Yazar "Yildirim, Ferhat" seçeneğine göre listele

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    EFFECT OF LOW-VELOCITY IMPACT DAMAGE ON THE ELECTROMAGNETIC INTERFERENCE SHIELDING EFFECTIVENESS OF CFRP COMPOSITES
    (Konya Teknik Univ, 2023) Yildirim, Ferhat
    Carbon fiber reinforced polymer (CFRP) composites are widely used engineering materials in aerospace technologies. These electrically conductive carbon-based materials, due to the lightness advantages, are preferred as shields against electromagnetic radiation, especially in aircraft and satellites. However, the performance losses caused by damage because of flying object collision such as bird, hail, or projectile contain significant uncertainty. Herein, the CFRP composite material was structurally damaged by low velocity impact test set-up at various energy levels between 2.5 to 10 joules, and then its electromagnetic interference (EMI) shielding performance was investigated. In addition, the electrical properties of the material were also examined, and the occurred damage status was evaluated by microscopy studies. Intrinsically, the increase in impact energy increases the grade of damage on body of the material. This results in a drastic decrease in electrical conductivity and EMI performance. In experiments, where 5 joule energy is detected as a threshold level, it has been observed that irreparable damage occurs at energy levels above this value.
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    INVESTIGATION OF DRILLING PERFORMANCE OF REINFORCED POLYAMIDE 6 POLYMER COMPOSITE
    (Konya Teknik Univ, 2023) Genc, Abdurrahman; Yildirim, Ferhat; Koyunbakan, Murat; Yetgin, Salih Hakan; Eskizeybek, Volkan; Kus, Gozde
    Polyamides are preferred polymer materials for manufacturing industrial products due to their lightness, resistance to corrosion, ease of processing, and recyclability. In this study, the machinability properties of Polyamide 6 (PA6) polymer composite plates reinforced with chopped carbon fiber (CF) and multi-walled carbon nanotube (MWCNT) in different proportions were investigated by the drilling method using different cutting tools and cutting parameters. The experiments were carried out according to the L16 orthogonal array. Drilling experiments were carried out in a dry environment. The deformations occurring on the inlet and outlet surfaces of the drilled samples were calculated, and the surface roughness (Ra) of the hole walls was measured. According to the results obtained, the particle addition made to the PA6 polymer reduced the Ra. It has been observed that high cutting speed and low feed rate are ideal parameters to achieve low Ra and low inlet-outlet deformations.
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    Multi-walled carbon nanotube grafted 3D spacer multi-scale composites for electromagnetic interference shielding
    (Wiley, 2022) Yildirim, Ferhat; Kabakci, Elif; Sas, Hatice S.; Eskizeybek, Volkan
    The development of structural fiber reinforced polymer composites with various additional functionalities is becoming a hot research area to achieve the application of multi-functional composites in the aerospace and automotive industries. An innovative material solution is 3D spacer composites with distinctive anisotropic structural characteristics. Herein, we report the manufacturing of multi-walled carbon nanotubes (MWCNTs) grafted of 3D spacer glass/epoxy multi-scale composites and their electromagnetic interference shielding efficiencies (EMSE). To manufacture multi-scale composites, we utilized dip coating, vacuum filtering, and vacuum infusion methods to introduce MWCNTs of the woven fabric, while we also modified the epoxy resin with MWCNTs to increase electrical conductivity of intrinsic insulator epoxy resin. Owing to the rectangular-shaped channel structure, which is beneficial for multiple reflection and scattering between top and bottom face sheets, the resultant 3D spacer multi-scale composite represented a good EMSE performance of -18.3 dB in the frequency range of 8.2-12.4 GHz with an increase of 107% comparing the corresponding neat composite counterpart. Moreover, we measured the in-plane conductivity as 1.89E-2 S/m after MWCNTs grafting, while the out-of-plane conductivity remained three times lower than the in-plane conductivity. Dynamic mechanical analysis revealed that the storage modulus increased almost three times with the MWCNTs grafting, while glass transition temperature shifted to higher temperatures (from 77.5 to 89.7 degrees C). Therefore, we anticipate that our study will expand the use of 3D spacer composites in the aviation and automotive industries.