Rocketry materials tensile testing

[Ravenex]

My primary place of work has given me permission to use our basic tensile tester for some personal stuff so I'm thinking about doing some tests on materials I use in my recovery system. I'm thinking of testing various sizes of Kevlar as well as different methods of tying ends and loops. I'm also going to test some of my favorite swivels, u-bolts, and eye bolts. Most of the items rocketeers use have a load rating of some sort, but we don't know how these ratings are determined and with what safety factor so I'm going to do my own testing and compile and post the results. I would also be willing to test other items if any of our vendors or fliers want to send me samples. The tensile tester is hydraulic with three load cells, 1000lb, 2000lb, and 20,000lb it reads only peak pull, but that should be enough to help with component selection and sizing.

Over the next few days or week I will put together a list of the tests I am already thinking of doing. I would also love to get input from everyone on what you would like to see tested so let me know.

 

[rstaff3]

This should be stickied. Please post all results here, lest they go the way of rocketmaterials.org

 

[JohnCoker]

Knots vs sewn bridle loops, perhaps Nylon and Kevlar.

 

[dhbarr]

Holy cow, what an opportunity! Please throw a couple of lengths of "550 Paracord" on the list so folks can see what a gamble it is.

 

[markkoelsch]

Knots vs sewn bridle loops, perhaps Nylon and Kevlar.

John, I would expand on this a little- different knot types and how they effect strength relative to each other.


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[dr wogz]

Very cool!

Add some nylon cord and strapping / webbing to the pile..

And knots, lotsa knot testing.. Bowline in cord, braid, and strap / webbing. The classic 'trilene' fishing knot.. figure-8 knot, again, in cord, braid and strapping.. square knot, water knot, sheet bend..

And, the adding of CA or epoxy to a knot too..

I'd also be curious as to the pull strength of a fin, TTW style.. if for nothing else teh video to see what pulls apart first..

 

[Rob702Martinez]

Amazing opportunity. I would be interested in sending you samples of different composites I make compared to the G10 that is out there.

 

[mad4hws]

This should be stickied. Please post all results here, lest they go the way of rocketmaterials.org

+1. This is a question I have been wondering alot about lately.

 

[manixFan]

I have a variety of Kevlar strengths that are mil-spec surplus ends. It would be interesting to have them tested after they have been in my workroom for about 10 years. I would also like to compare the strength of a threaded loop vs. knots. (By threaded I mean where you thread the cord into itself by opening the braid and pulling the cord into the center of the braid.) I'd be happy to supply a variety of kevlar strengths for testing purposes.

How long of a sample can you test? Threaded loops need a fair length to work.


Tony

 

[brianc]

This should be stickied. Please post all results here, lest they go the way of rocketmaterials.org

Internet Wayback Machine has a fairly good snapshot of Rocket Materials.

https://web.archive.org/web/20150322005406/https://www.rocketmaterials.org/

 

[The_Lone_Beagle]

Internet Wayback Machine has a fairly good snapshot of Rocket Materials.

https://web.archive.org/web/20150322005406/https://www.rocketmaterials.org/

Thanks for posting that link, I remember looking at it a couple years back, and I've been racking my brains trying to remember it...

 

[rstaff3]

Yeah, I thought of that after I posted. It took some googling to find the site name.

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[Steve Shannon]

This should be stickied. Please post all results here, lest they go the way of rocketmaterials.org

I haven’t tracked what happened with it. What happened with it? I thought the site was hosted on the server Darrell Mobley had for Rocketry Planet.
Mark Koelsch, did you back it up once?


Steve Shannon

 

[djs]

How about closed eyebolts vs open. Everyone says "don't use open eyebolts- they'll fail on you", which I've seen happen, but would be interesting to get some data behind it.

Is this going to be the rocket version of the Hydraulic Press Channel on youtube?

 

[LithosphereRocketry]

I may be able to help a bit with the fins part... I did some foldover testing on TTW plywood fins & LOC tube for my G80-10 eater to prepare for going Mach 1.3 and 5500ft on a CTI 6 grain full H. I got about 500kPa shear strength at the root using TB3 and no internal fillets. The tabs sheared at the root glue joint and then peeled a layer off the BT as they folded.

Very cool!

Add some nylon cord and strapping / webbing to the pile..

And knots, lotsa knot testing.. Bowline in cord, braid, and strap / webbing. The classic 'trilene' fishing knot.. figure-8 knot, again, in cord, braid and strapping.. square knot, water knot, sheet bend..

And, the adding of CA or epoxy to a knot too..

I'd also be curious as to the pull strength of a fin, TTW style.. if for nothing else teh video to see what pulls apart first..

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[Ravenex]

Okay, so the response to this has been more enthusiastic than I expected which is great. I am going to admit up front that my testing will not be as good as the old rocketmaterials.com test. My tensile tester only reads peak stress and only at 1lb increments. The tester I have access to is Also due to time limitations it may take a while for me to test and post results.

I will need to design and make, or purchase fixtures for my tester and do some other development work before getting start. Once that's done I can start testing. I could use some help from this community developing a wish list and making/acquiring samples. I will make a public google doc and post it here shortly to start collecting test ideas.

 

[markkoelsch]

I haven’t tracked what happened with it. What happened with it? I thought the site was hosted on the server Darrell Mobley had for Rocketry Planet.
Mark Koelsch, did you back it up once?


Steve Shannon

Steve, I cannot remember for certain. As you likely recall, I was in high speed mode trying to save folks sites hosted by Darrel after he died with the server being in poor shape. Let me see what I can find.


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[markkoelsch]

I checked. I no longer have the site files. I backed them up I think at one time, and sent them to the various site owners. I kept them for a while. Once we shutdown RP, I deleted the files as they were not mine, and I had not intention of ever using them.

There might be a server with them on it, but you have the reigns to that, Steve Shannon.

 

[JohnCoker]

Okay, so the response to this has been more enthusiastic than I expected which is great. I am going to admit up front that my testing will not be as good as the old rocketmaterials.com test. My tensile tester only reads peak stress and only at 1lb increments.

That's why I suggested knots and sewn loops; they're a simple pull-apart test that shouldn't require a fixture. But it might be helpful if you posted a picture of the machine and how samples attach the the spreader bits so people could have a clearer idea of how to design experiments.

 

[JohnCoker]

Internet Wayback Machine has a fairly good snapshot of Rocket Materials.

I also have the lap-shear test results he did for me on my site:
jcrocket.com/adhesives.shtml