Browsing by Author "Jha, Ashutosh"

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    Crashworthiness and dimensional stability analysis of zero Poisson’s ratio fish cells lattice structures
    (Elsevier, 2023-11-03) Jha, Ashutosh; Cimolai, Guglielmo; Dayyani, Iman
    The present article introduces Zero Poisson's Ratio (ZPR) Fish Cells metamaterial and investigates the effects of Poisson's Ratio on the crashworthiness of Positive (PPR), Negative (NPR), and Zero Poisson's Ratio lattice structures. High-fidelity Finite Element models of the proposed sandwich structures are built, based on identical domains for unit cells. Impact performances of lattice structures are addressed for low (2 m/s) and high (5 m/s) impact velocities in three orthogonal directions. The parameters investigated for crashworthiness include impactor's penetration depth, von Mises stress distribution, edges deformation and dimensional stability. Numerical results demonstrate that, unlike PPR and NPR models, the Fish Cells ZPR model possesses greater lateral stability and structural integrity with minimal edge deformations in all three directions. This leads to reduced lateral impact transfer to adjacent components and localised damaged zones, increasing the life span of structural components while reducing maintenance and repair downtime. Experimental analyses are conducted on the Fish Cells metamaterial through a drop tower test for demonstrating agreement with simulations and validation of the proposed modelling approach.
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    Shape optimisation and buckling analysis of large strain Zero Poisson’s Ratio fish-cells metamaterial for morphing structures
    (Elsevier, 2021-04-17) Jha, Ashutosh; Dayyani, Iman
    This article investigates the potential of a large strain morphing skin based on a Zero Poisson’s Ratio (ZPR) Fish-Cells metamaterial. A multi-objective genetic algorithm shape optimisation is performed to improve the ZPR characteristics of the Fish-Cells metamaterial. High-fidelity finite element models are developed to assess the performance of the optimised Fish-Cells metamaterial for large non-linear strains. A detailed joint design study is devised to obtain consistent ZPR behaviour over a maximum strain range. Trends of Poisson’s ratio, effective elastic modulus and von-mises stress for the different geometries are discussed in detail. Results provide valuable insight into non-linear behaviour of the Fish-Cells ZPR metamaterial. Furthermore, experimental investigations are conducted to verify the enhanced mechanical behaviour of shape optimised ZPR samples. Linear buckling analysis is performed to assess the performance of the optimised metamaterial under compressive loads. Finally, a preliminary study is conducted to evaluate the performance of the shape optimised ZPR metamaterial as a candidate skin for a morphing aircraft wing.