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Conceptual studies of a composite-aluminum hybrid wing box demonstrator
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, The Institute of Technology.
Saab AB, Linköping, Sweden.
2014 (English)In: Aerospace Science and Technology, ISSN 1270-9638, E-ISSN 1626-3219, Vol. 32, no 1, 42-50 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a study of two different hybrid composite-aluminum concepts applied to a winglike structure which is exposed to mechanical  and thermal load. The aim of the study is to determine the most suitable  hybrid concept to later on be used in structural fatigue and static testing. In both concepts, the mass is optimized with respect to two different sets of requirements, one of which is currently in use in the fighter aircraft industry and one which is a modified version of the current requirement set. The issues considered in the study are mass, thermal behavior, buckling, bolted joints, failure criteria and fatigue damage, and they are examined in the frame of both requirement sets. The results clearly indicate the order of criticality between the different criteria in the different parts of each concept. Also, the comparison of two requirement sets gives an idea of the degree of influence of the modified criteria on the hybrid concepts and their mass. Based on the mass and the structural behavior in a thermal-mechanical loading one of the hybrid concepts is chosen for further studies and testing.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 32, no 1, 42-50 p.
Keyword [en]
Hybrid structure, Wing structure, Composite-aluminum, Thermal load, Conceptual study
National Category
Aerospace Engineering
Identifiers
URN: urn:nbn:se:liu:diva-91892DOI: 10.1016/j.ast.2013.11.002ISI: 000331921900006OAI: oai:DiVA.org:liu-91892DiVA: diva2:619498
Available from: 2013-05-03 Created: 2013-05-03 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Strength analysis and modeling of hybrid composite-aluminum aircraft structures
Open this publication in new window or tab >>Strength analysis and modeling of hybrid composite-aluminum aircraft structures
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The current trend in aircraft design is to increase the proportion of fiber composites in the structures. Since many primary parts also are constructed using metals, the number of hybrid metal-composite structures is increasing. Such structures have traditionally often been avoided as an option because of the lack of methodology to handle the mismatch between the material properties. Composite and metal properties differ with respect to: thermal expansion, failure mechanisms, plasticity, sensitivity to load type, fatigue accumulation and scatter, impact resistance and residual strength, anisotropy, environmental sensitivity, density etc. Based on these differences, the materials are subject to different design and certification requirements. The issues that arise in certification of hybrid structures are: thermally induced loads, multiplicity of failure modes, damage tolerance, buckling and permanent deformations, material property scatter, significant load states etc. From the design point of view, it is a challenge to construct a weight optimal hybrid structure with the right material in the right place. With a growing number of hybrid structures, these problems need to be addressed. The purpose of the current research is to assess the strength, durability and thermo-mechanical behavior of a hybrid composite-aluminum wing structure by testing and analysis. The work performed in this thesis focuses on the analysis part of the research and is divided into two parts. In the first part, the theoretical framework and the background are outlined.Significant material properties, aircraft certification aspects and the modeling framework are discussed.In the second part, two papers are appended. In the first paper, the interaction of composite and aluminum, and their requirements profiles,is examined in conceptual studies of the wing structure. The influence of the hybrid structure constitution and requirement profiles on the mass, strength, fatigue durability, stability and thermo-mechanical behavior is considered. Based on the conceptual studies, a hybrid concept to be used in the subsequent structural testing is chosen. The second paper focuses on the virtual testing of the wing structure. In particular, the local behavior of hybrid fastener joints is modeled in detail usingthe finite element method, and the result is then incorporated into a global model using line elements. Damage accumulation and failure behavior of the composite material are given special attention. Computations of progressive fastener failure in the experimental setup are performed. The analysis results indicate the critical features of the hybrid wing structure from static, fatigue, damage tolerance and thermo-mechanical points of view.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 54 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1590
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:liu:diva-91894 (URN)LIU–TEK–LIC–2013:24 (Local ID)978-91-7519-628-2 (ISBN)LIU–TEK–LIC–2013:24 (Archive number)LIU–TEK–LIC–2013:24 (OAI)
Presentation
2013-05-24, Hus A, plan 3, föreläsningssal A35, Campus Valla, Linköping University, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2013-05-08 Created: 2013-05-03 Last updated: 2013-05-08Bibliographically approved
2. Static and Fatigue Failure of Bolted Joints in Hybrid Composite-Aluminium Aircraft Structures
Open this publication in new window or tab >>Static and Fatigue Failure of Bolted Joints in Hybrid Composite-Aluminium Aircraft Structures
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The use of fibre composites in the design of load carrying aircraft structures has been increasing over the last few decades. At the same time, aluminium alloys are still present in many structural parts, which has led to an increase of the number of hybrid composite-aluminium structures. Often, these materials are joined at their interface by bolted connections. Due to their different response to thermal, mechanical and environmental impact, the composite and the aluminium alloy parts are subject to different design and certification practices and are therefore considered separately.The current methodologies used in the aircraft industry lack well-developed methods to account for the effects of the mismatch of material properties at the interface.One such effect is the thermally induced load which arises at elevated temperature due to the different thermal expansion properties of the constituent materials. With a growing number of hybrid structures, these matters need to be addressed. 

The rapid growth of computational power and development of simulation tools in recent years have made it possible to evaluate the material and structural response of hybrid structures without having to entirely rely on complex and expensive testing procedures.However, as the failure process of composite materials is not entirely understood, further research efforts are needed in order to develop reliable material models for the existing simulation tools.

The work presented in this dissertation involves modelling and testing of bolted joints in hybrid composite-aluminium structures.The main focus is directed towards understanding the failure behaviour of the composite material under static and fatigue loading, and how to include this behaviour in large scale models of a typical bolted airframe structure in an efficient way. In addition to that, the influence of thermally induced loads on the strength and fatigue life is evaluated in order to establish a design strategy that can be used in the industrial context.

The dissertation is divided into two parts. In the first one, the background and the theory are presented while the second one consists of five scientific papers.

Place, publisher, year, edition, pages
Linköping University Electronic Press, 2015. 53 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1706
Keyword
Hybrid structures; Composites; Bearing failure; Bolted joints
National Category
Aerospace Engineering
Identifiers
urn:nbn:se:liu:diva-122349 (URN)10.3384/diss.diva-122349 (DOI)978-91-7685-942-1 (ISBN)
Public defence
2015-12-03, C3, Hus C, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2015-11-02 Created: 2015-10-29 Last updated: 2015-11-02Bibliographically approved

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