Resin transfer molding process for making composite pipe

A resin transfer molding process for making composite pipe comprising the steps of:

• a. disposing a preform on a mandrel;
• b. jacketing a heat-shrinkable sleeve over the preform disposed on the mandrel wherein an annular gap is maintained between the sleeve and the preform to form a buffer chamber in the annular gap;
• c. filling a thermosetting resin into the buffer chamber through an inlet port of the buffer chamber, then sealing the inlet port and gravitationally levelling and settling the resin in the buffer chamber to form a resin pool in the buffer chamber;
• d. thermally shrinking the heat-shrinkable sleeve by heating the sleeve with a heating means, said heating occurring in a heating zone comprising an upper portion and a lower portion, said heating zone movable from a lower portion of the sleeve adjacent to the inlet port of the buffer chamber towards an upper portion of the sleeve, whereby upon heating of the sleeve, the sleeve is shrunk to boost the resin in the resin pool to flow centripetally and upwardly to homogeneously penetrate the resin into the preform to impregnate the preform and to force bubbles existing in the resin and preform upwardly to vent and remove the bubbles therefrom;
• and
• e. heating and curing the resin at a hardening temperature of the resin to harden the resin impregnated preform disposed on the mandrel and then removing the sleeve to form a composite pipe;
• wherein
• the step of thermally shrinking the heat-shrinkable sleeve includes providing a first fastening ring fastened on said sleeve adjacent to the upper portion of said heating zone to limit an upward resin flow and to enhance centripetal resin flow, and providing a second fastening ring fastened on said sleeve adjacent to the lower portion of the heating zone for keeping a constant diameter of the pipe, said heating zone and said heating means moving upwardly along said sleeve to thermally shrink said sleeve.