Trans-l,4-polyisoprene (TPI) shape memory polymer composites with different chopped carbon fiber mass fractions were prepared to study the effects of different chopped carbon fiber mass fractions and temperatures on the TPI shape memory polymer composites in this paper. While guaranteeing the shape memory effect of TPI shape memory polymers, the carbon fiber fillers also significantly enhanced the mechanical properties of the polymers. The thermodynamic properties and shape memory properties of TPI shape memory polymers were studied by a differential scanning calorimeter (DSC) test, dynamic mechanical analysis (DMA) test, thermal conductivity test, static tensile test, mechanical cycle test, thermodynamic cycling test and shape memory test. Furthermore, the tensile fracture interface of TPI shape memory polymer composites was analyzed by scanning electron microscopy. The experimental results show that when the chopped carbon mass fraction fiber is 8%, TPI shape memory polymers have good shape memory properties and the best mechanical properties.Keywords: polymer composite; mechanical properties; shape memory properties; thermodynamics IntroduceAs a new smart material having broad application space, according to differences of recovery stimulation, shape memory polymers (SMPs) can be divided into the following groups: thermo-responsive SMPs, chemo-responsive SMPs and photo-responsive SMPs [1-3]. Compared with shape memory alloys (SMAs), SMPs have done well in many aspects such as light weight, large recovery ability [4], excellent molding ability [5] and low cost [6]. In recent years, SMPs have been under development in some new fields such as functional clothing [7], information carriers [8,9], two-way actuators [10][11][12] and active assembly/disassembly [13]. Although there is a wide variety of SMPs, thermo-responsive SMPs are still the most basic and the most common SMP materials [14][15][16].The thermomechanical deformation process of SMPs is schematically shown in Figure 1. The thermomechanical deformation process of SMPs consists of the following steps: (1) heat and deform SMP above the transition temperature T trans ; (2) cool SMP until below T trans and remove the applying force; (3) heat the pre-deformed SMP above T trans and then it will recover to its original shape; (4) cool SMP below T trans with its original shape kept. A 3D stress-strain-temperature diagram illustrating the thermomechanical behavior of SMPs is shown in Figure 2 and the thermomechanical behavior of SMPs can be illustrated in four steps [17][18][19]. The first step (state A→B) is a high-temperature deformation state. At this step, the elastic modulus of the SMP is low, the fracture elongation is large, and some of the SMP material shows obvious viscoelastic properties. The second step (state B→C) is a

In this study, a thermodynamics viscoelastic constitutive model was developed to describe behaviors of the typical thermo-mechanical cycle experimentations. In this model, the changes of thermodynamic and mechanics for SMPs in cooling/heating process were described clearly and the irreversible deformations were calculated. A new type of microstructure of SMPs was proposed and new definitions of phases: active phase and frozen phase were set forth in the present study. The new thermodynamics viscoelastic model is series by two parts: mechanical parts and thermal parts. A new transform equation for the transformation of frozen phase was proposed, and the transform delay time and cooling/heating rate were considered in this transform equation. A transform equation based on the transformation of frozen phase was proposed to describe the change of thermal expansion coefficient of SMPs. Finally, the typical thermo-mechanical cycle experimentation processes were calculated using the new thermodynamics viscoelastic constitutive model. Through the comparison between the calculated results and experimental results, the rationality and accuracy of the new thermodynamics viscoelastic constitutive model was finally verified.

The state of charge (SOC) of lithium-ion batteries reflects their remaining capacity. Accurate estimation of SOC helps battery safety and is beneficial to the efficient management of batteries. The charging and discharging processes of lithium-Ion batteries are very complicated, and it is difficult to obtain accurate SOC estimation results. Therefore, it is important to study improved algorithms for SOC estimation for this nonlinear non-Gaussian battery system. In this paper, we propose an unscented H-infinity filter (UHF) based SOC estimation method, which combines the advantages of both the unscented Kalman filter (UKF) and the H-infinity filter (HF). The UKF propagates the sigma points through the nonlinear system and does not need the first-order linear approximation of the system equation, while the HF can suppress the non-Gaussian noise in the system to the greatest extent. The proposed UHF based SOC estimation algorithm is verified and evaluated in the battery management system, and further optimized in practical problems. Experimental results show that the proposed UHF based algorithm can perform accurate SOC estimation for lithium-ion batteries, and is superior to the UKF based SOC estimation. Keywords Index terms-unscented kalman filterer • H-infinity filter • State of charge* Zhiwei He

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In this work, we have synthesized a novel graphene oxide/trans-1,4-polyisoprene (GO/TPI) shape memory polymer (SMP) nanocomposite by adding GO (0.0-1.5 phr) to bulk TPI polymer to enhance its mechanical properties. We have studied and examined its mechanical, thermal and thermomechanical properties through systematic tests from microscale to macroscale. The shape memory properties and the effect of the GO content on the thermal and mechanical properties of the manufactured SMP nanocomposites were studied by differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, thermal conductivity, and static tensile and mechanical as well as thermomechanical cyclic loading tests. The experimental results indicate that the SMP nanocomposite with 0.9 phr GO has superior thermal and mechanical properties compared to all other cases, and good shape memory was obtained in the GO/TPI nanocomposites.

It is of great importance to decode motion dynamics of the human limbs such as the joint angle and torque in order to improve the functionality and provide more intuitive control in human-machine collaborative systems. In order to achieve feasible prediction, both the surface electromyography (sEMG) and A-mode ultrasound were applied to detect muscle deformation and motor intent. Six abled subjects were recruited to perform five trails elbow isokinetic flexion and extension, and each trail contained five repetitions, with muscle deformation and sEMG signals recorded simultaneously. The experimental datasets were categorized as: the ultrasound-EMG combined datasets, ultrasound-only datasets and EMG-only datasets. The support vector machine (SVM) regression model was developed for both elbow joint angle and torque prediction, based on the above three kinds of datasets. The root-mean-square error (RMSE) and the correlation coefficients (R) were applied to evaluate the prediction accuracy. The results across all the subjects for different datasets indicated that the combined datasets and the ultrasound datasets were superior to the sEMG datasets both on elbow joint angle and torque prediction, and there were no significant differences between the combined datasets and the ultrasound datasets. It turns out that elbow angle and torque can be reconstructed by Amode ultrasound, and the significant findings pave the way towards the application of musculature-driven human-machine collaborative systems.Angle, torque, surface electromyography (sEMG), ultrasound, support vector machine (SVM), regression, isokinetic contraction.

In this paper, a new hyperchaotic system is constructed by introducing an additional state variable into the third-order Lorenz system. Some basic properties, including dissipativity, equlibria, stability and Hopf bifurcation, of this hyperchaotic system are analyzed in detail, and the bifurcation routes to hyperchaos from periodic, chaotic evolutions are observed. The existence of hyperchaos is verified with Lyapunov exponent spectrum. Moreover, an analog electronic circuit is designed, and various hyperchaotic attractors of this system are observed from the circuit experiments.

Filler/matrix interfacial cohesion exerts a straightforward effect on stress transfer at the interface in composite structures, thereby significantly affecting their integrated mechanical properties.