Browsing by Author "Ekici, Recep"

Now showing 1 - 7 of 7

The Effect of Artificial Aging on the Impact Behavior of Sic Nanoparticle-Glass Fiber-Reinforced Polymer Matrix Composites
(Wiley, 2022) Kosedag, Ertan; Caliskan, Umut; Ekici, Recep
The low-velocity impact behavior of SiC nanoparticle-glass fiber-reinforced polymer matrix composites (PMC) in terms of different weight fraction of nanoparticle, artificial aging time, and impact energy was investigated in this article. In this context, silicon carbide (SiC-70 nm) ceramic nanoparticle in weight fractions of 0%, 0.1%, 1%, 2%, 3% filled glass fiber-reinforced PMCs were produced by vacuum infusion technique. The specimens were artificially aged in 0, 750, and 1500 h, 85% relative humidity and 70 degrees C in air conditioning cabinet. The after-impact damage regions were obtained using ultrasonic scanning technique for three different impact energies of 10, 20, and 30 J. The weight of specimens was measured at certain periods during aging and the weight change was examined. As the weight fraction and aging time were increased, the impact resistance of specimens decreased. At the beginning of aging period, the weight of specimens increased; however, the increase in weight decreased over time. Ultrasonic scanning results showed that the damage geometry changed and increasing discontinuity with increasing weight fraction and artificial aging time.
Effect of Sic and Graphene Nanoparticles on the Mechanical Properties of Carbon Fiber-Reinforced Epoxy Composites
(Wiley, 2023) Kosedag, Ertan; Ekici, Recep; Yildiz, Nail; Caliskan, Umut
This study experimentally investigates the mechanical properties of carbon fiber reinforced epoxy composites (CFRECs) filled with Graphene (Gr) and Silicon Carbide (SiC) nanoparticles. Gr and SiC nanoparticle filled CFREC plates at 0%, 0.5%, 1%, and 2% weight ratios were fabricated using a vacuum infusion technique from unidirectional carbon fiber fabric with both 0 and 90 & DEG; fiber orientation. According to ASTM standards, tensile, compression, and three point bending tests were performed to determine the effects of additive type and weight ratios. CFRECs with Gr additive exhibit improved tensile properties compared to the unfilled composites, especially at higher filler contents and at specific fiber orientations. Also, the Gr additive showed a better improvement in the tensile behavior of the CFRECs than the SiC additive. In general, it was found that the elastic modulus values of nanoparticle additive samples were higher than that of the unfilled composite material in both fiber orientations. Except for the 0.5% SiC ratio with 0 & DEG; fiber orientation, the particle added nanocomposites did not exceed the value of the unfilled composite and did not make a positive effect on the compressive strength. It has been observed that Gr additives give more positive results on the bending strength of CFRECs than SiC, especially at a 2% weight ratio. Highlights center dot Effects of nanoparticle types on mechanical properties of CFRECs were compared. center dot Weight ratio effects on the properties of nanoparticle-filled CFRECs were studied. center dot The load-bearing capacity decreased as the additive ratio increased. center dot Additives and ratios should be carefully selected for the intended applications. center dot Overall, presence Gr resulted in enhanced properties much prominently for composites.
Effect of Stacking Sequence and Metal Volume Fraction on the Ballistic Impact Behaviors of Arall Fiber-Metal Laminates: an Experimental Study
(Wiley, 2022) Kosedag, Ertan; Aydin, Murat; Ekici, Recep
Thanks to their superior mechanical properties, polymer matrix composites have gained considerable importance. In order to improve the impact resistance of polymer matrix composite materials, a new hybrid material known as fiber metal laminate (FML) has been developed. The aim of this study was to reveal the effect of stacking sequence (SS), metal volume fraction (MVF), and number of layers on ballistic resistance in fiber metal laminates (FMLs). Four types of FMLs in different sequences and MVF (25% and 50%) were produced with hot press and vacuum. Ballistic tests were carried out with a single stage gas gun system. The absorbed energy was calculated from the energy difference that occurred by taking into account the FMLs entry and exit velocity of the projectile and the projectile mass. Damage types were examined after ballistic testing. It was determined that the stacking sequence and MVF significantly affect the impact resistance of FMLs. It was determined that the metal layer, which first encounters the projectile, compared to the polymer matrix composite, is more effective on the impact resistance of FMLs, and the impact resistance increased with the increase of MVF. In addition, the increase in the number of layers, if the top layers remain the same, adversely affected the impact resistance. It was observed that the first layer that encounters the projectile and the amount of MVF have a significant effect on the ballistic impact strength. As the amount of MVF increases, the ballistic impact resistance increases.
Free Vibration Analysis of Foam-Core Sandwich Structures
(Gazi Univ, 2021) Kosedag, Ertan; Ekici, Recep
In this paper, the free vibration analyses of aluminum-foam sandwich structures were completed numerically. Foam and aluminum (Al) were used for the core and surface layers of the sandwich structure, respectively. In addition, an adhesive was used as a thin film. Natural frequencies and mode shapes of the sandwich structure were obtained for different thickness core and surface materials. For this, three different sandwich structures, different thickness of the core with same surface layers and the same core thickness with different surface layers thickness, were modeled as SS1, SS2 and SS3. Analyses were performed by ABAQUS/Standard finite element software. The increase in the thickness of the Al layer generally caused a decrease in the frequency, but this decrease is not very dramatic. The increase in the thickness of the core has caused a serious increase in the frequency of the sandwich structure.
Low-Velocity and Ballistic Impact Resistances of Particle Reinforced Metal-Matrix Composites: an Experimental Study
(Sage Publications Ltd, 2022) Kosedag, Ertan; Ekici, Recep
This study investigates the low-velocity and ballistic impact responses of SiC-reinforced Al6061 metal-matrix composites in different reinforcement volume fractions. Low-velocity impact (LVI) tests were performed with samples having SiC particle volume fractions of 0, 5, 10, 15, 20, 30, and 40%, while ballistic tests were carried out with samples having volume fractions of 0, 10, 20, and 30%. The weight-drop test method was used for LVI by applying 50 J (4.45 m/s) energy to all samples. Ballistic tests were carried out under the same conditions on all samples with the projectile launched at an average velocity of 500 m/s. For the determination of the ballistic resistance of the samples, the projectile penetrations in the witness structures were taken into consideration. The damage and deformations caused by both the LVI and the ballistic test in composites were examined. By the LVI test results, composite samples have absorbed less impact energy by increasing the reinforcement volume fraction, as well as demonstrated superior performance compared to unreinforced samples. In addition, the crack formation was mainly observed in the samples containing 30% reinforcement, while the composite material with a 40% volume fraction was completely broken. With the increase in the reinforcement volume fraction, the ballistic resistance of the samples increased significantly.
Low-Velocity Impact Behaviors of B4c/Sic Hybrid Ceramic Reinforced Al6061 Based Composites: an Experimental and Numerical Study
(Elsevier Science Sa, 2025) Kosedag, Ertan; Ekici, Recep
This study studied the low-velocity impact behavior of silicon carbide (SiC), boron carbide (B4C), and hybrid B4C/SiC reinforced aluminum 6061 alloy (Al 6061) matrix composites experimentally and numerically. The effect of hybridization, reinforcement volume fraction, and reinforcement type on low-velocity impact was investigated. 16 different metal-matrix composite materials were manufactured for the study, including 9 hybrid samples, 6 non-hybrid samples for each reinforcing ceramic particle, and 1 unreinforced sample. The powder metallurgy - hot press method was used in experimental production and then low-velocity impact tests were carried out. Numerical study was carried out using the non-linear finite element method (FEM). A Python algorithm running on ABAQUS/Explicit was utilized to determine ceramic particle distribution based on volume fraction, hybridization ratio, and random particle arrangement. The Johnson-Cook Plasticity Model was used for the non-linear relationship between stress and strain in the Al 6061 metal-matrix during impact. The results were interpreted with the contact force-time, contact force-displacement, and energy-time data obtained from lowvelocity impact tests. In addition, the amount of collapse that occurred during the impact was measured and compared, and finally, SEM/EDX analysis was performed for the microstructure characterizations of the composite sample. Impact tests revealed that the collapse of composite samples ranged from 3.06 mm to 3.58 mm, with the unreinforced S6 sample collapsing 4.18 mm, indicating that increased reinforcement elements reduce ductility, while a lower B4C ratio or higher SiC ratio in hybrid composites leads to greater collapse. Keeping the hybridization rate constant while increasing the reinforcement ratio leads to an increase in contact force and a decrease in contact time. Hybrid composites exhibited higher stiffness as SiC content increased, while B4C reinforced non-hybrid composites showed more significant stiffness. There is good agreement between the numerical and experimental results. Non-hybrid samples have a better match between numerical predictions and experimental results than hybrid samples.
Repeated Low-Velocity Impact Responses of Sic Particle Reinforced Al Metal-Matrix Composites
(Elsevier Sci Ltd, 2022) Ekici, Recep; Kosedag, Ertan; Demir, Mert
This study aimed to investigate experimentally the repeated low-velocity impact behaviors of SiC reinforced aluminum 6061 metal-matrix composites for different volume fractions and energy levels. In addition, the hardness variations were measured by the Vickers hardness tests from the impacted and impact-free cross-sections of the particle reinforced metal-matrix composites. Low-velocity impact tests were applied to composite samples manufactured by powder metallurgy (in 10, 20, and 30% volume fractions) at two total energy levels (15 and 60 J as single) and in repetitions equal to the sum of these energy levels (5 + 5 + 5 and 20 + 20 + 20 J as repeated). As a result, in increasing the impact number for all volume fractions, the total contact time was shortened and the peak contact force increased, whereas both the permanent central deflection and the absorbed energies reduced. Hence, these variations obtained under repeated impacts (5 + 5 + 5 and 20 + 20 + 20 J) revealed that metal-matrix composites showed a tougher behavior with an increase in the impact numbers from 1st to 3rd, particularly because of the strain hardening effect. Furthermore, an increase in volume fraction from 10 to 30% resulted in an increase in the impact strength under all repeated and single impacts despite changing deformation and damage mechanisms due to increasing the strain hardening effect and particle fractures. The hardness was affected by the volume fraction and increased as the volume fraction increased in both the impacted and impact-free zones. The repeated impact increased the impacted zone hardness more than the single impact for all volume fractions. Additionally, the hardness of the impacted zone under 20 + 20 + 20 J repeated impact was measured as the highest value in the 30% volume fraction. Therefore, metal-matrix composites can behave harder with the strain hardening effect under repeated impacts.