#functionally graded materials

[materialsscienceandengineering]

Functionally graded materials (FGMs) are high-performance materials with expected applications in aerospace, automobiles, defense, and medicine. These materials are usually employed in conditions of extreme temperature and pressure, therefore making it important for them to be as defect-free as possible. Now, researchers have found a way to minimize defects in FGMs by manipulating the gradient of the elemental composition.

Materials used in the fields of aerospace, automobiles, medical equipment, defense need to withstand extremely harsh environments. Small flaws in the materials, i.e. cracks, can lead to catastrophic consequences and massive economic loss. However, most materials cannot handle such high temperatures and pressures. Multimaterials, like functionally graded materials (FGMs), which combine different materials to produce improved performance, are ideal in this situation.

Multimaterials are normally made by additive manufacturing (AM), where layers of different materials are deposited one over the other. However, cracks and pores are common at the boundary layers due to the different properties of the materials. FGMs seek to reduce these cracks by creating a 'gradient' to the composition change across the volume of the material. Now, researchers from Korea Maritime and Ocean University have developed a way to synthesize a high-performance FGM made of Inconel 718 and stainless steel (STS) 316L and minimize its defects. According to Professor Do-Sik Shim, who led the study, "Inconel 718 has excellent properties, but it is expensive. By mixing it with STS 316L to create a high-performance FGM, we have not only improved its technical and commercial advantages, but its economic feasibility as well." Their findings are published in Journal of Materials Research and Technology.

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[materialsscienceandengineering]

Additive manufacturing of cellulose-based materials with continuous, multidirectional stiffness gradients

Functionally graded materials (FGM) allow diverse applications in multidisciplinary fields from biomedicine to architecture. However, their fabrication can be tedious relative to gradient continuity, interfacial bending and directional freedom. Most commercial design software does not include property gradient data—hindering the exploration of design space suited for FGMs. In a new report on Science Advances, Pedro A.G.S. Giachini and a research team in architecture and urban planning, physical intelligence and medicine, in the U.S., Germany and Turkey designed a combined approach of materials engineering and digital processing. The method facilitated extrusion-based multimaterial, additive manufacturing of cellulose-based, tunable viscoelastic materials.

The constructs maintained continuous, high-contrast and multidimensional stiffness gradients. Giachini et al. established a method to engineer sets of cellulose-based materials with similar compositions, yet with distinct mechanical and rheological properties. The team also parallelly developed a digital workflow to embed gradient information into design models with integrated fabrication path planning. The team combined the physical and digital tools to achieve similar stiffness gradients through multiple pathways to achieve open design possibilities that were previously limited to rigid coupling of material and geometry.

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