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Title: Mechanical behaviours of periodic lattices
Author: Gu, Huaiyuan
ISNI:       0000 0004 8500 0826
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2019
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This dissertation provide a comprehensive study of the mechanical properties of lattice structures. Two types of topologies were considered including two-dimensional triangular lattice and three-dimensional octet-truss lattice. Prior analytical and numerical studies have shown that the triangular lattice is one of the stiffest geometries of two-dimensional lattices. In this work the modulus, tensile strength and fracture toughness of the lattice have been measured experimentally using the specimens cut from an Aluminium sheet. The dependence of the mechanical properties on the orientation of the lattice has also been revealed. It has been found that the tensile strengths and fracture behaviours vary markedly with the lattice orientation, while the modulus was almost isotropic. A significant property anisotropy was also observed in the octet-truss lattices that its modulus can be varied by 20% and the strength can be double when lattice orientation was changed. The validity of linear elastic fracture mechanics (LEFM) was examined on three-dimensional lattices. It shows that the LEFM can be adequately adopted in the lattices with straight crack fronts, while a curved crack front generates more complexity in the structure configuration ahead of the crack tip, and results in a significant discrepancy in the measured toughness compared to the models with linear crack fronts. Experimentation has been performed to characterise the fracture behaviour of three-dimensional octet-truss lattices manufactured using a Selective Laser Melting(SLM) technique. The fracture toughness and KR curves have been measured. An increase in fracture resistance was observed during the crack extension. Furthermore the influence of lattice orientation on the fracture behaviour has been illustrated. It shows that a change in orientation will result in a different crack path, but the effect on fracture toughness is small. Numerical approaches were applied to simulate the progressive damage behaviour of the lattices, where a fairly well agreement was achieved between the numerical predictions and experimental measurements.
Supervisor: Pavier, Martyn Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available