Architectured materials in engineering and biology: fabrication, structure, mechanics and performance

Abstract

Ever-increasing requirements for structural performance drive the research and the development of stronger, tougher and lighter materials. Specific microstructures, heterogeneities or hybrid compositions are now used in modern materials to generate high performance structures. Pushed to the extreme, these concepts lead to architectured materials, which contain highly controlled structures at length scales which are intermediate between the microscale and the size of the component. This review focuses on dense architectured materials made of building blocks of well-defined size and shape, arranged in two or three dimensions. These building blocks are stiff so their deformation remains small and within elastic limits, but their interfaces can channel cracks and undergo large deformations. These basic principles lead to building blocks which can slide, rotate, separate or interlock collectively, providing a wealth of tunable mechanisms. Nature is well ahead of engineers in making use of architectured materials. Materials such as bone, teeth or mollusc shells are made of stiff building blocks of well-defined sizes and shapes, bonded together by deformable bio-adhesives. These natural materials demonstrate how the interplay between building block properties, shape, size and arrangement together with non-linear behaviour at the interfaces generate unusual combinations of stiffness, strength and toughness. In this review we discuss the general principles underlying the structure and mechanics of engineering architectured materials and of biological and bio-inspired architectured materials. Recent progress and remaining issues in the modelling, design optimisation and fabrication of these materials are also presented. The discussion draws from examples in the engineering and natural worlds, emphasising not only how natural materials can help us improve existing architectured materials, but also how they can inspire entirely new structural materials with unusual and highly attractive combinations of properties.