Papers by Author: M. Lutfy Öveçoğlu

Abstract: The lightweight materials such as composites are often used for the aerospace structures. One of the uses of these materials is for the tail boom of helicopters. Tail booms are the structures connecting the tail rotor to the fuselage. It is mainly subjected to the pitching moment and torsion. Because it is long to obtain the enough distance between the tail rotor and the main rotor, the materials used for manufacturing the tail boom needs to be a lightweight material. The structural optimization of the tail boom is also necessary. In this study, two different tail booms are manufactured by using laminated composites. The tail booms considered in this study are a semi-monocoque structure consisted of skins and stiffeners. These skins and stiffeners are made of carbon/epoxy. One is produced by using 3-ply carbon/epoxy and it is strengthened using stiffeners. The other is produced by using honeycomb between 2-layers of carbon/epoxy. A hand lay-up technique is used for the manufacturing of the tail booms. The vacuum bagging and a moderate heat are used to cure the composite structure. The bending and bending with torsion tests are performed to determine the structural performance of the tail booms. The tail boom is also modeled using the finite element method and analyses are performed. The results are presented and discussed.

Abstract: Composite biomaterials of calcinated bovine bone derived hydroxyapatite (HA) doped with 5 and 10 wt% commercial inert glass (CIG) were prepared by sintering. The production of HA from natural sources satisfies economic and time-saving aims, while the use of CIGs is directed by economic and ecological aspects. The produced composites were subjected to scanning electron microscopy (SEM) and X-ray diffraction analysis. Measurements of compression strength, microhardness, and density were also carried out. The experimental results and their discussion showed that the type and the composition of incorporated glass are of crucial importance. Consequently, provided that an optimum amount of glass is incorporated, the resultant materials can exhibit good values of compression strength and microhardness and hence they can be suggested for potential use in load-bearing biomedical applications.