What do adhesives have to do with lightweighting? A great deal, it turns out. Even though as engineers, we have been trained to question conventional wisdom, some things that come to us through intuition are hard to overcome.
For example, in elementary school art class, many of us came to the conclusion that school glue does a poor job of bonding materials together. For many of us, that experience colors our view of glues and adhesives for the rest of our lives. We reach for fasteners or a welding torch when an adhesive would do a better job without adding significant mass to the finished product.
In reality, adhesives offer a superior bond when compared to welding or rivets. In fact, you cannot bond mixed materials without using adhesives. If you directly weld aluminum and steel, and you don’t protect it from corrosion then you will have a significant bi-metallic corrosion issue. The adhesive provides a protective barrier between the two metals that prevents corrosion.
Lightweighting relies on using dissimilar, lightweight materials. To form the best combination of structure you need to use aluminum, steel, composites or plastics to give it the best lightweighting opportunity. A continuous layer of adhesive can enable reduction of fasteners in a vehicle whether they be welds, rivets or bolts.
If you imagine a typical vehicle joined by welds, there are areas of stiffness just around the weld, but with adhesives you have a continuum of stiffness all the way where the adhesive is applied. This helps as the gauge of metals go down and we have the ability to improve stiffness without increasing the gauge of the metal.
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