Is glue really stronger than wood?

[Normand Leblanc]

Just found that video. All the tests went like expected with the exception of end grain maple.


https://www.youtube.com/watch?v=me42lw-BWak

[Patrick Chase]

Just found that video. All the tests went like expected with the exception of end grain maple.

IMO all that really shows is the flakiness/imprecision of his test.

The axial and bending tests are basically the same in terms of applied load at the glue joint, which may have something to do with why glue makers don't (and don't need to) specify performance in bending. Bending creates an axial stress distribution with compression at the top and tension at the bottom of the sample. The samples in the bending test all failed in tension, i.e. they failed by pulling apart along the bottom edge instead of, say, buckling at the top. This means that any difference in performance between the "axial" and "bending" tests reflects test-to-test variation rather than some deeper phenomenon.

[Mark Canada]

Would have been better if they used ASTM test coupons that are specifically designed to test this sort of thing... it also would have been good to have data from a larger sample size. We had 3 large instrons at a previous employer, and broke hundreds of carbonfibre/fibreglass/kevlar/other composite layups of every resin and cloth we could get. The coupon shape and size matters a lot, as does having 10 or so test pieces for each material/method so you can average out process errors.

It's good that he actually used a proper tensile tester though!

[Warren Mickley]

Just found that video. All the tests went like expected with the exception of end grain maple.



None of the maple tests went as expected because he actually used maple with the wrong orientation. He was apparently unaware of the difference between end grain and long grain. He used cutoffs from the end of a board so the grain was running in the short direction. Pitiful test.

[Patrick Chase]

None of the maple tests went as expected because he actually used maple with the wrong orientation. He was apparently unaware of the difference between end grain and long grain. He used cutoffs from the end of a board so the grain was running in the short direction. Pitiful test.

You mean there's a reason why we use scarf joints? :-)

In fairness he did acknowledge the end-grain issue even if he didn't bother to fix it.

[Warren Mickley]

No, the maple samples all have the grain going crosswise and he does not even notice it. He calls joints end grain to end grain which are not that at all. They break where he does not expect it because he thinks the grain is the same direction as the pine samples.

[Pat Barry]

Was anything unexpected in the actual tests that were done (regardless of his commentary I mean)? It seems to me that the failure for end grain to end grain was in the adhesive or cohesive bond (expected), and in the long grain to long grain the failure was in the wood. Yes, No?

[Lee Schierer]

Was anything unexpected in the actual tests that were done (regardless of his commentary I mean)? It seems to me that the failure for end grain to end grain was in the adhesive or cohesive bond (expected), and in the long grain to long grain the failure was in the wood. Yes, No?

Yes, I was concerned with the relief cuts he made on the lap joint pieces. By cutting the corners with a saw, and none too precisely, he created a stress point in the wood. His clamping method leaves a bit to be desired as well. I also saw the test piece of maple for the bending test was cut the wrong way.

[Normand Leblanc]

No, the maple samples all have the grain going crosswise and he does not even notice it. He calls joints end grain to end grain which are not that at all. They break where he does not expect it because he thinks the grain is the same direction as the pine samples.

You have a good eye Warren. I look closely to this video and you're right.

[Todd Stock]

This appears to be a video by an undergrad engineering student with a poor understanding of anisotropic materials, adhesives, and how to design an adhesive properties experiment.

[Simon MacGowen]

This appears to be a video by an undergrad engineering student with a poor understanding of anisotropic materials, adhesives, and how to design an adhesive properties experiment.

The same can be said of countless youtube woodworking videos except that the video producers are "(social media) woodworkers with a (very) poor understanding of proper woodworking techniques or safety."

Simon

[Art Mann]

Now that he has finished this informative test, maybe he should do one that proves that oak is stronger than Styrofoam.

[Patrick Chase]

You have a good eye Warren. I look closely to this video and you're right.

Yeah, I missed that as well. Nice catch, Warren!

[Tristan Fogt]

I had made this video for a school project, I didn’t notice how much I’d overlooked! I’m quite green when it comes to proper woodworking, thanks for the expertise :)
I made an updated version with your comments in mind, I hope it does a more effective job:
https://www.youtube.com/watch?v=cGdhEQW3JdA

<span class="s1">
https://www.youtube.com/watch?v=cGdhEQW3JdA

[Todd Stock]

I had made this video for a school project, I didn’t notice how much I’d overlooked! I’m quite green when it comes to proper woodworking, thanks for the expertise :)
I made an updated version with your comments in mind, I hope it does a more effective job:
https://www.youtube.com/watch?v=cGdhEQW3JdA

<span class="s1">
https://www.youtube.com/watch?v=cGdhEQW3JdA

The great thing about posting here is that you have your pick of mentors that know everything ;-)

[Patrick Chase]

The great thing about posting here is that you have your pick of mentors that know everything ;-)

Tristan didn't even post (Normand did) and he still got "mentored". Nice job handling the feedback, Tristan.

[Todd Stock]

Tristan didn't even post (Normand did) and he still got "mentored". Nice job handling the feedback, Tristan.

I agree...well done.

I did an independent structures project my senior year at Clark, and had to do an oral presentation/defense. One of the structures profs present was not one of my biggest fans - washed-out navy COD pilot - and I usually came to his class directly from the flight line in my zoom bag, so painful reminder for him. His comment at close of the brief was something along the lines of suggesting that while Dr. Lee (head of the aerostructures/aerocomposites efforts at UofM) may have a use for my talents, he'd rather wait for an undergrad transfer from the Theater Arts program if he had need of an RA. Ouch. Mentoring.

[Jim Koepke]

I had made this video for a school project, I didn’t notice how much I’d overlooked! I’m quite green when it comes to proper woodworking, thanks for the expertise :)
[edit]


Howdy Tristan and welcome to the Creek.

jtk