Foam Core Tube Walls

Hello All,
Looking for information about fabricating a foam core tube wall using resin infusion. My plan is to make a hollow tube with and internal and external carbon fiber wall and a foam core in between to increase overall wall thickness. I was considering using resin infusion over a mandrel initially but possible moving to a split mold and through bagging to achieve a better finish on the OD. The foam core would most likely be Soric XF. Attached is a representative image, with green carbon inner and outer and a blue foam core, so as not to be confused with a solid foam core tube.
Has anyone built something like this? Any thoughts or advice are welcome.


Hello Jake,
What size OD, ID and especially the length & shape do you wish to fabricate?, I have manufactured many compound shapes & curves and ended up using Aluminium Heated Split moulds, happy to share my experiences with you.

Hi John,
Right now I haven’t really decided as I’m trying to work through the theoretical side of it. I would most likely be looking at 50 mm O.D. and inner and outer skins of 1 mm with a 2 mm foam, Soric, in between, making I.D. 42 mm. Length would be 800 to 900 mm. At the moment this is a straight tube. Application is a bicycle downtube.
Before even getting into carbon layup, I’m trying to get an approximate calculation on the stiffness of this. If you use just the Area Moment of Inertia for a hollow cylindrical section , obviously, having the increased wall thickness improves stiffness. However, I don’t want to create a solid wall, I want to make a sandwich panel for a wall. I’m not sure how to figure a sandwich panel construction into these calculations for a tube.

Check out my website - - Custom Projects, this shows the Aluminium Heated Tooling using Carbon - Unis, D/Bias & Twill pre-preg and Expancel which is contained in a sealed “Sausage” placed in the composite stack then heated to 115 deg.C for 2 1/2 hrs. this exerts pressure on the carbon laminate forcing it against the Alum. Tooling which comes out as a glossy tube with the Twill Carbon as the surface finish, very strong and long lasting on the Outrigger Canoe to connect the Float to the Hull in all conditions etc. see other pics. of the canoe on the water, I use this system is used for Bicycle frames and other structural components.