There is provided an apparatus and method for consolidation joining a thermoplastic preform to form a duct. The apparatus includes first and second longitudinally extending support structures. The first support structure at least partially defines a cavity for supporting the preform in a desired configuration of the duct. The second support structure extends in the cavity such that the preform can be supported between the first and second support structures. The second support structures can include an elastomeric device that is configured to adjust radially and urge the interface of the preform against the first support structure. A heater is configured to heat an interface of the preform to above a glass transition temperature. The resulting duct is has a longitudinal consolidation joint and defines a passage.