Composite fabrication system and associated methods. In one embodiment, a composite fabrication system comprises a molding tool that includes a forming surface at least partially disposed within a constrained space, and a foamable material that expands inside of the constrained space to form an expanded material that presses a layup of one or more composite layers against the molding tool. The composite fabrication system further comprises a curing device configured to cure the layup to form a composite part, and a cutting wire embedded in the constrained space that is heated and configured to cut the expanded material into pieces that are removable from the constrained space.