Methods of forming a mandrel for forming composite structures, methods of forming composite structures, and related tools

A tool for forming a composite structure, the tool comprising:

• two or more segments formed from a polymer material;
• a crush insert disposed between the two or more segments;
• and
• a support shaft removably coupled between the two or more segments through complementary alignment structures.

A method of fabricating a composite structure, the method comprising:

• assembling a mandrel comprising:
• forming two or more segments of the mandrel from a polymer material through an additive manufacturing process;
• assembling the segments relative to one another;
• positioning a crush insert between each of the segments;
• and
• removably coupling the segments to a support shaft through complementary alignment structures;
• coupling the support shaft to a winding machine;
• winding composite fibers around the mandrel to form the composite structure;
• heating the composite structure;
• and
• separating the mandrel from the composite structure.