Page 69 - Australasian Paint & Panel Mar-Apr 2019

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ADHESIVE JOINS ON THE RISE
WITH MORE OEM’S WRITING REPAIR PROCEDURES IN THE FUTURE CALLING FOR 3M IRSA AND STRUCTURAL REPAIR ADHESIVES IT IS VITAL THAT REPAIRERS ARE UP TO DATE WITH THE TECHNOLOGY AS IT’S USAGE EXPANDS.
IMPERATIVES TO IMPROVE OCCUPANT
safety, reduce fuel consumption, im- prove battery range and boost ride dy- namics has driven vehicle design to not only changing the materials used in manufacturing, but also the methods needed to join them.
The collision repair industry over the past 10 years has encountered thinner sheet metal gauges, advanced strength steels, composites, aluminium and mag- nesium alloys and more “crumple zones” with less sectioning.
As the structural members of vehicle design become stronger and more rig- id, they transfer more crash energy than they absorb. This means that the joints experience higher stresses with Advanced High Strength Steel (AHSS) than older mild steel designs. Joint strength must keep up with struc- ture advancement, otherwise the de- sign fails.
Spot joining techniques such as, spot welds, rivets and bolts or screws gener- ally have excellent pull-out or “Peel” strength, but poor stress (shear) distri- bution. A strategy to increase joint strength in AHSS structures could be to add additional spots. This will increase joint strength however, there is a func- tional limit to the number of spots that can be added.
Additional spot welds will increase heat damage to panels, increase weld tip maintenance, increase cycle time in as- sembly and will also have a minimum weld pitch i.e. there is limited room for spot welds.
Additional rivets or screws will in- crease cost (fasteners are expensive), increase weight (each fastener adds mass), increase cycle time in assembly
and again, include minimum spacing as there is only so much room.
Adding adhesives to the ex- isting joint design can dramat- ically increase strength, with- out adding much weight, cost, or cycle time.
Hence the development of “hybrid-joining”, in this context it is the process of using an adhesive in conjunc- tion with spot attachments (such as riv- ets, screws or spot welds) to create a stronger, more efficient structural con- nection.
The addition of significant amounts of adhesives have had other benefits for ve- hicle design;
Structural Adhesive PN 07333 (3M IRSA) is a room temperature curing epoxy that has excellent shear, peel and impact strength for use in 'true' automotive structural joints.
It features a balanced adhesive perfor- mance profile which allows OEM’s to write more structural joint repair proce- dures, allowing for a less-intrusive re-
As the structural members
of vehicle design become stronger and more rigid, they transfer more crash energy than they absorb.”
pair that closer matches the orig- inal design intent for the joint and allows repairers to have a choice in “body in white” struc- tural repair adhesives.
3M IRSA cures at room tem- perature and does not require heating the bond to achieve the quoted performance values. It’s not necessary for repairers to take up floor or booth time to
resulting overall in stiffer body struc- tures which provide improved ride dy- namics making the vehicle more respon- sive, a reduction in noise, vibration and harshness and allowing for better crash energy management.
Adhesives provide “built-in” intra- panel sealing with fewer water, dust and air leaks, better corrosion protec- tion and improved vehicle longevity and durability.
3M has developed a structural repair adhesive specifically for the collision re- pair industry. 3M Impact Resistant
heat a joint, although the adhesive can be heated to accelerate the final cure. The adhesive's colour changing chemis- try from silver to purple gives the tech- nician feedback that the adhesive was mixed and dispensed properly, and that the product has started curing.
3M IRSA employs a corrosion inhib- iting formula to provide corrosion pro- tection to bare metals in the joint. This allows repairers to simply remove all coatings down to bare metal as a sur- face preparation step, requiring no complicated primers or wipes. It will
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