U.S. patent application 20170291404 (applicant Boeing Co., Chicago, Ill.):
"Systems and methods are provided for forming composite parts. One embodiment is an apparatus that includes a forming tool. The forming tool includes a body, which includes an exterior that defines a shape for forming a laminate that will be cured into a composite part. The body also includes elements of phase change material that provide rigidity to the body below a threshold temperature, and that exhibit a phase change above the threshold temperature causing the body to become pliable. Further, the body includes flexible material that encloses the elements of phase change material."