Fabricating carbon exhaust muffler tubes?

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#1

I purchased a couple carbon fiber mufflers and cut them apart to try to figure out how these things are made. I have a couple questions to make sure this is correct before I attempt to make some of these myself (tired of outsourcing these parts from China).

The best way I can see is to first make your plug. That is covered, I will cut the templates and use my hotwire. For building the mold though, that is where the questions come. Is the mold to make a tube just a two-piece mold with prepreg then vacuumed? Is it that simple or am I missing something?

#2

Which way do you want to do it. Enclosed mold, or wrapped around a mandrel. Also your final finish desired can determine a few steps as well.

I do this often with both wet layup and prepeg. Both setups too. Very simple way can be to wet layup and use a PVC(heavy) mandrel and vacuum bag it over it with just release fabric(rough finish) or no fabric at all(just bag, semi gloss finish). Take a little practice, need to work excess resin from the center of the tube out to the ends(rubber body filler spreader works). No need to prep the mandrel either, just wrap a tight layer of baggin film around the tube and you can blow the tube right off the mandrel with compressed air like water on ice. Just make sure the tube is smooth(no burrs)

#3

I have seen bole mufflers that are filament wound,and then heatshrink tape wrapped (or tensioned mylar, same effect), which leaves a raised flash of resin due to the tape thickness. It was left like that, and I’m sure you can sand it down a tiny bit.

That said, it prob can be made with a simple tube. Wrap prepreg, wrap tape, bag if you want too, and cook. Pulling off will be tricky. Have a EVER so slight draft helps. No burrs. Shapes should pull off as well, but you might need to make the mandrel have a pulling ring, and wrap a compression system on the carbon tube, and pull off with hydraulic rams.