Mechanical Engineering / Makina Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4129
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Article Citation - WoS: 29Citation - Scopus: 31Cure Kinetics of Epoxy Resin-Natural Zeolite Composites(Springer Verlag, 2008) Cansever Erdoğan, Beyhan; Seyhan, Abdullah Tuğrul; Ocak, Yılmaz; Tanoğlu, Metin; Balköse, Devrim; Ülkü, SemraThe cure kinetics of epoxy resin and epoxy resin containing 10 mass% of natural zeolite were investigated using differential scanning calorimetry (DSC). The conformity of the cure kinetic data of epoxy and epoxy-zeolite system was checked with the auto-catalytic cure rate model. The results indicated that the hydroxyl group on the zeolite surface played a significant role in the autocatalytic reaction mechanism. This group was able to form a new transition state between anhydride hardener and epoxide group. The natural zeolite particles acted as catalyst for the epoxy system by promoting its curing rate.Article Citation - WoS: 78Citation - Scopus: 106Critical Aspects Related To Processing of Carbon Nanotube/Unsaturated Thermoset Polyester Nanocomposites(Elsevier Ltd., 2007) Seyhan, Abdullah Tuğrul; Gojny, Florian H.; Tanoğlu, Metin; Schulte, KarlCarbon nanotubes (CNTs) have outstanding mechanical, thermal and electrical properties. As a result, particular interest has been recently given in exploiting these properties by incorporating carbon nanotubes into some form of matrix. Although unsaturated polyesters with styrene have widespread use in the industrial applications, surprisingly there is no study in the literature about CNT/thermoset polyester nanocomposite systems. In the present paper, we underline some important issues and limitations during the processing of unsaturated polyester resins with different types of carbon nanotubes. In that manner, 3-roll mill and sonication techniques were comparatively evaluated to process nanocomposites made of CNTs with and without amine (NH2) functional groups and polyesters. It was found that styrene evaporation from the polyester resin system was a critical issue for nanocomposite processing. Rheological behaviour of the suspensions containing CNTs and tensile strengths of their resulting nanocomposites were characterized. CNT/polyester suspensions exhibited a shear thinning behaviour, while polyester resin blends act as a Newtonian fluid. It was also found that nanotubes with amine functional groups have better tensile strength, as compared to those with untreated CNTs. Transmission electron microscopy (TEM) was also employed to reveal the degree of dispersion of CNTs in the matrix.Article Citation - WoS: 182Citation - Scopus: 214Mode I and Mode Ii Fracture Toughness of E-Glass Non-Crimp Fabric/Carbon Nanotube (cnt) Modified Polymer Based Composites(Elsevier Ltd., 2008) Seyhan, Abdullah Tuğrul; Tanoğlu, Metin; Schulte, KarlIn this study, mode I and mode II interlaminar fracture toughness, and interlaminar shear strength of E-glass non-crimp fabric/carbon nanotube modified polymer matrix composites were investigated. The matrix resin containing 0.1 wt.% of amino functionalized multi walled carbon nanotubes were prepared, utilizing the 3-roll milling technique. Composite laminates were manufactured via vacuum assisted resin transfer molding process. Carbon nanotube modified laminates were found to exhibit 8% and 11% higher mode II interlaminar fracture toughness and interlaminar shear strength values, respectively, as compared to the base laminates. However, no significant improvement was observed for mode I interlaminar fracture toughness values. Furthermore, Optical microscopy and scanning electron microscopy were utilized to monitor the distribution of carbon nanotubes within the composite microstructure and to examine the fracture surfaces of the failed specimens, respectively. © 2008 Elsevier Ltd. All rights reserved.Article Citation - WoS: 91Citation - Scopus: 113Rheological and Dynamic-Mechanical Behavior of Carbon Nanotube/Vinyl Ester-Polyester Suspensions and Their Nanocomposites(Elsevier Ltd., 2007) Seyhan, Abdullah Tuğrul; Gojny, F. H.; Tanoğlu, Metin; Schulte, K.Rheological properties of vinyl ester-polyester resin suspensions containing various amounts (0.05, 0.1 and 0.3 wt.%) of multi walled carbon nanotubes (MWCNT) with and without amine functional groups (-NH2) were investigated by utilization of oscillatory rheometer with parallel plate geometry. Dispersion of corresponding carbon nanotubes within the resin blend was accomplished employing high shear mixing technique (3-roll milling). Based on the dynamic viscoelastic measurements, it was observed that at 0.3 wt.% of CNT loadings, storage modulus (G′) values of suspensions containing MWCNTs and MWCNT-NH2 exhibited frequency-independent pseudo solid like behavior especially at lower frequencies. Moreover, the loss modulus (G″) values of the resin suspensions with respect to frequency were observed to increase with an increase in contents of CNTs within the resin blend. In addition, steady shear viscosity measurements implied that at each given loading rate, the resin suspensions demonstrated shear thinning behavior regardless of amine functional groups, while the neat resin blend was almost the Newtonian fluid. Furthermore, dynamic mechanical behavior of the nanocomposites achieved by polymerizing the resin blend suspensions with MWCNTs and MWCNT-NH2 was investigated through dynamic mechanical thermal analyzer (DMTA). It was revealed that storage modulus (E′) and the loss modulus (E″) values of the resulting nanocomposites increased with regard to carbon nanotubes incorporated into the resin blend. In addition, at each given loading rate, nanocomposites containing MWCNT-NH2 possessed larger loss and storage modulus values as well as higher glass transition temperatures (Tg) as compared to those with MWCNTs. These findings were attributed to evidences for contribution of amine functional groups to chemical interactions at the interface between CNTs and the resin blend matrix. Transmission electron microscopy (TEM) studies performed on the cured resin samples approved that the dispersion state of carbon nanotubes with and without amine functional groups within the matrix resin blend was adequate. This implies that 3-roll milling process described herein is very appropriate technique for blending of carbon nanotubes with a liquid thermoset resin to manufacture nanocomposites with enhanced final properties.Conference Object Citation - WoS: 39Citation - Scopus: 48Temperature Dependence of Electrical Conductivity in Double-Wall and Multi-Wall Carbon Nanotube/Polyester Nanocomposites(Springer Verlag, 2007) Şimşek, Yılmaz; Özyüzer, Lütfi; Seyhan, Abdullah Tuğrul; Tanoğlu, Metin; Schulte, KarlThe aim of this study is to investigate temperature dependence of electrical conductivity of carbon nanotube (CNT)/polyester nanocomposites from room temperature to 77 K using four-point probe test method. To produce nanocomposites, various types and amounts of CNTs (0.1, 0.3 and 0.5 wt.%) were dispersed via 3-roll mill technique within a specially formulized resin blend of thermoset polyesters. CNTs used in the study include multi walled carbon nanotubes (MWCNT) and double-walled carbon nanotubes (DWCNT) with and without amine functional groups (-NH2). It was observed that the incorporation of carbon nanotubes into resin blend yields electrically percolating networks and electrical conductivity of the resulting nanocomposites increases with increasing amount of nanotubes. However, nanocomposites containing amino functionalized carbon nanotubes exhibit relatively lower electrical conductivity compared to those with non-functionalized carbon nanotubes. To get better interpretation of the mechanism leading to conductive network via CNTs with and without amine functional groups, the experimental results were fitted to fluctuation-induced tunneling through the barriers between the metallic regions model. It was found that the results are in good agreement with prediction of proposed model.Article Citation - WoS: 48Citation - Scopus: 58Investigating the Effects of a Polyester Preforming Binder on the Mechanical and Ballistic Performance of E-Glass Fiber Reinforced Polyester Composites(Elsevier Ltd., 2003) Tanoğlu, Metin; Seyhan, Abdullah TuğrulAn experimental investigation was carried out to determine the effects of a preforming binder on the mechanical properties and ballistic performance of E-glass-fiber/polyester composite systems. The glass preforms were consolidated by application of heat and pressure over plies of the glass fabrics coated with various concentrations of a thermoplastic polyester binder. The peel strength of the preforms with various binder content was measured and the highest peel strength was obtained from preforms prepared with about 9 wt% of the binder. Composite laminates with and without binder were fabricated using VARTM technique and the effects of the binder on the composite mechanical properties were evaluated. It was found that the flexural strength and mode I interlaminar fracture toughness decreases by 15% and 40%, respectively, due to the presence of 3 wt% of the binder. Ballistic test was performed on E-glass/polyester composite panels using 1.1-g fragment-simulating projectiles and it was found that the binder amount has some considerable effect on the damage extension of the impacted composites. The results showed that the preforming binder has significant potential to tailor composite properties.Article Citation - WoS: 18Citation - Scopus: 26Compressive Mechanical Behaviour of E-glass/Polyester Composite Laminates Tailored With a Thermoplastic Preforming Binder(Elsevier Ltd., 2003) Tanoğlu, Metin; Seyhan, Abdullah TuğrulCompressive mechanical behaviour and failure modes of E (electrical)-glass/polyester composite laminates tailored with a thermoplastic preforming polyester binder were investigated under ply-lay up and in-plane loading directions. Fiber preforms with various amount of the binder were consolidated under heat and pressure. The preform compaction experiments were performed by applying compressive pressure to the preforms, and the average thickness as a function of pressure was measured. It was found that the highest compaction of the preforms and therefore the highest fiber volume fraction can be obtained with 3 wt.% of the binder. Further increase of the amount of binder decreases the degree of compaction. Composite panels were fabricated by vacuum-assisted resin transfer molding using fabric preforms with various binder concentrations. The present investigation reveals that there are considerable effects of the binder on the compressive mechanical behaviour of the composites. Compression testing of the composites showed that the average strength values are in the range of 400-600 and 150-300 MPa for ply-lay up and in-plane directions, respectively. Also, both the strength and modulus values increase up to 3 wt.% of the binder, and these values decrease with further addition of the binder. Scanning electron microscopy showed that failure modes of the composites are altered significantly by the presence of the binder. Furthermore, the interaction between the binder and the reacting resin was followed to determine the extent of the binder dissolution and its effects on the viscosity of the resin and the mechanical behaviour of the matrix polymer. The results indicate that there is a partial dissolution of the binder within the matrix resin.