Haibao Lv

Fiber reinforced shape-memory polymer composite and its application in a deployable hinge

This paper investigates the shape recovery behavior of thermoset styrene-based shape-memory polymer composite (SMPC) reinforced by carbon fiber fabrics, and demonstrates the feasibility of using an SMPC hinge as a deployable structure. The major advantages of shape-memory polymers (SMPs) are their extremely high recovery strain, low density and low cost. However, relatively low modulus and low strength are their intrinsic drawbacks. A fiber reinforced SMPC which may overcome the above-mentioned disadvantages is studied here. The investigation was conducted by three types of test, namely dynamic mechanical analysis (DMA), a shape recovery test, and optical microscopic observations of the deformation mechanism for an SMPC specimen. Results reveal that the SMPC exhibits a higher storage modulus than that of a pure SMP. At/above Tg, the shape recovery ratio of the SMPC upon bending is above 90%. The shape recovery properties of the SMPC become relatively stable after some packaging/deployment cycles. Additionally, fiber microbuckling is the primary mechanism for obtaining a large strain in the bending of the SMPC. Moreover, an SMPC hinge has been fabricated, and a prototype of a solar array actuated by the SMPC hinge has been successfully deployed.

Electroactivate shape-memory polymer filled with nanocarbon particles and short carbon fibers

In addition to the fabrication of shape-memory thermoset polymer nanocomposites filled with conductive nanoparticles and fiber fillers, this paper is focused on factors which would influence the electrical property of this type of material. It is shown that the particulate additives are dispersed homogeneously within the matrix and served as interconnections between the fibers, while the fibrous additives act as long distance charge transporter by forming local conductive paths. The electrical conductivity of the nanocomposite which contains 5wt% carbon nanoparticles and 2wt% short carbon fiber is 2.32S∕cm by four-point van der Pauw method, and can be induced by 24V voltages.

Synergic effect of carbon black and short carbon fiber on shape memory polymer actuation by electricity

This paper presents a study on the effect of carbon black (CB) and short carbon fibers (SCFs) on shape memory polymer (SMP) actuation by applying electric current. The coexistence of CB and SCF electrically conductive networks, supporting each other, resulting in significant improvement of electrical properties, was supported by optical microscopy, while the roles of particulate and fibrous fillers were distinguished by scanning electron microscopy. In sequence, the volume resistivity curves of one filler systems and two fillers systems were figured out and compared. Moreover, experimental results substantiated that the actuation voltage of two-filler SMP composites’ shape recovery was prominently lower in comparison with that of one-filler systems at the same filler content. Additional, the response of glass transition temperature (Tg) and thermomechanical properties to filler content and two fillers’ synergic effect were characterized and illuminated experimentally.

Electrospun silica/nafion hybrid products: mechanical property improvement, wettability tuning and periodic structure adjustment

The sol–gel process and electrospinning were used to fabricate a series of silica/Nafion electrospun hybrid products with no aggregation of the inorganic component. The excellent flexibility of the as-obtained silica/Nafion non-woven membrane and a single hybrid fiber was demonstrated and compared with the brittleness of pure electrospun silica membrane. The difference in wettability between the electrospun silica/Nafion hybrid product and bulk aqueous sol could be caused by the molecular orientation of Nafion during the electrospinning process. The hydrophobic behaviour, improved mechanical performance and good thermal stability made the silica/Nafion hybrid membrane a good candidate for oil–water separation. One-dimensional periodic structures still formed in silica/Nafion hybrid products with a lower Nafion content, although they disappeared completely at a higher Nafion content.

Electro-induced shape-memory polymer nanocomposite containing conductive particles and short fibers

This present paper is focused on the effect of conductive particulate and fibrous fillers on the characterized property of styrene-based shape memory polymer incorporating carbon black (CB) and short carbon fiber (SCF). It was shown that the particulate additives are dispersed homogeneously within matrix and served as interconnections between the fibers, while the fibrous additives may be considered as a rigid long aggregate of carbon, leading to easy formation of continuous conductive networks. The glass transition temperature of nanocomposites drops sharply as compared with that of pure SMP from the differential scanning calorimetry (DSC). For the composite containing 5 wt% CB and 2 wt% SCF, the storage modulus increases by 16.2% compared to that of the composite containing 5 wt% CB and 1 wt% SCF; the peak of tangent delta curve is an alternative definition of Tg, thus Tg defined in such a way is determined as 69.44°C from Dynamic Mechanical Analyzer (DMA) test which is higher than 25.78°C obtained from DSC test. The electrical conductivity of the composite achieves 3 S/cm by four-point Van De Pauw method, and the shape recovery can be activated with a constant voltage of 25 V through them.

Investigation of mechanical and conductive properties of shape memory polymer composite (SMPC)

This paper is concerned about an investigation of mechanical and electrical conductive properties of carbon fiber fabric reinforced shape memory polymer composite (SMPC). The shape memory polymer (SMP) is a thermoset styrene-based resin. SMP is a promising smart material, which is under intensive investigation at present. Its primary advantages over other smart materials are the high strain capacity (200% reversible strain), low density and low cost etc.. But its major drawbacks are low strength, low modulus and low recovery stress. So the fiber reinforced SMPC was naturally considered to be investigated in this paper, which may overcome the disadvantages mentioned above. The investigation was conducted with experimental methods: Dynamic Mechanical Analyzer (DMA), static and mechanical cycle loading tests, microscope observation of microstructural deformation mechanism, conductivity and shape recovery tests. Results indicated that SMPC showed higher glass transition temperature (Tg) than neat SMP and improved the storage modulus, bending modulus, strength and resistance against relaxation and creep. Both fiber microbuckling and fracture of SMPC were observed after the static 3-ponit bending test at the constant room temperature. SMPC showed favorable recovery performances during thermomechanical cycles of the bending recovery test and the fiber microbuckling was obvious. Moreover, the conductive SMPC of this study experienced low electrical resistivity and performed a good shape memory effect during numerous thermomechanical cycles.

Electro-activate styrene-based shape memory polymer nanocomposite filled with multi-walled carbon nanotubes

The fabrication and characterization, especially mechanical and electrical properties, of styrene-based shape memory polymer mixed with multi-walled carbon nanotubes (MWNTs) are presented in this paper. It is found that surface-modified MWNTs incorporated very well with resin processed by royal water, and dispersion was achieved by high-energy sonication in the solution. Scanning Electron Microscope (SEM) is shown that the particulate additives were dispersed homogeneously within matrix and served as local conductive paths. The glass transition temperature (Tg) of the composite containing MWNTs is lower than that of the pure SMP obtained from Differential Scanning Calorimetry (DSC). With the increasing filler content, resulting in the reduction of Tg increases. The composites have a better thermodynamic stability awarding to the results of Thermal Gravity Analyzer (TGA). The vibration of MWNTs in composite system was obtained from Raman spectrums. For the mechanical property of SMP composite with 8 wt% MWNTs, its Youngs modulus increases by 12.1% and the tensile strength by 8.1% as compared with that of the pure SMP. Four-point Van De Pauw method is introduced to investigate the electrical property of composites. An electrical conductivity of 1.25×10-3 S/cm is obtained for 8 wt% MWNTs composite.

Shape memory polymer composite and its application in deployable hinge for space structure

This paper is concerned about the basic properties of deployment for shape memory polymer composite (SMPC) and its application in deployable hinge for space structure. Shape-memory polymers (SMP) are an emerging class of active polymers that have dual-shape capability. One of another advantage, compared with other traditional material hinge, the SMPC carpenter type hinge is that it will not produce a large shock when it spring into the deployed position. There are several kinds of shape memory polymer composite (fiber reinforced, powder reinforced, etc,). Epoxy SMPs, carbon fibre fabric reinforced SMPC was introduced in this work. In order to investigate the basic performances of SMPC hinge, the experimental methods are used as follows: dynamic mechanical analysis (DMA), three point bending test and the radio of shape recovery. In the end, the structure of the carpenter type hinge is introduced. The carpenter type hinge is one mechanism that has the advantage of high-reliability of the deployment; light weighted, and low cost. This SMPC carpenter type hinge performs good deployment performances during numerous thermomechanical cycles. So the potential applications for such materials as active medical devices are highlighted.

Mechanical properties and shape memory effect of short fiber reinforced SMP composite

By adding randomly distributed short fiber into a shape memory polymer (SMP) matrix, both the mechanical properties and the shape memory behavior are improved significantly, overcoming some traditional defects of SMP composite reinforced by long fiber and particles. In this paper, the short fiber reinforced SMP composite are developed for the improvement of the mechanical and thermal properties of styrene-based SMP bulk. The specimens with different chopped fiber weight fractions are prepared, and then their mechanical behavior and electrical properties are investigated. As a result, the resistance against mechanical and thermal mechanical loads in the developed materials increases due to the role of reinforcement fiber. For the conducting composite filled with short carbon fiber, not only the actuation of SMP composite can be driven by low voltage, but also its tensile, bending strength, glass transition temperature, storage modulus and thermal conductivity increase by a factor of filler content of carbon fiber increasing. The results show meaningful guidance for further design and the performance evaluation of such composite materials.