A Look at Lightweighting

If we’re so concerned with lightweighting, why don’t we just make everything out of carbon fiber? Or aluminum?

The aerospace and automotive industries have been working hard to reduce weight for decades. The main goal has been to lightweight so that cars and planes need less fuel to cover the same distance. Besides meeting regulatory targets, lightweighting a car means that a smaller engine can meet performance criteria—and that has all sorts of other implications like less load on the brakes, a slimmed-down suspension, smaller tires, different handling. It becomes, perhaps, a completely different car than the original specs detailed.

Most car chassis are made of low carbon steel, the choice for over a century. Steel is relatively inexpensive and so established that its material characteristics led to the welding and other manufacturing processes that prevail in the automotive industry. But it is heavy and therefore not ideal to meet tomorrow’s fuel economy standards.

Materials Change Everything

Reducing a product’s weight sounds simple—just replace everything heavy with something light—but requires complex engineering and manufacturing techniques that are made possible by advances in material science, manufacturing processes and cheaper, faster simulation.

Today’s lightweight materials include high-strength steel, magnesium and aluminum alloys, and carbon fiber plastics. They typically cost more than the materials they are replacing, in part because they’re harder to produce but also because they’re not as widely used. This leads designers to make a trade-off between cost and weight, resulting in hybrid designs that optimize the system as a whole. The resulting mix of steel and other materials can cause significant disruption in long-held manufacturing processes. To look at only one aspect: Steel has a melting point of around 2600°F, while aluminum and magnesium melt at around 1200°F. Welding steel to aluminum, therefore, requires new techniques that are still being developed.

3D Printing, Simulation and Lightweighting

New techniques, such as additive manufacturing, make it possible to fabricate completely new part concepts and offer an opportunity to rethink traditional designs. For example, car makers are developing aluminum alloy castings that—with one assembly—can replace dozens of smaller parts that had to be hand assembled. In addition to lightweighting, this redesign decreases manufacturing complexity, saves production time and leads to a higher level of repeatable quality. This can’t happen without consciously thinking about a part and reframing its design objectives to include weight, manufacturability, quality and other criteria—and spending the time to get the design right.

Simulation is of tremendous help in lightweighting. Engineers can cycle through many combinations of part geometries, materials and use cases to discover the best combination. Finite element analysis (FEA) of 3D-printed or additively manufactured parts is still evolving because there are so many parameters unique to each manufacturing process, but analysts making cautious assumptions about part quality, for example, can evaluate the lighter part’s performance and fitness for purpose before producing a part. Iterating through so many alternatives takes time, even with massive cloud CPU capacity, but is typically worth the effort and cost because of savings in other parts of the product’s lifecycle.

The lessons learned in aerospace and automotive are being applied across industries because the economics are impressive. Anything that has to be transported from the point of manufacture to the final customer can be redesigned to weigh less while still meeting performance criteria. And this opportunity to reconsider many aspects of the design can open the door to all sorts of other improvements, too. Lighter flat packs of DIY furniture can lead to more unit sales because it’s easier for a consumer to get the box up the stairs. Redesigned industrial equipment might not need the same kind of foundations, saving on install costs. Lower transportation costs can be passed along to customers—or not, and can be used to increase profit. Laundry detergent can be recast as environmentally friendly and fetch a premium price.

Engineers, regardless of industry, need to create part-specific materials strategies that take into account function, formability, strength, temperature profile and so on, and weigh that against the cost of each material. Often “light” means “light enough”—there is, as yet, no perfect material that is the single, ultimate answer for every situation.