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Title: Mechanical properties of woodpile lattice materials fabricated using additive manufacturing
Author: Cuan Urquizo, Enrique
ISNI:       0000 0004 6347 8829
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2017
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The relationship between the structure and the property of lattice materials and structures fabricated using fused filament fabrication process is studied analytically, computationally and experimentally. Lattices with specified structural parameters were fabricated in a controlled manner using customised G-codes that generate the tool path as desired. The characterisation of the parent material to fabricate lattices was carried out by tensile testing of single filaments. Single filament properties were then used to predict the response of woodpile lattice bars in tension, when the loading direction is along the filaments. Good agreement with experimental measurements was observed. Following the simplest loading case of tension along the fibres, more complex scenarios of structures made of filaments in woodpile arrangement under bending and torsion were considered. It was shown that woodpile beams in flexure, as opposed to solid beams, are extremely sensitive to shear deformation. The contributions of the bending and shear stiffness were identified and analytical models were developed to account for these two primary mechanisms of filament deformation. The apparent shear of the woodpile lattice resulted to be dominated by the bending of the individual filaments. An analytical expression for the apparent shear modulus of lattice beams was derived on the basis of filament bending. Contribution from apparent bending and apparent shear in the transverse response of lattice beams was quantitatively brought out. The twist of beams in woodpile arrangement was also studied. The deformation mechanism was identified as twist and flexure of the filaments. The torsional stiffness found to be extremely sensitive to the amount of overlap at the location of bonding between filaments. Analytical models for displacement-only-constraint and displacement and relative rotation constraints were developed. The compressive response along the stacking direction of structures in woodpile arrangement was also studied. The so-called aligned and the staggered stacking of filaments was considered. While the compression of the staggered arrangement resulted to be bending-dominated, the aligned configuration is dominated by the elastic compression at each junction of filaments. Analytical models were derived accounting for filament flexure and discs diametrically compressed. Excellent agreement with numerical results was obtained.
Supervisor: Bhaskar, Atul Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available