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oai:riubu.ubu.es:10259/68212023-12-14T10:23:41Zcom_10259_4201com_10259_5086com_10259_2604col_10259_4505

Verbeeten, Wilco M.H. Lorenzo Bañuelos, Miriam 2022-11 The effect that the infill orientation angle has on the strain-rate dependence of the yield stress for material extrusion additive manufactured (ME-AM) PolyLactic Acid (PLA) material was investigated. Symmetric angleply stacking sequences were used to produce ME-AM tensile test samples. Measured yield stresses were compensated for the voided structure, typical of ME-AM components. Furthermore, molecular orientation and stretch was macroscopically assessed by a thermal shrinkage procedure. Additionally, hot-press compression molded (CM) samples were manufactured and mechanically characterized in uniaxial tensile and compression in order to determine the material’s isotropic bulk properties. Initial model parameters for the Ree–Eyring modification of the Eyring flow rule were determined using CM data. According to SEM fractography, all samples showed microscopically brittle fracture behavior. Notwithstanding, contrary to CM samples, ME-AM specimens showed macroscopically ductile stress–strain behavior and a transition from a regime with only a primary 𝛼-deformation process, at low strain rates, to a regime with 2 deformation processes (𝛼 + 𝛽), at high strain rates. These effects are an influence of the processing step and are attributed to the molecular orientation and stretch of the polymer chains, provoking anisotropic mechanical properties. As a consequence, a deformation-induced change of the Eyring rate constants is needed to adequately describe the strain-rate dependence of the ME-AM yield stress behavior, leaving the initial activation volumes unchanged. Taking this deformation-dependence of the rate constants into account, yield stresses as a function of infill orientation angle can be appropriately predicted. application/pdf http://hdl.handle.net/10259/6821 eng Elsevier Material Extrusion Additive Manufacturing of Poly(Lactic Acid): Influence of infill orientation angle info:eu-repo/semantics/article TEXT RIUBU. Repositorio Institucional de la Universidad de Burgos Hispana