Try running, or even a couple of trips upstairs, using a 30kg backpack and it soon becomes obvious how much hard work it takes to carry that extra weight.
Lightweight technology is even more pressing with the rise of electric vehicles, as evidenced by the award-winning Jaguar I-Pace. It makes no sense to build an EV with a heavier steel chassis and body and then compensate for that weight with a larger, heavier battery.
When it comes to fuel consumption, a lighter car needs less energy to move – its that simple. Pushing a classic Mini on your own is easy, but moving a full-size SUV is anything but. Therefore, manufacturers are always looking to reduce the weight or at least reduce the spiral weight, mainly by using lightweight steel and aluminium alloys in the body construction. Although much cheaper than carbon fiber, aluminum construction is expensive, partly due to the material itself and partly due to construction methods. Thats why it only appears to a large extent in high-end cars.
Steel is a relatively easy material to work with and the panels can be pressed and bent with sharp, sharp edges. Aluminum panels are less susceptible to sharp creases, and if the radii of a stamping line are too small or too intricate in shape, the material may crack. Designers and engineers have to work more closely together to achieve the shapes designers want.
Putting things together also becomes more difficult. While manufacturers have been joining steel for decades using MIG or spot welding, screwing and, to a lesser extent, riveting, some different methods are needed for aluminium. A favourite for joining panels is joining (gluing) and riveting with self-drilling rivets. A conventional rivet is pushed through a drilled and tapped hole, but self-drilling rivets push through the first layer of undrilled aluminium and extend outwards in a second layer but without drilling it. In the cross section, it resembles a wisdom tooth with those big roots and once inside, like the tooth, it doesnt want to come out.