Bioinspired tungsten-copper composites with Bouligand-type architectures mimicking fish scales

The microscopic Bouligand-type architectures of fish scales demonstrate a notable efficiency in enhancing the damage tolerance of materials;nevertheless,it is challenging to reproduce in metals.Here bioinspired tungsten-copper composites with different Bouligand-type architectures mimicking fish scales were fabricated by infiltrating a copper melt into woven contextures of tungsten fibers.These composites exhibit a synergetic enhancement in both strength and ductility at room temperature along with an improved resistance to high-temperature oxidization.The strengths were interpreted by adapting the classical laminate theory to incorporate the characteristics of Bouligand-type architectures.In particular,under load the tungsten fibers can reorient adaptively within the copper matrix by their straightening,stretching,interfacial sliding with the matrix,and the cooperative kinking deformation of fiber grids,representing a successful implementation of the optimizing mechanisms of the Bouligand-type architectures to enhance strength and toughness.This study may serve to promote the development of new high-performance tungsten-copper composites for applications,e.g.,as electrical contacts or heat sinks,and offer a viable approach for constructing bioinspired architectures in metallic materials.

Ice-templated porous tungsten and tungsten carbide inspired by natural wood

The structures of tungsten and tungsten carbide scaffolds play a key role in determining the properties of their infiltrated composites for multifunctional applications.However,it is challenging to construct and control the architectures by means of self-assembly in W/WC systems because of their large densities.Here we present the development of unidirectionally porous architectures,with high porosities exceeding 65 vol.%,for W and WC scaffolds which in many respects reproduce the design motif of natural wood using a direct ice-templating technique.This was achieved by adjusting the viscosities of suspensions to retard sedimentation during freezing.The processing,structural characteristics and mechanical properties of the resulting scaffolds were investigated with the correlations between them explored.Quantitative relationships were established to describe their strengths based on the mechanics of cellular solids by taking into account both inter-and intra-lamellar pores.The fracture mechanisms were also identified,especially in light of the porosity.This study extends the effectiveness of the ice-templating technique for systems with large densities or particle sizes.It further provides preforms for developing new natureinspired multifunctional materials,as represented by W/WC-Cu composites.

Natural Cornstalk Pith as an Effective Energy Absorbing Cellular Material

The replacement of synthetic foam materials using natural biological ones is of great significance for saving energy/resources and reducing environmental pollutions.Here we characterized the microstructure and mechanical properties of natural cornstalk pith,which has a large annual output yet lacks an effective exploitation,and evaluated its feasibility for applications as a substitute for synthetic foam materials.The cornstalk pith was revealed to be a cellular material composed of closed cells elongated along the growth direction of com plant and reinforced by well-aligned vascular bundles penetrating the foam matrix.The compressive behavior is featured by a stable stress plateau which is favorable for energy absorption with its mechanical properties largely dependent on the hydration state and loading configuration.In particular,the initial dimension and mechanical properties of cornstalk pith can be effectively recovered after deformation simply by hydration treatment owing to swelling effect caused by the turgor pressure from osmosis.The cornstalk pith demonstrates an outstanding combination of low density and high energy absorption efficiency among various foam materials,specifically with its plateau stress and energy absorption comparable or even superior to those of some typical synthetic foam materials.These along with the huge resources and good biodegradability make it a promising natural energy absorbing cellular material for replacing synthetic counterparts.