Research on Engineering Structures and Materials

1-18

Authors: Özgür Demircan, Naser Rezaei Ansaroudi, Fatma Burcu Uzunoğlu

In this study, the effect of hexagonal boron nitride (hBN) and modified (carboxylic acid functionalized) multi-walled carbon nanotubes (MWCNTs-COOH) on tensile and flexural behaviour of 30% short glass fiber reinforced Polyamide 66 (PA 66/30SGF) is investigated. Initially, MWCNTs-COOH, hBN and MWCNTs-COOH/hBN are mechanically mixed with PA 66/30SGF granules in ethanol and stirred via a magnetic stirrer for one hour. After ethanol evaporates, MWCNTs-COOH, hBN and MWCNTs-COOH/hBN integrated granules are conditioned in an oven and the obtained granules are transferred to the plastic injection moulding machine for the fabrication process of specimens. Thus five types of specimens are produced; and their mechanical behaviors are examined by Instron 5982 test machine. The test results show that elastic modulus and flexural properties of PA 66/30SGF are improved with the addition of MWCNTs-COOH, hBN and MWCNTs-COOH+hBN.

45-56

Authors: Anil Kumar, Surjit Angra, Arindam Kumar Chanda

A sandwich structure consists of three main parts i.e. the facing skins, the core and the adhesive. It acts in a way similar to that of the I- Beam. In this research, a sandwich structure has been designed with a regular hexagon honey-comb core made up of Kevlar® and face sheet of carbon fiber. The design has been modelled and the model has also been validated with the experimental and analytical method. Six different configurations of sandwich structures have been proposed. Out of these six, three configurations have the varying cell size i.e. 3.2 mm, 4 mm and 4.8 mm and the other three configurations have the varying panel width i.e. 40 mm, 45 mm and 50 mm keeping rest of the design parameters unchanged. Using ANSYS, analysis has been performed for all these six configurations and equivalent stiffness has been calculated. It has been observed that the honeycomb core cell size does not have a significant effect on the stiffness properties of a composite sandwich panel. The analysis also reveals that with the increased panel width the stiffness of composite panel increases significantly.

75-89

Authors: Emre Esener, Aysema Ünlü

The plastic behavior of a material can be represented by plasticity models. The ability of plasticity models to represent material behavior depends on their mathematical form, the assumptions they hold, and the sensitivity of the input parameters. Plasticity models are of great importance, especially in finite element analysis. While the mathematical forms of plasticity models are implemented in finite element analysis software, some coding-related inaccuracies may occur. Therefore, the capacity of the plasticity model to represent the plastic behavior of the material can be revealed more accurately by examining it analytically. After this verification, the choice of the plasticity model to be used in the finite element analysis can be realized with more accuracy and less time loss. In this direction, in this study, the capacity of plasticity models, which are frequently used today, to model the plastic behavior of anisotropic materials was evaluated. For this purpose, Hill48, Barlat89, Hu2003 and Poly6 plasticity models were analyzed analytically and TBF1050 3rd generation advanced high strength steel and 5XXX series aluminum alloy were used as materials. The predictive capacities of the plasticity models were evaluated with the yield locus and angular variations of anisotropy coefficient and yield stress ratios. As a result, it has been revealed that polynomial-based models can model the plasticity behavior of the material more accurately for both material groups.

101-115

Authors: Ashwini K, Srinivasa Rao P

The strength and durability properties of concrete using nano-silica and alccofine after exposed to higher temperatures were investigated in this study. Concrete with 3% nano-silica and 15% alccofine were prepared and water cured for 28 days. In an electric boogie furnace, concrete specimens with and without nano-silica and alccofine were heated to 400°C and 800°C for 4 hours. The specimens then were allowed to cool until they reached room temperature. The compressive strength test was used to determine strength, whereas the water absorption, porosity, and rapid chloride permeability tests were conducted to check durability properties. SEM images were used to examine the microstructure of concrete specimens at elevated temperatures. According to the test results, the strength and durability properties of concrete using nano-silica and alccofine deteriorated at high temperatures. At room temperature, concretes containing alccofine and nano silica performed better than control mixes. A severe loss in strength and a significant increase in charge pass, water absorption and porosity were observed at 800°C for concrete using alccofine and nano silica. The microstructural analysis using scanning electron microscopy methods also reported that the porosity increased with increase in temperature.

127-154

Authors: Gaurav D. Dhadse, Gangadhar Ramtekkar, Govardhan Bhatt

The finite element (FE) modeling of interface in Soil-Structure Interaction (SSI) problem is most important aspect from early days of modeling i.e. during 1960. The overall performance of the structure is completely influenced due to behavior of interface. Such as realistic interface modeling of SSI system subjected to lateral loads leads to appropriate evaluation of lateral sway and base shear stress. During recent times, many modifications have been done in interface modeling such as incorporation of slip and bonding effects. Also the interface joining variable degrees of freedom system (interface for solid to skeletal contact) has come into existence. Still the de-bonding behavior, interface non-linearity as well as modification in solid to skeletal contact has been unexplored in literatures. Hence there is necessity to develop a FE-SSI model and to study the influence of interface in SSI system considering unexplored features. In this paper, an attempt has been made to show the influence due to interface (including de-bonding and non-linearity) in FE modeling of SSI system using modified 5 noded zero thickness interface element. The performance of modified interface element is a novel contribution in present paper. The present study is limited to static loading conditions only. The effect of interface has been studied by determining bending moment, lateral sway, base shear stress and footing settlement in structure. The inclusion of modified interface has improved the performance of structure by reducing the base shear stress and allowing the sway. Also the true redistribution of bending moment has been observed after considering the modified interface.

179-203

Authors: Muhammed Mücahid Toprak, Ceyda Kök, Suha Orçun Mert

The importance of green energy has increased in recent years. Vehicles that don't run on fossil fuels and have zero CO2 emissions are on the agenda of many developed countries. Battery-based vehicles have long charge times and low range problems, making hydrogen-based fuel cell vehicles a good alternative candidate as a solution. Fuel cell system designs used in these vehicles is one of the most important subjects in the dawn of the renewable energy age. The present study compares different flow channel pattern designs for PEM fuel cells used in vehicles, all of which were designed and modeled as part of the study. Simulations were run on the three-dimensional flow channel designs to determine the most efficient patterns. Efficiency analyses were extended to include the membrane surfaces, where different properties of fuel flow channels, overall energy efficiency, and certain other parameters used in the PEM fuel cell systems were investigated. The study also includes comparison of the designed systems with fuel cell designs currently in commercial use. Finally, the effects of H2 and O2 concentrations used in the system were also investigated.