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عدد المساهمات : 18959 التقييم : 35383 تاريخ التسجيل : 01/07/2009 الدولة : مصر العمل : مدير منتدى هندسة الإنتاج والتصميم الميكانيكى
| موضوع: بحث بعنوان A Composite Sandwich Plate With a Novel Core Design الأربعاء 09 سبتمبر 2020, 1:06 am | |
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أخوانى فى الله أحضرت لكم بحث بعنوان A Composite Sandwich Plate With a Novel Core Design Anil Uzal,1 Fazil O. Sonmez,*1, Fatih E. Oz1, Kenan Cinar,1,2 Nuri Ersoy1 1Department of Mechanical Engineering, Bogazici University, Istanbul, Bebek 34342, Turkey 2Department of Mechanical Engineering, Namik Kemal University, Tekirdag, Corlu 59860, Turkey
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ABSTRACT In this study, a new core design is introduced for sandwich composite structures. Its strength and failure behavior are investigated via three-point bending tests. E-glass-fiber-reinforced epoxy resin is selected as the material for both the core and the face sheets. The core has an egg-crate shape. Acoustic emission (AE) method is used to detect the progression of damage. Signals due to elastic waves caused by activated damage mechanisms are investigated in order to identify the corresponding failure modes. A finite element model of the sandwich structure is developed to predict the failure behavior of the specimens under the loading conditions in the tests. A promising agreement between the results of the finite element model and the experiments is observed. The force-deflection- relation, the failure load as well as the region where damage initiates are accurately predicted. Keywords: Sandwich panels; Composite materials; Acoustic emission; Out-of-plane loading; Three-point bending; Finite element modeling 6. CONCLUSIONS In this study, the failure behavior of a sandwich plate with an egg-crate shaped core design is investigated. The structure is manufactured by vacuum infusion method. The resin used is epoxy and the reinforcement is non-crimp fabric made of E-glass-fibers. In order to understand the failure behavior under out-of-plane loading, the sandwich plates are tested using a three-point bending setup under real-time acoustic emission monitoring. The collected AE data are post-processed and classified according to their dominant frequency characteristics. It is found out that under transverse forces, the sandwich plates can withstand loads up to 5 kN; first-ply failure occurs due to local buckling of side walls at about 4.1 kN. In the deflection-controlled experiments, beyond the peak load level, the structure is observed to withstand further deformation without catastrophic failure. After some point, extensive fiber failures are observed; still the part can carry 1.8 kN load even after the transverse deflection exceeds three times the plate thickness. In order to predict the failure behavior of the sandwich plate, a Python Script code is29 developed to model the structure and simulate three-point bending tests. As the failure measure, Tsai-Hill failure criterion is adopted. The failure load is found iteratively using the secant algorithm and the outcome is compared with the experimental results. The region of failure, mode of failure, and the load level at which failure initiates are predicted within reasonable accuracy. The FE element model can predict the first-ply-failure load level within 5% error margin. In this study, a procedure is proposed to determine the strength properties of the laminates reinforced by non-crimp fabrics, using tension test and AE results for specimens with [0/45/−45/ 90]???? and [0/90]2???? layup sequences and a progressive failure model. Using this procedure, longitudinal and transverse tensile strengths, ???????? and ????????, and shear strength, ????, can be obtained. Structural design optimization of the core and comparison of the new sandwich design with conventional sandwich designs like corrugated and foam filled sandwiches are left as future studies. Acknowledgment This paper is based on the study supported by Bogazici University Research Fund with grant number 11168-16A06P2. The authors would also like to thank to Istanbul Development Agency, which supported the development of the infrastructure of Composites Laboratory in Bogazici University under project code ISTKA/BIL/2012/58.
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