Additive Manufacturing (AM) provides a collection of cutting-edge technologies that allow manufacturing lightweight solutions with complex geometries and advanced functionalities. The degree of customization ensured by AM techniques has enabled their application in several industry sectors such as in the sport and medical industries. For example, in the footwear industry, the possibility to fabricate 3D printed orthotic insoles exploiting lattice structures as an alternative to stochastic foams has been investigated in the last years. The aim is to provide innovative solutions to treat foot disorders, correct the human posture, and adjust the biomechanics of the foot by providing superior comfort, stability, support and shock absorption capability compared to traditional insoles. In this thesis, three unit cells were studied: two bending-dominated structures, such as the Diamond and the Kelvin, and one stretching-dominated structure, such as the Octet. Lattice structures based on these types of cells with variable array dimensions were printed. Then, the effect of two types of density gradients was investigated: a linear density gradient along the thickness of the printed samples and a radial density gradient from the center to the edges of the printed structures. The specimens were printed via stereolithography (SLA) using the Formlabs Flexible 80A resin and the Form 3B printer and tested under quasi-static compression. Results demonstrated that the architected materials investigated can be considered as valid alternatives to stochastic foams to design orthotic insoles. The possibility to tune the mechanical properties of the structure such as the stiffness and energy absorption by controlling its geometrical parameters, make them suitable candidates for the realization of customized products. However, to evaluate the feasibility to employ these mesoscale structures in applications such as foot orthoses, further research activities should be carried out.
La manifattura additiva fornisce una raccolta di tecnologie all'avanguardia che consentono la realizzazione di prodotti leggeri con geometrie complesse e funzionalità avanzate, difficilmente raggiungibili con i processi di manifattura tradizionali. Il livello di customizzazione raggiungibile con le tecniche di AM ne ha consentito l'applicazione in diversi settori industriali come quello sportivo e medico. Ad esempio, nel settore ortesico, negli ultimi anni è stata studiata la possibilità di realizzare solette ortotiche basate su strutture reticolari stampate in 3D come alternativa alle schiume stocastiche. L'obiettivo è fornire soluzioni innovative per curare i disturbi del piede, correggere la postura e la biomeccanica del piede fornendo comfort, stabilità, supporto e capacità di assorbimento degli impatti superiori rispetto alle solette tradizionali. In questa tesi sono state studiate tre celle unitarie: due strutture “bending-dominated”, la Diamond e la Kelvin, e una struttura “stretching-dominated”, la Octet. Sono state stampate strutture reticolari basate su questi tipi di celle con array di dimensioni variabili. Quindi, è stato studiato l'effetto di due tipi di gradiente di densità: un gradiente di densità lineare lungo lo spessore dei campioni stampati e un gradiente di densità radiale dal centro ai bordi delle strutture. I campioni sono stati stampati tramite stereolitografia utilizzando la resina Formlabs Flexible 80A e la stampante Form 3B e caratterizzati con test di compressione quasi statica. I risultati sperimentali hanno dimostrato che le strutture reticolari analizzate possono essere considerate come una valida alternativa alle schiume per lo sviluppo di solette ortotiche. La possibilità di modulare le proprietà meccaniche della struttura come la rigidità e l'assorbimento di energia controllandone i parametri geometrici, fa di queste strutture i candidati ideali per la produzione di prodotti customizzati. Tuttavia, per valutare la reale fattibilità di utilizzo di queste strutture in tali applicazioni, ulteriori attività di ricerca sono necessarie.
Design, 3D printing and characterization of graded density lattice structures for foot orthoses
Porcaro, Giorgio
2020/2021
Abstract
Additive Manufacturing (AM) provides a collection of cutting-edge technologies that allow manufacturing lightweight solutions with complex geometries and advanced functionalities. The degree of customization ensured by AM techniques has enabled their application in several industry sectors such as in the sport and medical industries. For example, in the footwear industry, the possibility to fabricate 3D printed orthotic insoles exploiting lattice structures as an alternative to stochastic foams has been investigated in the last years. The aim is to provide innovative solutions to treat foot disorders, correct the human posture, and adjust the biomechanics of the foot by providing superior comfort, stability, support and shock absorption capability compared to traditional insoles. In this thesis, three unit cells were studied: two bending-dominated structures, such as the Diamond and the Kelvin, and one stretching-dominated structure, such as the Octet. Lattice structures based on these types of cells with variable array dimensions were printed. Then, the effect of two types of density gradients was investigated: a linear density gradient along the thickness of the printed samples and a radial density gradient from the center to the edges of the printed structures. The specimens were printed via stereolithography (SLA) using the Formlabs Flexible 80A resin and the Form 3B printer and tested under quasi-static compression. Results demonstrated that the architected materials investigated can be considered as valid alternatives to stochastic foams to design orthotic insoles. The possibility to tune the mechanical properties of the structure such as the stiffness and energy absorption by controlling its geometrical parameters, make them suitable candidates for the realization of customized products. However, to evaluate the feasibility to employ these mesoscale structures in applications such as foot orthoses, further research activities should be carried out.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/187414