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2 2023

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Identification of phase percolation in bainitic structures

Deroszewska Martyna, Saraczyn Robert, Miłek Tomasz, Troska Jakub

Polish Technical Review

2023

No. 2

23--28

The aim of this study was to identify and study the phenomenon of phase percolation in bainite structures. SEM microscopic tests were carried out on bainitized iron alloy samples, in the FEM tests austenitic SS316 steel was used as the filled phase. Physical models, which were produced in the form of cubes and tensile samples, were made in FDM technology on the Original Prusa Mini+ printer from ASA filament (modified ABS copolymer). The static tensile test was performed on a LabTest 5.20 SP1 testing machine at a tensile speed of 10mm/min. Complex states of stress in the analyzed systems were identified, which prove the complexity of the phenomenon in multiphase materials. The obtained results were correlated, which allowed to indicate that the phenomenon of percolation indeed affects the mechanical properties of multiphase materials and incremental techniques can be used to analyze the level of this impact.

Celem pracy było rozpoznanie i zbadanie zjawiska perkolacji fazowej w strukturach bainitu. Badania mikroskopowe SEM przeprowadzono na bainityzowanych próbkach stopu żelaza, w badaniach MES jako fazę wypełnioną zastosowano stal austenityczną SS316. Modele fizyczne, które wykonano w postaci kostek i próbek rozciągliwych, wykonano w technologii FDM na drukarce Original Prusa Mini+ z filamentu ASA (modyfikowany kopolimer ABS). Statyczną próbę rozciągania przeprowadzono na maszynie wytrzymałościowej LabTest 5.20 SP1 przy prędkości rozciągania 10 mm/min. Zidentyfikowano złożone stany naprężeń w analizowanych układach, które świadczą o złożoności zjawiska w materiałach wielofazowych. Uzyskane wyniki skorelowano, co pozwoliło wskazać, że zjawisko perkolacji rzeczywiście wpływa na właściwości mechaniczne materiałów wielofazowych, a techniki przyrostowe mogą być wykorzystane do analizy poziomu tego oddziaływania.

Supported by 2D and 3D Imaging Methods Investigation of the Influence of Fiber Orientation on the Mechanical Properties of the Composites Reinforced with Fibers in a Polymer Matrix

Saraczyn Robert, Deroszewska Martyna, Kowaluk Tomasz, Skołek Emilia, Rządkowski Witold, Myszka Dawid

Advances in Science and Technology. Research Journal

2023

Vol. 17, no 3

170--183

The aim of this study was to examine the behavior of the carbon fiber reinforced polymer (CFRP) composites depending on the fiber orientation and to understand the influence of microstructural discontinuities on mechanical properties. For the tests 210 gsm prepreg composite and 200 gsm carbon fabric with polymer matrix have been used. Samples were structured and later examined according to the ASTM-D3039 and ASTM-D3878 (equivalents are ISO 20975, ISO 527-4 and ISO 527-5). Accordingly, to the number of layers, three ways of the fibers arranging in relation to the applied force were used. Mechanical properties were determined in a static tensile test. The results of imaging studies, which included analyzes of Digital Image Correlation, Computed Tomography and Scanning Electron Microscopy, showed structural discontinuities, specific stress distribution and propagation of stresses depending on the production technology, which were correlated with the obtained strength results. The source of the gradual development of the degradation of the composite structure was observed in local microdamages and microcracks. As a result of a sub-critical crack growth within the resin matrix material, the defects are subject to a complex, multi-axial stress field on the micro-scale, even if the globally applied force is axial. Samples in which the load was applied along the axis of the fibers behave like an elastic material, while samples, where the force is applied at an angle to the axis of the fibers, tend to behave like an elastic-plastic material.