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Title: Thermo-mechanical and dynamic behaviour of gradient cellular and nanocomposite structures
Author: Boldrin, Luca
ISNI:       0000 0004 5924 2266
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2014
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The aim of the research project is to evaluate the suitability of novel materials and structures, such as functionally graded cellular lattices and nanocomposite materials with carbon nanotube inclusions, to be adopted as potential fillers in aero-engine and general aero-structural designs for optimum light-weight performance and augmented energy dissipation. Potential benefits of tailoring the geometry of cellular cores employed in sandwich-like structures in order to achieve a desired thermo-mechanical performance have stimulated a wealth of research studies in the context of functional gradation applied to lattice materials. On such basis, the present dissertation investigates the mechanical properties and equivalent thermal conductivities of iso-volume periodic honeycomb concepts with 3- and 4-connectivities along the in-plane and out-of-plane principal directions. A centre-symmetric 3-connected hexagonal topology and a centre symmetric 4-connected cross-chiral topology are considered in the investigation, the latter conducted adopting both analytical techniques and finite element procedures. Results highlight how variations in cell topology, size and cell-wall thickness allow for a tailoring of the mechanical properties and relative density along the cellular tessellation, suggesting how dropping the assumption of periodicity of a cellular lattice in favour of a graded configuration might be a feasible design solution for achieving a desired mechanical/thermal response ill structural sandwich panels or core fillers. As case study, a band-graded cellular structure based on the family of hexagonal re-entrant topologies is investigated as potential core filler in an aerofoil model, resulting into a light-weight solution which optimizes the material layout within the fixed space of the aerofoil cross-section. In the second part of' the dissertation, an investigation of the nature of frictional damping in CNT-based polymer composites is presented, highlighting how dispersions of carbon nanotubes in a polymeric matrix could lead to consistent increases in energy dissipation under cyclic loading. Attention is focused on the relation between damping augmentation and design parameters, such as volume fractions of the constituents, nanotube aspect ratios alld particularly the interface shear strength governing the quality of stress transfer between carbon nanotubes and surrounding matrix.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available