Development of functionally graded aluminum matrix composite materials for defense industry applications

Download
2019
Yılmaz, Taha
Functionally graded materials (FGMs) are advanced class of composite materials that have a gradual change in composition and structure over the entire material and many different properties can be obtained by altering the structure. Therefore, they have many different application areas. This study aims to develop functionally graded aluminum matrix composite materials for defense applications. Firstly, porous ceramic pellets and preforms, made of alumina (Al2O3) and olivine ((Mg,Fe)SiO4), were produced with conventional pressing and sintering processes for frontal layer of FGM. Effect of different sintering temperatures, different particle size fractions (for olivine) and different amount of metal powder addition (for alumina) on relative densities of pellets were measured. Secondly, porous ceramic preforms were infiltrated with high strength aluminum alloy AA7075 (Al-Zn-Cu-Mg) by using metal infiltration method. Thirdly, metal matrix composites (MMCs) were produced by melt stirring and squeeze casting methods for backing layer of FGMs using AA7075 (Al-Zn-Cu-Mg) as matrix material and olivine 5-7.5-10 wt. % as reinforcement material. Some of MMCs were T6 heat treated to observe the effect of heat treatment on mechanical properties. All samples were characterized mechanically, physically and microstructurally. Density measurements of pellets showed that from 38 % to 87 % relative densities were achieved with different sintering temperatures, particle fractions and metal alloy addition. T6 heat treatments increased both hardness and flexure strength properties of MMCs. Maximum hardness was measured from 10 wt.% olivine reinforced MMC as 183 HB and maximum flexure strength was measured as 636 MPa from 5 wt.% olivine reinforced MMC. In melt infiltrated preforms maximum hardness was measured as 458 HB from melt infiltrated alumina preforms sintered at 1400 °C and maximum flexure strength was measured as 487 MPa from melt infiltrated olivine preforms sintered at 1250 °C. Olivine as a reinforcement material in MMC and as a preform in melt infiltration process was used successfully with this thesis study for the first time in the literature. By changing process and material parameters preforms with different densities were produced for FGM layers.

Suggestions

Finite element modeling of beams with functionally graded materials
Gürol, Tolga; Sarıtaş, Afşin; Department of Civil Engineering (2014)
In this thesis a new beam element that is based on force formulation is proposed for modeling elastic and inelastic analysis of beams with functionally graded materials. The attempt of producing functionally graded materials (FGM) arose from mixing two materials in such a way that both of them preserve their physical, mechanical and thermal properties most effectively. FGM shows a gradation through the depth from typically a metallic material such as steel or aluminum at one face of the beam’s section depth...
Thermal stress problem for an FGM strip containing periodic cracks
Köse, Ayşe; Kadıoğlu, Fevzi Suat; Department of Mechanical Engineering (2013)
In this study the plane linear elastic problem of a functionally graded layer which contains periodic cracks is considered. The main objective of this study is to determine the thermal stress intensity factors for edge cracks. In order to find an analytic solution, Young’s modulus and thermal conductivity are assumed to be varying exponentially across the thickness, whereas Poisson ratio and thermal diffusivity are taken as constant. First, one dimensional transient and steady state conduction problems are ...
Hybrid finite element for analysis of functionally graded beams
Sarıtaş, Afşin; Soydas, Ozan (2017-01-01)
A hybrid finite element model is presented, where stiffness and mass distributions over a beam with functionally graded material (FGM) are accurately modeled for both elastic and inelastic material responses. Von Mises and Drucker-Prager plasticity models are implemented for metallic and ceramic parts of FGM, respectively. Three-dimensional stress-strain relations are solved by a general closest point projection algorithm, and then condensed to the dimensions of the beam element. Numerical examples and veri...
Mixed-mode fracture analysis of orthotropic FGM coatings under mechanical and thermal loads
İlhan, Küçük Ayşe; Dağ, Serkan; Department of Mechanical Engineering (2007)
In this study, it is aimed to investigate the mixed-mode fracture behavior of orthotropic functionally graded material (FGM) coatings bonded to a homogeneous substrate through a homogeneous bond-coat. Analytical and computational methods are used to solve the embedded cracking problems under mechanical or thermal loading conditions. It is assumed that the material property gradation of the FGM coating is in the thickness direction and cracks are parallel to the boundaries. The principal axes of orthotropy a...
Development of a 2D and 3D computational algorithm for discontinuity structural geometry identification by artificial intelligence based on image processing techniques
Azarafza, Mohammad; Ghazifard, Akbar; Akgün, Haluk; Asghari-Kaljahi, Ebrahim (2019-07-01)
Block geometry is commonly the most important feature determining the behaviour of a rock mass and directly controls the structural instability in underground openings or surface cuttings. Various methods are used to estimate block geometry and to perform a block survey, and these are standardly divided into empirical-based methods (e.g. spot mapping, linear mapping, areal mapping) and computer-based methods (e.g. laser scanning, image processing, digital image mapping). Empirical approaches are associated ...
Citation Formats
T. Yılmaz, “Development of functionally graded aluminum matrix composite materials for defense industry applications,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Metallurgical and Materials Engineering., Middle East Technical University, 2019.