Inner shroud sector for an aircraft turbomachine

An inner shroud sector configured to be mounted in an aircraft turbomachine, the inner shroud being a revolving part defined with respect to a longitudinal axis oriented from upstream to downstream configured to internally delimit a secondary flow path of the aircraft turbomachine, the inner shroud sector comprising a downstream end comprising:

• an upstream longitudinal portion located at a first radial distance from the longitudinal axis and configured to extend in the upstream extension of an inner fan duct,
• a downstream longitudinal portion located at a second radial distance from the longitudinal axis less than the first radial distance and configured to extend inwardly of the inner fan duct, and
• a middle portion connecting the upstream longitudinal portion and the downstream longitudinal portion,
• the inner shroud sector comprising at least one inner layer of composite material and at least one outer layer of composite material, the composite material being in the form of a plurality of reinforcing fibers in a matrix, the middle portion of the downstream end comprising at least one volume of intumescent material sandwiched between the at least one inner layer of composite material and the at least one outer layer of composite material so as to form a local extra thickness in the longitudinal direction, the at least one layers of composite material and the at least one volume of intumescent material being malleable and adapted to harden during a heating and compression step, the at least one volume of intumescent material being adapted to expand during the heating and compression step.