Abstract
In this paper a study was carried out on the fatigue life of fibre-reinforced composite T-joints subjected to a tensile pull-out loading. The composite T-joints have been made of glass fabric infused with epoxy resin using a vacuum assisted resin transfer moulding technique. Methods such as the use of veil layers, tufting techniques and 3D weave have been employed to improve the interlaminar fracture toughness of the composite T-joints. All the tests were conducted in an Instron testing machine using a specially designed test fixture. Fatigue tests were performed in a load control mode with a stress ratio of R = σmin/σmax = 0.1. The cyclic loading pattern was a sinusoidal wave with a frequency of 6 Hz. The specimens were cycled at a series of constant maximum load values up to failure. Fatigue loads versus life data for each T-joint type were produced at various maximum applied loads. The 3D weave T-joints were found to have the best performance in both static and fatigue loading. Increasing the static properties increases fatigue life performance; the increasing rate in fatigue life is changed with the number of stress cycles. The location for the through-thickness reinforcement plays an important role in improving fatigue life of the Tjoints. Fatigue life is significantly improved if the web is reinforced in through-thickness direction. A finite element (FE) failure model was also created using ABAQUS to determine the location where delamination is initiated and its subsequent propagation.
Highlights
T-joints are found in structural components such as skinspar in wind turbine blades and aircraft wings and road vehicles
It can be seen from the figure, the σ–δ behaviour is sensitive to the composite Tjoint architectures. 3D woven T-joint always shows the best pull-out performance compared with other type Tjoints
When the defection is less than a certain value, a linear relationship exists between the deflection and the applied stress produced by the load
Summary
T-joints are found in structural components such as skinspar in wind turbine blades and aircraft wings and road vehicles. 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]. 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 initiation of delamination in the composite T-joint is almost always initiated on the joint’s corner due to the maximum stresses developed in this region. Delamination crack propagation behaviour plays an important role in the control of fatigue failure of the T-joint
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