Browsing by Author "Tas, H"

Now showing 1 - 11 of 11
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    Effect of drop weight impact on the torsional-loading behavior of filament wound and prepreg-wrapped composite tubes
    Soykok, IF; Tas, H; Ozdemir, O; Kandas, H
    This article presents an experimental study on the torsional behavior of composite tubes subjected to impact loadings. Four types of composite tubes with the winding angle of 30 degrees, 45 degrees, 60 degrees, and 75 degrees ([+/- 30](FW), [+/- 45](FW), [+/- 60](FW), and [+/- 75](FW)) were produced with the filament winding method. Besides, a [0,90](PP) composite tube was manufactured with the prepreg wrapping technique. After the composite tubes were impacted at 2.5 J, 5.0 J, and 7.5 J, non-impacted and impacted composite tubes were tested under torsional loading. Contact force-deformation curves of impacted tubes are presented. Torsional moment-twist angle relations for both impacted and non-impacted composite tubes were obtained. In addition, front view and side view of the impacted zone of composite tubes are given. The results showed that sample [+/- 60](FW) had the best impact performance with regard to absorbed energy. The impacted samples of [+/- 60](FW) and [+/- 75](FW) had the lowest torsional strength for each energy level.
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    Determinating optimum combination of ageing and manufacturing parameters for laminated composites using response surface methodology
    Oeztuerk, R; Tas, H; Soykok, IF
    This study mainly focuses on the effects of ageing and manufacturing parameters on the water absorption behaviour and mechanical characteristics of the glass -fibre reinforced polymer (GFRP) composites, and multiple optimizations of these parameters based on the quasi-static mechanical properties and low-velocity impact performances. Utilizing response surface methodology (RSM), an experimental design was executed varying curing temperature (20-100 degrees C ), ageing temperature (20-70 degrees C) and salinity (3-35%). After 59-days ageing period, gravimetric, tensile and low-velocity impact tests were conducted to assess weight gain at saturation, changes in tensile strength, elasticity modulus, peak force and peak energy. Tensile fracture surfaces of aged and un-aged samples were examined using scanning electron microscopy. ANOVA results indicated the adequacy of RSM models, supported by high R-2 (>80 %) and R-adj(2) (> 65%) and proper residual distribution. Gravimetric tests revealed that higher curing and ageing temperatures resulted in greater water sorption-induced weight gain, while elevated salinity had the opposite effect. Ageing temperature and salinity are the most influential factors on tensile strength change. Optimal mechanical properties, minimizing differences between aged and un-aged samples, were achieved at 100 degrees C curing temperature, 20 degrees C ageing temperature and 19.8% salinity. Data from this study can be a valuable reference for designing GFRP composites, particularly in marine applications.
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    Evaluation of the failure responses of filament wound and pre-preg wrapped glass fiber/epoxy composite tubes under quasi-static torsional loading
    Soykok, IF; Ozcan, AR; Tas, H
    This paper introduces an experimental and numerical investigation into hollow cylindrical thin-walled glass fibre reinforced epoxy matrix composite shafts produced by using both pre-preg wrapping and filament winding methods. The filament wound samples were manufactured with four different helix angles ([+/- 30](FW), [+/- 45](FW), [+/- 60](FW), and [+/- 75](FW)), whereas [0, 90]pp pre-pregs was utilised for producing the wrapped kind of samples. In order to assess the quasi-static failure responses, the samples were subjected to increasing amount of torsional load at a fixed angular rotation speed. The experimental findings of [+/- 30](FW), [+/- 45](FW), and [+/- 60](FW) samples were found to be very compatible with those obtained via Finite Element Analysis (FEA). Contrarily, the numerical model were not able to describe accurately the load-displacement behaviour of [+/- 75](FW) and [0, 90](PP) with the exception of the initial loading phase. [+/- 45](FW) was found as the most favourable option for designers in terms of torsional stiffness. Whereas, those characterised by [+/- 30](FW), and [+/- 60](FW) exhibited very close torsional resistances in a difference range of only 5%. [0, 90](P)(P) exhibited the lowest average torsional failure resistant and stiffness but the highest average rotation angle before rupture.
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    Effects of support patches on the mechanical characteristics of adhesively bonded aluminium alloy single lap joints
    Tas, H
    In the current work, the effect of support patches bonded to the lateral surfaces of the adherends in adhesively bonded single lap joints (SLJs) was investigated experimentally. Loctite EA 9466 epoxy was employed as the adhesive, while AA5754 aluminium alloy was utilized as both the adherend and the support patch. The impact of support patch length (0, 5, 15, and 25 mm), patch location (patches were located at the centre and at both ends of the side surfaces of adherends in the joint region), and number of support patches stacked on top of each other (0, 1, and 2) on the mechanical behaviour of the SLJ subjected to tensile loading was studied. According to the findings, bonding support patches increased the load-carrying and deformation capacity of the SLJs by 13.1% to 78.4% and 16.3% to 119.5%, depending on the patch length, location, and layer number. Additionally, support patch location and layer number are key parameters significantly influencing the mechanical properties of the SLJ, even when the bonding area remains unchanged. Increasing the patch layer number and placing the support patches at both ends of the lateral surfaces of adherends resulted in improved mechanical characteristics of the SLJ.
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    Effects of natural mica particle fillers on the mechanical properties of glass fiber/epoxy composite plates
    Soykok, IF; Tas, H
    Due to its high tensile and bending strength as well as high modulus (172 GN/m2), mica is a promising additive to improve the performance of polymer composites. Additionally, since it is abundant in nature and therefore cost-effective, it can be an alternative to commonly used but costly particles like carbon nanotube, graphene, and silica. This study focused on the effect of mica particles on the mechanical characteristics of glass fiber-reinforced laminated composites. Unlike the conventional production methods, a layer-wise method was adopted in order to add micro-mica particles into the glass fiber/epoxy composite. Composite plates with 1-, 3-, and 5-layer mica treatment as well as untreated composite plates were manufactured. Mechanical characteristics determined by tensile, three-point bending, and low-velocity impact tests were examined as a function of micaceous layer number. The interior structure of the composites was scanned by the use of scanning electron microscopy. According to the tensile and three-point bending tests, the micro-mica particle fillers failed to display the anticipated positive effect on strength values. Nevertheless, remarkable increases were observed in the average flexural modulus of mica-filled samples in comparison to the control samples without mica content. Also, the average peak energies during low-velocity impact tests were increased by the effect of mica fillers such that the average peak energies for the 1-layer, 3-layer, and 5-layer samples increased by 12.9, 1.9, and 10.3%, respectively, in comparison to the control samples.
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    Investigation of the Low Velocity Impact Behaviour of Shear Thickening Fluid Impregnated Kevlar, Hybrid (Kevlar/Carbon) and Carbon Fabrics
    Tas, H; Soykok, IF
    In this study, unlike the previous studies focusing merely on high-performance fabrics (i.e, aramid based Twaron, Kevlar) low velocity impact behaviour of neat and shear thickening fluid (STF) impregnated kevlar, hybrid (Kevlar/Carbon) and carbon fabrics was investigated. In the first stage, STFs with the silica concentrations of 5 wt%, 10 wt%, 15 wt% and 20 wt% were produced separately and the rheological measurement of each individual fluid concentration were carried out. In the second stage of the study, kevlar, hybrid and carbon fabrics were impregnated by STF having a silica content of 20 wt%. Yarn pull-out tests, dynamic puncture tests and quasi-static (QS) puncture tests were carried out on both the neat and impregnated fabrics. The rheological measurements showed that, the resulting silica/PEG400 suspensions exhibit good shear thickening behaviours, however it is not the case for those under a critical silica concentration. The yarn pull out tests revealed that, STF enhances the inter-yarn frictions of all three types of fabric. Correspondingly, STF positively affected the dynamic puncture resistance of kevlar and hybrid fabrics, while it had an adverse effect on carbon fabric. Besides, STF caused increases on the QS puncture resistances of all three fabric types.
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    Investigating fabric interlayer effects on tensile loading limits of adhesively bonded single-lap composite joints
    Tas, H; Soykok, IF
    This paper investigates enhancing the effectiveness of glass fiber/epoxy composite single-lap bonded joints by using fabric interlayers between the adherends. It was aimed to evaluate the changes in the joint tensile strength depending on the parameters such as different interlayer fabric types (S2-glass fabric and Kevlar fabric), numbers of interlayers (0, 1, 2, and 3), clamping pressure (0, 4, and 6 MPa), and temperature (20, 55, and 80 degrees C) applied to the joint region throughout the curing period. Significant enhancements in peak tensile forces were observed by varying these parameters. The most substantial increase in tensile properties was achieved for the joint with two-layer S2 fabric fabricated at 4 MPa pressure and 55 degrees C curing temperature, denoted as 2L-S2-P4-T55. Compared to a non-layered joint, those with 1, 2, and 3 S2 fabric interlayers exhibited 35.5%, 39.6%, and 45.2% increases in tensile peak force, respectively. Increasing bonding pressure from 0 MPa to 4 MPa resulted in a 5.2% tensile failure load increase for double S2 fabric interlayered joints cured at 20 degrees C, but a 6.7% decrease at 6 MPa. Using one-layer Kevlar fabric instead of one-layer S2 fabric caused a 15.2% drop in tensile peak force, still 14.9% higher than the non-layered joint.
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    Effects of Stainless Steel Woven Wire Mesh Reinforcement on the Load-Bearing Capacity of Adhesively Bonded Aluminium Alloy Single-Lap Joints
    Tas, H
    In this paper, the impact of stainless steel woven wire mesh (SSWWM) reinforcement within the adhesive layer on the load-carrying capacity of the adhesively bonded single-lap joints (SLJs) was studied. SLJs were fabricated using Loctite EA 9466 epoxy as the adhesive, AA5083 aluminium alloy as the adherend, and SSWWMs as the reinforcement. The influence of mesh count (20, 40, 60, and 80) and area (10mmx10mm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$10{\text{ mm }} \times 10{\text{ mm}}$$\end{document}, 20mmx20mm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$20{\text{ mm }} \times 20{\text{ mm}}$$\end{document}, and 25mmx25mm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$25{\text{ mm }} \times 25{\text{ mm}}$$\end{document}) of the SSWWM on the SLJ strength was investigated. Furthermore, considering the failure mechanism of the SLJ, the SSWWMs were strategically placed at the centre and at both ends of the adhesive layer, thereby examining the influence of the SSWWM location on the SLJ strength. According to the results obtained from tensile tests, the inclusion of the SSWWM into the adhesive layer increases the peak force of the SLJs between 7 and 46%, depending on the mesh count, area, and location of the SSWWM. Also, the location and area of the SSWWM are critical factors for joint strength. Increasing the area of the SSWWM and placing the SSWWM close to the ends of the overlap region considerably contributes to the SLJ strength.
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    Puncture resistance of STF impregnated MWCNTs-grafted carbon fabrics
    Tas, H; Soykok, IF
    In this study, STF with the silica concentration of 20 wt% was fabricated. Functionalized multi-walled carbon nanotubes (MWCNTs) were chemically bonded onto the carbon fibers by using grafting technique. In grafting technique, DMF/PAN fiber/MWCNTs suspension sprayed onto each surface of carbon fabric and MWCNTs were grafted by a thermal treatment at 250 degrees C. Neat and MWCNTs-Grafted carbon fabrics were impregnated with STF with the silica loading of 20 wt%. Then, dynamic and quasi-static puncture resistance of neat, STF impregnated, MWCNTs-Grafted and MWCNTs-Grafted-STF impregnated carbon fabrics were examined. STF impregnation was detected to lead to a decrease in dynamic puncture resistance and an increase in quasi-static puncture resistance. Dynamic puncture resistance of MWCNTs-Grafted carbon fabric was found to be less than neat fabrics due to larger gaps between yarns occurred after thermal stabilization. Also, due to the greater gap between yarns, complete perforation occurred at lower penetration depth in MWCNTs-Grafted carbon fabrics than neat carbon fabrics in quasi-static puncture tests.
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    Effects of carbon nanotube inclusion into the carbon fiber reinforced laminated composites on flexural stiffness: A numerical and theoretical study
    Tas, H; Soykok, IF
    Because of increased usage areas, and advances in characterization of the nanostructured materials, determination of the engineering properties of composites that includes carbon nanotubes has gained importance. It is possible to designate material properties of carbon nanotube based composites theoretically and experimentally. In this study, engineering constants of carbon nanotube based unidirectional carbon fiber reinforced composite lamina determined theoretically with two different approaches. Then, a composite plate whose laminas were stacked up as a [0 degrees+45 degrees-45 degrees/90 degrees](s) layup was built up in ANSYS, ACP Module. Finally, three point bending analyzes were performed separately under concentrated and distributed load. The results showed that there were negligible differences between the engineering constants obtained from two different theoretical approaches. Engineering constants, E-1, E-2, G(12) and G(23), increased as the added carbon nanotube fraction is increased. Besides that, flexural rigidity of composite plate also showed ever-decreasingly increase, as carbon nanotube content is increased. The results of theoretical and numerical bending analyzes exhibited a good agreement with the maximum percentage relative error of 9.1.
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    Investigation of the low velocity puncture resistance of shear thickening fluid impregnated S2 glass fiber fabrics
    Tas, H; Soykök, IF; Halimi, AJ
    In this study, unlike the studies available in the literature, low velocity puncture resistance and quasi-static puncture resistance of S2 glass fiber fabrics with high strength and impact resistance impregnated with shear thickening fluid (STF) was determined. For this purpose, firstly, a polyethylene glycol 400 (PEG400: 400 g/mole of molecular weight) suspension with the silica loading of 20 wt% was fabricated and then, theological measurements were carried out Then, drop weight puncture tests for the drop height of 200 mm, 300 mm and 400 mm and quasi-static puncture tests (6 mm/min of puncture velocity) were applied to neat and STF impregnated fabrics. Damages in fabrics and deformation marks on backing material were discussed in detail. As a result of the theological tests, it was observed that the PEG400/silica suspension exhibits shear thickening behavior. With the STF impregnation, a decrease of 30.7%, 17.7% and 20.7% was observed in the penetration depth of the penetrator into the backing material for the drop height of 200 mm, 300 mm and 400 mm, respectively. In addition, It has been seen that the impregnation of STF gives more reasonable results in terms of weight increase than increasing the number of fabric layers. As a result of quasi-static puncture tests, neat and STF impregnated fabrics showed close characteristics.