A screw-type pump having at least two rotors which are composed of a male and female rotors with helically extending lands and grooves is increasingly used in industrial cooling plants, heat pumps and turbo chargers because it has a smaller weight to power ratio and produces less noise and vibration compared to conventional reciprocating pumps. Moreover, the capacity of a screw type pump can be varied continuously from 10% to 100% by the position control of the sliding valve.
Most male and female rotors of the screw type pump have been manufactured by machining. The manufacturing time is long because the amount of material cut-away is considerable and the manufacturing cost is high because the screw rotors have a complicated shape and require high degree of accuracy in machining. Therefore, there are many attempts to manufacture the screw rotors with plastics and ceramics using different manufacturing methods such as injection molding and casting.
Since the lands of rotors manufactured with polymer composite materials have resilient deflecting characteristics when clashed with other rotors, in this thesis, the composite screw rotor was manufactured with chopped carbon fiber reinforced epoxy composite materials by resin transfer molding.
In order to make the demolding of the screw easy, the mold for the screw rotor was manufactured with the high strength carbon fiber epoxy composite material whose coefficient of thermal expansion is very low. The surface of the mold was coated with the fine grade gelcoat to make the surface of the mold very smooth.
The interfacial strength between the screw and the aluminum core shaft was tested with respect to the surface knurling size of the aluminum core shaft and the surface treatment. Also, the tensile modulus, flexural strength and coefficient of thermal expansion were tested.
Using the tested data, the optimal composite screw rotors were manufactured by resin transfer molding.