Experimental characterization of the thermo-electro-mechanical properties of a shape memory composite during electric activation

Abstract

This works investigates in detail the electro-thermo-mechanical properties of a Shape Memory Composite (SMC) during shape memory cycles in which the heating is a result of resistive heating. The SMC is a covalently cross-linked poly(ε-caprolactone) network filled with 3 wt% of multiwall carbon nanotubes. The characterization is performed with the help of a custom-made tensile test bench that is able to couple the mechanical characterization with the thermal and electrical ones. A PI (Proportional Integral) controller using the lambda tuning method is used in order to control the temperature achieved by resistive heating of the SMC. The electrical resistivity of the SMC shows a non-linear and non-monotonic dependence on temperature and strain. The resistivity is also found to vary among successive shape memory cycles, suggesting that a (first) training cycle is necessary not only to stabilize the mechanical but also the electrical properties of the SMC. A fuzzy logic controller for constant load control is also used to investigate the strain variation with temperature related to the two-way shape memory effect of the SMC. The results give evidence of the strong interplay between the electrical and (thermo-)mechanical characteristics of electroactive SMCs.

Construction, characterization, properties and multifunctional applications of stimuli-responsive shape memory polymeric nanoarchitectures: a review

“…Chemically functionalizing CNT, is an effectual strategy, as chemically functionalization has the propensity of increasing the compatibility between CNTs and SMP matrices. [47] The fabrication of CNT@polymeric nanoarchitectures is generally conducted using varying strategies (direct, solution and melt-mixing as well as insitu polymerization. Using conventional steps (extruding or injection molding, available polymeric matrix is prepared into its initial, permanent configuration B.…”

Review of Thermoresponsive Electroactive and Magnetoactive Shape Memory Polymer Nanocomposites

“…Other material properties such as the heat capacity or the thermal conductivity are also shown to affect the resulting temperature of the SMC. We also used a bespoke tensile test bench with integrated controllers for resistive heating in order to investigate the evolution of the electrical resistivity of the same SMC during 1W-SM cycles performed with uniaxial tensile deformation . Using a proposed dedicated PI controller, the resulting temperature on the surface of the SMC due to resistive heating can be efficiently and accurately controlled in order to follow a certain heating/cooling ramp or in order to maintain a constant temperature even though the electrical resistivity varies with time.…”

“…We also used a bespoke tensile test bench with integrated controllers for resistive heating in order to investigate the evolution of the electrical resistivity of the same SMC during 1W-SM cycles performed with uniaxial tensile deformation. 101 Using a proposed dedicated PI controller, the resulting temperature on the surface of the SMC due to resistive heating can be efficiently and accurately controlled in order to follow a certain heating/cooling ramp or in order to maintain a constant temperature even though the electrical resistivity varies with time. The results presented in ref ( 101 ) give also indications of the interplay among the electrical, thermal, and mechanical properties of the electroactive composite within shape memory cycles.…”

“… 101 Using a proposed dedicated PI controller, the resulting temperature on the surface of the SMC due to resistive heating can be efficiently and accurately controlled in order to follow a certain heating/cooling ramp or in order to maintain a constant temperature even though the electrical resistivity varies with time. The results presented in ref ( 101 ) give also indications of the interplay among the electrical, thermal, and mechanical properties of the electroactive composite within shape memory cycles. An example of this interplay is shown in Figure 6 , where the strain in the loading direction is shown as a function of a thermal cycle performed at a constant stress of 600 kPa in order to investigate the 2W-SM characteristics of the SMC.…”

“…The electrical resistivity during the process is also depicted. Further information on these measurements can be found in ref ( 101 ).…”