PhD.Dissertation Defense:Aryan Kheyabani

ADVANCED MULTISCALE MODELING OF LAYERED AND

SANDWICH COMPOSITES USING COUPLED

MICROMECHANICAL, ZIGZAG, AND ISOGEOMETRIC

METHODS

Aryan Kheyabani
Manufacturing Engineering, PhD Dissertation, 2024

Thesis Jury

Assoc. Prof. Adnan Kefal (Thesis Advisor)

Prof..Ing. Dominik Schillinger

Asst. Prof. M. Erden Yıldızdağ

Assoc. Prof. Bekir Bediz

Asst. Prof. Hatice Sinem Şaş Çaycı

Date & Time: 12 December, 2024 – 14:00

Place: FENS L065

Zoom Link: https://sabanciuniv.zoom.us/j/6884897474

Keywords : PHFGMC micromechanics, Refined Zigzag Theory, Isogeometric

Analysis, Composite Materials, Multiscale Damage Modeling

Abstract

Fiber-reinforced composites (FRC) are widely favored over conventional metallic materials for their superior mechanical characteristics and the ability to provide directional properties. However, predicting their structural performance is complex and requires development of robust and efficient numerical approaches. The parametric high fidelity generalized method of cells (PHFGMC) is a micromechanical approach that can be used to understand behavior of composite materials. In this method, a repeating unit cell (RUC) is determined based on the microstructure and analyzed for obtaining the effective composite behavior at the macro level. On the other hand, refined zigzag theory (RZT) provides a robust, efficient, and reliable technique for modeling thin and thick layered composite structures. In this framework, a laminate is modeled as a single layer regardless of the stacking sequence and number of plies. Furthermore, isogeometric analysis (IGA) provides a numerical approach highly capable of modeling complex geometries with lower number of elements by employing non-uniform rational B-splines (NURBS). In the current dissertation, a novel modeling framework is developed for advanced multiscale linear and nonlinear analysis of composite materials. For this purpose, established capabilities of the PHFGMC, RZT, and IGA frameworks are leveraged.

The final main objective of the thesis is to be reached through following several fundamental method development steps. First, a multiscale analysis technique is proposed by using the PHFGMC micromechanical approach and the RZT based IGA plate formulation in a common framework. In this step, material constants for a composite layer are computed based on the constituent properties by employing the PHFGMC method. Then, macroscale analyses are performed on thick sandwich structures by employing the RZT based IGA formulation. In the next step, dimensional consistency is provided in the proposed multiscale framework by developing a novel higher order RZT^{3,2} based IGA plate formulation. This improvement facilitates direct exchange of data between the micro and macro levels without additional requirements and thus provides ease of implementation. In the meantime, outcomes of the proposed linear and higher order multiscale techniques are validated using experimental studies in this step. In the final stage, the framework is extended to support progressive damage modeling of composite materials and soft-core sandwiches. This is enabled by incorporating the Ramberg Osgood (RO) model and Hashin criteria for plasticity and failure assessments, respectively. Furthermore, a multipatch formulation is presented to apply the method on stiffened plates.

As an additional contribution to the field, a macroscale damage modeling technique is developed in the scope of this thesis by integrating the continuum damage mechanics (CDM) into the IGA-RZT^{3,2} plate formulation. This step provides an efficient and easy-to-implement phenomenological approach for failure analysis of composite materials. In this context, the concept of mesh dependency is addressed by using the crack band theory. Finally, the method is validated through predicting final failure loads of notched tensile laminates.