North American International Auto Show 2016: The Future is Now, and Adhesives are Making it Happen

Posted on 2/1/2016 8:45:21 PM By Marc Benevento
  

An air of excitement prevailed at the North American International Auto Show (NAIAS, aka, the Detroit Auto Show), fueled by a dichotomy of driving forces.  Pending regulation on greenhouse gas emissions has generated interest in fuel saving technologies such as turbo charging, advanced transmissions, and lightweight materials.  However, the current, sky-high rate vehicle sales, coupled with low gasoline prices, had OEMs showing powerful performance coupes and sedans featuring an array of advanced materials and electronics.  Despite these driving forces coming from somewhat different directions, they are pushing the industry toward an interesting new mix of materials that will require more structural adhesives in production and service than ever before.

Steel continues to be the most common material of construction in light vehicles, and the vast majority of vehicles on display at the auto show had steel-intensive designs.  The Steel Market Development Institute demonstrated innovative uses of high and ultra-high strength steel that have helped manufacturers reach their weight, safety, and performance targets in passenger cars and light trucks.  Vehicle bodies on display were color coded to show where different grades of high strength steels had been applied to reduce weight.  

A challenge faced by design engineers is that, as the thickness of steel is reduced to save weight, stiffness may decrease proportionally.  Strategically applied structural adhesives, in conjunction with spot welds, supplement strength and stiffness,  improve vehicle dynamics and safety, and also reduce the amount of road and engine noise that reaches the passenger compartment. Therefore, an abundance of adhesives and sealants was observed in the high strength steel vehicle bodies on display.

The real excitement at the show, however, was the number of vehicles featuring combinations of steel, aluminum, and composite body materials.  In the past, manufacturers generally made an either/or decision about the white body materials in order to reduce concerns such as joining, painting, and corrosion prevention.  In an effort to more aggressively shed and properly distribute weight to improve vehicle dynamics, manufactures are creating structures that combine materials to take best advantage of what each has to offer.  While examples of multi-material design are available from many manufacturers, perhaps the best demonstration on display at the auto show was the Lexus LC500.

The Lexus LC500 display featured not only the finished car (photo 3), but also an unfinished body-in-white that clearly illustrated where high strength steel, aluminum, and composite materials were applied to achieve performance goals (photo 4).

The result is a body that is stiffer than the carbon fiber reinforced composite LFA supercar developed by Lexus just a few years ago.  Aluminum and composite materials were applied strategically to the steel body move the center of gravity lower and toward the center of the car, in both closure panels and structural applications.

Because the LC500 uses a front engine layout, elimination of weight from the outermost front surfaces was critical to properly position the vehicle’s center of gravity.  This explains the selection of lightweight materials for the front closure panels, with fenders (aluminum), hood (aluminum), doors (composite inner / aluminum outer), and optional roof (carbon fiber composite) being constructed of lightweight materials.

Adhesives are required to bond composite to metals, such as between the door inner and outer, as well as the roof to the body.

In addition, the front shock towers are made of cast aluminum, an application that is beginning to surface in platforms from a number of manufactures.

The shock tower takes heavy cyclical loading, and the use of structural adhesive in addition to riveting can reduce stress concentrations at the rivets, improving fatigue life, while helping to isolate the aluminum from steel, preventing galvanic corrosion.

The examples cited above are just a few of many observed while roaming COBO hall for a few hours at this year’s show.  Others will be the subject of future blogs.  While this is not a comprehensive list of multi-material applications, it serves notice that the automotive future is arriving in showrooms now.  Regulatory pressures and consumer demands are increasing the pace of change in the industry, and opportunities abound for providers of lightweight materials, adhesives, and other technologies that will enable these designs to enter the mass production mainstream.  The future is upon us, and adhesives are making it happen.

Marc Benevento is a transportation industry contributor to adhesives.org. Marc is Managing Director at Industrial Market Insight and can be reached by email HERE