Fatigue life prediction of composite marine propellers

Master thesis (2023)

Authors

T. van Herwerden Mechanical Engineering

Contributors

C. Kassapoglou Aerospace Structures & Computational Mechanics - Aerospace Engineering (mentor)
Lotfollah Pahlavan Ship and Offshore Structures - Mechanical, Maritime and Materials Engineering (coach)
A.J. Huijer Ship and Offshore Structures - Mechanical, Maritime and Materials Engineering (graduation committee member)
J.H. den Besten Ship and Offshore Structures - Mechanical, Maritime and Materials Engineering (graduation committee member)
Faculty
Mechanical Engineering, Mechanical Engineering
Copyright: © 2023 Thijs van Herwerden
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Published Date

29-03-2023

Language

English

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Faculty

Mechanical Engineering

Abstract

Fiber reinforced composites have been increasingly used in the aerospace and automotive industry, due to their potential advantages for designing flexible, strong and lightweight structures. More recently they are also being considered for the manufacturing of marine propellers. Since they have the potential to lower the weight, lower the maintenance costs, increase the efficiency at off-design conditions, improve cavitation inception speed and minimize acoustic signatures. Exploiting the full potential of composite propellers however requires that they need to be cost-effective and to do so it is required that the lifetime of the blade is sufficient. To determine the lifetime of the blade it is
crucial to determine how the composite blade will respond to a wide variety of environmental and loading conditions that it will experience over its life. Basically one needs to determine what effects fatigue will have on the material properties of the blade. The main objective of this thesis is to estimate the fatigue lifetime of composite marine propellers subjected to a pressure distribution determined by a Fluid-Structure Interaction
(FSI)model with the use of a progressive damage model integrated into a Finite
Element Model (FEM). The fluid structure interaction model to determine the pressure distribution has already been created Maljaars (2019). Currently the mostly used and most reliable approach is to use an experimental approach in order to estimate the fatigue life. However, for custom designs such as marine propellers this is a long and costly process. Modelling fatigue the fatigue performance in an earlier stage of the design cycle will result in significant cost and time savings.

The expected fatigue lifetime of the composite marine propeller is concluded to be at least 1012 cycles under the considered loading condition. If the propeller would rotate at 600 rpm for 24 hours per day this would translate to over 3000 years. The reason behind this large number is that the combination of the applied pressure load and the strength of the carbon fiber propeller is such that the stresses in each ply are very low. These low stresses create almost no damage throughout the propeller blade even for ultra high cycles.