Adjustable-stiffness and programmable shape memory polystyrene composites with elastic fibers for complex structure smart molds

Smart molds based on shape memory polymers (SMPs) with active deformation characteristics enable demolding of complex structures in response to external stimuli. However, for large-cavity components, smart molds made of common SMPs often have problems such as limited deformation and being prone to blowing during molding. Based on free radical polymerization, a rigid-flexible cross-linked network structure was constructed, achieving a large deformation up to 370 % for thermosetting shape memory styrene. On this basis, composites with nylon-spandex elastic fiber was prepared. The introduction of ± 45° laid elastic fibers hinders the crack propagation in the matrix and can improve the deformation capacity of the composites. Further, the programmable composites were applied to reusable shape memory smart molds, accomplishing shape convertion from 2D planes to 3D structures and 3D mandrels to 4D deformable components with variable cross-sections, curvatures, and structures, which is expected to pave a new way for smart molds.