Design, manufacture, and characterization of innovative metal-ceramic interpenetrating phase composites

• Autor(a) principal: Santos, Simão Cordeiro
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/40007
• topic: Interpenetrating phase composites (IPCs); Additive manufacturing; Digital light processing; Investment casting; Aluminium-alumina; Triply periodic minimal surfaces (TPMS)

Interpenetrating Phase Composites (IPCs) is a class of composite materials with promising attributes, rendering them useful in applications where multiple distinct properties need to be optimized. Triply Periodic Minimal Surface (TPMS) structures are a class of lattice structures very attractive due to their continuous and smooth shell features. This dissertation focuses on the design, manufacture, and characterization of TPMS-based aluminium-alumina IPCs. Multiple ceramic TPMS structures with different geometries and volume ratios were designed and fabricated using an additive manufacturing technology - Digital Light Processing (DLP). Afterwards, these ceramic structures were filled with an aluminium alloy via investment casting, giving rise to aluminium-alumina IPCs. A global characterization was performed, including ceramics printability, shrinkage and mass loss; specimens’ morphology; chemical and crystalline characterization; density analysis and mechanical testing. Among the 60 experimental groups that were designed, 24 were considered for fabrication and further analysis, encompassing 3 TPMS structures (Schwarz P, Schwarz D and Gyroid) with 4 distinct volume ratios (12.5%, 15%, 17.5% and 20%) and 2 different unit cell numbers (2x2x2 and 3x3x3). Overall, DLP technology was found effective for producing these highly complex ceramic structures, with high surface quality. The sintered alumina structures presented a relative density of around 76.3% and a pseudo-ductile layer-by-layer failure behaviour, with Schwarz D TPMS exhibiting the highest compressive strength. Regarding the IPCs, the addition of aluminium significantly changed the compressive behaviour of the samples, presenting an energy absorption behaviour. The integration of the alumina phase into the aluminium alloy led to a substantial improvement on the compressive offset stress of 28.74% when compared to the theoretical value of the aluminium alloy. Schwarz D and Gyroid IPCs demonstrated similar mechanical behaviour while Schwarz P IPCs presented an inferior mechanical performance.