Fatigue Behaviour of Composite T-Joints in Wind Turbine Blade Applications
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Fatigue Behaviour of Composite T-Joints in Wind Turbine Blade Applications Y. Wang 1 & C. Soutis 1
Received: 31 August 2016 / Accepted: 30 September 2016 # The Author(s) 2016. This article is published with open access at Springerlink.com
Abstract This paper presents a study of fatigue performance of composite T-joints used in wind-turbine blades. A T-joint with various fibre reinforcement architectures were selected to investigate its fatigue behaviour. The 3D angle interlock T-joint was found to have the best performance in both static and fatigue loading. Increasing the static properties increases fatigue performance while the increasing rate in life performance is changed with the number of fatigue cycles. A finite element (FE) model was developed that can determine the stress distribution and the initiation and propagation of a delamination crack. The location for through-thickness reinforcement is very important to improve fatigue performance of composite T-joints. Fatigue performance is significantly improved for the web with through-thickness reinforcement while fatigue performance is decreased if the through-thickness reinforcement is applied to the flange-skin regions. The interlaminar veil significantly increases the ultimate strength under static load but fatigue performance at high stress cycles is increased but not significantly. Keywords Composite structures . T-joint . Finite element analysis . Fatigue . Delamination
1 Introduction A typical wind turbine blade when in service is subjected to flexural bending that induces tensile and compressive stresses and torsion that leads to development of shear stresses. Beside these, the wind blade must endure several orders of magnitude more cycles of fatigue loading than an aircraft, which makes wind turbines fatigue critical structures. The wind-turbine blades are often made of composite materials due to their low density and excellent mechanical properties combination of strength, stiffness, fatigue performance and better corrosion resistance than metals [1]. Wind turbine blade failures, when in service are due to various complicated reasons but blade failures account for most accidents and damage to wind turbines * C. Soutis [email protected]
1
School of Materials, University of Manchester, James Lighthill Building, Sackville Street, Manchester M1 3NJ, UK
Appl Compos Mater
[2]. Therefore, it is important to understand the way the composite T-joint fails and develop methods of improving fatigue life performance to enhance the durability of wind turbines. The composite materials used in blade construction are typically fabrics containing a variety of configurations (e.g. non-crimp fabrics (NCF), uniweave and woven). The formation of internal detailed shapes within the blade, allowing features such as spars, shear webs and other connections, inevitably requires these 2D material configurations to be formed into three-dimensional (3D) shapes. This introduces sites within the structure where load transfer occurs across regions with l
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