# Two-Way Shape Memory Effect of a Shape Memory Composite Strip
## 4 Future Applications  
A flower-like, space-deployable antenna model with a folding-deploying ratio 0.85 (195 mm for folding and 230 mm for deploying state) was demonstrated in ref [35]. Here, we proposed an improved method shown in Figure 10 to reduce the folding diameter of antenna model based on the following fabrication steps: (1) Preparing four SMA composite strips, pair of cylinder base structures (inner 6 mm and outer diameter 55 mm), a screw, and nut; (2) Assembling these components into the skeleton of the antenna model; (3) Gluing a ring-shaped polyimide (PI) film (inner 80 mm and outer diameter 200 mm) with a curved SMA thin film (length 70 mm \(\times\) width 2 mm \(\times\) thickness 0.3 mm) between two adjacent SMA composite strips on the top surface of SMA composite strips by silicon adhesive to form the space-deployable antenna model.  
The results showed that the folding-deploying ratio of the antenna diameter could be reduced to 0.72 (165 mm for folding and 230 mm for deploying state) within 10 min at an oven temperature of 120 \({}^{\circ}\)C, as shown in Figure 11. The main reason was the aided actuation effect of the SMA thin film to predetermine the bending direction of the PI thin film under the heating process.  
Figure 10: Fabricating process of space deployable antenna model: (**a**) Fabricating of antenna components. (**b**) Skeleton of antenna model. (**c**) Antenna model with PI film.  
Figure 9: Two-way reversible bending angles for the first 20 cycles.  
As mentioned above, the low stiffness of the rubber-based SMA composite strips at low temperature meant that they could not provide high load-bearing ability. An antenna model based on SMP-based SMA composite strips was developed to improve the load-bearing ability and verify the two-way reversible bending SME at 120 \({}^{\circ}\)C and 35 \({}^{\circ}\)C, as shown in Figure 12.  
The folding process of the SMP-based antenna model shown in Figure 12 was similar to that shown in Figure 11, and the folding-deploying ratio of the antenna diameter was  
Figure 11: Two-way SME of an antenna model of rubber-based SMA composite strips with a curved SMA thin film: (**a1–a6**) Self-folding process at 120 \({}^{\circ}\)C. (**b1–b12**) self-deploying process at room temperature.  
Figure 12: Two-way SME of an antenna model of SMP-based SMA composite strips with a curved SMA thin film: (**a1–a6**) Self-folding process of SMP-based antenna model at 120 \({}^{\circ}\)C. (**b1–b12**) self-deploying process at 35 \({}^{\circ}\)C.  
0.74 (161 mm for folding and 217 mm for deploying state) due to the SME the SMA wire. However, the deploying process of the SMP-based antenna model was obviously different from that of the rubber-based model due to the restrictive effect of the increasing stiffness of the SMP matrix at glass state. In addition, the creep properties of SMP, as shown in ref [44; 45], could delay the deploying process, and the total deploying process took 80 min at 35 \({}^{\circ}\)C to achieve a diameter of 216 mm. The recovery time was eight times that of the rubber-based model during the deployment process.