Additive manufacturing of metallic auxetic structures for biomedical Applications

• Autor(a) principal: Vilhena, Iuri David Deus
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/153466
• topic: Additive manufacturing; L-PBF; Auxetic materials; Negative Poisson's ratio; Metamaterials; Schwarz P; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia dos Materiais

Within the world of orthopedic implants for bone regeneration, metallic scaffolds have found their suitability overshadowed by issues regarding their high elastic modulus and stress shielding. Solving these issues poses not only an interesting challenge, due to their naturally high elastic modulus, but a worthwhile one given their application in healthcare. The advent and popularization of additive manufacturing technologies has, in its wake, enabled the man-ufacture of novel types of structures with tailored behaviors and porosity, allowing for their study and manufacturing as metallic materials. As such, in this work, structures based on the Schwarz P triply periodic minimal surface were modelled, manufactured from SS 316L and Ti-6Al-4V alloys by laser powder bed fusion, and characterized, with the intent of verifying if auxetic structures with properties relevant to biomedical application as bone scaffolding could be achieved. Results show that, although the Schwarz P geometry could be replicated, samples dis-played significant warping due to issues of heat dissipation during manufacturing. Further-more, samples exhibited relative densities below their modelled values with results demon-strating that the "a" parameter affects both sample geometry and density. The elastic modulus of samples was shown to increase with the sample's density, however the values obtained were significantly below their expected values for relative densities at 30% and above. All samples displayed quasi-auxetic behavior during testing. Though negative values for Pois-son's ratio could not be reached, values below 0.1 were obtained for all samples, implying the feasibility of this objective through further optimization of the structures.