Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Investigating the Effects of Functionalized Single Wall Carbon Nanotubes on the Cure Behavior of a Carbon/Epoxy Prepreg System by an Optimized Parameter Approach(Wiley, 2025) Oz, Murat; Uz, Yusuf Can; Tanoglu, Gamze; Tanoglu, Metin; Barisik, MuratCarbon/Epoxy composite materials are used in a wide range of applications due to their superior performance. However, their properties are strongly related to cross-linking reactions occurring during the curing process, and a prior estimation of curing parameters is the key to manufacturing the desired material. This study builds a mathematical model to solve the inverse kinetic problem based on differential scanning calorimetry data and later presents its use in curing experiments. The method derived (Gamze-Murat-Neslisah (GMN) approach) determines the pre-exponential and activation energy of the curing process. Later, an extended experimental study was performed. Functionalized single-wall carbon nanotubes (F-SWCNTs) were prepared by oxidizing their surface with carboxyl to enhance the dispersion of the nanoparticulates. The epoxy resin systems were modified with 0.05%, 0.1%, and 0.2% wt. F-SWCNTs, which were impregnated on carbon fibers (CFs). The curing behavior was studied, cure kinetic parameters were determined, and the thermal behavior was characterized. Differential scanning calorimetry (DSC) data sets for CF/epoxy prepregs containing F-SWCNTs were used for the verification of the proposed method. It was found that the GMN approach is in good agreement with the experimentally measured data for all kinetic parameters. The addition of F-SWCNTs increased the material's curing efficiency as the CNTs enhanced heat transport in composites, reducing the activation energy. The results obtained from the GMN algorithm were also found in good agreement with the well-known Kissinger-Akahira-Sunose (KAS) and Kissinger methods, while the current GMN method revealed itself as an accurate algorithm to obtain the activation energy.Article Influence of Intra-Ply Discontinuities on the Mechanical Behavior of Continuous E-Glass Fiber Reinforced Composites(Sage Publications Ltd, 2024) Kilicoglu, Ahmet Suha; Tanoglu, Metin; Bilmez, Sinan Ali; Gunes, Mehmet Deniz; Erdogan, Hakan SalihThis study examines how structural discontinuities created during production affect glass fiber-reinforced composite plates. Due to geometrical constraints, the composite microstructure's discontinuities can be categorized as inter-ply and intra-ply. Material testing was conducted at the coupon level as an initial step to ascertain material characteristics. Two full-scale models of intra-ply composite samples were manufactured by employing layers of glass fiber-reinforced prepregs. Discontinuities were generated in the samples using a computer numeric control cutter and then manually applied. The discontinuities' impact on the composite laminate's mechanical properties was assessed through full-scale pieces using three-point bending quasi-static tests. Servo-hydraulic actuators were used to conduct tests on the items. The experimental test results were compared with CAE analysis predictions by evaluating sectional fiber volume fraction. The characteristics of local discontinuities were analyzed using a microscope to enhance the findings of the CAE model. This comprehensive approach offers insights into the intricate connection between internal structural inconsistencies and the mechanical properties of continuous glass fiber-reinforced materials. It supports optimizing composite manufacturing processes and improves composite parts' structural reliability. Dislocation areas were found to result in the formation of resin-rich zones in this investigation. The exothermic curing process in the component's zones results in elevated temperatures, leading to a color change in the resin from clear to yellow. The yellow areas are easily recognizable and show decreased mechanical durability.Article Fatigue-Resistant Design of Carbon/Epoxy Composites Based on a Failure Tensor Polynomial Model by Particle Swarm Optimization-Sequential Quadratic Programming Algorithm(Sage Publications Ltd, 2024) Deveci, Hamza Arda; Artem, Hatice Secil; Guenes, Mehmet Deniz; Tanoglu, MetinThis article introduces a design procedure to find the optimum fiber orientations of carbon/epoxy composite laminates for fatigue life advancement. The approach incorporates a fatigue failure tensor polynomial model and employs a hybrid algorithm, combining particle swarm optimization and sequential quadratic programming. Firstly, material properties of quasi-static and fatigue of the carbon/epoxy composites, fabricated by the vacuum-assisted resin transfer molding method, were determined to be used in the model. Various design problems involving two optimization scenarios were then solved using the hybrid algorithm. The algorithm's performance was also evaluated by specific test problems, confirming its speed and robustness. The optimally fiber-oriented carbon/epoxy composite laminates having maximum fatigue lives were obtained for many critical in-plane cyclic loading cases. To validate the proposed design procedure, two optimum designs were experimentally verified under uniaxial loading conditions. The results indicated a good correlation between the estimated fatigue life of the optimally designed laminates and experimental data. This methodology offers a promising approach for the design of carbon/epoxy composite laminates with superior fatigue strength, particularly significant in specific industrial applications.Article Citation - WoS: 7Citation - Scopus: 7Improving Mechanical Behavior of Adhesively Bonded Composite Joints by Incorporating Reduced Graphene Oxide Added Polyamide 6,6 Electrospun Nanofibers(Elsevier Sci Ltd, 2024) Yeke, Melisa; Barisik, Murat; Tanoglu, Metin; Ulas, M. Erdal; Nuhogu, Kaan; Esenoglu, Gozde; Iris, M. ErdemAdhesive joining of fiber-reinforced polymer (FRP) composites requires adequate interface tailoring and careful surface preparation to obtain a strong bond between components. This study aimed to improve the mechanical performance of adhesively bonded unidirectional carbon fiber-based (CFRP) composite parts by modifying joint surfaces with graphene-added electrospun Polyamide 6,6 (PA66) nanofibers. Reduced graphene oxide (rGO) was dispersed at 10 % wt/v PA66 solution at three different concentrations below rGO saturation limits. Bead-free nanofibers with homogenous graphene distribution were obtained on a prepreg by electrospinning. Addition of up to 2 % rGO yielded complete dispersion through the nanofiber network while the higher values created local agglomerations. Surface wetting experiments showed conversion of slightly hydrophobic surfaces to complete hydrophilic with electrospun nanofiber coating and the lowest contact angle was obtained at 2 % wt/v rGO addition (26.18 degrees +/- 2.03 degrees). Composite plates were produced in a hot press keeping the modified prepregs on top. Plates with different surface treatments joined by secondary bonding using 3 plies of FM 300 K film adhesive. Mechanical properties of adhesively bonded composites were tested by Single lap joint and Charpy impact tests. We achieved an 18 % increase in shear strength and 31 % increase in impact strength by adding 2 % wt/v ratio rGO into PA66 electrospun nanofiber.