Articles written in Sadhana

    • Parametric studies of fused filament fabrication towards fabrication of 2D auxetic metamaterial cellular structure followed by auxeticity simulation


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      As compared to conventional materials, auxetic metamaterials correspond to cellular structures with low density and better mechanical properties. Mechanical properties of auxetic metamaterials are influenced by both the base material and the geometry (topology) of the unit cell. The high strength-to-weight ratio and tunable mechanical properties of auxetic structures make them suitable for wide engineering applications. In this work, auxetic behavior of novel chiral honeycomb structures (anti-tetra chiral) is studied using Finite Element Method(FEM). In addition, fabrication of a few tensile specimens is carried out by Fused Filament Fabrication (FFF). FFF is an efficient rapid prototyping technology which offers design freedom to fabricate complex geometrical structures (difficult or impossible to manufacture through conventional routes). Several FFF parameters do influence part quality and process performance. In order to study effects of process parameters on part quality (tensile strength, roughness, material consumption) and build time, tensile specimens are fabricated at different build orientations and build styles (dense and sparse). Fractured surface morphologies are observed through scanning electron microscopy to understand the bonding pattern between the layers of FFF parts. Finally, anappropriate combination of FFF parameters is determined through Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) to ensure the maximum part tensile strength, the minimum part surface roughnessand the minimum build timing. Finally, an auxetic anti-tetra chiral candidate specimen of ABS plastic is built through FFF. From finite element simulation, the Poisson’s ratio of anti-tetra chiral 2D structure is found to be close to -1. Poisson’s ratio of anti-tetra chiral 2D honeycomb is found insensitive to the dimensionless topological parameter (i.e. ratio of ligament length-to-node radius). It is experienced that part tensile strength decreases with increase in build orientation angle as well as the air gap (from ‘dense’ to ‘sparse’ building style). The build time of FFF parts depends on the height of the part along the build direction. FFF part fabricated using ‘dense’ build style at 45° build orientation exhibits the best quality and corresponds to the minimum fabricationtime.

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