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    Characterization of unmodified and modified apricot kernel shell/epoxy resin biocomposites by ultrasonic wave velocities
    (Springer, 2023) Oral, Imran; Kocaman, Suheyla; Ahmetli, Gulnare
    The main goal of this research was to develop highly durable, low-cost eco-friendly biocomposites from apricot kernel shell (AKS) wastes and ultrasonic characterization of AKS-based obtained biocomposites. Natural AKS wastes were chemically modified using 5 wt% sodium hydroxide (NaOH) and 99 wt% glacial acetic acid (AA). These modified apricot kernel shells (MAKS) and unmodified apricot kernel shells (UMAKS) were added into bisphenol-A type epoxy resin (ER) in varied compositions such as 10-50 wt% to prepare the MAKS/ER and the UMAKS/ER biocomposites. The epoxy resin-mixture in the weight ratios of resin/hardener/accelerator was 100:30:1. The effect of AKS powder ratios and modifiers on the elastic properties (Young's moduli [E], bulk moduli [K], longitudinal moduli [L], shear moduli [G], and Poisson's ratio [mu]), density (rho), damping properties (attenuation coefficient [alpha], loss tangent [tan delta], and quality factor [Q]), ultrasonic micro-hardness (H), and acoustic impedance (Z) of biocomposites was investigated by the ultrasonic testing (UT) method. The morphological structure of the ER and biocomposites was figured out using scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The results revealed an increase in elastic properties of most of the AKS/ER biocomposites compared to the neat ER. On the other hand, results have shown that SEM and XRD images' analysis confirmed the amorphous structure of ER and biocomposites. The highest rho, v(L), v(S), L, G, E, H, and Z values were obtained in MAKS-AA/ER-5 biocomposite. Thus, it can be stated that the MAKS-AA/ER-5 biocomposite sample has the best mechanical properties. Also, the results revealed that the MAKS-AA/ER-1 sample can be used as an alternative material for its high Q-factor value instead of wood in producing musical tools.
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    Determination of mechanical and damping properties of hazelnut shell powder reinforced biocomposites by ultrasonic method
    (Wiley, 2023) Oral, Imran; Kocaman, Suheyla; Cerit, Alaaddin; Ahmetli, Gulnare
    This research was carried out to figure out the effect of chemical treatments of hazelnut shell powders (HSPs) on the elastic properties, ultrasonic wave velocities, and damping properties of bio-based epoxy resin (BER) biocomposites. Natural hazelnut shells (HSs) were chemically treated using sodium hydroxide (NaOH), and acetic anhydride (AA). Then, HSs that were chemically treated with NaOH and AA, and HSs that were not subjected to chemical treatment were ground to obtain HSPs. The treated HSPs (HSP-NaOH and HSP-AA), and untreated HSPs were contributed to the neat BER in varied compositions such as 10-50 wt% to obtain the BER/HSP, BER/HSP-NaOH, and BER/HSP-AA biocomposites. The effect of untreated, and treated HSP ratios on the density, ultrasonic wave velocities, Young's modulus, Bulk modulus, Shear modulus, Poisson ratio, microhardness, and damping characteristics (attenuation coefficient, loss tangent and quality factor) of the novel HSP-based biocomposites, was investigated by the ultrasonic pulse-echo overlap method (PEOM). A significant increase in the density, ultrasonic wave velocities, and elastic modulus values of the biocomposites was seen compared to the neat BER. Based on the obtained elastic modulus values, the most appropriate combination ratio between the neat BER, and HSP-NaOH was determined as 50:50.
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    Mechanical and thermal studies on epoxy toluene oligomer-modified epoxy resin/marble waste composites
    (Wiley, 2012) Ahmetli, Gulnare; Kocak, Nuriye; Dag, Mustafa; Kurbanli, Refika
    In this research, marble dust waste was recycled as raw material for the preparation of composite materials. Epoxy toluene oligomer (ETO) was synthesized from toluene and epichlorohydrin, which was used as a comatrix in 50 wt% with commercial epoxy resin (ER). Its chemical structure was characterized with Fourier transform infrared spectroscopy and chemical analyses. The rigid filler used in epoxy polymer matrix was the marble processing waste obtained from wastewater using different coagulants, such as sepiolite, zeolite, or pumice. The thermal and mechanical properties of the composites were evaluated with thermogravimetric and mechanical analyses. The results showed that the marble wastes with all coagulants can significantly improve the thermal stability of an ERETO matrix at temperatures above 350 degrees C. Composites exhibited a higher thermal degradation temperature with a much higher char yield. Surface hardness and tensile strength of the composites were higher than those of pure epoxy polymer matrix, as well. Scanning electron microscopy was used for the characterization of surface and cross-sections of the composites to verify the results. POLYM. COMPOS., 2012. (c) 2012 Society of Plastics Engineers
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    Preparation and ultrasonic characterization of modified epoxy resin/coconut shell powder biocomposites
    (Wiley, 2022) Oral, Imran; Kocaman, Suheyla; Ahmetli, Gulnare
    A new bio-based epoxy resin (BER) is produced by the esterification reaction between sebacic acid (SAc) as bio-based acid and epichlorohydrin (ECH). The epoxy resin (ER) is modified with the BER. The biocomposites are prepared using untreated coconut shell powder (CSP), modified coconut shell powder (MCSP), and MER. The CSP and MCSP particles are mixed with MER in varied compositions (10-50 wt%) for preparation of the MER/CSP and MER/MCSP biocomposites. The influences of CSP and MCSP bio-fillers amounts on the physical properties (density, elastic constants, acoustic impedance, ultrasonic micro-hardness, and attenuation coefficient) of biocomposites are investigated using the ultrasonic pulse-echo overlap method (PEOM). It was seen that the densities, both ultrasonic longitudinal and shear waves' velocity values of obtained biocomposites were higher than those of the MER. All elastic moduli of the MER/MCSP biocomposites have higher values than of the neat MER and MER/CSP biocomposites.
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    Ultrasonic Characterisation of Epoxy Resin/Polyethylene Terephthalate (PET) Char Powder Composites
    (Kaunas Univ Tech, 2016) Oral, Imran; Ahmetli, Gulnare
    This study is carried out in order to determine the elastic properties of the Epoxy Resin (ER) / Polyethylene terephthalate (PET) Char Powder Composites by ultrasonic wave velocity measurement method. Plastic waste was recycled as raw material for the preparation of epoxy composite materials. The supplied chars were mixed with epoxy resin matrix at weight percentages of 10 %, 20 % and 30 % for preparing ER/PET Char Powder (PCP) composites. The effect of PET char powder on the elastic properties of ER/PCP composites were investigated by ultrasonic pulse-echo method. According to the obtained results, the composition ratio of 80: 20 is the most appropriate composition ratio, which gave the highest elastic constants values for ER/PCP composites. On the other hand, the best electrical conductivity value was obtained for 70: 30 composition ratio. It was observed that ultrasonic shear wave velocity correlated more perfectly than any other parameters with hardness.