Delamination Initiation and Propagation in Composite Laminates

Fibre-reinforced polymer composite laminates are used extensively nowadays in various applications due to their superior mechanical properties. However, a great weakness of composite laminates is their susceptibility to out-of-plane concentrated loading (which can be broadly divided into quasi-static indentation and impact) owing to their weak...

Novel insights into the physics of fatigue crack growth: Theoretical and experimental research on the fundamentals of crack growth in isotropic materials

Fatigue crack growth in metals has been studied intensively for more than half a century. This research field has been closely connected to the engineering industry throughout history. It is therefore no surprise that the main focus has mostly been on developing better prediction models rather than on understanding the phenomenon of fatigue...

The energy dissipation during fatigue crack growth

Fatigue failures are a major concern in aeronautics. The growth of fatigue cracks in metallic structures and adhesively bonded joints has been studied for decades. Nowadays, most researchers evaluate and predict the fatigue damage growth rate (da/dN) with empirical and phenomenon based approaches, using Linear Elastic Fracture Mechanics with...

Fatigue analysis of wind turbine blade materials using a continuum damage mechanics framework

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...

Towards fundamental understanding of interlaminar ply delamination growth under mode II and mixed-mode loading

In a context of many studies addressing delamination growth in laminated composites, this thesis provides understanding of the underlying physics of this phenomenon. The models currently used to assess delamination growth are phenomenological in nature and rely almost solely on curve fittings and experimental data. These empirical models are...

Lay-up Optimisation of Fibre Metal Laminates: Development of a Design Methodology for Wing Structures

The lower wing skin is one of the primary structures of an aircraft. To further improve the fatigue and damage tolerance (F&DT) performance of the lower wing, fibre metal laminates (FML) are proposed as a new material solution. FML consist of thin metal layers bonded with layers of fibre composites. This concept has potentially a large design...

Low-velocity impact on fibre-metal laminates

Generating high-energy absorbing FML concepts is challenging because aluminium and composite failure mechanisms are acting concurrently during the impact process. Because the impact process involves energy transformation, an analytical energy balance method was used to assess the contribution of the material constituents in the low-velocity...