Defining Materials in the Digital Age (or, Reinventing the Lowly Materials Specification)

Aerospace materials specifications, alongside other standards, define our products. They have existed for over a century, and are necessary for the procurement and construction of aerospace designs. They generally exist as scanned electronic copies of printed paper, requiring a minimal sets of certification tests. This contrasts sharply with other aspects of engineering design, which have largely converted to true digital datasets. Only the lowly materials specification remains in the hardcopy realm.

Materials properties are a function of chemistry and microstructure. Microstructural features (e.g. grain size) are state variables that depend on input state and subsequent processing. As such, the best metrics for material quality should be chemistry and microstructure. But it has always been impractical to conduct detailed microstructural evaluations for simple and frequent lot release testing, so this is usually forgone and only sample chemistry and simple mechanical properties (e.g. tensile strength, hardness) measured instead. Although commonplace, these limitations add cost and flow time. Furthermore, requirements have increased with time as aerospace customers and certification agencies have come to demand more reliability, durability and safety. This has resulted in more extended supplier qualification exercises and complicated document management systems, which are burdensome and confusing. It’s time to consider something new.

Recent advances in constitutive modeling, nondestructive evaluation technology and computing power suggest that it may be possible to develop methods for defining and certifying materials in a more direct manner that measures salient microstructural features that control the properties of interest. Such methods could be automated. They would also generate digital materials descriptors, permitting the mathematical description of a material, ready for constitutive modeling. This presentation describes a vision for how such a program might be constructed, with benefits for materials developers, suppliers and end users, and why the time is right to begin.