Browsing by Author "Demircioglu, TK"

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    Experimental investigation on low-velocity impact response of wood skinned sandwich composites with different core configurations
    Demircioglu, TK; Balikoglu, F; Inala, O; Arslan, N; Ay, I; Atas, A
    In this paper, an experimental investigation on the low-velocity impact response of wood skinned hybrid sandwich composites was presented. Several alternative design configurations were developed by using rubber-cork and E-glass composite layers between the foam core and wood skin in order to improve the impact performance of conventional sandwich composites. Low-velocity impact (LVI) testing was performed using a drop weight test machine at different impact energies and destructive cross-sectioning was performed to examine the interior damage growth and penetration depth of the specimens. The impact performance of the specimens was evaluated in terms of energy absorption capacity, maximum contact force and penetration depth. The multi-core design concept significantly improved the energy absorption capacity with a reduced extent of impact induced damage. The proportion of recyclable materials in each configuration and the energy absorption level per unit cost were also presented for the interest of product designers.
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    Mechanical performance of marine sandwich composites subjected to flatwise compression and flexural loading: Effect of resin pins
    Balikoglu, F; Demircioglu, TK; Yildiz, M; Arslan, N; Atas, A
    Mechanical performance of marine sandwich panels comprising E-glass/vinyl ester face sheets and perforated poly-vinyl chloride foam core was evaluated and compared with conventional foam core sandwich panels. Circular holes through the foam core thickness were drilled with 12 different arrangements in square patterns and the holes were filled with the resin during the infusion process which created the through-the-thickness solid resin pins. The effect of each pattern on the flatwise compression and core shear properties of the sandwich panels were experimentally investigated. The three-point bending maximum failure load of perforated foam core sandwich panels was increased over 133.8% by increasing the diameter of the resin pins at the expense of increased panel weight up to 67%. The flatwise compression stress to induce core crushing was significantly increased by reinforcing the resin pins.
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    Compression after low velocity impact tests of marine sandwich composites: Effect of intermediate wooden layers
    Balikoglu, F; Demircioglu, TK; Inal, O; Arslan, N; Atas, A
    In the present work, compression after impact (CAI) behavior of sandwich composite materials with intermediate wooden layers was investigated. Sandwich panels were manufactured by using vacuum assisted resin transfer molding (VARTM) method with pinewood and ashwood intermediate layers. 15 and 25 mm thick PVC foams with a same density of 80 kg/m(3) were chosen in conjunction with the face sheets composed of non-crimp biaxial E-glass fabrics and bisphenol-A epoxy vinyl ester resin material system. Impact tests were performed under 30 J (low) and 60 J (high) energy levels with conical and hemispherical impactors. CAI tests were conducted in accordance with the ASTMC364/C364M-07 standard. Using pinewood and ashwood intermediate layers increased the residual CAI strength and decreased the depth of the impact damage. The intermediate wooden layers have also a potential to reduce the thickness of the composite face sheets and foam core which may increase the proportion of the recyclable wooden materials within the sandwich structure. (C) 2017 Elsevier Ltd. All rights reserved.
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    Improving four-point bending performance of marine composite sandwich beams by core modification
    Balikoglu, F; Arslan, N; Demircioglu, TK; Inal, O; Iren, M; Atas, A
    The aim of this study was to improve four-point bending performance of foam core sandwich composite beams by applying various core machining configurations. Sandwich composites have been manufactured using perforated and grooved foam cores by vacuum-assisted resin transfer moulding method with vinyl-ester resin system. The influence of grooves and perforations on the mechanical performance of marine sandwich composite beams was investigated under four-point bending test considering the weight gain. Bending strength and effective bending stiffness increased up to 34% and 61%, respectively, in comparison to a control beam without core modification. Analytical equations were utilised for calculating the mid-span deflection, equivalent bending stiffness and ultimate bending strength of the sandwich beams. Finite element analysis was also performed to analyse the flexural response of the specimens taking into account the combined effect of orthotropic linear elasticity of the face sheet and the non-linear behaviour of the foam core.