Experimental study of the effect of preload and bolt arrangement on the performance of composite joints of nacelle cover and nose cone of MW wind turbine

The nacelle cover and nose cones of most megawatt wind turbines are made of composite sheets. Due to the different shapes and geometries as well as the large dimensions of this components, this components are composed of several parts that must be connected to each other by non-permanent mechanical connections such as bolts. Therefore, it is very important to know all the effective parameters affecting composite joints. One of the most important design parameters of bolt connections is the amount of blot preload or tightening torque. Due to the composite material of the sheets on both sides of the joint, it is not possible to increase the preload without any concern. Because, this in itself can lead to damage to the composite sheets. Therefore, in this paper, first, the effect of bolt preload or bolt tightening torque on composite joints has been evaluated experimentally. For this purpose, identical specimens with bolt tightening torques of 2, 10, 20, 30, 40 and 50 Nm have been fabricated and subjected to tensile testing. Then, after determining the optimal preload force, 4 different types of arrangement were experimentally tested to find the best bolt arrangement. Finally, by examining different aspects, the best arrangement for connecting different parts of the nacelle cover and nose cone is determined.