if you use Duct Seal or Green Glue, you will decouple one face from the other, thus negating the the reason for it being there. The glue must fasten the two faces together, but be flexible enough to allow some microscopic bending of all the layers but not viscoelastic, as we get into the realms of cld.
Just by coincidence I came across specimen (part of a door from a door/window merchant in London) which comprises a core of 10mm mdf, with 7mm layers of expanded polystyrene, then facings of a thin plastic (unknown type) in a sandwich type construction. On the side I had written DF = 0.366.
I ran some numbers (much to spoiler's chagrin, no doubt!) subbing the unknown plastic with 10mm acrylic and using the damping factor already mentioned. Looks very good |(well, it would with that DF) but about the same as acrylic/mdf/acrylic.
The Link might be off track on bonding acrylic layers but it certainly is not a method that produces a viscoelastic bond.
When Glazing an Architectural Facade with exposed glass edges the Glass Support is usually designed to pick up 30% of the thickness of the outermost lamination of glass.
Ensuring the seating is correct to the designed method is a common QA check point.
This is because over time the Glass can creep.
I think that will suggest that PVB used as an adhesive allows for microscopic movement.
https://www.brettmartin.com/~/media...ical-Documents-English/PFS_App_Laminating.pdf
When Glazing an Architectural Facade with exposed glass edges the Glass Support is usually designed to pick up 30% of the thickness of the outermost lamination of glass.
Ensuring the seating is correct to the designed method is a common QA check point.
This is because over time the Glass can creep.
I think that will suggest that PVB used as an adhesive allows for microscopic movement.
https://www.brettmartin.com/~/media...ical-Documents-English/PFS_App_Laminating.pdf
John,
Interesting paper you've posted.
I'm not sure I can easily get polyvinyl butyl (PVB) adhesive. But the second choice they mention is "two part polyurethane adhesive (PUR)". I'm thinking this retail adhesive might suffice.
https://www.homedepot.ca/product/sika-flex-construction-sealant/1000172271
What do you think?
The one that's in the C clamps right now is a Latex version from GE that remains stretchy.
The next combo may use a stiffer Polyurethane adhesive or Contact cement.
For me, these tests help figure out what supports will be used for the Linear Tracking Arm. So, yes - a little off track, but still useful.
Hugh
Interesting paper you've posted.
I'm not sure I can easily get polyvinyl butyl (PVB) adhesive. But the second choice they mention is "two part polyurethane adhesive (PUR)". I'm thinking this retail adhesive might suffice.
https://www.homedepot.ca/product/sika-flex-construction-sealant/1000172271
What do you think?
The one that's in the C clamps right now is a Latex version from GE that remains stretchy.
The next combo may use a stiffer Polyurethane adhesive or Contact cement.
For me, these tests help figure out what supports will be used for the Linear Tracking Arm. So, yes - a little off track, but still useful.
Hugh
if you use Duct Seal or Green Glue, you will decouple one face from the other, thus negating the the reason for it being there. The glue must fasten the two faces together, but be flexible enough to allow some microscopic bending of all the layers but not viscoelastic, as we get into the realms of cld...
Cats,
Did you ever post anything describing what disappointed you about the CLD combinations you tried? On Audioqualia maybe? Just so you're not having to repeat yourself, is there a link you can post?
Hugh
misko1989,
Maybe that will turn out to be a good choice if Cats is right about the flexibility of the adhesive.
From recollection there is information to be discovered using 3M Tapes on CLD Plinth Designs on the Lenco Heaven Forum.
When the surfaces to be contacted are degreased, my experiences when working with 3 - 4mm thick metals is that the 3M Tape is almost impossible to separate without damaging/deforming one of the bonded layers.
When the surfaces to be contacted are degreased, my experiences when working with 3 - 4mm thick metals is that the 3M Tape is almost impossible to separate without damaging/deforming one of the bonded layers.
Acrylic mdf Acrylic
Here's a screen grab of what the accelerometer picks up. These two waveforms have been equalized and are displayed in decibels.
The right side uses Ductseal between the layers. (12mm Acrylic/14mm mdf/ 12mm Acrylic). I'm calling this one CLD.
The left side uses a Latex/Silicone Caulking called GE Max Stretch. I think this one may also be in CLD territory. Oddly, the resonance is higher.
The waveform as displayed dies out in about 1/5th the time as Acrylic on it's own. (I.e 2 milliseconds vs 12.7 mS for Acrylic). So, it seems to be effective. I got a about 0.2 when I calculated the DF.
I'll pull it all apart and try an adhesive that's stiffer next.
Hugh
Here's a screen grab of what the accelerometer picks up. These two waveforms have been equalized and are displayed in decibels.
The right side uses Ductseal between the layers. (12mm Acrylic/14mm mdf/ 12mm Acrylic). I'm calling this one CLD.
The left side uses a Latex/Silicone Caulking called GE Max Stretch. I think this one may also be in CLD territory. Oddly, the resonance is higher.
The waveform as displayed dies out in about 1/5th the time as Acrylic on it's own. (I.e 2 milliseconds vs 12.7 mS for Acrylic). So, it seems to be effective. I got a about 0.2 when I calculated the DF.
I'll pull it all apart and try an adhesive that's stiffer next.
Hugh
Attachments
Foam
Cats,
Does the expanded Polystyrene in that specimen seem at all spongy? I ask because the kind that's meant for windows stays soft. It seems to damp composites better than the normal expanding foam. Maybe it helps the DF.
Hugh
Just by coincidence I came across specimen (part of a door from a door/window merchant in London) which comprises a core of 10mm mdf, with 7mm layers of expanded polystyrene, then facings of a thin plastic (unknown type) in a sandwich type construction. On the side I had written DF = 0.366.
.
Cats,
Does the expanded Polystyrene in that specimen seem at all spongy? I ask because the kind that's meant for windows stays soft. It seems to damp composites better than the normal expanding foam. Maybe it helps the DF.
Hugh
as far as I can tell, it looks like 'ordinary' EPS, not spongy. And I'm pretty sure it was part of a door as it came from a waste bin (with owner's permission!) of door bits. The mdf gave it structural integrity.
Those scans you posted look highly suspicious. Try not to use the log (dB) scale except to look for linearity. The frequencies are not correct, and way outside the capabilities of the accelerometer. For mdf alone, 100mm x 100mm x 10mm should have a fundamental resonance frequency around 500 Hz, the other layer/s would increase that slightly.
As regards cld, I apply that term to very thin layers of material which must be able to flex (to work properly). All other constructions with layers are called laminates, specifically glued laminates, or 'glulams', much loved by the building industry since Victorian times.
Those scans you posted look highly suspicious. Try not to use the log (dB) scale except to look for linearity. The frequencies are not correct, and way outside the capabilities of the accelerometer. For mdf alone, 100mm x 100mm x 10mm should have a fundamental resonance frequency around 500 Hz, the other layer/s would increase that slightly.
As regards cld, I apply that term to very thin layers of material which must be able to flex (to work properly). All other constructions with layers are called laminates, specifically glued laminates, or 'glulams', much loved by the building industry since Victorian times.
Last edited:
Acrylic mdf Acrylic
I should look things over more carefully before I post. I believe the earlier results were the resonance based on material thickness. Hopefully this one is based on the width and height.
The "adhesive" is GE Maxstretch. I think I got it at Lowe's. I wouldn't recommend it for any real application. It stretches and breaks apart too easily. But for this test, it will hopefully be easy to strip apart.
With a bit of HF filtering, here's what I get fro the Acrylic/mdf/Acrylic sandwich.
Resonance is about 650 to 700 hz. DF is around 0.33.
Cats, does this look credible? I found lots of ways to muck it up.
Hugh
I should look things over more carefully before I post. I believe the earlier results were the resonance based on material thickness. Hopefully this one is based on the width and height.
The "adhesive" is GE Maxstretch. I think I got it at Lowe's. I wouldn't recommend it for any real application. It stretches and breaks apart too easily. But for this test, it will hopefully be easy to strip apart.
With a bit of HF filtering, here's what I get fro the Acrylic/mdf/Acrylic sandwich.
Resonance is about 650 to 700 hz. DF is around 0.33.
Cats, does this look credible? I found lots of ways to muck it up.
Hugh
Attachments
Hi Hugh,
it certainly looks better, and more like what I would get.
BUT, the waveforms are very asymmetrical, leading to wide variation in results, but calculations look about right.
Although asymmetry is often present, it's maybe not as much as you have. Can you show a scan of just mdf?
What you seem to have with your construction is extensional damping, where one piece of mdf is being damped by the caulking and the other piece of mdf. If you have the accelerometer on one bit of mdf and you tap it on the other, it may give you a more representative answer. Try measuring and tapping on the same side.
it certainly looks better, and more like what I would get.
BUT, the waveforms are very asymmetrical, leading to wide variation in results, but calculations look about right.
Although asymmetry is often present, it's maybe not as much as you have. Can you show a scan of just mdf?
What you seem to have with your construction is extensional damping, where one piece of mdf is being damped by the caulking and the other piece of mdf. If you have the accelerometer on one bit of mdf and you tap it on the other, it may give you a more representative answer. Try measuring and tapping on the same side.
Hi Hugh,
Although asymmetry is often present, it's maybe not as much as you have. Can you show a scan of just mdf?
What you seem to have with your construction is extensional damping, where one piece of mdf is being damped by the caulking and the other piece of mdf. If you have the accelerometer on one bit of mdf and you tap it on the other, it may give you a more representative answer. Try measuring and tapping on the same side.
Bryan,
I'm thinking you meant to say "Acrylic" in a couple of places in that last paragraph rather than mdf. It was 14mm MDF with 12mm Acrylic on the outside layers. Yes, I'll try hitting it on the other side.
MDF on it's own was a mess, but I think I have one semi-decent example I'll post a little later.
Thanks,
Hugh
Bryan,
Here's a repeat test on the Acrylic/mdf/Acrylic with MaxStretch caulking in between. This time I tapped on the side with the Accelerometer.
It was much tougher finding a logarithmic set of pulses. In this example, the DF appears higher, but I had to try several Low and High pass filters to get something close. I don't put much faith in that 0.4 DF.
Hugh
Here's a repeat test on the Acrylic/mdf/Acrylic with MaxStretch caulking in between. This time I tapped on the side with the Accelerometer.
It was much tougher finding a logarithmic set of pulses. In this example, the DF appears higher, but I had to try several Low and High pass filters to get something close. I don't put much faith in that 0.4 DF.
Hugh
Attachments
Yes, it's elastic. Do you consider this as a good combination?
The label says "800%", but that's likely based on when it snaps off when stretched. It's firmer than green glue.
Is there a standard, simple way to quantify elasticity? Durometer test maybe?
I'm planning to try something firmer yet just to see what happens to the DF.
The label says "800%", but that's likely based on when it snaps off when stretched. It's firmer than green glue.
Is there a standard, simple way to quantify elasticity? Durometer test maybe?
I'm planning to try something firmer yet just to see what happens to the DF.
