Delamination OR something else?

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RealMcCoy
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Delamination OR something else?

Post by RealMcCoy »

Hi! I'm new to the forum but have built three snow boards already.

My most recent build seemed to come out great however after my first ride I have what looks like some kind of delamination. I had an imperfection in my press and epoxy slumped from the tail down to the flat behind the rear binding. I suspect the fiberglass floated off the core and the flex of the board caused the excess epoxy to crack when ridden.

Board has no top sheet, just raw epoxy.

So....to fix it? I've done fiberglass work on wood boats before and have sanded off the epoxy and glass to get to wood and patch bad fiberglass. Can i do this with a snowboard? Will the overlap from the original layup and the new layup create a fatal weak point?

I've never posted pics to a forum like this, so I haven't figured out how. they can be found here though, https://mccoyfire.sharefile.com/d-s66fd ... 3507ba662e

I'll work on figuring out the posting of pics!

Thanks!
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chrismp
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Re: Delamination OR something else?

Post by chrismp »

I think a repair should work, but will definitely create a weak spot. The question is if it will be to weak to ride.

If you want to make absolutely sure, you could sand the whole top layer off and press on an entire new top layer.

For posting images, you can either use the "Attachments" section below the text box or you can simply drag and drop images into the text box, which adds them as an attachment, too. Then you can simply click the "Place inline" button to place the image wherever your text cursor currently is. Keep in mind though that only files up to 1 MB in size are supported that way. If you want to add larger files, you need to use an external image hosting service.
RealMcCoy
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Re: Delamination OR something else?

Post by RealMcCoy »

Thanks Chrismp.

I did consider a complete sand down of the top and that is likely the best solution, but was hoping for something simpler!

I guess I’ve got some work to do!

Thanks.
TimW
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Re: Delamination OR something else?

Post by TimW »

That looks like compression failure of the laminate (compression stress in the laminate from bending, not the pressure of your feet). Compression strength would suffer from insufficient matrix strength(mixing ratio, cure cycle?) or poor fibre interface strength( fabric moisture? age/ storage?).

I've had this when riding a board without postcuring it.

So it could well be that the full laminate is affected, do a local repair is a bit of a risk. So you might want to do the whole top. Don't worry about the bottom laminate, that is mostly loaded in tension.

Regards, Tim
RealMcCoy
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Re: Delamination OR something else?

Post by RealMcCoy »

Thanks Tim!

This makes sense! My resin was left over from a boat project I did a few years ago and might have been too old. And I’m sure there was inadequate post-cure as well since I rode it less than two weeks after press. My previous boards were made in The summer or early fall and had several months to fully cure.

Regarding post-cure is there a process or Just time to allow full cure?

In your opinion is it with sanding down the whole top and relaying the glass or should I just start over with fresh materials?

Thanks again.
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chrismp
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Re: Delamination OR something else?

Post by chrismp »

The required post-cure depends on your epoxy resin - you can check the TDS if it requires a post-cure. For many resins a post-cure is optional and only increases the glass transition temeperature. In those cases it should be sufficient to just keep the board for a few days at room temperature to fully cure. For my boards I usually keep them for at least 7 days at room temperature before cutting the flashing.
TimW
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Re: Delamination OR something else?

Post by TimW »

It is not just the Tg that goes up with post cure, other mechanical properties increase as well, especially compression. You simply increase conversion of your resin, with that the matrix strength, and compression properties are directly dependent on that (as it stabilizes the fibres, without resin support it is just a fabric).

If nothing is specified it is safe to do something like 70°C for a few hours.
Note that while post curing you may/will go over the current Tg (which will then increase during the post cure). This means that the epoxy will go to a rubber like state temporarily, so you may need to support your board(esp. tip and tail), otherwise it may deform. So best to do it on the mould.

I'd guess it is more the lack of cure than the age of the epoxy. If the rest of top laminate looks undamaged(no white spots indicating matrix damage of fibre debonding), then you could try a local repair. The rest of the laminate should improve in strength with cure.

Regarding sanding down the whole top vs starting from scratch, just do whatever is faster for you. I'd expect board quality will not be a big difference, and with a new board new mistakes can always happen.
SleepingAwake
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Re: Delamination OR something else?

Post by SleepingAwake »

Care to share the layup and core material with us? Might also just be insufficient strength wise.
In my experience from work it is usually not the epoxy, even though that certainly doesn't help (still might be the cause...)

Also the finish on the fabric will go bad over time, which might have just as big of an impact on compression strength.
TimW
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Re: Delamination OR something else?

Post by TimW »

Ah yes because you mentioned cure maybe I focused a bit to much on that. If your fabric was also old and not stored dry (humidity), the fibre sizing may also be the culprit.
And as said it could simply be insufficient strength.
RealMcCoy
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Re: Delamination OR something else?

Post by RealMcCoy »

In Response to SleepingAwake, here's my layup details....

I bought a sintered base sheet and poplar core from Snowboardmateirals.com and used those, although on my other boards I laminated up my own core and will likely do that in the future.

I had left over Epoxy Resin from a previous boat building project and it happened to be just enough! So I used it. I do not have a fiberglass supplier near by, so I used 8oz automotive fiberglass that i could buy at the hardware store and layered it up to get 16oz "biax" and then laid strips at 45 degrees to get "triax". I used this same method on my previous boards to good results.

So total layup as follows:
Base Sheet
16oz fiberglass (2 layers 8oz)
Polar Core
24oz fiberglass from the rear binding to the tip (three layers 8oz, on layer set at 45 Degrees)
16oz fiberglass from the rear binding to the tail. the board is shaped like a Ride Warpig and I more or less used their specs.
I did not use a top sheet, just left raw epoxy.
I used Aeromarine brand resin and hardener. It has very similar characteristics to West System 105 with 205 hardener.

My press was an experiment that I have mixed feelings about. My first press was laminated MDF and particle board. Overall I was happy with the results, though after removing the board from the press it relaxed and I lost the camber. The drawback to this press is the weight. It weights 85#. its hard to store and move. This time I used high density foam adhered to a plywood base. I made my layup next to the press, sandwiched between two sheets of aluminum. Then moved it to the press and clamped it all together.

I really like the ease of modification for different shapes and lengths. I made one mistake though! Since the board is basically flat I used the plywood as my bottom press with shaped tip and tail foam, but for the top piece I needed one continuous piece of foam shaped to the profile of the bottom. My foam blocks were not long enough so I had to but two pieces together when I stuck them to the plywood backing. I ended up with a deformity at this joint that allowed my epoxy to slump and pool at this joint. I think this allowed my fiberglass to float up into the epoxy pool. Everything seemed good when i pulled it out of the press, though I could tell epoxy had pooled.

A week after taking it out of the press it was ready to ride. I loved the way it rides. Very poppy and floats nicely in powder. About half way through the day I noticed the compression fracturing in the epoxy and realized what must have happened.

Pics of the press and board can be seen here. https://mccoyfire.sharefile.com/d-s0fe7 ... 1972b92072
TimW
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Re: Delamination OR something else?

Post by TimW »

Your total fabric weight should be ok. But the spec is a bit vague. :-). Glass fibers come in different qualities and with different sizings(= surface finish) suitable for different resins. Epoxy is quite easy going in this, but the fabric is probably far from optimal.

The floating of the fabric in the resin will affect the alignment of the fibres. If fibres are not straight compression strength will suffer. Glass fibre laminates are not as sensitive as carbon fibre laminates to this, but still it is something where you can lose quite a bit of strength.

So it may well be a combination of factors that led to this. Not the best fabric, not the best laminate, sub optimal cure, and you end up with a weak overall laminate.
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chrismp
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Re: Delamination OR something else?

Post by chrismp »

TimW wrote: Thu Jan 12, 2023 2:46 am It is not just the Tg that goes up with post cure, other mechanical properties increase as well, especially compression.
For the Sicomin resins we use, that is not the case. E.g. with the Sicomin SR 1280/SZ 8525 combo we use, with longer or higher temp post cures pretty much all relevant properties including compression strength suffer from a post cure. The only other property that increases apart from Tg is impact strength, which isn't really relevant in a snowboard.
TimW
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Re: Delamination OR something else?

Post by TimW »

I did not mean to imply that mechanical properties go up with higher post cure temperature. I was comparing to no post cure at all, as I understand from RealMcCoy that he just did a room temperature cure.

Regarding the Sicomin resin, I just checked the datasheet. Be careful with the interpretation of those values and how they convert to the properties of a laminate. A standout change is the doubling of the tensile strain to failure (and the charpy). I'd expect the laminate properties to be better for the higher cure temperature, especially fatigue properties should be much better because of the higher toughness.
RealMcCoy
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Re: Delamination OR something else?

Post by RealMcCoy »

Regarding post cure….I did cure at room temp 75 degrees.

If I heat my press or the press room higher than that do I get better post cure or just faster cure?
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chrismp
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Re: Delamination OR something else?

Post by chrismp »

TimW wrote: Fri Jan 20, 2023 7:28 am A standout change is the doubling of the tensile strain to failure (and the charpy). I'd expect the laminate properties to be better for the higher cure temperature, especially fatigue properties should be much better because of the higher toughness.
Dang, totally overlooked that one! Good thing we always cure our skis at 100°C :D
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