With more OEMs writing repair procedures in the future calling for 3M IRSA and structural repair adhesives, it's vital that repairers are up to date with the technology as its usage expands.
Imperatives to improve occupant safety, reduce fuel consumption, improve battery range and boost ride dynamics 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 magnesium alloys and more “crumple zones” with less sectioning.
As the structural members of vehicle design become stronger and more rigid, 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 structure advancement, otherwise the design fails.
Spot joining techniques such as, spot welds, rivets and bolts or screws generally have excellent pull-out or “Peel” strength, but poor stress (shear) distribution. A strategy to increase joint strength in AHSS structures could be to add additional spots. This will increase joint strength however, there is a functional 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 assembly and will also have a minimum weld pitch i.e. there is limited room for spot welds.
Additional rivets or screws will increase 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 existing joint design can dramatically increase strength, without 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 conjunction with spot attachments (such as rivets, screws or spot welds) to create a stronger, more efficient structural connection.
The addition of significant amounts of adhesives have had other benefits for vehicle design;
resulting overall in stiffer body structures which provide improved ride dynamics making the vehicle more responsive, 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 protection and improved vehicle longevity and durability.
3M has developed a structural repair adhesive specifically for the collision repair industry. 3M Impact Resistant 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 performance profile which allows OEM’s to write more structural joint repair procedures, allowing for a less-intrusive repair that closer matches the original design intent for the joint and allows repairers to have a choice in “body in white” structural repair adhesives.
3M IRSA cures at room temperature 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 heat a joint, although the adhesive can be heated to accelerate the final cure. The adhesive's colour changing chemistry from silver to purple gives the technician feedback that the adhesive was mixed and dispensed properly, and that the product has started curing.
3M IRSA employs a corrosion inhibiting formula to provide corrosion protection to bare metals in the joint. This allows repairers to simply remove all coatings down to bare metal as a surface preparation step, requiring no complicated primers or wipes. It will bond to properly prepared steel, aluminium, magnesium, and composites in all combinations with the added benefit of preventing galvanic corrosion in multi-material joints. The inclusion of glass spacer beads pre-mixed with the adhesive maintains the optimum minimum bondline thickness which allows parts to more easily slide across each other during positioning and repairers to securely clamp or fasten parts together without the concern of ‘starving’ the bondline and reducing bond performance.
As vehicle technology progresses to demand lighter and stronger components, the joints that hold it all together must also evolve.
Combining welds or rivets with adhesives like 3M IRSA allows repairers to restore complex connections between mixed or sensitive materials in a manner that preserves strength and durability.
While the terms hybrid joining, rivet bonding and weld sealing sound complicated, the process is straightforward and approachable.
Most Automotive OEM’s are using body structure adhesives in manufacturing and some OEM’s are writing repair procedures that call for 3M IRSA including General Motors, Tesla, Jaguar Land Rover, Honda and Hyundai.
For further information on 3M IRSA, call: 136 136.