Development of a new spectral modeling approach to investigate the dynamic and buckling behavior of composite structures

Official URL: https://risc01.sabanciuniv.edu/record=b2583870_(Table of contents)

In recent years, composite materials have become increasingly important due to rapidly increasing applications in aerospace, civil, offshore engineering and structural systems in other modern industries. The use of composite materials in the automotive and aerospace industry continues to become widespread due to its high specific strength and high specific rigidity. Since, the composite structures are critical to the functional and failure characteristics of a myriad of systems, understanding and predicting the static, buckling, and dynamic/vibration behavior of these systems is highly crucial. A composite material is obtained basically by mixing two or more materials having different physical and/or chemical properties. The material properties of the obtained material have different physical and chemical properties. According to the reinforcement type, composite materials are classified as fiber-reinforced, particle-reinforced, and laminated/sandwich composite materials. Also, another category of composite materials are functionally graded materials. Due to the flexibility of the reinforcing process using functionally graded materials, it is possible to design and produce composite materials with desired properties along the specific direction of the structure. Predicting the strains and stresses, buckling instability and dynamics of composite materials is critical to the functional and failure characteristics of a myriad of systems. Furthermore, during the design stage of a composite structure, it is necessary to perform dynamic/structural analysis for the entire design alternatives. Although there are many analytical/numerical modeling methods developed for composite structures in the literature, they are either for composite structures having simple geometries (one-dimensional models such as beam or two-dimensional models such as plates) or computationally inefficient such as finite element technique. Therefore, in literature, there is no comprehensive modeling technique that can accurately and efficiently calculate the deformation, buckling loads (instability), the vibrational behavior of composite structures having arbitrary geometries under mixed boundary conditions. In this thesis, it is aimed to develop a new modeling technique for accurate and efficient prediction of two-dimensional and three-dimensional vibration/dynamic behavior, static, and buckling behavior of composite structures and to integrate the proposed solution approach with an optimization algorithm to determine the optimum design. In the proposed modeling technique, first order deformation theory as a two-dimensional modeling and three-dimensional elasticity equations will be used and above-mentioned analysis will be performed using kinetic and strain energies of the composite structure. Since the material properties of composite structures may vary continuously/discontinuously or depend on the direction, the constitutive relationship between strains and stresses needs to be expressed to include all the different material properties specified. Furthermore, to simplify the domain of the boundary value problem, necessary coordinate transformations will be derived to transform the geometries of composite structures having variable curvature along one or two directions. To obtain high accuracy and high computational efficiency in the analyses, a spectral solution technique will be used incorporating Chebyshev polynomials in discretizing the problem domain. As a general conclusion, this research aims to present an accurate approach to decrease the cost of analysing of composite structures with complex materials and geometries to be a promising method for optimization studies.