From Process Signatures to Structural Performance: Mechanical Characterization of Additively Manufactured Polymers and Architected Structures

Additive Manufacturing (AM) of polymers is increasingly adopted for functional components and tooling in industrial sectors where lightweight design, geometric freedom and rapid customization are required. However, the mechanical reliability of additively manufactured polymers is strongly influenced by process induced features such as anisotropy, interlayer bonding, thermal history and microstructural heterogeneity, which are not adequately captured by conventional material models. This doctoral thesis investigates the process–structure–property relationships of polymer materials manufactured by Material Extrusion (FDM/HT-FDM) and Multi Jet Fusion (MJF), through an integrated experimental framework combining mechanical testing, thermal analysis and microstructural characterization. The study addresses both fundamental aspects of additive manufacturing and application driven industrial scenarios, ranging from qualification of aerospace-grade polymers to the design of energya bsorbing lattice structures. The work first establishes and validates advanced mechanical characterization methodologies using PLA as a reference material, demonstrating the dominant role of thermal conditions and interlayer adhesion in governing tensile performance and fractured behavior. These methodologies are then extended to highperformance PAEK materials, with a focus on PEEK processed by high-temperature FDM. Tensile, compressive and thermo-mechanical analyses are combined with DSC and DMA to quantify the influence of crystallinity, annealing and temperature-dependent behavior, with specific relevance to high-temperature tooling applications. Finally, the compressive behavior of architected lattice structures manufactured by FDM (PA6-CF) and MJF (TPU) is systematically investigated. The results highlight topology-dependent deformation mechanisms, process-induced anisotropy and strain-rate effects, and are interpreted within an extended Gibson–Ashby framework. For TPU lattices, cyclic and rate-dependent tests enable the identification of optimized configurations for impact and energy absorption applications. Overall, this thesis provides a comprehensive experimental basis for understanding and qualifying additively manufactured polymer materials, emphasizing the importance of process-aware mechanical characterization to support reliable industrial adoption of AM technologies.