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In order to make up for the defects of trans-1,4-polyisoprene (TPI) shape memory polymer, TPI/high density polyethylene (HDPE) hybrid shape memory matrix was prepared from the perspective of matrix composition. The carbon nanotubes (CNTs) with excellent mechanical properties were introduced into the hybrid shape memory matrix. Due to the difference of the inherent properties and geometry of nano-fillers, the change of the content of nano-fillers directly affects the bonding state within the composites. Therefore, it is very important to choose the appropriate content. In order to give full play to the potential of thermodynamics of nano-filler, the TPI/HDPE/CNTs ternary hybrid shape memory nanocomposites were prepared by mechanical melt blending technology combined with dynamic vulcanization and hot-pressing forming technology. The addition of CNTs promotes the formation of the crystal structure of TPI and HDPE, and facilitates the energy transfer between different interface, which greatly improves the thermal conductivity and mechanical properties of the nanocomposites at the same time. The effect of the changes of filler content on the thermodynamic properties of the composite materials were revealed by series of tests. The results show that the CNTs act as nucleating agents in the crystallization region of TPI and HDPE. However, the excessive addition of CNTs can inhibit the formation of HDPE crystal structure. Meanwhile, the crystallinity of nanocomposites is also an important factor affecting its thermal conductivity. The specimens with the CNTs content of 0.5 wt% have excellent tensile resistance and cyclic recovery ability, and it can improve the shape recovery properties. Therefore, the nanocomposite with the CNTs content of 0.5 wt% has the best thermodynamic and shape memory properties.

In recent years, shape memory smart materials have developed rapidly, and more and more novel shape memory polymers have been developed and applied. In sharp contrast to the rapid development of shape memory smart materials, its theoretical research is obviously lagging behind. Therefore, it is necessary to clearly understand and master the thermodynamic dynamic response mechanism of shape memory polymers. In view of the fact that the influence of thermodynamic properties of hybrid shape memory polymer under the coupling effect of multiple factors is still very vague, a novel hybrid shape memory polymer composites (SMPC) thermodynamic viscoelastic constitutive model is proposed for the first time by combining the macroscopic phenomenological viscoelastic theory with the microscopic phenomenological phase transition model, and a microstructure composed of two parts of reversible phase and stationary phase in parallel is constructed. At the same time, a three-dimensional parameter equation with temperature effect and capable of describing the coordinated changes of various parameters in the phase transition process is established. Through the validation of the model, it can be found that the variation trend of the simulation curve is in good agreement with the experimental curve during the whole static loading process, and the error of the fracture stress is less than 2%. Through the dynamic evolution of multi-content and wide-temperature range, the consistency between the simulation results and the experimental results is successfully proved, and the microscopic mechanism of the macroscopic static mechanical behavior of the hybrid SMPC is revealed. The model established in this paper can accurately describe the internal phase change of the mixed matrix, and realize the effective prediction of the stress-strain response under the coupling effect of the matrix composition and the external environment. The proposal of this model provides a new idea for the exploration of hybrid SMPC thermodynamic viscoelastic theory, and also provides an important theoretical reference for the development and application of novel hybrid shape memory materials in the future.

Filler/matrix interfacial cohesion exerts a straightforward effect on stress transfer at the interface in composite structures, thereby significantly affecting their integrated mechanical properties. Thus, controlling the interface interaction of polymers/fillers is essential for the fabrication of high-performance polymer composites. In this work, a functionalized core–shell structured hybrid was prepared via charge attraction and applied as a novel filler in the trans-1,4-polyisoprene matrix to improve the interfacial interaction of the filler/matrix. A series of tests on the micro- and macroscale was performed to investigate its thermal, mechanical and shape memory performances. The obtained results show that while guaranteeing the shape memory properties of the composites, the utilization of the core–shell structured hybrid not only improved the heat resistant performance, but also contributed to better mechanical properties. This provides solid evidence for the potential of the innovative method presented herein, which may shed some light on the improvement of the interface design strategy and the development of composites with high performances.

In this work, a functionalized hybrid Al2O3-GO was fabricated and introduced into trans-1,4-polyisoprene (TPI) matrix as a new filler. The incorporation of the hybrid optimized the heat resistance, mechanical strength, and fracture toughness of the composites simultaneously. The ultrathin GO shells at Al2O3-TPI interfaces were considered to be the main reason for the enhancement. They effectively enhanced the interfacial interaction of the Al2O3-GO/TPI nanocomposites, thus greatly improved the thermodynamic properties of the TPI. The mechanical, thermal, and shape memory properties of nanocomposites were characterized through systematic tests from microscale to macroscale. According to the experimental results, the nanocomposite samples with GO (0.9 wt%) and Al2O3 nanoparticles (1.2 wt%) show the best thermal and mechanical properties in comparison with other samples, and a good shape memory property was obtained or realized in the fabricated nanocomposites. We believe this new and effective approach may open a novel interface design strategy for developing high performance composites. Keywords: Al2O3-GO nanohybrids, Polymer nanocomposite, Thermodynamic properties, Shape memory

Regulating the interfacial interaction between fillers and matrices is crucial for fabricating high-performance polymer composites. In this research, a functionalized core–shell hybrid silica@graphene oxide was produced by the charge attraction method, and then added to a trans-1,4-polyisoprene matrix as a neoteric filler to obtain a brand-new silica@graphene oxide/trans-1,4-polyisoprene polymer nanocomposite. The hybrid incorporation simultaneously improved the fracture toughness, mechanical strength and heat resistance of the nanocomposites. We examined the thermal, mechanical and shape memory properties of the nanocomposites via methodical measurements from the microscale to the macroscale. The experimental results demonstrated that, compared with other samples, the nanocomposite sample with 1.0 wt% silica@graphene oxide exhibited the best mechanical and thermal performance, and the fabricated nanocomposites showed good shape memory properties. This new and feasible approach is likely to enable a new strategy for the design of interfaces for developing nanocomposites with high performance.

In order to overcome the shortcomings of high cost of traditional high-performance reinforced fillers, low-cost high-density polyethylene (HDPE) was introduced into TPI matrix as reinforcement phase in this study, and the TPI/HDPE hybrid shape memory polymer composites (SMPCs) was vulcanized by dynamic vulcanization technology. Due to the different vulcanization degree of TPI components the properties of TPI SMPCs are different, so it is particularly important to choose the appropriate content of vulcanizing agent. In order to realize the complementary advantages of the rubber-plastic thermoplastic elastomers, the vulcanization degree of TPI component was controlled by changing the amount of sulfur in the dynamic vulcanization system. The strengthened cross-linked structure made the excellent characteristics of plastics and rubber fully demonstrated. Through a series experiments, the effect of dynamic vulcanization system on the thermodynamics and shape memory properties of TPI/HDPE hybrid SMPCs was revealed. The results show that the TPI/HDPE SMPCs with the sulfur content of 2% has the best thermodynamics and shape memory properties.

In this article, hybrid composite laminates with shape memory alloy (SMA) and glass fiber (GF) as the reinforced phase, and epoxy resin as the host material, were manufactured by vacuum-assisted resin injection (VARI) processing. The SMA wires were embedded into the GF/epoxy composites with three kinds of modes. The effect of SMA content and the position on the flexural, low-velocity impact performance of the hybrid composite laminates was investigated. It was found that the bonding performance between the SMA wire and the host material is the key factor that determined the final overall performance of the hybrid composite laminates in both the static and dynamics tests. Based on these experimental phenomenon, we further carried out the fiber pull-out experiment to improve the interfacial shear strength between the SMA and epoxy resin. It was found that the interfacial performance could be enhanced significantly by adding nanoparticles in the interface phase.

The traditional processing technology of shape memory polymer composites is complex and the cost of high performance filler is high. Therefore, low-cost high density polyethylene (HDPE) was introduced into trans-1,4-polyisoprene (TPI) matrix as reinforcing phase, and a novel shape memory polymer was prepared by mechanical melt blending, which fully exerted the excellent properties of plastic and rubber. Because of the difference in molecular chain distribution between different blend ratios of TPI/HDPE hybrid SMPCs specimens, the change of the blend ratio of the two components affects the thermodynamic and shape memory properties of the SMPCs. A series experimental results show that the TPI/HDPE hybrid SMPCs with the blend ratio of 80/20 has excellent thermodynamic and shape memory properties. And we believe that the relevant conclusions of this study can provide valuable design reference for the development of high-performance TPI SMPCs.