Analysis and optimization of cylindrical structures manufactured by automated fiber placement technique

Güldü, Sedat
Automated Fiber Placement (AFP) is a highly automated manufacturing process which has made it possible to manufacture composite parts utilizing curved tow paths resulting in variable stiffness composite structures. During the manufacturing of the composite structures with the automated fiber placement machines, fiber orientation angle can be changed according to the specific design needs. Therefore, variable fiber orientation can be sought in an optimization framework for favorable structural response. The purpose of this thesis is to show how the structural behavior of the cylindrical shell can be improved through the use of fiber placement technology in the manufacturing of the layers of the cylindrical shell of revolution. For this purpose, a methodology is developed for generating the finite element model of tow-placed variable-stiffness laminated composite cylindrical shells. The developed method allows the calculation of the ply thicknesses including the gaps and overlaps which occur as a result of the manufacturing of the plies of the cylindrical shell using curvilinear fiber paths. Fiber orientation angle of each element is determined by making use of the reference fiber path which is defined by two parameters. Along the reference fiber path, fiber orientation angle changes linearly in a specified direction. Finite element model creation and analyses are carried out using the finite element program MSC.NASTRAN®. For the optimization of the reference fiber path, Particle Swarm Optimization (PSO) code is developed in Matlab environment. PSO is a robust optimization technique based on the movement and intelligence of swarms. Optimization of the parameters of the reference fiber path is performed for axially and circumferentially variable stiffness cylinders including the strength and manufacturing constraints. Optimization results are also compared with results of the baseline constant stiffness cylinders. The objective of the optimization is taken as the maximization of the buckling factor of the cylindrical shell subjected to different load cases. Results show that higher buckling load factors can be obtained for variable stiffness cylinders compared to the constant stiffness laminated cylinders.


Design of Retaining Walls Using Big Bang-Big Crunch Optimization
Camp, Charles V.; Akin, Alper (American Society of Civil Engineers (ASCE), 2012-03-01)
A procedure is developed for designing low-cost or low-weight cantilever reinforced concrete retaining walls, with base shear keys, using big bang-big crunch (BB-BC) optimization. The objective of the optimization is to minimize the total cost or total weight per unit length of the retaining structure subjected to constraints on the basis of stability, bending moment, and shear force capacities and the requirements of the American Concrete Institute (ACI 318-05). An iterative population-based heuristic sear...
Gozluklu, B.; Uyar, I; Çöker, Demirkan (2014-07-25)
In wind energy and aerospace industries, new advances in composite manufacturing technology enable to produce primary load carrying elements as composite materials in wide variety of shapes large such as an L-shape. However, due to the geometry, Interlaminar Normal Stresses (ILNS) are induced once a moderately thick laminate takes highly curved shape. In the curved part of the L-shaped structure, the development of ILNS promotes mode-I type of delamination propagation which is the weakest fracture mode. Thi...
Precise mapping of the magnetic field in the CMS barrel yoke using cosmic rays
Chatrchyan, S.; et. al. (IOP Publishing, 2010-03-01)
The CMS detector is designed around a large 4 T superconducting solenoid, enclosed in a 12 000-tonne steel return yoke. A detailed map of the magnetic field is required for the accurate simulation and reconstruction of physics events in the CMS detector, not only in the inner tracking region inside the solenoid but also in the large and complex structure of the steel yoke, which is instrumented with muon chambers. Using a large sample of cosmic muon events collected by CMS in 2008, the field in the steel of...
Investigation of variable bead widths in FFF process
Gharehpapagh, Bahar; Dölen, Melik; Yaman, Ulaş (2019-01-01)
Fused filament fabrication technology provides the opportunity to produce complex objects with sophisticated interior features. Here, extruding variable bead widths for desktop 3D printers is presented in order to improve resolution and to decrease the build time. In the proposed method, the cross-section is continuously varied according to the geometric features associated with the layers. That is, thinner beads can be utilized to print features with higher accuracy such as the outer surfaces, edges/corner...
Determination of cracking related properties of engineering cementitious composites
Keskin, Süleyman Bahadır; Şahmaran, Mustafa; Yaman, İsmail Özgür (null; 2017-09-12)
Engineered Cementitious Composites (ECC) are relatively new types of fiber reinforced cementitious materials with enhanced mechanical properties such as tensile strain hardening accompanying high tensile strain capacity. This is mainly attributed to close and multiple cracks with widths remaining under 60 µm which contributes to durability of ECC material. These properties are only achievable as a result of a micro-mechanical design that requires special ingredients that make ECC costly to be used alone, ho...
Citation Formats
S. Güldü, “Analysis and optimization of cylindrical structures manufactured by automated fiber placement technique,” M.S. - Master of Science, Middle East Technical University, 2014.