u/Fit-Split-1782

A follow-up to my previous thread. As per a suggestion there, I blowtorched my carbon tube to determine the true nature of the layers (thank you so much for this advice, it worked amazingly well).

As one can clearly see, my original request of the manufacturer, which was "0-degree (longitudinal) in all layers except the very outer layer, which should be 0/90" was NOT what I was given.

Now, the fact that I'm not getting what I asked for is its own concern, but I have at least determined that it's not the end of the world, since I have now also blowtorched previous batches I have received, and they are identical, which means all the strength testing I have done previously is still applicable to this batch. The tubes have performed well. And it seems like perhaps mostly 0-degree fibers would have sucked anyways?

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So a new question arises: is this a good layup? Should I bother telling them to do it differently? As far as I can tell, it works well for my application, but I'm wondering how much more strength/weight I could be getting without losing some of the "toughness" of the hoops and 0/90s.

For context, these tubes are about 21" long, 29mm OD (~1.15"), 1mm wall thickness, and they fit together like tent poles. The direction of the force is primarily longitudinal compression. Do you guys think that, given these circumstances, this layup is close to optimal already?

A couple of videos showing the tubes in action, so you can understand the forces at work:

https://www.youtube.com/watch?v=ih3FQw-j66o

https://www.youtube.com/watch?v=eBpAHqe993c

I ordered a batch of CF tubing requesting that all the layers be 0-degree fibers except for the outermost layer, which I wanted to be 0/90. The tubing is 1mm wall thickness and 29mm OD, for a bit of extra context.

Today I wanted to confirm that the layers are as I specified, so I took a knife and delaminated one of the tubes into 3 sloppy pieces (bottom is the innermost layer, middle is the middle, and top is the outermost layer).

The *bottom* piece in the picture is the innermost part, which means it should definitely be 0-degree at this point. However, that looks like 0/90 to me (red circled section). I know that 0-degree cloth often has some 90-degree fibers just to kinda hold it all together for layup, but would that appear this way when it's cut/delaminated? Or, maybe I'm just seeing resin weaved through and it's giving me the illusion of 0/90 fibers?

I don't have enough experience to know what 0-degree looks like post-resin, so I'm hoping someone could offer some insight.

Also, what's up with the 90-degree fibers that are clearly visible in all 3 pieces? Does some "0-degree" cloth come with a fine layer of integrated 90-degree carbon just to add a bit of crush resistance?

Any insight from those more experienced would be appreciated.