Stronger, thinner, lighter and quieter
sub-assemblies
The value and importance of adhesives in manufactured goods has been steadily trending for over a decade. That’s because the number of advantages are mounting given the demands of the marketplace. This seems to be of particular importance to the automotive and aerospace industries where I think you will see this trend sharpen in the next five to ten years.
There’s a logical reason
Consumers like quieter cars that are safe, responsive and fuel-efficient. We also have to fly on occasion. But airlines are squeezed to the drink carts trying to deliver profit, given the high cost of fossil fuel. And the auto industry is beginning a go for broke-weight-loss program because by 2025, cars sold in the U.S. must nearly double their fuel efficiency on average. [54.5 miles per gallon compared to 28.6 mpg required at the end of 2011] To meet these demands, automakers will improve oil dependent engines and they’ll develop and market more alternative-fuel vehicles. But that will not be enough. These changes will require stronger, lighter and more rigid automobiles.
Engines and motors aside, designers and scientists are responding with new technologies and new combinations of both raw and synthetic material. Meanwhile manufacturers are trying to reduce material cost (for example, thinner and/or less steel used) as they compete in a more vivacious worldwide market. In the end, adhesive technology may provide the glue to bring all these facets together.
A progressive line
The use of adhesives in auto assembly is nothing new. Car windscreens have been attached using polyurethane epoxies for eons. In the last decade, General Motors engineers attached plastic body cladding on their Saturn cars with adhesives instead of welds. And Ford has been steadily reducing spot welds and is actively reducing the gauge of steel wherever it is used. These measures are made possible with the use of adhesives.
The use of alternative materials is nothing new either. Corvette continues a legacy of non-traditional materials that began on the assembly line in 1953. Fiberglass offered an economical way to answer the inherent low-volume demand of a sports car without investing in expensive sheetmetal-stamping dies. Today with the launch of the C5, you’ll find materials including balsawood in the floor and an aluminum chassis. In the ZR1, a magnesium roof structure and engine cradle and extensive use of carbon-fiber body panels.
What’s more, BMW is committing more than $1 billion readying itself for a customer who doesn’t even exist yet. The all-electric BMW i3 is due in the fall of 2013. The manufacturer will utilize “glues and screws” to assemble a high-strength, lightweight, carbon fiber-reinforced plastic passenger compartment to an aluminum chassis. The planned supply chain spans three continents increasing demand for some of the most advanced automotive parts plants in the world.
As far back as 1999 BMW has experimented with “joining technology”, the so-called adhesion plus spot-welding process. I visited the BMW assembly plant in Dingolfing, Germany (about 90 minutes NW of Munich). In a production run, a moment before robots place a spot weld, a special high-performance adhesive is applied (also by robots in this case) to one of the surfaces. The resulting joined assembly of two (thinner) steel plates produces a stronger bond that is better sealed while it offers a noise-dampening bonus. Flanged joints with a larger than normal surface areas are now possible with the addition of adhesives and that helps to increase the auto body stiffness, which ultimately gives the consumer a better ride with improved crash damage resistance.
Almost ironically, ExxonMobil is developing impact-resistant plastics to make car parts such as bumpers and fuel tanks lighter in order to aid fuel efficiency.
Double action performance
Adhesive bonding as a joining technology has an enormous potential for sub-assemblies and parts. It is possible to join materials of the same type and of different types (synthetic materials and steel) to form a bonded and non-positive joint. The adhesives double action is taken advantage of in this process. The parts to be joined are bonded by adhesion (stickiness of the glue to the component) and cohesion (molecular strength of the glue) at a low temperature. Toughener polymers can be added to the epoxy to boost the dynamic fracturing behavior of the adhesive such that any cracking in the material takes place in a stable, controlled manner. This lets bonded structural members absorb maximum energy and helps keep joints intact in the event of a crash.
Last word
After decades of playing with various material combinations, and developing new ones the world is now calling for new standards of performance. Advances aimed at cutting cost, reducing weight and eliminating reliance on natural resources is here. The use of adhesives in this context could easily skyrocket. Granted, most of the experimentation is focused on final assembly processes but there’s no reason to believe these techniques will not someday soon manifest as demand from new supply chains. Obviously, these changes will once again challenge the status quo.
HIT Solutions believes the more your business keeps up with important trends, the more you will improve your product, and improve your bottom line.
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