Browsing by Author "Eltahir, Sara Saeed Abdulrahman"

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Failure Analysis of Fused Deposition Modeling 3D Printed Poly Lactic Acid Polymer
(Sage Publications Ltd, 2025) Yilmaz, Cagatay; Eltahir, Sara Saeed Abdulrahman
Additive manufacturing, commonly known as 3D printing (AM), has emerged as one of the most transformative technological advances in the last few decades in global manufacturing, as it allows for the production of intricate components without the use of costly molds. Fused Deposition Modeling (FDM) is widely adopted among various AM techniques due to its accessibility and effectiveness. FDM 3D-printed PLA (Poly Lactic Acid) shows a transversely isotopic symmetry similar to laminated composite structures. Therefore, classical lamination theory can be applied to FDM 3D-printed PLA. This study attempts to expand the knowledge by relying on classical lamination theory and several imposed failure theories like maximum stress, Tsai-Hill, Tsai-Wu, and Hashin to determine how FDM 3D printing of PLA fails. We investigate eight different raster orientations (0 degrees, 10 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees) and compare the theoretical prediction of strength with experimental findings. With this comprehensive analysis, we are seeking to better understand the failure analysis of FDM 3D printed PLA. The maximum stress, Tsai-Wu, Tsai-Hill, and Hashin failure theories show good agreement with experimental findings for 0 degrees and 90 degrees raster orientations. As the raster orientation shifts from 0 degrees, the discrepancy between experimental results and theoretical predictions increases, peaks at mid-angles, and then decreases, becoming negligible at 90 degrees.
Effect of Crosshead Displacements Rates on the Out of Plane Mechanical Properties of S2-Glass Fiber Reinforced Polymers
(2025) Yilmaz, Cagatay; Eltahir, Sara Saeed Abdulrahman
Test hızları, fiber takviyeli polimerik malzemelerin mekanik tepkisini değiştiren önemli parametrelerdir. Bu çalışma kapsamında, düzlem dışı yükleme koşulu altında farklı test hızları ile S2-cam elyaf takviyeli polimerik malzemelerin eğilme davranışlarını incelenmiştir. Düzlem dışı yükleme koşulu üç noktalı eğilme fikstürüyle sağlanmıştır. 2 mm/dk, 20 mm/dk, 40 mm/dk ve 60 mm/dk olmak üzere dört farklı test hızı bu çalışmada kullanılmıştır. Maksimum yükte sehim miktarı, eğilme modülü ve eğilme mukavemeti test hızına bağlı olarak analiz edilmiştir. Test hızı 2 mm/dk’dan 20 mm/dk ve oradan da 40 mm/dk'ya çıktıkça hem eğilme mukavemetinin hem de eğilme modülünün artış eğilimi gösterdiği bulunmuştur. Bununla birlikte, test hızı 40 mm/dk'dan 60 mm/dk'ya yükseldiğinde eğilme mukavemetinde ve modülde bir düşüş gözlemlenmiştir.