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3M rolled out a fastening tape called "VHB tape" that it claims to be able to replace fasteners like screws and rivets. What is the potential and feature of this tape? ENGINEERING.com correspondent interviewed 3M's bonding project manager, Peter Rebstock at his show booth. Below is the highlight of his talk on the tape:
1. 3M VHB Tape is a through-and-through acrylic, closed-cell foam tape that does a great job of bonding dissimilar materials, provides quick handling strength, clean bonds and lack of post-process finishing. If you think about welding a material or riveting a material together, you’ve got pre-process, which is drilling the holes or prepping the surface. Post-process is cleaning off the welds, grinding down or refinishing any type of rivet scratches or paint marks. With 3M VHB Tape, you'll eliminate all of that. You basically apply the tape to a material, take off a removable liner and apply the second material. Applying pressure along the bond line of about 15 psi, you have immediate handling strength.
2. We're also highlighting the ability of the same tape to work in a pre- or post-powder coat process. For pre-powder coat, where you're going to send it through a bake cycle after you apply the tape, we have the 3M VHB Tape 4611, which can survive up to 450 degrees Fahrenheit during a bake cycle. For post-powder coat, you look at the surface that you’re bonding to. You're no longer bonding to metal in a post-powder coat, you're bonding to plastic.
3.Basically what we've engineered into all of our 3M VHB Tapes is the ability to absorb dynamic loading, so you've got the ability to stretch and deform, but return back to your original form. So if you think about the thermal co-efficient of expansion between a plastic and a metal it's obviously going to be different, depending on the thickness of the metal as well. With a hot or cold situation, the ability to absorb that expansion in the bond line and not transfer that stress to the metal or the plastic is critical and that's what 3M VHB Tapes allow you to do.
4. If you think of mechanical fastening, what you're getting is a localized strength. You've got holes drilled along the bond line, which you fastened for a defined length with a mechanical fastener. When you submit that to stress, you're getting a localized stress around that actual hole, which creates stress points and actually weakens the material. With a 3M VHB Tape bond, you're distributing the stress of that bond along the whole bond line, so you actually get a much greater ability to absorb dynamic stresses with a 3M VHB Tape.
5. 3M VHB Tapes typically have about 250 to 300 psi in overlap shear. With structural you can get much higher than that, with some getting about 4,000 psi.
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