Engineers demand a lot from the materials they use. But of all the mechanical and physical properties that figure into the materials selection process, strength often tops the list. Higher tensile properties are just about always a good thing — as long as they exist in balance with other desirable attributes such as weight and cost.
That balance has always been difficult to achieve. But in the pages that follow you'll see some products and technologies that make some strides in balancing strength against weight, cost and other attractive properties.
Consider what's going on with steel right now, particularly in the automotive world. With yield strengths that start at 550 MPa, advanced high-strength steels (AHSS) have been making inroads into a variety of vehicle structures that can most benefit from the added strength these materials offer compared to lower-strength traditional steels (see chart).
High strength comes at a premium price, though. And one thing that's helping the more expensive AHSS grades gain ground against less pricey steels is their use in tailored blanks. Tailored steel products — usually, but not always, laser welded blanks — allow different grades and gauges of steel to be combined in a single component. Peter Mould, program director of the American Iron & Steel Institute's newly formed Tailored Steel Product Alliance, explains that the tailored blanks allow the strongest steels to be used most efficiently. "You can use them only where they're most needed," he says. The rest of a blank can consist of lower cost steels. Blanks can also save money by allowing selective downgauging within the same blank — which allows the use of relatively thin, yet strong AHSS grades where loads permit.
Steel isn't the only place where suppliers are looking for new ways to balance strength against other performance attributes. That same struggle affects engineering plastics too, even some unexpected ones not normally thought of as structural materials. Consider the sustainable polymers DuPont is rolling out next year. The company's Global Vice President of Technology, Nandan Rao, explains that engineers often associate polymers derived from biological processes as lacking in the mechanical properties department. Biodegradeable starch-based polymers, for example, are better suited to disposable packaging than durable goods. But DuPont's new Sorona polymer, a polytrimethylene terephthalate derived partially from corn sugar, has mechanical properties comparable with PBT, an engineering plastic used in demanding applications such as electrical connectors.
To see more about materials that are getting stronger without sacrificing other properties, read the Materials/Joining Trend Watch.