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Micromechanical Investigation of Elastic Properties for Polypropylene Fiber-Matrix Composite

100%
Günay E.
Acta Physica Polonica A
|
2017
|
vol. 131
|
issue 1
143-146
EN
In this study, the mechanical properties of unidirectional fiber composites were determined by using the representative volume element method. The aim of this study was to determine the equivalent elastic constants for the "fiber composite polymer (PPE/PP) thermoplastic material" used in a wide variety of engineering applications. At the first step, the micromechanical model was applied to the polypropylene (PP) fiber-matrix composite, and then the microstructure form of the material was analyzed by finite element method considering "rule of mixture". The symmetry boundary conditions have been applied by using the representative volume elements in 3D finite element models. The SOLID187 mesh element of ANSYS was used for the presentation of the microstructure form of the fiber-matrix composite. The elastic constants obtained in this study were respectively as follows: the longitudinal elastic modulus and the Poisson ratio E₁, ν₁₂, the transverse elastic modulus and the Poisson ratio E₂, ν₂₃. For verification, the numerical results were also compared with the literature.
2
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Micromechanics Investigation of Wood Cell Walls under Compression Loading

63%
Günay E., Golmohammadi H.
Acta Physica Polonica A
|
2016
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vol. 129
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issue 4
459-463
EN
The aim of this study was to detect the determinations of the 3D cell deformations of pine wood (Pinus sylvestris L.) in micro-scale(µm) under mechanical compression loading. The 20× 20× 50 mm^3 sized wood specimens were tested under compressive pressure load through 35-40 MPa parallel to the grain orientations. The pressure applied samples were divided into three parts, then processed to form smaller cubic pieces and this pieces stained with gold liquid in order to get scanning electron microscopy images (12× 12× 12 mm^3 parts). The deformed cells were photographed in 3D-plane with magnification of (100×), (1500×) and in the range of 3.0-5.0 kV light voltage under the scanning electron microscope. Unloaded and loaded pine wood specimens were visualized and photographed to observe and examine the contraction or expansion of the cell walls comparatively. Based on the experimentally obtained microstructural permanent deformations of the cell structures, a numerical model had been proposed to explain the complex behaviour of cell structures under compression loading. Using the finite element method and ANSYS code, the permanent deformation ratios of three different pinewood cell models were simulated for 35-40 MPa loading to explain the overall stiffness and strength of the pinewood cells. In this way, by considering the results obtained from scanning electron microscopy measurements and related finite element analysis solutions, permanent deformation of honeycomb type pinewood cells was examined in detail.
3
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Analysis of a Skid Type Landing Gear of a Rotary Wing UAV by Experimental and Numerical Methods

51%
Yildirim O., Günay E., Anil Ö., Aygün C.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 4
1170-1175
EN
The objective of this study was to analyze the results obtained from tests done by simulating the crash landing of a rotary wing unmanned air vehicle with a skid type landing gear. The experimental and computational methods were used in the simulation tests. In the first portion of the test; namely with the experimental method, the impact loads induced by the simulated crash landing and the stresses, strains, deformations generated by these loads, were recorded by drop test apparatus. In the second portion of the test with the computational method, free falling of the skid type landing gear was modeled and crash landing test was simulated numerically by using ANSYS code. Experimental methods were applied on four skid landing gear specimens with different shapes. Each of the test samples used in the following test was evolved because each sample was developed and redesigned based on the feedback results obtained from the former test.The first three test specimens were manufactured from 2024 T3, 7075 T6 and 6061 T6 aluminum alloys respectively and all of them were curved in Π-form with a solid cross section. The last and fourth specimen was also manufactured from 6061 T6 aluminum alloy and it was curved in a hollow semi-circle form (∩-form). It is concluded that the last and fourth developed specimen was the best in absorbing the impact energy and enduring the crash.
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