Numerical Implementation Of The Refined Zigzag Theory For Structural Analysis Of Curvilinear Fiber Reinforced Composite And Functionally Graded Plate Structures

Official URL: https://risc01.sabanciuniv.edu/record=b3205852

The use of composite structures is becoming increasingly prevalent in structural engineering, due to their superior specific strength and stiffness. Fiber steering and functional grading of material to produce a Variable Stiffness (VS) composite or a Functionally Graded (FG) material composite, are two widely used tailoring methods for achieving the desired mechanical properties in composite structures to prevent their failure. However, the increased expansion in the design space for tailoring in these structures can pose a substantial challenge during structural analysis. It is essential to address this challenge by utilizing computationally efficient and accurate evaluations, particularly during determining the optimal fiber angles and the right material Compositional Gradient (CG) profiles based on the mechanical requirements. This study aims to comprehensively adopt and reformulate the Refined Zigzag theory (RZT) to accurately predict the strain and stress of different VS composite and FG sandwich plate laminates under static deformation. Therefore, the second chapter of this thesis proposes an RZT-based model which considers the variation of the curvilinear fiber angles in calculation of the ZigZag (ZZ) functions and utilizes their derivatives with respect to inplane coordinates in the definition of strains. Also, in the same chapter, the ZZ functions of the proposed model are enhanced to account for the continuous thickness-wise variation of the material. This enhancement allows the model to be capable of analyzing sandwich panels and composite plates consisting of FG and/or VS layers composite plates. Furthermore, a shear locking-free three node triangle RZT element is adopted to keep the degree of freedom in its minimum level and increase the computational efficiency. In order to accurately predict thickness-wise transverse stresses, a recovery procedure based on the integration of the Cauchy’s equilibrium equations is presented. In the third and fourth chapters, by solving numerical problems it is shown that the results of this procedure have a high level of accuracy, comparable to more computationally demanding three-dimensional Finite Element (FE) approaches or other higher-order theories. Therefore, the proposed model in this thesis provides an efficient and accurate method for analyzing VS and FG composite laminates. This model can be reliably integrated to design platforms to serve for tailoring the curvilinear fiber orientations and the material CG profiles and potentially improve the structural performance of these structures.