Sidewall Lamination Experiment

Damon · Post by **Damon** » Thu May 14, 2009 9:55 am

Curing as I type.

Setup:
5'x4"x1/2" piece of maple w/ white UHMWPE sidewalls (1/2")

broken up into 5 sections:
1. holes drilled 1.5" apart vertically (thru) and horizontally (1/8 - 1/4" deep) into PE + flame
2. holes drilled 2" apart horizontally (1/8" to 1/4") into PE + flame
3. flame only
4. 80 grit sanding then flame
5. 80 grit only

layed up with a 5:1 ratio of jeffco 1397 and 3198 hardner. Flame treating consisted of three passes, about 3-4" away, and moving about 1"/sec.

I will be planing the sample to 7-9mm.

Anyone have a good idea on how to quantitatively test delamination? I was thinking a 3 point flexural, but there might be a better way.

Results coming soon.

Damon

KevyWevy · Post by **KevyWevy** » Thu May 14, 2009 11:35 am

im a little confused on the holes.... pictures?

Damon · Post by **Damon** » Thu May 14, 2009 12:01 pm

I'll get some pics tomorrow.

Just picture holes drill in the sides and tops of the sidewall, on the edge next to the wood. What I'm hoping to accomplish is some type of "epoxy fastener." I want the epoxy to bond to itself in a T shape to take the load instead of a single bond between wood/sidewall or fiber/sidewall.

Damon · Post by **Damon** » Wed May 20, 2009 5:08 pm

I'm having doubts about the 3 point test - I don't think it is going to accurately give me the data I want. This is the result of the sanding only sample, I'm wondering if the large drop in load was the delam - however it was a pretty audible snap, and the maple was starting to splinter underneath. When I took the sample out the epoxy was still holding the sidewall, but pulled apart with hardly any force.

twizzstyle · Post by **twizzstyle** » Tue May 26, 2009 10:54 am

This really makes me miss my days at K2.

I would love to see a photo of your test rig (what is doing the pulling? Instron kinda deal?). By 3 point is this 2 points holding it in place on the outside, with the 3rd point pull in the middle? That would give you the stiffness of the sidewall material resisting it from pulling off the wood (if that makes sense). I would think just a free-ended pull would be easier. Pull straight out sideways from a free end, with the other end fixed. The ultimate load will be lower, but might be more representative.

It looks like there are a few skips in the data around 800 lbs and again at ~850 lbs which could be wood fibers breaking down, or small bits of delam here and there. But crap, 900lbs is a lot of force, that is a damn good bond. With our best bonded sidewalls, I'm sure we could still pull it off by hand (thats what she said) without insane effort.

My issue isn't with sidewall-to-core bonding, but sidewall-to-topsheet bonding. After 4 days of skiing on my piggy sticks, you can see quite a lot of spots where it has delammed (from the other ski hitting it, etc)

This looks like an awesome legit look into bonding techniques though Damon! I'm gonna keep watching this!

twizzstyle · Post by **twizzstyle** » Tue May 26, 2009 10:58 am

Also, ultimate tensile strength... what are the units? That sounds like a failure threshold to me (its been a few years since school, so a lot of this has escaped me) so is that the failure of the p-tex in a tensile load? Or something completely unrelated?

Damon · Post by **Damon** » Tue May 26, 2009 11:15 am

Just got done with the other samples. These were tensile tested - I'll describe more later when I have time... just the results right now.

Sample 1

Sample 2

Sample 3

Sample 4

Right click -> view to see better...

twizzstyle · Post by **twizzstyle** » Tue May 26, 2009 7:05 pm

(you need to label your plots

I don't know which plot is what bonding method, its just a bunch of plots)

Damon · Post by **Damon** » Thu May 28, 2009 12:46 am

So here's how the testing went:

Each sample was cut into (3) 2" strips. The reason there are 3 subsets in each sample. The numbers correlate with above, but for a reminder:

1. Vertical and horizontal drill, flame
2. horizontal drill, flame
3. flame
4. 80 grit then flame
5. 80 grit, no flame (omit)

Tested under tensile, with a setup similar to this:

With the top jaw clamped to the polyethylene, and the bottom jaw clamped to the maple. The peak load is representing the force it took to pull the two apart - which might not be the most representative in skiing terms, but just to quantitatively find the bond strength between samples, I think it works.

I'll have pictures of what I did for the drilling soon - It's tough to drag the nice cam into the lab.

As far as results... I don't think there can be any conclusions unfortunately. The variation within the sample is too great to really call one a winner. Plus my hole experiment didn't work - one issue is having the epoxy fill the hole completely.

bobbyrobie · Post by **bobbyrobie** » Thu May 28, 2009 12:57 am

you wouldn't happen to have access to a bell peel type test would you.

twizzstyle · Post by **twizzstyle** » Thu May 28, 2009 5:55 am

It would be easy enough to setup a peel test using the rig he has.

Also for the epoxy filling the holes, you can thicken up the epoxy to help it stay in there better, and use a small syringe to fill each hole (but I imagine that would take a LONG time...)

twizzstyle · Post by **twizzstyle** » Thu May 28, 2009 5:57 am

Also, another suggestion (sorry for all the critiquing damon, but you know my work revolves around data, so I am picky about these things)

If you could, a plot with all samples together would be an easier way to compare them, whether or not the data is conclusive at all. Scrolling between different plots is pretty useless, especially when the scales are not the same.

Damon · Post by **Damon** » Sat May 30, 2009 1:39 pm

Yeah sorry about the multiple graphs, I can't change it either. The testing software is a bit archaic, coupled with my lack of knowledge on it = print screen + paint...

As far as the peel tests go... the machine can do it, but we don't have the jaws.

For the holes.... I'm thinking about drilling vertically after the sidewalls have been attached to the cores, to create a bond between the two layers of fiberglass. When under a vacuum, the epoxy should fill the holes easily.

So here are some pictures... I guess I need a macro lens.

This is the horizontally drilled sample. The epoxy filled the interface between the wood and PE, but failed to penetrate any deeper into the hole.

The horizontal and vertical sample on top, with the horizontal on bottom. The epoxy filled this hole a little better, but still failed to completely fill both holes.

knightsofnii · Post by **knightsofnii** » Fri Jun 12, 2009 11:14 am

i'm setting up some tests as well, I'm going to have like....20-30 different samples I hope, got 2 full sheets of PE to screw with, and some bamboo even.

But what you did here was pretty cool, sucks that it was inconclusive.
Next test, I would suggest a layer of glass inbetween. But what are you looking for? A stronger bond between sidewall and core? Or resistance to delam between sidewall and glass or other layers above/below?

I'm trying to eliminate delam first, if the sucker delams, it doesnt matter how strongly it's bonded to the core, once that's eliminated i'll move inside

Damon · Post by **Damon** » Sat Jun 13, 2009 10:26 am

Well really I wanted to find what method produced the strongest bond. So I figured having the whole layup was not necessary for my test - If I did find a method that was much stronger, I would have moved on to a more full scale test w/ fiberglass, VDS, and base/topsheet material. I think I'll be trying this again in the fall when class starts back up.

Have any ideas on how you'll test them?

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Sidewall Lamination Experiment

Sidewall Lamination Experiment