Process for molding composite articles

A method of molding a composite article comprising the steps:

• a. arranging in a spaced apart opposed relationship a first mold section comprising a first semi-rigid membrane removably mounted to a first rigid housing to define a first fluid tight chamber therein and a second mold section comprising a second semi-rigid membrane removably mounted to a second rigid housing to define a second fluid tight chamber therein;
• b. defining a mold plenum between the first and second semi-rigid membranes when the first and second mold sections are closed together to mold articles;
• c. filling the first and second fluid tight chambers with a substantially non-compressible backing fluid to support each membrane during injection of a molding fluid;
• d. accommodating thermal expansion of the backing fluid by an expansion chamber in fluid communication with the first and second fluid tight chambers;
• e. inserting reinforcement materials between the first and second semi-rigid membranes prior to closing the first and second mold sections together to mold articles;
• f. closing the first and second mold sections towards each other such that the reinforcement materials are sandwiched in the mold plenum;
• g. rigidly retaining the first and second mold sections together with the reinforcement materials sandwiched in the mold plenum;
• h. injecting molding fluid under pressure into the mold plenum;
• i. distributing a resulting injection pressure by the backing fluid;
• and
• j. curing the molding fluid by heating at least one of the backing fluid to produce a molded article.