Aluminum adhesives 1

[rocketgeek]

I'm considering adhesive bonding as an alternative to riveting for a 2024-T3 aluminum sheet metal structure for a one-off project. Since it's a one-off, and my company hasn't used structural adhesives on any major projects in the past, I don't have the budget for (or access to) any curing tools more expensive than heat lamps. I'd also like something can can cure to full strength in two days or less under those circumstances, preferably less than 24 hours. I need suggestions about products to look into and references on joint design and surface preparation. Thx in advance and all that.

 

[TVP]

3M, Loctite, Hexcel, etc. all have websites...

 

[rocketgeek]

@TVP -- Unfortunately, those websites have relatively limited help beyond just a list of different adhesives and their technical datasheets, and maybe some application notes. The exception is 3M, which I have found has a nice product selector, but I would like to find some more comprehensive information that covers different companies, surface preparations, joint design, and the like. Google hasn't been quite its usual helpful self on the subject -- much of what I've found has been not particularly useful.

 

[aepeszel]

Call one of these companies direct, 3M and Lord are typically good. Or try a vendor like Ellsworth Adhesive.
In any case call, do not email, and have the data sheets emailed to you.
A

 

[TVP]

In addition to the 3M website, I have found the following references to be useful:

Loctite Design Guide for Bonding Metals (LT-3371a vol4)

http://www.loctite.com/int_henkel/loctite_us/binarydata/pdf/lt3371a-v4_MetalBondingGuide.pdf

Redux Adhesives Selector Tool

http://www.hexcel.com/Products/Selector+Guides/ReduxSelGuide.htm?sg=Redux+Adhesives

REDUX BONDING TECHNOLOGY

http://www.hexcel.com/NR/rdonlyres/2BCC65F5-AB64-4D9B-810A-705E77ADD3D2/0/redux.pdf

Other information from Hexcel on sandwich panels, design with honeycomb cores, etc.

http://www.hexcel.com/Products/Downloads/Brochures/

MIL-HDBK-337 ADHESIVE BONDED AEROSPACE STRUCTURE REPAIR
MIL-HDBK-691B ADHESIVE BONDING
MIL-HDBK-725 ADHESIVES

http://assist.daps.dla.mil/quicksearch/

Defence Standard 03-2 Cleaning and Preparation of Metal Surfaces
DEF STAN 00-970 Part 7/1 Section 4 Detail Design and Strength of Materials (Leaflet 402)

http://www.dstan.mod.uk/

 

[GregLocock]

I've used Hexcel's Redux in the past and would say it was the most reliable adhesive I've used.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MintJulep]

ASTM D6465 Guide for Selecting Adhesive and Sealant

Surface Preparation and Pretreatment of Structural Adhesives
-Ciba Adhesives

 

[SomeYahoo]

I've used Hysol products in the past and they worked well.

Remember that rivets still help to hold things in place when the adhesive is curing, but you can use smaller (and fewer) rivets.

 

[GregLocock]

I don't like rivets for thin sheets, better to use proper, frequent, clamps. I especially hate the aerospace guys who put pop rivets through composites to hold a glued joint together while it cures.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Philrock]

You shouldn't need any special equipment other than heat lamps and adequate clamping equipment.

For surface preparation see:

http://www.vishay.com/company/brands/measurements-group/guide/ib/b129/129index.htm

If your company has not done bonding before, and you're on limited budget, it seems like you are taking a bit of a chance. How critical is the application?

 

[Heckler]

I've used 3M Scotch-Weld Epoxy Adhesive DP420.

 

[IFRs]

I've used acrylic adhesive in tape form and a methacrylate two part that worked very well. Try getting a vendor to help you. The strength you need from the adhesive is a critical item you must determine. Try searching the internet for methacrylate adhesives.

 

[blfarrar]

I have used CIBA Geigy Araladite on many tasks with very good results. They have both quick setting & standard (4 hours).

If the joint is a safety critical joint you may want to speak to their technical people, remember adhesives such as these work on aero structures & can join differing materials.

The joint is only as good as the materials it is joining & a test of the adhesive is good practice.

The secret with any adhesive is:

1)The surfaces have got to be a good mechanical fit - ie the two surfaces have to be compatible geometry.

2)Surface preparation, ideally the surfaces need to be rough NOT smooth (roughen with emery or score with blade. Increasinfg roughness increases surface area & allows the adhesive to key.
3) Then the surface needs to be clean & grease free, use detergent & water to clean the surface, then use solvent (that has fast air evaporation - in UK Tricloroethane type properties). From here you dont touch the surfaces with you bare fingers (oils in skin etc)
4) the adhesive has to be accurateley mixed (with catalyst type hardener) - no rough guess work allowed.
5) observe the temperature part of the instructions - if in a cold climate it takes longer to set.
6) spread the adhesive onto both surfaces with clean spreader spatula.
7) Bring the components together & postion the joint as its meant to be located (adjust) - apply pressure to close the joint - but dont use that much pressure or weight that theadhesive is squeezed out.
8) let the adhesive cure for the full time stated in instructions.

Decide whether the joint is to be subjected to extremes of cold or wet environments.

Good Luck !

Bruce L Farrar.
Works Engineering Manager
Marshalls Mono PLC.Brookfoot Works.
Halifax W.Yorks UK

 

[TVP]

FYI, Ciba Geigy is no longer the owner of the Araldite tradename. Huntsman Advanced Materials is the current manufacturer of Araldite.