||Homogenization and Localization for Composite Structures with Relieved Periodicity in the Thickness Direction
Nasution, Muhammad Ridlo Erdata
This thesis aims to develop a novel asymptotic expansion (AE) homogenization and localization analysis for advanced composite structures by relieving periodicity in the thickness direction. Introduction of relieved periodicity is an enhanced approach in homogenization and localization method whereby the years developed method usually implements the periodicity in three directions, i.e. in-plane and out-of-plane directions of the unit-cell. In this regard, a modified periodic function is introduced in the numerical formulation. The present formulation and finite element implementation of AE homogenization and localization method are given, and utilized to investigate several types of composites, namely 2-D laminated composites, brick composites, 3-D orthogonal interlock composites and sandwich composites. Homogenized thermomechanical properties and stress responses within the unit-cell due to application of thermal and mechanical loads are of the main interests. It is found that relieving periodicity in the thickness direction has larger influence on the analyses of composites having geometrical and/or material non-uniformity in the in-plane direction. Some certain results of homogenization and localization analysis are compared with analytical and finite element analysis results. Based on the obtained outcomes, it can be emphasized that the application of free-traction boundary condition only on the top and bottom surfaces of the macroscopic model cannot accurately simulate the real condition. The relieving periodicity throughout the thickness direction of unit-cell is necessary in order to be able to obtain the accurate results.