Experimental and simulation studies on the compressive behavior of the 3D printed graded re-entrant auxetic structures

نوع: Type: thesis

مقطع: Segment: masters

عنوان: Title: Experimental and simulation studies on the compressive behavior of the 3D printed graded re-entrant auxetic structures

ارائه دهنده: Provider: Mohammad Hosseini

اساتید راهنما: Supervisors: Dr. Hashem Mazaheri

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr. Amirhossein Mahmoodi and Dr. Abas Pak

زمان و تاریخ ارائه: Time and date of presentation: 2022/10/08-5-7pm

مکان ارائه: Place of presentation: Seminar NO. 3

چکیده: Abstract: Because of their unique properties, such as high energy absorption, specific deformation against stress, impact resistance, and impermeability, auxetic structures have been widely used in various industries, especially sports equipment, in recent years. In various studies, attempts have been made to change the geometry of these structures to optimize energy absorption and properties. In this research, using the FDM 3D printer, different types of these structures have been made. At first, a suitable layering method in 3D printing of tensile test samples to determine the mechanical properties of PLA and PLA+ materials was investigated. Then, three types of structures in the form of homogeneous re-entrant, unilateral graded thickness UGT, and bilateral graded thickness BGT were made using brittle PLA and ductile PLA+ materials that energy absorption and plateau stress are compared in them. The simulation results have been validated by modeling the structures in two ways: brittle materials and ductile materials by Abaqus software. Using simulation, the best kind of bilateral graded thickness was extracted, which is 0.8-1-1-2.1. In another part, several models of auxetic structures were introduced, and these structures are in three sets of graded angle, compound, and reinforced core structures. Through simulation, the best designs were selected in each group: UGA-A, BGA-A, UGA-H, AHC, and LCA structures. Selected structures were made with 3dprinter with PLA+ material, and the amount of energy absorption, Poisson's ratio, etc., have been checked in more detail. Finally, this section chose the UGA-A model as the best structure for absorbing energy. In the final, the optimal models of each BGT, UGA-A, and LCA group that can be combined were selected, and four new combined models were designed. Among the designed models, the unilateral graded angle structure with a reinforced core (UGA-A+Core) with a specific energy absorption of 5.458 KJ/g and a 336% increase in energy absorption compared to the homogeneous re-entrant in this thesis, the most optimal structure was known. This model can be used in sports equipment design and manufacture

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