Carbon nanotube enhanced shape memory epoxy for improved mechanical properties and electroactive shape recovery

This paper focuses on the processing, fabrication and characterization of a novel carbon nanotube (CNT) based electroactive shape memory epoxy nanocomposite with significant improvements in static and dynamic mechanical properties. Electro-active shape memory specimens have been fabricated by soaking CNT membranes (buckypaper) in shape memory epoxy polymer (SMEP) through a specialized fabrication process developed in-house that results in a high CNT wt. fraction of 30 wt%. The novel fabrication approach leads to drastic improvement in mechanical performance due to effective interfacial interaction between the SMEP and CNTs at the nanoscale. This is accomplished as the SMEP thoroughly permeates the buckypaper through the nano- and micro-pores, owing to the microstructure-induced capillary action. The improvement in quasistatic and dynamic mechanical properties of the baseline SMEP using CNT buckypaper is demonstrated and correlated with the microstructure through scanning electron microscopy characterization. For the buckypaper-enhanced SMEP (CNT-SMEP), the improvement in elastic modulus in the temperature extremes of 20 and 50ׄ°C was found to be 52% (1810 MPa compared to 2740 MPa) and 514% (7.6 MPa compared to 46.7 MPa), respectively. Furthermore, through the dynamic mechanical measurements, the increase in storage modulus in the range of 30-90ׄ°C was found to be 60% and 82%, respectively. In addition, the shape memory recovery response for this material system is characterized by stress-free electrical actuation of the CNT-SMEP using a 12V DC supply as well as using stress and temperature control testing.