Grand Challenges in Structural Materials

Abstract

INTRODUCTION The motto “citius, altius, fortius” (Latin for “faster, higher, stronger”) is known worldwide in the context of the Olympic Games and could also be viewed – with the inevitable addition of “cheaper” – as the catch-cry of the structural materials industry throughout the nineteenth and twentieth centuries. Steel, concrete, wood, structural ceramics, glass, nonferrous metals, and a wide range of composites underpin the entirety of modern society. Taller and more ambitious structures placed in more extreme service environments demand materials with higher performance: strength, durability, and scope for repair and retrofitting in challenging environments. Rapid construction not only influences costs related to performance but also demands improved materials and manufacturing. The U.S. Materials Genome Initiative Strategic Plan lists “Lightweight and Structural Materials” to be of primary importance across sectors: national security, human health and welfare, clean energy systems, and infrastructure, and consumer goods (National Science and Technology Council Committee on Technology, 2014). The goal of sustainability was added to the core ambitions of the structural materials industry around the beginning of the twenty-first century, as environmental footprints and resource depletion were better understood. As recently as 1999, the U.S. National Academy of Engineering published a report entitled “Structural Materials: Challenges and Opportunities” (Starke and Williams, 1999) without mentioning sustainability; from this point, we can observe a rapid shift in emphasis toward sustainable development objectives in less than two decades, where it would now be unthinkable to omit this aspect from a discussion of challenges in the science and engineering of structural materials. Today, we are facing scientific and technological challenges linked to provision of durable and reliable infrastructure to the billions worldwide who live without appropriate housing, energy, and/or sanitation. Solutions here will not necessarily involve advanced structural materials as such, but will be related to optimizing structural characteristics and durability at low financial and environmental costs. This requires creativity to rely on locally available resources, which means that we should not always count on one-size-fits-all solutions. Modern materials design thus goes far beyond pure technical performance. To “do more with less” has given additional impetus to research on materials recycling, reuse, and substitution, including in the improvement of material durability. The above goals can only be achieved through a thorough scientific approach to materials design that also exploits recent advances in high-throughput, combinatorial and computational methodologies in manufacturing, analytical and dataprocessing facilities. The result is that we are able to precisely specify almost all material characteristics for any given application. The present article offers a summary of the key areas of research and challenges facing structural materials researchers with particular focus on areas with major advances to be made. This discussion is by no means exhaustive as the topic merits analysis in far more depth than is possible within the context of an overview article.