Mechanical properties of epoxy/glass/mica composite at high temperature

The stator windings of large rotating machines are insulated with mica-glass fabric impregnated with epoxy resin. These composites are exposed to thermal, mechanical and electrical stresses. The mechanical behaviour of two different forms (foil and tape) of cured epoxy/glass/mica composite was studied during this experiment. Specimens were made of calcinated mica paper and a glass cloth, bonded together with epoxy-novolac resin. These materials are used for the insulation of coils and bars of the electric machines in thermal insulation class F. The aim of this experiment is to compare the present material with the modified one. The improvement is based on the use of innovated glass cloth and in modification of epoxy-novolac bonding resin. Tensile and bending strength of these materials are investigated at room temperature and at temperatures 130, 155 and 180 °C. Decreasing of tensile strength and bending strength of both materials with increased temperature is shown.