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    Fracture characterization and modeling of Gyroid filled 3D printed PLA structures
    (Walter De Gruyter Gmbh, 2021) Torun, Ahmet Refah; Dike, Ali Sinan; Yildiz, Ege Can; Saglam, Ismail; Choupani, Naghdali
    Polylactic acid (PLA) is a commonly used biodegradable material in medical and increasingly in industrial applications. These materials are often exposed to various flaws and faults due to working and production conditions, and increasing the demand for PLA for various applications requires a full understanding of its fracture behavior. In addition to ABS, PLA is a widely used polymeric material in 3D printing. The gyroid type of filling is advantageous for overcoming the relatively higher brittleness of PLA in comparison with conventional thermoplastic polymers. In this study, the effects of various filling ratios on the fracture toughness of 3D printed PLA samples with gyroid pattern were investigated numerically and experimentally for pure mode I, combined mode I/II, and pure mode II. Two-dimensional finite element modeling was created, and the two-dimensional functions of stress intensity coefficients were extracted in loading mode I, mode I/II, and mode II at varied filling ratios of the gyroid PLA samples. Mixed-mode fracture tests for 3D printed PLA samples with a gyroid pattern at various filling ratios were performed by using a specially developed fracture testing fixture. The results showed that the amount of fracture toughness of the samples under study in tensile mode was much higher than those values in shear mode. Also, as the percentages of the filling ratios in the samples increased, both tensile and shear fracture toughness improved.
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    Öğe
    Mixed-mode fracture behavior of 3D-printed PLA with zigzag filling
    (Ice Publishing, 2021) Torun, Ahmet Refah; Yildiz, Ege Can; Kaya, Seyma Helin; Choupani, Naghdali
    Polylactic acid (PLA) is a widely used biomaterial in medical applications as a biodegradable and renewable aliphatic polyester type of material. This material is often subjected to different defects and damages from in-service and manufacturing conditions, and the increasing demand for PLA for different applications requires a thorough understanding of its fracture behavior. In this work, a numerical and experimental study of the mixed-mode fracture behaviors of three-dimensional (3D)-printed PLA samples with a zigzag pattern of different filling ratios was performed using a recently developed special loading fixture. The 3D-printed samples were produced with a 200 degrees C nozzle at 60 degrees C bed temperature and 50mm/s printing speed. Mixed-mode fracture tests from pure tensile to pure shear loading were performed by varying the loading angle, alpha, from 0 to 90 degrees. Finite-element analyses were conducted by using the Abaqus software program, and geometrical factors were obtained at different loading angles. As a result, the fracture toughness values of pure tensile loading, pure shear loading and mixed modes were determined.