Multi-level segmented mandrel system and method for composite shapes with negative draft

A method producing a closed-end hollow ceramic matrix composite (CMC) part with a negative draft on a mandrel formed of layers, the CMC part having a proximal open end and a distal closed end, comprising:

• forming a first layer of the mandrel with a first plurality of segments, the first layer configured for a first portion of the CMC part and having a first distal surface adjacent the closed end of the CMC part to be formed thereon;
• forming a second layer of the mandrel with a second plurality of segments, the second layer configured for a second portion of the CMC part and having a second distal surface adjacent a proximal surface of the first layer;
• forming a preform of the CMC part on the mandrel;
• densifying the preform to form the CMC part;
• extracting the second plurality of segments from the proximal open end of the CMC part;
• and
• extracting the first plurality of segments from the proximal open end of the CMC part after the second plurality of segments have been extracted.

A method of forming a layer of a multi-layer mandrel for a ceramic matrix composite (CMC) part, comprising:

• forming a graphite core having a shape of the layer of the multi-layer mandrel;
• cutting a circular shape in the graphite core transverse a plane of the layer to form a central cylindrical segment;
• making two converging cuts substantially tangent to the circular shape to form a first positive draft segment;
• making two converging cuts substantially tangent to the circular shape to form a second positive draft segment;
• making a first cut substantially normal to the circular shape to form two remaining segments, at least one of which is a positive draft segment;
• and
• making a second cut substantially normal to the circular shape to form an additional two remaining segments, at least one of which is a positive draft segment.