Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Language: search.filters.language.enSubject: search.filters.subject.Glass fibers

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  • Master Thesis
    Enhancement of Ballistic Properties by Hybridization Method of Multi-Layered Composite Panels
    (01. Izmir Institute of Technology, 2020) Üstün, Hikmet Sinan; Tanoğlu, Metin
    High performance fiber reinforced composite structures are used for ballistic applications in recent years due to several advantages lightweight, high strength and high energy absorbing capability. In this regard, it is aimed to enhance ballistic performance of fiber reinforced composites by hybridization method in this thesis. Two of most used fiber types were selected as reinforcement which are E-Glass and Aramid fibers. As matrix epoxy resin was used. Homogeneous and hybrid structures were manufactured. In hybrid structures configuration was arranged as E-Glass layers are at the front and Aramid layers are at the back. Two different hybrid composites were manufactured with 50:50 and 70:30 Aramid and E-Glass layers. The effect of volume fraction of fabric layers on ballistic properties was investigated. Since there is a linear relationship between V50 and thickness, composite structures were manufactured with two different thicknesses and by the equation derived V50 values for different thicknesses could be determined. Mechanical and ballistic tests were carried out in the study. Tensile, 3-Point bending and short beam strength tests were applied as mechanical tests and a V50 test was carried out as ballistic test. Composite structures were compared with each other based on test results. Consequently, it was found that hybridization method increased mechanical and ballistic properties. Mass efficiency of hybrid structures were found to be higher than 1 (E-Glass composite was used as reference). It was also found that presence of E-Glass layers assists aramid structures to experience more delamination during impact and therefore increased energy absorbing capability.
  • Master Thesis
    Joining and Interfacial Properties of Aluminum/Glass Fiber Reinforced Polypropylene Sandwich Composites
    (Izmir Institute of Technology, 2009) Guruşçu, Aslı; Tanoğlu, Metin
    The joining of separate components using a suitable technique is a critical step in the manufacture of composite structures. For good property performance of aluminum/glass fiber reinforced polypropylene (Al/GFPP) laminates, one of the most important problems is to obtain good adhesive bond strength.In the present study, Al/GFPP laminates have been manufactured with various surface pretreatment techniques. Adhesion at the composite/metal interface has been achieved by surface pretreatment of Al with amino based silane coupling agent, incorporation of polyolefin based adhesive film and modification with PP based film containing 20 wt. % a maleic anhydride modified polypropylene (PP-g-MA). The mechanical properties shear, peel and bending strength of the adhesively bonded Al/GFPP laminates were investigated to evaluate the effects of those various surface treatments. In addition, peel strengths of Al foam/GFPP laminates with various surface treatments were measured. The fracture surfaces have been examined by scanning electron microscope (SEM). Results showed that the adhesion of the laminated Al/GFPP systems were improved by treatment of aluminum surfaces with amino-based silane coupling agent. Based on peel and bending strength results, Al/GFPP laminates with incorporation of polyolefin based adhesive films exhibited significant increase on the adhesive behaviour. Modification of Al/GFPP interfaces with PP-g-MA layer leads to highest improvement on the adhesion properties.
  • Master Thesis
    Experimental Study on Improving Local Buckling Behavior of Steel Plates Strengthened With Glass Fiber Reinforced Polymers
    (Izmir Institute of Technology, 2009) Güven, Can Ali; Eğilmez, Oğuz Özgür
    Glass Fiber Reinforced Polymer (GFRP) applications becoming one of the most efficient strengthening methods to improve mechanical properties of previously built steel structures. In strengthening applications FRP materials generally used in web or flange sections of steel members to provide a bracing against local buckling. By the help of their easy application and their tailorable mechanical properties, FRPs provide various options for selecting the most suitable FRP material for applications. This study focuses on using GFRP to enhance the buckling behavior of GFRPstrengthened steel plates under axial loading. For that purpose, a detailed experimental study program has been followed revealing mechanical properties of GFRP material, steel and interaction between steel-GFRP. Previous studies showed that the surface bond between GFRP and steel section as the weakest link of the structure. As a result of this, various epoxies, surface preparation primers, surface treatments are used to produce Lap-Shear specimens to provide most efficient surface interaction between GFRP and steel. Results of these experiments provided us data to decide most suitable surface treatment, surface primer and epoxy combination in the GFRP Strengthened Steel Plate Tests with the ability to in-situ application. 350x200x20 mm steel plates are strengthened with various thickness (2, 4 and 16 layers) and surface areas (80mm x 300mm, 160 x 300mm) of GFRP to compare the stabilization in buckling values with bare steel plates. Plates are strengthened with GFRP on both sides and they are tested in compression testing equipment. LVDTs are used to collect axial and lateral buckling while strain-gauges attached to both composite used to collect axial and lateral buckling while strain-gauges attached to both composite plates strengthened with GFRP material showed that application of GFRP provides enhancement to the plastic buckling of steel plates.
  • Master Thesis
    Processing and Characterization of Polymer Based Composites With Superior Impact Resistance
    (Izmir Institute of Technology, 2003) Seyhan, Abdullah Tuğrul; Tanoğlu, Metin
    Fiber reinforced polymeric composite materials have recently gained widespread use in military, transportation, energy and civil engineering applications. Resin Transfer Molding (RTM) and Vacuum Assisted Resin Transfer Molding (VARTM) process have become important in the manufacture of these types of composites. In those techniques, use of fiber preforms offer some distinct advantages. Using thermoplastic binders that bond the fabrics together allows the plies to be consolidated into near net shape preform.In the present work, glass preforms were consolidated by application of heat and pressure over plies of the glass fabrics that were coated with various concentration of thermoplastic polyester binder. Composite laminates with and without binder were fabricated by utilizing VARTM technique. The peel strength of the preforms with various binder contents was measured to determine the optimum binder concentration. The highest peel strength was obtained from preforms that were prepared with about 9 wt.% of the binder. Preform compression test was also performed using universal test machine with preforms composed of eight plies of glass fabrics with binder (3,6 and 9 wt.%) and without binder. It was observed that the binder has significant effect on the degree of preform compaction. The highest thickness reduction and therefore fiber volume fraction of the preforms was reached via 3 wt.% of binder. The flexural strength and modulus, compressive strength and modulus through ply-lay up and in-plane loading directions, apparent interlaminar shear strength, mode I interlaminar fracture toughness of the composites with and without binder were measured to evaluate the effects of the binder on the mechanical properties of the composite plates. It was found that the flexural strength, mode I interlaminar fracture toughness of the E-glass/polyester composite system decreases 30 and 40 percentage, respectively due to the presence of 3 wt.% and 6 wt.% of binder. On the other hand, the flexural modulus of the composite increases while the apparent interlaminar shear strength remains almost constant by the introduction of the binder. The ply-lay up compressive strength and modulus were found to increase up to 3 wt.% of binder and decrease upon further addition of binder. The same findings are valid for the compressive strength and modulus through in-plane loading direction. Ballistic test was performed on E-glass/polyester composite panels according to NATO standards 2920 using 1.1-gr. fragment-simulating projectiles (FSPs) to evaluate the effects of the binder on the ballistic performance of the E-glass/polyester composite laminates. The ultrasonic C-scan test method was used to monitor the extent of the damage on the panels due to ballistic impact. It was seen that the damage on the ballistically impacted composite panels decreases with increasing binder. A model matrix material was prepared adding various concentrations of the binder to the reacting resin system in order to follow the extend of binder dissolution within the matrix resin. It was found that there is no complete dissolution of the binder in the matrix resin.