For many years the automotive industry has been using adhesive to join or bond extrusions together, indeed bonding Aluminium is commonplace in many industries.
It is sometimes difficult to convince the safety designer to use bonding and not conventional fixing methods such as Rivets, screws, or Welding. Though these all have their place in aluminium fabrications they will all have some adverse effect on the material adjacent to the point of joining.
Some of you will remember (if you are as old as me) the Comet airliner sometimes called the Whispering Giant and now the Nimrod. This plane was the first to have completely bonded wing spars and when the first one was decommissioned and broken down, the wing spars were found to be stronger than the day it was built.
The reason is clear, rivets cause fretting around the hole and can start a fracture so too will screw and although welding will give a lasting joint the adjacent aluminium will be stressed by the heat and can cause stress fractures.
Bonding, as long as the surfaces have been properly prepared will hold the two sections together without putting any stress on them, also due to there not being any movement between the bonded aluminium components there will be no fretting and subsequent breaking of the aluminium.
Preparation of surfaces to be bonded.
In the next Blog we will talk a little more about the preparation of the bonding surfaces and joining without adhesives, however, should you require to bond aluminium you must carefully follow the aluminium adhesive manufacturers preparation instructions.