Frank Kerstan, global programme manager automotive composites at Henkel, tells Mike Richardson about the company’s new multi-substrate adhesives and matrix resins for both high end and large-scale automotive production.
Henkel used the last JEC World exhibition to highlight some of its advanced automotive lightweight composite applications. With its headlights trained on high performance composites that provide car makers with new ways to design innovative lightweight solutions into their vehicles, the worldwide provider of high-impact solutions based on adhesives, sealants and functional coatings majored on cost-efficient production of composite components for large volume production.
Henkel says its high performance lightweight composites based on glass or carbon fibres with thermosetting resins can be tailored to provide the right levels of strength where they are needed. For automotive manufacturers, this translates into reduced fuel consumption and CO2 emissions, along with enhanced safety and crash behaviour. Henkel works closely with its partners along the value chain to create ideal integrated solutions in composites that can be made cost-effectively, in high volumes, and at high speed.
In pole position on the Henkel stand at JEC was an example of what is now possible with automotive composites created with its materials and technical know-how: a ground-breaking leaf spring based on Loctite MAX 2 polyurethane matrix resin and continuous glass fibre reinforcement.
Spring into action
The leaf spring, which debuted in late 2014 on the rear suspension of the Volvo XC90 premium crossover SUV, now features at the core of a lightweight rear axle concept implemented on various models. Volvo’s premium V90 estate and S90 models now also incorporate the innovative design, which is produced using high-pressure resin transfer moulding (HP-RTM).
With its low viscosity, Loctite MAX 2 rapidly fills the mould and quickly yet gently impregnates the fibre material, resulting in short injection times. The polyurethane resin’s curing rate is also substantially higher than that of comparable epoxy resins, so total cycle times are shorter too.
Many automotive OEMs are also considering carbon fibre reinforced composites for wheels in place of aluminium. Henkel will highlight a new product in its Loctite MAX resin series that is suitable for use in production of such composite wheels, thanks to its very high temperature resistance and excellent toughness. The new Loctite MAX 5 resin withstands service temperatures beyond 200°C and has a very high durability performance due to its outstanding toughness. As with Loctite MAX 2, its high curing speed and ability to be injected quickly facilitate high volume production.
“Volvo is upscaling its model platforms and there are production plans for 200,000 parts per year,” begins Henkel’s global programme manager for automotive composites, Frank Kerstan (above). “In collaboration with Benteler-SGL, we’ve developed an advanced composite matrix resin based on polyurethanes to produce the first composite leaf spring manufactured in RTM process for high-speed mass production which is running successfully.
“Although our new binder technology is a side product, it’s an important one, because it shows we understand our customers’ manufacturing chain and the different production steps involved, such as preforming, injecting the resin and applying adhesives, plus the need for compatibility of different materials. Matching our binder system to our resins enables the customers to run reliable and smooth production.”
Answering this call, Henkel launched a new adhesive for such hybrid material concepts, Loctite UK 2015, which is based on two-component polyurethane technology and is ideal for use on structural body parts, regardless of whether they are made of fibre-reinforced plastics, e-coated steel or e-coated aluminium.
“Henkel offers the complete solution consisting of resins and ancillary products, plus we have adhesives for multi-substrate bonding, i.e. joining traditional metals and composite materials. Henkel differentiates itself from the competition through its process know-how. We have a Composite Lab test facility in Heidelberg, Germany and one in Tokyo, Japan too with equipment in close-to-series production conditions.
“We utilise prototyping moulds and invite customers to develop their applications in order to run the materials on a machine which is very close to production conditions. They can carry out trials on our own HP-RTM equipment, which has resin injection units for polyurethanes and epoxies coupled to a 380-ton press. This is very important to the customer, because the processes are fairly new. Our product offering of resins, adhesives and process know-how is where we really set ourselves apart from the competition.”
The car is the star
Kerstan believes that many automotive OEMs are seriously rethinking their passenger car chassis designs as well as for pickup and light vehicle trucks. For example, Henkel products are now specified onto the Mercedes Sprinter front axle when the car maker replaced the steel leaf spring with a composite one.
“It’s a very interesting application to have glass fibre leaf springs for heavier trucks. The cost hurdle for carbon fibre composites is gradually getting lower, plus the application for composites penetration is scalable too. For example, the mould for the Volvo leaf spring comprises a 12-cavity mould which is injected with one shot. This is how we keep the cycle times relatively short. When you consider that this involves over 300,000 parts per year running across Volvo’s model platforms this can create some very interesting cost effects.”
Kerstan goes on to explain how Henkel is helping to re-educate customers to consider different production methods using composite materials, and run their process line faster with a shorter curing times through the use of its innovative catalysts that are added to increase resin curing speed and offer a smooth release agent behaviour.
“We’ve developed a new epoxy resin called Loctite MAX 5,” he concludes. “It’s available now to target the manufacture of automotive wheels made entirely from carbon fibre composites. Automotive OEMs are becoming very interested. “Henkel’s Loctite MAX 5 resin system product targets this very area. It has very high temperature resistance, which means it can operate at temperatures beyond 200°C. This is important because car brakes release a lot of heat, plus it also needs to be very durable and fatigue resistant. These wheels need to possess a quality visual grade carbon fibre aesthetic appearance. There’s a lot of interesting movement taking place in the automotive industry, and perhaps the price point for this kind of wheel technology will gradually become more affordable within the next couple of years.”
