Composite insulators were introduced in the late sixties. The basic idea consists of the combination of different materials, which perform different duties in the insulator function corresponding to their particular strength and properties.

The end fittings are typically made of metal, such as forged steel or aluminium. For line insulators, a high degree of standardisation has been achieved for the end fittings, which enables the easy replacement of existing conventional insulators by composite solutions.

The glass fibre reinforced resin rod is responsible for bearing the mechanical loads, which can be tension, bending or compression, or a combination of all three, depending on the application and load scenario.

Materials for the housing are as manifold as the corresponding methods of manufacturing.
For special applications such as railway catenary line fittings, high strength coquille aluminium is often used.

The steel end fittings are hot dip galvanized. The thickness of the galvanizing follows the recommendations of IEC 60383. Enhanced thickness for heavily corrosive in situ conditions or DC applications can be provided on request.

Details of the dimensions and their relation to force rating are shown in the insulator design catalogue.

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