The composite insulator has the advantages of light weight, good anti-fouling performance and strong anti-human damage performance, and is increasingly welcomed by users. It has become the main force in the insulator industry in the urban agricultural network reconstruction project. As insulators, there are two basic requirements, namely, the external insulation performance and the stable mechanical properties. Both are equally important and indispensable. Therefore, studying the mechanical properties of composite insulators is an important part of our further expansion of the composite insulator market. The outer insulation of the composite insulator is provided by silicone rubber, the mechanical load of which is mainly provided by the inner glass fiber drawing rod, and the connection of the metal fitting and the glass fiber drawing rod. Therefore, the research and analysis of the mechanical properties of composite insulators is the key to safe operation.

1 End fitting connection structure and mandrel utilization

The composite insulator mainly relies on a one-way glass fiber reinforced resin drawing rod (commonly known as a core rod) to bear the mechanical load. The most outstanding performance characteristics of FRP rods are high tensile strength and specific strength. The glass fibers in the drawing rod are arranged in the axial direction of the bearing direction, so that they have a high axial tensile strength, generally up to 1000 MPa or more. Therefore, the tensile strength of the drawing rod with a diameter of only 18 mm can reach more than 250 kN. Since the density of the drawn rod is generally only 2.0 g/cm3, the specific strength (ratio of tensile strength to weight) is 5-6 times that of the high quality carbon structural steel. The high strength and high specific strength of the drawing rod is the basis for the high strength, light weight and thin rod diameter of the composite insulator.

Although the composite insulator relies entirely on the fiberglass rod to bear the mechanical load, the strength of the mandrel is not equal to the strength of the composite insulator. This is because the mandrel must transmit the load through the end attachment of the insulator to be able to connect with the tower of the transmission line. The wires are connected. The end joints are inevitably where the mechanical stress is most concentrated. Different joint structures also lead to different stress concentrations. Therefore, the mechanical strength of the composite insulator is actually not more dependent on the mechanical strength of the mandrel, but rather The mechanical strength of the end connection, that is, the strength of the core rod. Composite insulators using the same mandrel and different connection structures have different mechanical strengths, and therefore the strength of use of the mandrel is different.