Using Heat Shrink Tape

Well I did it again, this time with much more pleasing results (somewhat). I thought I should post this since it really includes good info. This of course, however is practice for later to be worked on carbon fiber. In this set up I used 4 layers of 8 Harness Satin fiberglass along with using perforated heat shrink tape from dunstone. I also did this using a hair dryer (best recommended use a heat gun capable of 300 degrees F+). After tightly wrapping the perforated tape around the laminated glass. I carefully applied heat (hot enough to the point the tape shrank) along the tape, while rotating the mandrel. This allowed me to not end up heating too much. I waited 5 minutes in between heating. This way the laminate cools down. I may have ended up heating too much since I still got some nasty bubbles that piled up. This is the somewhat part that was not pleasing, however I feel the bubbles are natural when it comes to fiberglass. With carbon you hardly see this since the fabric is more stiff. The pleasing parts was that the tape still neatly compacted the laminate. This in turn allows for more layers to be put into the laminate (need to test this still). The more layers the more stronger your part will be. Also less resin in your part since the perforations allow for bleed out.

Here is the tube after curing from the heat of the hair dryer.


Here shows how transparent this tube came out. If only the air bubbles wouldnt form this would have been a pretty glass tube.


Here is a shot of the tubes thickness. Originally this should have been 0.06" thick, but the compaction greatly reduces this. Will get a better picture when I cut it tomorrow.


Here is a shot of the bubbles that form. Probably caused from too much heating, the nature of the fiberglass, or Aeropoxy's epoxy just tends to produce air bubbles. I dont know maybe one of you can shed some light on this effect.


More to come on carbon fiber when I get some more.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

When I make tubes with Aeropoxy, I limit the temperature of the initial cure to <100°F. If the temperature is higher than that, I get bubbles like what you're showing that are hard to fix. I don't know why this gas is produced. Perhaps you're seeing the same thing?

When you do this again, I'd like to see some measurement or picture of the amount of expoxy being removed by the tape. Roughly, you should have around 50 grams of epoxy in the tube. A portion of this needs to be removed before any compaction occurs. Perhaps you can estimate the weight of the epoxy that bleeds through the holes?

Jim

From Jim's last comment it seems the issue is with the Aeropoxy. I am surprised that you were able to get the shrink tape to shrink with a hair dryer. To my knowledge, all hair dryers are limited from going to 140F because at that rough temperature the human skin starts to burn. That being said, I would be surprised if your hair dryer went over 130F. The PERFORATED HI-SHRINK TAPE from Dunstone is a polyester material and starts to shrink at 150F, so even if it did in fact shrink it couldn't of applied much force seeing as it probably shrank at a low percentage. Also if you use a heat gun, you do not want it to go over 300F, seeing as that is roughly the temperature at which maximum shrink will occur (most compressive force / around 20% shrink) and anything over that is approaching close with the maximum temperature usage of the shrink tape (which is 350F) and if using a heat gun without low settings one can easily reach the melting point of the shrink tape (which is around 484F for most). Note that to achieve maximum shrink you will need to hit 302F and maintain it for 15 minutes. I would also be curious to see how much epoxy is on the tube prior to wrapping it with shrink tape?

JimJarvis50 said:

When I make tubes with Aeropoxy, I limit the temperature of the initial cure to <100°F. If the temperature is higher than that, I get bubbles like what you're showing that are hard to fix. I don't know why this gas is produced. Perhaps you're seeing the same thing?

When you do this again, I'd like to see some measurement or picture of the amount of expoxy being removed by the tape. Roughly, you should have around 50 grams of epoxy in the tube. A portion of this needs to be removed before any compaction occurs. Perhaps you can estimate the weight of the epoxy that bleeds through the holes?

Jim

Click to expand...

Hi Jim, even without heat I get some bubbles from the epoxy. When I laminated the tube the bubbles were not present. I imagine even if I did this with peel ply I would still get bubbles. I have noticed them on my speedy gonzales tube.

If anything I may have reduced most of the epoxy while I was wrapping the tape, because I wanted to make sure it was tightly wrapped. I pulled on the tape and loads came out through the perforations. When I heated the tape not much came out.

I will most certainly have to try this again. I will do one more test with glass and then for certain I want to try it with carbon. I will continue to do this with Aeropoxy. I forgot I still have loads of infusion resin.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Here is the tube with the cut ends. Some areas varied in thickness. This obviously tells me some areas of the tape were not shrunk that much. However, I feel like two more layers could have been introduced into the laminate and end up with a 0.06" thick wall. Which in this case is my target.




Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

No disrespect intended but I think the issues with the bubbles is user technique. I think it would be very rare that bubbles would form with the addition of the amount of heat needed for the shrink tape. As you mentioned the bubbles form when you are not applying heat; I think that rules out bubble formation due to the application of heat epoxy.

Instead I think the bubbles are present during the lay up. This could be caused when mixing the resin/hardener together, however I would suspect that would not be the case this time. When you are rolling the fabric over the mandrel while simultaneously wetting it out, it would need to be done very diligently. During this process it is very easy to trap air bubbles in-between the layers, especially with both of them being wet. This can occur easier than one might think and can become very problematic, as you might of found out. Also the transparency of the glass makes spotting bubbles very easy. I also think that the reason the bubbles are more "visible," when trying to use heat shrink tape is because when heat is applied the bubbles will expand.

Anyways hopes this sheds some possible light into what the cause may be.



Cheers.

My guess would be that the heat makes air that is trapped bigger. Chances are that the bubbles are introduced in the measure and stir. I have seen some who heat their epoxy to help rid of such. But understand that will shorten your working time.


Kirk

Like I had mentioned to Jim, I have even done tubes with peel ply and they still end up having air bubbles trapped. When I mixed my epoxy there was no sign of bubbles. I am really careful when it comes to mixing to make sure I end up with none.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Got me a heat gun for $22. It has really high temp settings as you can see in the picture. So definitely I will test it on a piece of the shrink tape before trying it on the real deal. This way I can get an accurate measure of distance so I wont over heat it.



Some mohair rollers with 1/4" nap. A must for laminating.




Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

This is all based om my recent experiments with the Dunstone tape, I am by no means an expert...

At what spacing did you wrap the tape? This has an affect on compression as well. Tighter spacing, more compression. I think if you were to do 1/8-1/4" spacing you could get away with less shrink and need less heat. There is more uniform diameter versus length with tighter overlaps as well.

Also the perforations in the tape are for releasing gasses created in cure. Or at least that's what Dunstone says. I have found that plenty of excess resin bleeds out the tape spirals. I only mention this because it you wrap it like I suggest, you'll be blocking all of the perfs in layers of tape.

watheyak said:

This is all based om my recent experiments with the Dunstone tape, I am by no means an expert...

At what spacing did you wrap the tape? This has an affect on compression as well. Tighter spacing, more compression. I think if you were to do 1/8-1/4" spacing you could get away with less shrink and need less heat. There is more uniform diameter versus length with tighter overlaps as well.

Also the perforations in the tape are for releasing gasses created in cure. Or at least that's what Dunstone says. I have found that plenty of excess resin bleeds out the tape spirals. I only mention this because it you wrap it like I suggest, you'll be blocking all of the perfs in layers of tape.

Click to expand...

Just like you said, I spaced it farther apart to allow the resin to bleed out. I could try half ways of the width of the tape. If it bleeds more through the spirals, then I see no reason why not to try it.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

I made the run again. This time with a heat gun. I had an unfortunate mishap that I should have foreseen, but I didnt. My barrier to the mandrel is also heat shrink tape and it lumped up on me with the heat. However, I am still quite convinced that this can be done.

The story:

Here is a shot of my mixing skills. No bubbles what so ever.


50 grams of epoxy mixed and the here is the tube laminated. Might be small bubbles trapped, but doesnt look like it.


Shrink tape applied and you can see I pulled on it tightly that it removed quite a few resin.


Heat applied with the heat gun and no sign of bubbles.


Uh oh I noticed a little problem before the mishap. This was along the spiral of the tape. I dont know why that happened.


Here is the mishap. I had to remove everything (including the glass) and re did it and finished with teflon peel ply. I couldnt just scrap good glass.


I am very convinced this is possible. Taking your time and being careful will be the key to using the shrink tape with a heat gun. I definitely need to try this with carbon and for certain I need to get me a none-shrink polyester film to prevent that mishap.

Do any of you know a source where I can get 0.002" thick polyester film and is at least 3" wide?


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Going to order some supplies. I still have tons of resin infusion epoxy. All I need is more fiberglass and definitely a new barrier to my mandrel. I managed to get ahold of Rob from dunstone and they have some of their non shrink tape. I will order this next week. The fiberglass I will place an order asap.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Placed an order for this type of glass.

https://www.acpsales.com/6-oz.-Fabric-50-Wide-Tight-Weave.html

I am a huge fan of tight weave fabrics. I got the 50" wide version as to allow me to cut a one foot piece to experiment on and have 50" of glass to incorporate more layers than is required to get a 0.06" thickness on my laminate. This way I can estimate how many more layers I can add into the laminate and end up with a 0.06" thickness after the compaction of the shrink tape.

To start off I will go with 8 layers instead of 6 layers. More layers equals more strength.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

I may be able to shed a little light as this is what I do for a living. As for the bubbles. Typically there are two sources of bubbles. One is air introduces during the mix. Some resins/epoxies require a de-gas in a vac chamber prior to use. I suspect that the second source of bubbles, rapid outgassing, is your problem. As a point, the fabric used in the application won't make a difference. As the thermal mass increases, or the temp increases past the glass transition point, the chance of a exothermic spike increases. Most advanced, hi temp resin systems (BMI and Cyanate esters for example) transition at 350degF. Most other resins (Aeropoxy amoung them) trasition at around 250degF or lower. Hotter than that you will get outgass bubbling. This can be mittigated in an aoutclave or under a vav bag. The use of a perforated film (as you're using) and/or peel ply can help as well. If the resin gells rapidly (say from a heated force cure) these outgass bubbles can become entrapped. Typically for a wet layup we let it sit for as much as an hour under a vac bag before applying heat. Faster resins (many of the hobby grade resins) don't provide enough time for this. Fast cure resins are good as adhesives but not always as laminating resins. One+ hour cure times at room temp are best for layup.
As for your fabric; sounds like you're using a 7781 cloth. Typically it has a finished thickness of .011". The typical target ratio of glass to resin (by weight) is 60/40 to 70/30 with the latter being ideal for aerospace applications (also the toughest to achieve Out Of Auto Clave). Carbon is tougher to get to properly wet out at the core in higher ply count laminates so do a couple of test coupons before your final layup. Additionally a tin catalyzed Vinyl Ester resin seems to have te best wet out in carbon fabrics.
If your using a VARTM system you might try a double Vac bag system. A google search will yeild some good info on the method. It's proving a great way to get clave quality results out of clave. Additionally the University od Delaware is ground zero for Composite development. They have a good deal of info posted online for anyone interested.
FWIW.



View attachment aeropoxy pr2032 bulletin.pdf

This leads me to believe further that a heat gun versus a hair dryer was more sufficient. Despite the heat gun being higher in temperature. The hair dryer I had to held in place for a few moments to get some shrinkage of the tape. I believe this was the reason for those air bubbles on my first attempt. With the heat gun I can heat it, it will shrink and I can move on.

I am quite convinced that it doesnt matter, which fabric or epoxy you use this can still be done. All it is, is getting the appropriate form of heating with the heat gun.

By the way no vac bagging here. The purpose to the tape is pretty much the cheaper alternative to that. I need to keep practicing.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

SinfulDarkLord said:

By the way no vac bagging here. The purpose to the tape is pretty much the cheaper alternative to that. I need to keep practicing.

Click to expand...

Vacuum bagging tubes is a fool's errand. Tape is definitely the way to go.

Thanks Troy for sharing the info. I have definitely been a victim of the elevated temp bubbles.

watheyak said:

Vacuum bagging tubes is a fool's errand. Tape is definitely the way to go.

Thanks Troy for sharing the info. I have definitely been a victim of the elevated temp bubbles.

Click to expand...

Most agreed


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

for all of the trouble you are going through why not do it correctly and build a small oven. That tape or the shrink tube is going to work much better if you can control you temps.

flynfrog said:

for all of the trouble you are going through why not do it correctly and build a small oven. That tape or the shrink tube is going to work much better if you can control you temps.

Click to expand...

That would indeed be the best option. Here, I am merely trying to see if one can achieve it without an oven. It would be more frustrating of course. I plan on taking an approach other than an oven, however.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

I have a roll of Dunstone shrink tape and really want to take it for a test drive. I think a simple wooden box easy bake style oven would be the ticket. I already have a fancy thermostat to use on it.
-Ken

the real key to getting the tape to work is to tension it well as you wrap it and keep an even overlap probably a minimum of 75% overlap.


SDL all the careful mixing in the world is not going to do a bit of good with those paint rollers they are filling your resin with microbubbles.

I'm not sure why I didn't think if this earlier, but if your goal is to get decent compression without an oven, I had really good luck with the Soller Composites heat shrink tube and a heat gun.

https://www.sollercomposites.com/composites/carbon fiber sleeves.html#Shrink

Perfect surface finish, and good compression as far as I could tell. The tube I made used fused uni carbon that is hard to get wetted out and compressed, but it worked great with the shrink tube.

flynfrog said:

the real key to getting the tape to work is to tension it well as you wrap it and keep an even overlap probably a minimum of 75% overlap.


SDL all the careful mixing in the world is not going to do a bit of good with those paint rollers they are filling your resin with microbubbles.

Click to expand...

I am still quite convinced that the micro bubbles are due to the soft nature of fiberglass. Unlike carbon where it is more stiff the bubbles hardly form on it compared to fiberglass.

This is a piece of a 38mm carbon tube I made not too long ago. Notice the peel ply texture area and then notice the none textured area. Is it possible the none textured area is loaded with thousands of micro bubbles that I just cant see?




Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

watheyak said:

I'm not sure why I didn't think if this earlier, but if your goal is to get decent compression without an oven, I had really good luck with the Soller Composites heat shrink tube and a heat gun.

https://www.sollercomposites.com/composites/carbon fiber sleeves.html#Shrink

Perfect surface finish, and good compression as far as I could tell. The tube I made used fused uni carbon that is hard to get wetted out and compressed, but it worked great with the shrink tube.

View attachment 184157View attachment 184158View attachment 184159

Click to expand...

Pretty much, yeah that was the idea. I dont know if many of you know about the X-winder, but that set up uses a heat gun with some distance from the mandrel and also the mandrel is rotating and the heat gun moving sideways horizantally and parallel to the mandrel. I asked Turner Hunt on how their set up works and he told me that they use thermo lasers to make sure the temperature is consistant at 150F for about 3 to 4 hours.

Probably the shrink tube provides some compression, but not as much as the tape. I should make a test on that as well and see just how much compression it gives to the laminate. I'll later ditch the heat gun and just use an oven. I dont think I can hold the heat gun for 3 to 4 hours lol.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Alex, your really are making your life much harder than it needs to be by not building an oven. Heat guns are too uneven on heating the laminate, you cannot hold it long enough, and you are clearly really working at composites. Time to stop making tubes for a little bit and build an oven preferably with a rotisserie type deal to turn the tube as it cures.


Mark Koelsch
Sent from my iPhone using Rocketry Forum

markkoelsch said:

Alex, your really are making your life much harder than it needs to be by not building an oven. Heat guns are too uneven on heating the laminate, you cannot hold it long enough, and you are clearly really working at composites. Time to stop making tubes for a little bit and build an oven preferably with a rotisserie type deal to turn the tube as it cures.


Mark Koelsch
Sent from my iPhone using Rocketry Forum

Click to expand...

Dont worry I intend to build one. Not always will I use the tape though. I sometimes feel it is not required as much. It is only in the event that I want more strength to the tube.


Alexander Solis

Level 1 - Mariah 54 - CTI-I100 Red Lightning Longburn - 6,345 Feet

Felt the urge to experiment so I took some scrap 4HS carbon that I had and laminated almost close to 7 layers (was missing like an inch or so to complete the seven wraps). Then I got the shrink tape and fried it with the heat gun. Even saw the epoxy bubbling.

Here is a picture.


Will check tomorrow how it turns out.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

I'm quite pleased with this. I am confident that I can make carbon tubes with 8 layers. For sure, I believe the perforated shrink tape is not necessary. I will definitely have to try this again on a more longer tube. This one was only 4". Also with a non-perforated shrink tape. Recommended shrink tape width anyone?


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

Forgot the picture lol




Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet