A composite mold that facilitates the fabrication, in a single curing step, of composite articles having opposing sets of stiffening members disposed in combination with a main structural panel. The composite mold provides for simultaneous co-curing of the opposed stiffening members in combination with the main structural panel. The composite mold includes a rigid mold assembly and a "T" mold assembly, which, in combination, define a rigid lay-up surface for the prepreg laminates forming the main structural panel. The rigid mold assembly includes rigid members that act as reactive surfaces for cure pressures, and removable end and wedge members for assembling/disassembling of the rigid mold assembly, "T" mold assembly combination. The "T" mold assembly is operative during the cure process to generate the pressure required to cure the legs of one set of the stiffening members. The "T" mold assembly includes complementary first and second pressure blocks that define the configuration of the one set of stiffening members. At least one of the complementary pressure blocks has a thermally expansible material encapsulated therein that is operative, in response to elevated temperatures experienced during the cure process, to expand, causing the complementary pressure blocks to exert the pressure necessary to cure the legs of the one set of the stiffening members.