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4.Bonding


BONDING

There are many adhesives recommended for bonding aluminium, the foilnose is designed for use with an epoxy adhesive as it includes pips on the bonding area to ensure a 0.25mm thickness for the adhesive.

Araldite 2015 is a good choice of adhesive as it approved for use in the marine industry however other glues may be used depending upon the application.

A 1m length of the foilnose with a high quality bond (17N/mm²) will carry 52 tonnes in shear force (7 African elephants!).

It can be seen that there is plenty of safety margin if your glued joint isn't perfect.

For safety critical applications the addition of mechanical fasteners such as rivets is recommended. I would also reccomend performing a "water break test" to prepared surfaces prior to bonding to ensure you have a clean surface.

 

BONDING ADVICE FROM HUNTSMAN FOR ARALDITE 2015

The ideal thickness for 2015 adhesive is between 0.1 and 0.5 mm. so 0.25 mm is perfect. 
Bonding on anodized surface is highly recommenced, as well as a roughened surface (sand paper/ sandblasting/ etc..). degreasing is also important and you can use isopropanol or acetone (never use surfactant). 


SUBSTRATE PREPARATION 

In order to obtain the optimal adhesion on both substrates, it is highly recommended to prepare the substrates before bonding. In most cases, abrading the substrate (for example with sand paper) and degreasing by wiping with a solvent like acetone, ethanol or isopropanol will help to increase the durability of the bonded assembly. 

Substrate abrasion / Roughness 

The ideal roughness to bond metal substrate is 3 < Ra (micrometer) < 5. 

ESSENTIALS FOR MAXIMUM BOND STRENGTH 

Araldite® adhesives are simple to use, but to ensure successful bonding the directions given in the instructions supplied with the adhesive must be strictly observed. 
In particular: 
1.- Resin and hardener must be correctly proportioned and thoroughly mixed together. 
2.- Joint surfaces must be degreased and, when necessary, pre-treated. 
3.- Curing temperature and curing time must be correct. 
4.- Jigs or other fixtures must be used to prevent the bond surfaces from moving relative to one another during the curing process. 
5.- Though only light pressure is needed, it should be applied as evenly as possible over the whole bond area. Excessive pressure leaves the joint starved of adhesive. In laboratory conditions, the pressure applied is generally 30 – 50 N for a bonding area of 312.5 mm2. This figure may be adjusted when using products with high viscosity. 


 

Further aluminium bonding advice

http://www.henkelna.com/us/content_data/213261_LT3371_Metal_Bonding_Guide_022011_LR451580.pdf

http://www.aluminiumdesign.net/design-support/joining-aluminium/#toc-adhesive-bonding

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