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Composite Structure Optimization using a Homogenized Material Approach
Linköping University, Department of Management and Engineering, Mechanics. Linköping University, The Institute of Technology.
2014 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The increasing use of bre-reinforced composite materials in the manufacturing of high performance structures is primarily driven by their superior strength-toweight ratio when compared to traditional metallic alloys. This provides the ability to design and manufacture lighter structures with improved mechanical properties. However, the specic manufacturing process of composite structures, along with the orthotropic material properties exhibited by bre-reinforced composite materials, result in a complex structural design process where a number of dierent design parameters and manufacturing issues, which aect the mechanical properties of the composite structure, have to be considered. An ecient way to do this is to implement structural optimization techniques in the structural design process thus improving the ability of the design process to nd design solutions which satisfy the structural requirements imposed on the composite structure.

This thesis describes a two phase composite structure optimization method based on a novel material homogenization approach. The proposed method consists of a stiness optimization problem and a lay-up optimization problem, respectively, with the aim to obtain a manufacturable composite structure with maximized stiness properties. The homogenization material approach is applied in both optimization problems, such that the material properties of the composite structure are homogenized. In the proposed method the stiness optimization problem provides a composite structure with maximized stiness properties by nding the optimal distribution of composite material across the design domain. The aim of the lay-up optimization problem is to obtain a manufacturable lay-up sequence of bre-reinforced composite plies for the composite structure which, as far as possible, retains the stiness properties given by the stiness optimization problem. The ability of the composite structure optimization method to obtain manufacturable composite structures is tested and conrmed by a number of numerical tests.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. , 19 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1632
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-102316DOI: 10.3384/lic.diva-102316Local ID: LIU-TEK-LIC 2013:66ISBN: 978-91-7519-453-0 (print)OAI: oai:DiVA.org:liu-102316DiVA: diva2:676173
Presentation
2014-01-14, A31, A-huset, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2013-12-05 Created: 2013-12-05 Last updated: 2017-05-15Bibliographically approved
List of papers
1. Density Filter Control of Thickness-to-Length Change of Composite Structures
Open this publication in new window or tab >>Density Filter Control of Thickness-to-Length Change of Composite Structures
2013 (English)Conference paper, Oral presentation only (Other academic)
Abstract [en]

The homogenized material optimization (HMO) problem is a novel structural optimization problem that we have developed for optimization of fiber reinforced composite structures. In the HMO problem we apply a smeared-out approach to model the material properties of fiber reinforced composite materials. The objective of the HMO problem is to maximize the stiffness of a composite structure by means of finding the optimal distribution of composite material, belonging to a fixed set of fiber orientations, across the design domain. In order to obtain manufacturable solutions, we have introduced a linear density filter as a restriction method to control the thickness variation across the design domain. To examine the effect of the density filter on the thickness variation and the objective function value of composite structures, obtained in the HMO problem, we have performed numerical tests for different load cases, mesh densities and range of the filter radius.

It is observed that for the present problem the thickness variation was mesh-independent. Both the thickness variation and objective function value depend on the load case used in the HMO problem. For all load cases the thickness variations exhibits an approximately piece-wise linear behaviour for increased filter radius. Furthermore, it was observed that an increase of filter radius would result in an moderate increase in objective function value for the solutions obtained from the HMO problem. From these results we conclude that by using a density filter, the HMO problem can be used to obtain manufacturable designs for composite structures.

Keyword
Homogenized material optimization, composite structures, density filter, structural optimization
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-102314 (URN)
Conference
10th World Congress on Structural and Multidisciplinary Optimization, May 19-24, 2013, Orlando, Florida, USA
Available from: 2013-12-05 Created: 2013-12-05 Last updated: 2017-05-15Bibliographically approved
2. Stiness and Lay-up Optimization of Composite Structures based on a Homogenized Material Approach
Open this publication in new window or tab >>Stiness and Lay-up Optimization of Composite Structures based on a Homogenized Material Approach
2013 (English)Manuscript (preprint) (Other academic)
Abstract [en]

In the present work we propose a two phase composite structure optimization method based on a novel material homogenization approach. It consists of a stiffness and a lay-up optimization problem, respectively, with the aim of obtaining manufacturable composite structures with maximized stiffness properties. The method is applied to a cantilever plate, and numerical tests were performed for three load cases and for a number of parameters settings. The results show that the proposed method can obtain manufacturable composite structures with maximized stiffness properties. In the first phase of the method, the stiffness optimization problem provides an optimal distribution of the composite material, such that the stiffness properties of the structureare maximized. The second phase, the lay-up optimization problem, provides a manufacturable lay-up sequence of discrete plies which attempts to retain the stiffness properties of the structure from the first phase.

Keyword
Fibre-reinforced composites, Composite structures, Material homogenization, Lamination parameters, Variable thickness sheet, Stiffness optimization, Lay-up optimization, Stacking sequence optimization, Manufacturing constraints
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-102315 (URN)
Available from: 2013-12-05 Created: 2013-12-05 Last updated: 2017-05-15Bibliographically approved

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