Compression after Impact and Charpy Impact Characterizations of Glass Fiber/Epoxy/MWCNT Composites

Özgür Demircan,Kemal Kadıoğlu,Pınar Çolak,Erdinç Günaydın,Mustafa Doğu,Neslihan Topalömer,Volkan Eskizeybek 한국섬유공학회 2020 Fibers and polymers Vol.21 No.8

In this study, glass fiber/epoxy resin/multi-walled carbon nanotubes (MWCNTs) were used to fabricate hybridcomposites with biaxial warp-knitted fabrics. The biaxial warp-knitted fabrics were grafted with various amounts ofMWCNTs and the hybrid composites were fabricated using the resin transfer molding (RTM) method, subsequently. Thefabricated samples were subjected to compression after impact and Charpy impact tests. The hybrid composites exhibitedhigher compression after impact modulus and strength with 26 % and 17 % compared to the samples without nanotubes,respectively. Moreover, the MWCNTs integrated specimens showed 17 % improvement of Charpy impact strength againstspecimens without carbon nanotubes in 0odegree direction. Fracture surface analysis revealed lower number of cracks andshorter crack propagation lengths in the MWCNTs reinforced specimens. The improvement in mechanical properties of thehybrid composites can most likely be attributed to an increase in interfacial adhesion due to the presence of the carbonnanotubes.

Optimization of tetracycline removal with chitosan obtained from mussel shells using RSM

Murat Topal,E. Işıl Arslan Topal 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.84 No.-

In this study, the removal of tetracycline from aqueous solutions with chitosan obtained from musselshells was optimized and investigated using responce surface methodology. For this aim, the centralcomposite design was used to optimize the four variable factors (sorbent dosage (0.4–1.0 g), time(20 60 min), temparature (10 30 C) and initial TC concentration (50 100 mg/L)) for the removal of TCfrom aqueous solutions by chitosan obtained from mussel shells. According to the RSM analysis results,optimum conditions for maximum TC removal efficiency were determined as 90.5 mg/L for initial TCconcentration, 35.9 min for time, 29.9 C for temperature and 0.4 g for sorbent dosage. It was observedthat the tetracycline was crystallized on mussel shells. According to the results of XRD after adsorption,the content of mussel shells were observed as 60% calcite, 5.6% overite, 9.4% aragonite and calciumhydroxide 25%, respectively. As a result, experiments showed that chitosan obtained from mussel shellswere a good adsorbant for tetracycline removal from aqueous solutions.

Post-COVID-19 pain syndrome: a descriptive study in Turkish population

Topal, Ilknur,Ozcelik, Necdet,Atayoglu, Ali Timucin The Korean Pain Society 2022 The Korean Journal of Pain Vol.35 No.4

Background: The new type of corona virus has a wide range of symptoms. Some people who have COVID-19 can experience long-term effects from their infection, known as post-COVID conditions. The authors aimed to investigate prolonged musculoskeletal pain as a symptom of the post-COVID-19 condition. Methods: This is a descriptive study on the patients who were diagnosed with COVID-19 in a university hospital, between March 2020 and March 2021. Patient records and an extensive questionnaire were used to obtain relevant demographic and clinical characteristics, including hospitalization history, comorbidities, smoking history, duration of the pain, the area of pain, and the presence of accompanying neuropathic symptoms. Results: Of the diagnosed patients, 501 agreed to participate in the study. Among the participants, 318 had musculoskeletal pain during COVID-19 infection, and 69 of them reported prolonged pain symptoms as part of their a post-COVID condition which could not be attributed to any other cause. The mean duration of pain was 4.38 ± 1.73 months, and the mean pain level was 7.2 ± 4.3. Neuropathic pain symptoms such as burning sensation (n = 16, 23.2%), numbness (n = 15, 21.7%), tingling (n = 10, 14.5%), stinging (n = 4, 5.8%), freezing (n = 1, 1.4%) were accompanied in patients with prolonged musculoskeletal pain. Conclusions: Patients with COVID-19 may develop prolonged musculoskeletal pain. In some patients, neuropathic pain accompanies it. Awareness of prolonged post-COVID-19 pain is crucial for its early detection and management.

Buckling load optimization of laminated plates resting on Pasternak foundation using TLBO

Topal, Umut,Vo-Duy, Trung,Dede, Tayfun,Nazarimofrad, Ebrahim Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.67 No.6

This paper deals with the maximization of the critical buckling load of simply supported antisymmetric angle-ply plates resting on Pasternak foundation subjected to compressive loads using teaching learning based optimization method (TLBO). The first order shear deformation theory is used to obtain governing equations of the laminated plate. In the present optimization problem, the objective function is to maximize the buckling load factor and the design variables are the fibre orientation angles in the layers. Computer programming is developed in the MATLAB environment to estimate optimum stacking sequences of laminated plates. A comparison also has been performed between the TLBO, genetic algorithm (GA) and differential evolution algorithm (DE). Some examples are solved to show the applicability and usefulness of the TLBO for maximizing the buckling load of the plate via finding optimum stacking sequences of the plate. Additionally, the influences of different number of layers, plate aspect ratios, foundation parameters and load ratios on the optimal solutions are investigated.

Buckling load optimization of laminated plates via artificial bee colony algorithm

Topal, Umut,Ozturk, Hasan Tahsin Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.4

In this present work, Artificial Bee Colony Algorithm (ABCA) is used to optimize the stacking sequences of simply supported antisymmetric laminated composite plates with criticial buckling load as the objective functions. The fibre orientations of the layers are selected as the optimization design variables with the aim to find the optimal laminated plates. In order to perform the optimization based on the ABCA, a special code is written in MATLAB software environment. Several numerical examples are presented to illustrate this optimization algorithm for different plate aspect ratios, number of layers and load ratios.

Optimal design of laminated composite plates to maximise fundamental frequency using MFD method

Topal, Umut,Uzman, Umit Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.24 No.4

This paper deals with optimal fibre orientations of symmetrically laminated fibre reinforced composite structures for maximising the fundamental frequency of small-amplitude. A set of fiber orientation angles in the layers are considered as design variable. The Modified Feasible Direction method is used in order to obtain the optimal designs. The effects of number of layers, boundary conditions, laminate thicknesses, aspect ratios and in-plane loads on the optimal designs are studied.

Shear buckling analysis of cross-ply laminated plates resting on Pasternak foundation

Topal, Umut,Nazarimofrad, Ebrahim,Kholerdi, Seyed Ebrahim Sadat Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.3

This paper presents the shear buckling analysis of symmetrically laminated cross-ply plates resting on Pasternak foundation under pure in-plane uniform shear load. The classical laminated plate theory is used for the shear buckling analysis of laminated plates. The Rayleigh-Ritz method with novel plate shape functions is proposed to solve the differential equations and a computer programming is developed to obtain the shear buckling loads. Finally, the effects of the plate aspect ratios, boundary conditions, rotational restraint stiffness, translational restraint stiffness, thickness ratios, modulus ratios and foundation parameters on the shear buckling of the laminated plates are investigated.

Buckling load optimization of laminated plates via artificial bee colony algorithm

Umut Topal,Hasan Tahsin Öztürk 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.4

In this present work, Artificial Bee Colony Algorithm (ABCA) is used to optimize the stacking sequences of simply supported antisymmetric laminated composite plates with criticial buckling load as the objective functions. The fibre orientations of the layers are selected as the optimization design variables with the aim to find the optimal laminated plates. In order to perform the optimization based on the ABCA, a special code is written in MATLAB software environment. Several numerical examples are presented toillustrate this optimization algorithm for different plate aspect ratios, number of layers and load ratios.

Shear buckling analysis of cross-ply laminated plates resting on Pasternak foundation

Umut Topal,Ebrahim Nazarimofrad,Seyed Ebrahim Sadat Kholerdi 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.3

This paper presents the shear buckling analysis of symmetrically laminated cross-ply plates resting on Pasternak foundation under pure in-plane uniform shear load. The classical laminated plate theory is used for the shear buckling analysis of laminated plates. The Rayleigh-Ritz method with novel plate shape functions is proposed to solve the differential equations and a computer programming is developed to obtain the shear buckling loads. Finally, the effects of the plate aspect ratios, boundary conditions, rotational restraint stiffness, translational restraint stiffness, thickness ratios, modulus ratios and foundation parameters on the shear buckling of the laminated plates are investigated.

Application of a new extended layerwise approach to thermal buckling load optimization of laminated composite plates

Umut Topal 국제구조공학회 2013 Steel and Composite Structures, An International J Vol.14 No.3

This paper deals with the applicability of a new extended layerwise optimization method for thermal buckling load optimization of laminated composite plates. The design objective is the maximization of the critical thermal buckling of the laminated plates. The fibre orientations in the layers are considered as design variables. The first order shear deformation theory (FSDT) is used for the finite element solution of the laminates. Finally, the numerical analysis is carried out to show the applicability of extended layerwise optimization algorithm of laminated plates for different parameters such as plate aspect ratios and boundary conditions.