Dynamic Behavior of a Non-explosive Actuator with Shape Memory Composites

A non-explosive actuator (NEA) has been prototyped by using a complex sandwich architecture with carbon fiber (CF) plies, shape memory polymer (SMP) interlayers, SMP foams, and an embedded heater. The final shape memory polymer composite (SMPC) device has been manufactured by lamination and compression molding, with a size of 20 × 45 mm2. A single molding step has been adopted to co-cure the CF prepreg plies with the SMP interlayers and to join them to the foam elements and the embedded heater. Foams have been manufactured by solid-state foaming of the same SMP epoxy resin of the SMP interlayers. The SMPC-NEA has been tested in memory and constrained-recovery tests to evaluate the effect of the heater supply voltage (from 20 to 24 V with 1 V increments) and the loading rate of the memory stage (1, 5, 10, 20, and 50 mm/min). Many important shape memory (SM) characteristics have been extracted by the tests, with some important correlations. A master curve has been also built to show that the superposition between the supply voltage (related to the device temperature) and the test rate (related to the observation time) is possible. The regular shape of the master curve also shows that severe damages were absent during testing, with 25 memory-recovery consecutive cycles. In the best case, the SMPC-NEA applied a recovery load of 7.4 N. By increasing the device temperature, this actuation load may reduce, but very high shape fixity ratios, up to 99%, may be reached.