This thesis is focussed on the design, 3D printing and characterisation of bending-dominated lattice structures. This type of structures could be applied as energy absorbers, for example, in sports applications. Indeed, sports equipment manufacturers are showing a growing interest in the use of Additive Manufacturing (AM) technology to develop highly-customised and performing products. Nowadays, the most used materials for energy absorption purposes are foams, which are characterised by a stochastic arrangement. 3D printed lattice structures could represent a further alternative to foams, thanks to the possibility to design their behaviour, being defined by a non-stochastic arrangement. Two unit cells characterised by a bending-dominant mechanical behaviour were studied: the Kelvin and the BCC (Body Centered Cubic). Different arrays of lattice structures were designed, starting from these two types of cells. Specimens for quasi-static compression tests were 3D-printed via Fused Deposition Modelling (FDM) and Selective Laser Sintering (SLS) using Thermoplastic Polyurethane (TPU). Two different printing technologies were employed to also explore the influence of the printing process on the mechanical behaviour of these structures. Some of the SLS structures also underwent a post-processing phase. FEM analyses were performed in linear elastic conditions and compared with the experimental data. The results demonstrated that these unit cells could be exploited for energy absorption applications. Besides, their behaviour is also influenced by the printing process, but no significant influence of the post-processing phase was detected.
La tesi si focalizza sulla progettazione, stampa 3D e caratterizzazione di strutture reticolari di tipo "bending-dominated". Questa tipologia di strutture potrebbe risultare utile nell'assorbimento di energia, per esempio, in applicazioni sportive. Infatti, i produttori di attrezzature sportive stanno mostrando un crescente interesse nell'uso delle tecnologie di Additive Manufacturing (AM) per lo sviluppo di prodotti personalizzati e ad alte prestazioni. Al giorno d'oggi, i materiali più usati per l'assorbimento di energia sono le schiume, le quali sono caratterizzate da una disposizione casuale. Le strutture reticolari stampate in 3D possono rappresentare un'ulteriore alternativa alle schiume, grazie alla possibilità di progettare il loro comportamento nel dettaglio, essendo definite da una distribuzione spaziale non casuale. Nel lavoro di tesi sono state studiate due celle unitarie caratterizzate da un comportamento di tipo "bending-dominated": la Kelvin e la BCC (Cubica a corpo centrato). Sono state individuate diverse disposizioni di strutture reticolari partendo da questi due tipi di cella unitaria. Sono stati disegnati provini per prove a compressione quasi-statiche, successivamente stampati con tecnologie Fused Deposition Modelling (FDM) e Selective Laser Sintering (SLS) usando Poliuretano Termoplastico (TPU). Si è fatto uso di due diverse tecnologie di stampa per esplorare l'influenza del processo di fabbricazione sul comportamento meccanico di tali strutture. Alcune delle strutture SLS sono state sottoposte anche ad un successivo trattamento. Sono state condotte analisi FEM in condizioni elastiche lineari ed i risultati sono stati confrontati con i dati sperimentali. I risultati ottenuti dimostrano che queste celle unitarie potrebbero essere utilizzate per l'assorbimento di energia. Inoltre, il loro comportamento è influenzato dal processo di stampa, ma non dal trattamento successivo.
Design, 3D printing and characterisation of bending-dominated lattice structures for energy absorption in sports equipment
SENNA, SOFIA
2018/2019
Abstract
This thesis is focussed on the design, 3D printing and characterisation of bending-dominated lattice structures. This type of structures could be applied as energy absorbers, for example, in sports applications. Indeed, sports equipment manufacturers are showing a growing interest in the use of Additive Manufacturing (AM) technology to develop highly-customised and performing products. Nowadays, the most used materials for energy absorption purposes are foams, which are characterised by a stochastic arrangement. 3D printed lattice structures could represent a further alternative to foams, thanks to the possibility to design their behaviour, being defined by a non-stochastic arrangement. Two unit cells characterised by a bending-dominant mechanical behaviour were studied: the Kelvin and the BCC (Body Centered Cubic). Different arrays of lattice structures were designed, starting from these two types of cells. Specimens for quasi-static compression tests were 3D-printed via Fused Deposition Modelling (FDM) and Selective Laser Sintering (SLS) using Thermoplastic Polyurethane (TPU). Two different printing technologies were employed to also explore the influence of the printing process on the mechanical behaviour of these structures. Some of the SLS structures also underwent a post-processing phase. FEM analyses were performed in linear elastic conditions and compared with the experimental data. The results demonstrated that these unit cells could be exploited for energy absorption applications. Besides, their behaviour is also influenced by the printing process, but no significant influence of the post-processing phase was detected.| File | Dimensione | Formato | |
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2019_12_Senna.pdf
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Descrizione: Testo della tesi
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https://hdl.handle.net/10589/152112