Prediction models for fatigue in engineering applications are developed within a fatigue analysis framework, deliberately selected in some cases, but mostly chosen without substantiation. The proposition of this paper is that selecting the most appropriate framework can only be done with the knowledge and a complete overview of existing frameworks and their systematic categorization. In particular for composite materials, where due to coexistence of different mechanisms and their complex interaction under fatigue loading, only a unified approach can characterize the complete fatigue phenomenon. To that aid, this paper provides a complete overview of existing fatigue analysis frameworks for various materials along with such systematic categorization. Each analysis framework is based on a specific methodology that evolved over time. Hence, this overview is provided following the time stamp evolution of each methodology within different analysis frameworks. With such an overview, one can conclude that for fatigue analysis of composite materials, the theory of the thermodynamics of the irreversible processes and continuum damage mechanics framework provides the required unified approach. Additionally, this paper demonstrates that many material classes, like metals and composites, can be analysed using a common framework. This common framework has similarity up to a certain level, and at the detailed level, it differs by addressing the difference in material class-specific mechanisms.

The work done for this thesis is related to fatigue analysis of various material types used in the wind turbine blades. For the analysis, a framework from the thermodynamics of irreversible processes with internal variables and Continuum Damage Mechanics (CDM) is used. Thermodynamic principles provide a generic framework that is valid for the entire fatigue phenomenon. CDM framework is then applied to characterize a specific mechanism under consideration. As the fatigue phenomenon consists of many mechanisms and their interactions, the scope of work is limited to setting the generic framework and to characterize only a few and their interactions to demonstrate the framework potential. The thesis consists of four main sections: introduction, theory, mathematical formulation, and validation. Before starting the framework construction, a decent idea about vastness in fatigue analysis methodologies adopted by the research community is required. Hence chapter 1 is prepared to give readers, not in detail, but a helicopter view of the field. This overview allows drafting the achievable scope and methodology for this research work keeping in mind the ultimate goal of analysing full-scale wind turbine blade sustaining fatigue throughout its operational life.