extremely heavy for use in a final component. You ideally want something no heavier than a 90-100kg/M3 density, but can also take high temperatures without inhibition... There aren't many options that spring to mind for me, but I would suggest it will be an aerospace product. 

As Scott suggested, pre-preg may not be the most suitable choice for this one?

What about this
http://www.rohacell.com/product/rohacell/en

Yes
I ve looking for foam core solution for a project.
I know some guys use EPS polystyrene, but I don’t know if this require a preparation for using it with preg
What I found was
Rohacell
Soluble foam core from http://www.acmtucson.com/
sold by aeroconsultant.ch
Expandable foam core from https://www.tencatecomposites.com/products/adhesives-and-core
Epoxy foam for Sicomin http://www.sicomin.com/datasheets/product-pdf_fr19.pdf
I will give a try with the last one available in small qty and relatively cheep