Polymer/LMPA for manufacturing deformable structure by coaxial printing

Structures with variable stiffness during deformation are of great importance in many fields. The solid–liquid transformation method using low melting point alloys (LMPA) is a promising method to control structural deformation. In this study, a coaxial filamentary feature consisting of pure LMPA surrounded by thermoplastic polymer (TP) is three-dimensionally printed and deformable structure can be constructed. The Polymer/LMPA structure can reveal special and valuable performances: The flexural modulus of the printed TPU/LMPA unit is about 1152 MPa, which is almost 330 times that of TPU and it can achieve large-scale stiffness changes by regulating temperature. Due to its reversibility and variable stiffness, the structure can achieve drive response perturbations under large bias loads. The maximum output force of the TPU/LMPA composite structure is 8.5 N and the maximum driving displacement is 18.5 mm. The fundamental frequency variation of the structure is achieved during the heating of the structure and the change of temperature can change the damping effect according to adjusting the frequency. This study has an important role in the future design of controllable stiffness structures.