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New materials require new joining techniques

The automotive industry is working with the broadest variety of materials in its history - but what use are new materials if you can’t join them together? By Xavier Boucherat

Lightweighting and fuel efficiency have been hot topics since the birth of the automobile, and so when it comes to discussing how quickly the industry is making progress, it’s easy to get carried away. That’s according to Rajat Agarwal, Head of Innovation and Development at Henkel’s Transportation Division. “As much as we talk about it,” he says, “of the 80 million vehicles built every year, the number of vehicles actually exploiting lightweight multi-material solutions today is very small.”

In 2015, demand for traditional automotive sheet steel reached around 80 megatons (mt). By comparison, lightweight automotive aluminium reached just 1mt. Aluminium suppliers such as Novelis have been forthcoming on the matter – their products will not replace steel any time soon. Even though the total aluminium weight by its very nature would be considerably lower than the total steel weight, the current difference is marked.

That said, the 2015 figure does represent increased uptake; in 2010, overall demand was far lower at 0.2mt. A similar five-year growth figure is expected until 2020, when demand is predicted to reach 2.2mt. Aluminium might never supplant steel entirely, but there is a clear role for it in the multi-material strategies now being widely adopted by manufacturers. What’s more, it’s not alone, and this is great news for an adhesives and sealant supplier like Henkel.

Some assembly required

“We’ve entered a phase where we see the broadest variety of new materials being used in the automotive sector since its birth,” says Agarwal. All of these new materials will help OEMs to realise lightweighting and safety targets, but all will require OEMs to move away from the traditional joining techniques which the industry has grown up with, such as riveting and spot welding.

The use of adhesives enables products using new material sets to come to fruition

Bonding’s ability to join diverse ranges of materials remains its greatest strength, and according to Agarwal will account for a significant part of adhesive and sealant uptake. “Over the next ten years,” says Agarwal, “the biggest opportunities for us will come through joining steel to aluminium, aluminium to aluminium, aluminium to magnesium, magnesium to composites, and plastics to metals.”

The American Chemistry Council has suggested that using just one kilo of adhesives instead of spot welds and rivets can take 25 kilos of weight out of a vehicle. “Our work with Ford on the 2015 F-150 helped reach that saving of 700 pounds (317 kg),” says Dan Wohletz, Vice President of Henkel’s Automotive Division in North America. “We’re enablers – the use of adhesives enables products using new material sets to come to fruition.” Henkel, he adds, expects growth in demand for automotive sealants and adhesives to outpace the wider global growth in demand for vehicles.

In addition, adhesives can help to build safer cars. Traditionally welded parts can suffer stress at the joints, whereas adhesives provide a long bond line that distributes stress more evenly, and as a result is less likely to tear. “Many OEMs have been taking advantage of the safety benefits of adhesives for a long time,” says Wohletz, “even before the significant growth in multi-material sets.”

Following aerospace’s lead?

The key challenge moving forward, says Agarwal, will be educating and converting manufacturers in an industry that has been riveting for over 80 years. Understandably, a risk-averse industry will stick with what it knows, but Henkel is confident the knowledge and data now available on adhesives has seen acceptance of bonding rise in the automotive industry. No longer is opting for the company’s solutions associated with risk.

True innovation comes in when we partner with OEMs to optimise things from an overall system perspective

“It’s not simply some academic curiosity any more,” says Agarawl, adding that Henkel expects to see the same increase in uptake it experienced in the aerospace industry over previous decades. “If you look at a plane today, there are very few rivets compared to 30 years ago. They learnt how to bond. What will be interesting is watching the adoption take place on a completely different scale. Plane manufacturers build between 6,000 and 10,000 units a year. Automotive manufacturers build around 80 million.”

It’s telling, adds Wohletz, that Alan Mulally, former Chief Executive at Ford and one of the main proponents of the aluminium-intensive F-150 programme, moved to Ford from Boeing. “Sometimes it really takes an external force to kick-start the industry,” he says, “and we’re involved in so many industries, such as aerospace, composites and windmills, that there are many areas from which we can transfer knowledge.”

The need for innovation, coupled with the pressure of the regulatory environment, could accelerate the transition. Stefan Gmeiner, Head of Global Market Development & Technology Management at Henkel’s Automotive, Aerospace and Metal Division, suggests that external drivers such as CAFE and its European equivalents will drive suppliers like Henkel into closer partnerships with OEMs. This could transform the role of Henkel into that of design partner.

Many OEMs have been taking advantage of the safety benefits of adhesives for a long time, even before the significant growth in multi-material sets

“True innovation comes in when we partner with OEMs to optimise things from an overall system perspective,” he says. “This gives us the chance to really think holistically, and not just optimise the different joining and bonding spots, but provide additional functions. The adhesive solution has to provide added value.” Such additional functions could include minimising noise, vibration and harshness (NVH), or protecting electronics and HMIs. Increasing use of electronics and electrification in vehicles will also require both insulated and conductive materials.

Another development that could mean closer collaboration is the widespread adoption of global platforms, in which OEMs will seek to roll out identical designs across all five regions of the world in a very short time. This allows an industrial giant like Henkel to play to its strengths. “We can deliver the same solutions across all regions, whilst manufacturing locally to ensure consistent, reliable long-term supply,” says Agarwal.

In addition, rolling out global platforms entails greater risk. This requires suppliers to perform far more testing, and in turn, make significantly higher investments upfront. Only those with an established presence, and the necessary capital, will be able to work with OEMs on this. “We’re happy to make that upfront investment,” says Agarwal.

Smarter factories use glue

Adhesives could also help vehicle manufacturers build more efficient factories. “In many instances, adhesives will enable higher degrees of automation, and can replace labour-intensive manual processes,” says Gmeiner. There are also greater opportunities for parts consolidation. “You no longer need rivets in your factory,” notes Wohletz. “The technology is also more flexible, and can be used in different configurations. This means OEMs don’t need to invest so much in retooling a line when they move from one design to another.” This could prove especially attractive in an age when mid-cycle refreshes are becoming more radical.

Working upfront with OEMs provides the most significant opportunities to implement multi-material application

The other big saving, adds Agarwal, comes with reduced floor space, as bonding can consolidate processes. “You can perform more operations in parallel than you can with welding,” he says, “and this allows for shorter assembly lines. This can then translate into a more efficient factory, either by running a smaller factory with reduced energy costs, or by using the floor space saved to increase true production.”

However, stresses Wohletz, for OEMs to truly benefit, the key once again lies in early collaboration. Inserting processes into brownfield sites to take advantage of efficient materials can be costly, whereas technologies for use in greenfield designs can provide OEMs with significant savings.

“Working upfront with OEMs provides the most significant opportunities to implement multi-material application,” he says. “We have the expertise with adhesives, the automotive suppliers have their expertise in designing parts, and the OEMs know what the government regulations and customer needs are. When you put all that together, you can do really good things that are greener, healthier and safer for the end consumer.”

This article is part of an exclusive Automotive World report on lightweighting. Follow this link to download a copy of Special report: Vehicle lightweighting

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