A new method for fabricating SMA/CFRP smart hybrid composites

In order to suppress the microscopic mechanical damages in composite system, and thus to increase the reliability of carbon fiber reinforced plastics (CFRP), a smart composite SMA/CFRP is attracting much attention. In this application, the shape memory alloy (SMA) is expected to exert compressive stress to CFRP by reverse transformation upon heating after fabrication. However, one big problem in the fabrication process is that the curing temperature of the composite (130 °C) far exceeds the reverse transformation temperatures of Ti–Ni alloys (∼70 °C). This paper presents a new method to overcome this difficulty. The method consists of using heavily cold-worked wires to increase the reverse transformation temperatures, and of using flash electrical heating of the wires after fabrication in order to avoid damaging of the matrix around wires. By choosing the reduction of cold drawing and composition of TiNi alloys properly, it will be shown that the method is actually applicable without using special fixture jigs, which are necessary otherwise, to the fabrication of such smart composite as SMA/CFRP.