Phd Degree / Doktora

Permanent URI for this collectionhttps://hdl.handle.net/11147/2869

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Author: search.filters.author.Tanoğlu, MetinSubject: search.filters.subject.Carbon fibers

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  • Doctoral Thesis
    Examination of Fatigue Behaviour of Carbon Fiber Reinforced Polymer Composites
    (Izmir Institute of Technology, 2021) Güneş, Mehmet Deniz; Tanoğlu, Metin; Tanoğlu, Metin
    This PhD thesis aims to examine the fatigue behavior of sandwich panels fabricated from adhesively bonded aluminum honeycomb core and carbon fiber reinforced polymer composite face sheets. Initially, sandwich panels were manufactured with three different amounts of adhesive in their interface. Static flexural behavior was characterized with three-point bending tests. Load-displacement curves and static flexural failure modes were obtained and utilized to compare the static flexural behavior of fabricated sandwich. Fatigue behavior of sandwich panels were characterized with the three-point bending fatigue tests. Stiffness degradation curves were used to identify the failure cycles of sandwich panels. Fatigue failure modes and S-N curves were obtained to find out the effect of amount of adhesive on fatigue behavior of sandwich panels. The other study within this thesis was made to investigate the effect of core thickness on the fatigue behavior of the sandwich panels based on aluminum honeycomb core and carbon fiber reinforced polymer composite face sheets. Sandwich panels were fabricated by using three different aluminum honeycomb core thickness. Static flexural tests were carried out to determine the static flexural behavior of developed sandwich panels. Load-displacement curves and failure modes were obtained from flexural tests. In addition to this, core shear tests were performed to investigate the core shear strength of the honeycomb cores with different core thickness. Effect of core thickness on fatigue behavior of sandwich panels were characterized with fatigue failure modes and S-N curves. Stiffness degradation method was used to determine the fatigue failure cycles of the sandwich panels.
  • Doctoral Thesis
    Toughening of Carbon Fiber Based Composites With Electrospun Fabric Layers
    (Izmir Institute of Technology, 2017) Beylergil, Bertan; Tanoğlu, Metin; Aktaş, Engin
    The objective of this PhD thesis is to investigate interlaminar Mode-I fracture toughness of carbon fiber/epoxy composites interleaved by micro and/or nano scaled PA66 nonwoven veils. Also, the effects of electrospun PVA nanofibers on the mechanical performance of these composites were investigated. Additionally, this thesis also deals with the effects of aramid nonwoven veils on the mechanical properties of CF/EP composites. The produced nanofibers produced by electrospinning were directly deposited on carbon fiber fabrics. Then, reference and nano-modified laminates were manufactured by vacuum infusion method. A series of mechanical tests such as tensile, compression, three point bending, Charpy-impact, interlaminar shear strength and open hole tensile tests (OHT) were carried out on the prepared specimens. Double cantilever beam (DCB) tests were conducted on reference and interleaf-modified laminates. The effect of PA 66 nanofiber areal weight density was also evaluated with varying electrospinning time. Scanning electron microscopy (SEM) was used to investigate the fiber morphology and to understand the toughening mechanisms. Dynamic mechanic analysis (DMA) was used to investigate the thermo-mechanical behavior of reference and interleaf-modified composite specimens. Differential scanning calorimetry (DSC) was used to determine the thermal properties of micro and electrospun PA66 nonwoven veils. Comparing the mechanical test results, the most effective nonwoven interleaving system was determined in terms of higher delamination resistance and in-plane mechanical properties. Finite element method (FEM) was used to evaluate the effects of electrospun PA66 nonwoven veils on the CF/EP composites. Numerical simulations of Mode-I fracture toughness tests were carried out using ANSYS Workbench. The results showed that the most effective material was electrospun PA66 nonwovens considering the higher delamination resistance. Additionally, the electrospun PA 66 nonwovens also improved Charpy-impact and interlaminar shear strength of the reference CF/EP composites. Numerical results showed good agreement with the experimental ones.