Facile Fabrication of Eucommia Rubber Composites with High Shape Memory Performance

We processed a series of shape memory Eucommia rubber (ER) composites with both carbon–carbon and ionic cross-linking networks via a chemical cross-linking method. The influence of the carbon–carbon cross-linking and ion cross-linking degree of ER composites on curing, mechanical, thermal, and shape memory properties were studied by DSC, DMA, and other analytical techniques. Dicumyl peroxide (DCP) and zinc dimethacrylate (ZDMA) played a key role in preparing ER composites with a double cross-linking structure, where DCP initiated polymerization of ZDMA, and grafted ZDMA onto polymer molecular chains and cross-linked rubber molecular chains. Meanwhile, ZDMA combined with rubber macromolecules to build ionic cross-linking bonds in composites under the action of DCP and reinforced the ER composites. The result showed that the coexistence of these two cross-linking networks provide a sufficient restoring force for deformation of shape memory composites. The addition of ZDMA not only improved the mechanical properties of materials, but also significantly enhanced shape memory performance of composites. In particular, Eucommia rubber composites exhibited outstanding mechanical properties and shape memory performance when DCP content was 0.2 phr.

Electro-thermo-mechanical behavior of carbon nanopaper shape memory polymer composites

An electro-active composite based on carbon nanopaper (CNP) shape memory polymer (SMP) composite is proposed for actuating deployment of composite deployable structures. Carbon nanopaper shape memory composites are stimuli-responsive materials that can change between programmed shapes and the original shape by a voltage input. The proposed composite is a sandwich structure where the CNP layer acts as a flexible electrical heater when a voltage difference is applied. The shape change behavior of CNP-SMP composite presents a coupled electrical-thermal-structural problem. This paper presents a combined experimental, numerical, and analytical study of the time-dependent shape programming, stowage, and actuation of the CNP-SMP composite. The governing equations for the multiphysics behavior are derived. Characterization of the electrical and mechanical properties of the materials are carried out and employed in a nonlinear, fully coupled electrical-thermal-structural finite element model. Shape programming, stowage and actuation characteristics of the composite are investigated experimentally under axial loading. An analytical model is derived for the thermo-mechanical behavior of the composite which directly expresses the recovery over time through the creep compliance function. Close correlation is obtained between experimental measurements and numerical simulations. The proposed model can accurately predict the load and shape characteristics throughout programming, stowage, and actuation.