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KOÇ UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

MECHANICAL ENGINEERING

PhD THESIS DEFENSE BY GÖKHAN SERHAT

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Title: Multi-objective Optimization of Nonconventional Laminated Composite Panels

 

Speaker: Gökhan Serhat

 

Time: October 26, 2018, 10:00

 

Place: ENG 208

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Assoc. Prof. İpek Başdoğan (Advisor, Koç University)

Prof. Dr. Fabian Duddeck (Technical University of Munich)

Assoc. Prof. Murat Sözer (Koç University)

Assoc. Prof. Çetin Yilmaz (Boğaziçi University)

Asst. Prof. Bekir Bediz (Sabancı University)

 

Abstract:

Laminated composite panels are extensively used in various industries due to their high stiffness-to-weight ratio and directional properties that allow optimization of stiffness characteristics for specific applications. With the recent improvements in the manufacturing techniques, the technology trend has been shifting towards the development of nonconventional composites. This work aims to develop new methods for the design and optimization of nonconventional laminated composites. Lamination parameters method is used to characterize laminate stiffness matrices in a compact form. An optimization framework based on finite element analysis was developed to calculate the solutions for different panel geometries, boundary conditions and load cases. The first part of the work addresses the multi-objective optimization of composite laminates to maximize dynamic and load-carrying performances simultaneously. Conforming and conflicting behaviors of multiple objective functions are investigated by determining Pareto-optimal solutions, which provide a valuable insight for multi-objective optimization problems. In the second part, design of curved laminated panels for optimal dynamic response is studied in detail. Firstly, the designs yielding maximum fundamental frequency values are computed. Next, optimal designs minimizing equivalent radiated power are obtained for the panels under harmonic pressure excitation, and their effective frequency bands are shown. The relationship between these two design sets is investigated to study the effectiveness of the frequency maximization technique. In the last part, a new method based on lamination parameters is proposed for the design of variable-stiffness composite panels. The results demonstrate that the proposed method provides manufacturable designs with smooth fiber paths that outperform the constant-stiffness laminates, while utilizing the advantages of lamination parameters formulation.

 

 

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