Shape memory polymer composites (SMPCs) are being evaluated for aerospace applications due to their lightweight and ease of self-deployment. For such applications, the mechanical properties of SMPCs, including long-term behavior, need to be determined in the particularly harsh environments that are likely to be encountered. In this study, the storage modulus of carbon fiber-reinforced SMPCs (CF-SMPCs) was investigated under high vacuum condition and ultraviolet (UV) irradiation. The storage modulus of CF-SMPCs generally degrades as a function of time and temperature. However, the opposite behavior was observed under vacuum and UV exposure due to induced crosslinking. These two phenomena were characterized separately using acceleration tests at various temperatures under UV irradiation in a vacuum chamber and were modeled as two time-temperature superposition laws. The long-term mechanical behavior of CF-SMPCs in vacuum and UV environment is predicted by a linear product of shift factors obtained from the two acceleration tests.

The mechanical modeling and simulation of woven fabric-reinforced shape-memory polymer composites (wf-SMPCs) are quite complex tasks because a temperature change introduces thermal stress that dramatically affects the interaction between the matrix and fiber. This study aimed to develop a new homogenized constitutive model for wf-SMPCs considering the thermally induced residual stress. The orthotropic properties of the wf-SMPC due to the woven fabric reinforcement were modeled using classical anisotropic hyperelasticity theorems. The stress generated in the hyperelastic model was then complemented by combining with the stress generated in the SMP constitutive equation and the thermal residual stress according to Eshelby's inclusion theorem. The prediction capability of the proposed model was verified by three-point bending tests of the wf-SMPC having various fiber volume fractions. Finally, the unique features of the proposed constitutive model were investigated by experiments and simulation of a self-deployable antenna made of a wf-SMPC.

The elastocaloric cooling effect (eCE) of natural rubbers has been demonstrated in the context of cold storage; however, programming at room temperature is only possible at high strain rates. This study reports that shape memory cross-linked poly(cyclooctene) (PCO) exhibits an enhanced eCE at a relatively moderate strain rate due to its strain-induced crystallization behavior during deformation at room temperature. The elastocaloric heating and cooling effects of PCO were predicted using Green-Lagrangian strains obtained by 3D finite element analysis (FEA) with a suitable constitutive model and thermodynamic parameters such as the Clausius-Clapeyron factor and entropy changes. Good agreement between the simulation and experimental results suggests that implementation of the current method into 3D FEA can facilitate studies of portable cooling devices made of shape memory polymers.

The temperature-rate dependent thermomechanical behavior of shape-memory polymers (SMPs) is challenging to study, because the microstructure of SMPs cannot rearrange instantaneously to an equilibrium configuration in response to temperature changes. Herein, we report a temperature-rate dependent three-dimensional constitutive model for SMPs based on a two-phase model consisting of rubbery and glassy phases. To describe the effect of temperature rate on SMPs, the variation of the volume fraction of each phase affected by temperature was considered under different temperature-rate conditions. Additionally, the temperature-rate dependent thermal strain was incorporated into the two-phase model. The developed constitutive model was validated by simulating the shape-memory behavior of SMPs, and by comparing the simulation and experimental results under different temperature-rate conditions.

Transparent and stretchable electrodes (TSEs) are a key technology for the next generation of stretchable electronics and optoelectronics. Metallic nanofibers are widely used because of their good optoelectrical properties, but they demonstrate low stretchability. To enhance stretchability, fabricating in‐plane buckled nanofibers with the aid of a prestrained substrate has become crucial in this research field. Here, a composite comprising shape memory polymer–TSE (SMP–TSE) using crosslinked polycyclooctene as a substrate, which shows wrinkle‐free deformation and switchable optical transparency, is fabricated. Because of its considerable elongation without residual strain and the shape memory behavior of polycyclooctene, in‐plane buckled nanofibers are formed effectively. For fabrication of SMP–TSE, continuous and thin metallic nanofiber that can maintain its structural integrity is required; therefore, electrospinning and an ultraviolet reduction process to create a free‐standing, conductive, nanofiber network are used. Because of its in‐plane buckled nanofibers, the electrode maintained its resistance during 3000 cycles of a bending test and 900 cycles of a tensile test. Furthermore, SMP–TSE is able to electrically control its temperature, optical transparency, elastic modulus, and shape memory behavior. Finally, the use of SMP–TSE in a smart display that can control its optical and mechanical properties is demonstrated.