Shape memory alloy reinforced vitrimer composite for healing wide-opened cracks

摘要

A new 3D printable vitrimer based self-healing composite was fabricated and investigated in this study. In this new system, the vitrimer, which was designed and synthesized in our previous study, was used as the matrix of the composites. Tensile programed shape memory alloy (SMA) wires, with a concentration of 0.34% by volume, were used to serve as the crack closing device and provide a certain reinforcement to the composites. Polycaprolactone-diol (PCL-diol) was used as the external healing agent for the wide-opened crack healing. Four types of samples were prepared, which were composites with unknotted SMA wires or knotted SMA wires, but without PCL-diol healing agent in the vitrimer matrix; and composites with unknotted SMA wires or knotted SMA wires, but with PCL-diol powders dispersed in the vitrimer matrix as an external healing agent. Up to five tensile fracture/healing cycles were conducted. It is found that for a 1 mm wide tensile crack, all the composites can heal the damage to a certain extent. Instead of gradual reduction in healing efficiency as the fracture/healing cycle increases, the healing efficiency continuously increases from second fracture (41.1%) to fifth fracture (58.6%), most likely due to the gradual compaction of the PCL-diol adhesive layer, better interfacial bonding and physical entanglement, and possible transesterification reaction between the PCL healing agent and the vitrimer matrix.