Jinsong Leng

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.

Synergistic effect of carbon nanofiber and carbon nanopaper on shape memory polymer composite

The present work studies the synergistic effect of carbon nanofiber (CNF) and carbon nanopaper on the shape recovery of shape memory polymer (SMP) composite. The combination of CNF and carbon nanopaper was used to improve the thermal and electrical conductivities of the SMP composite. The carbon nanopaper was coated on the surface of the SMP composite in order to achieve the actuation by electrical resistive heating. CNFs were blended with the SMP resin to improve the thermal conductivity to facilitate the heat transfer from the nanopaper to the underlying SMP composite to accelerate the electroactive responses.

Analysis and manufacture of an energy harvester based on a Mooney-Rivlin?type dielectric elastomer

We studied a typical failure model of a Mooney-Rivlin–type silicone energy harvester, illustrated the allowable area under equal-biaxial and unequal-biaxial conditions, calculated the energy generated in one cycle of an energy harvester, designed a new harvester, and conducted its primary tests. When the ratio between principal planar stretches p=1 (λ2=pλ1) and the material constant ratio k=0.1 (C2=kC1), the energy density generated by the harvester is 6.81 J/g. We think that these results can be used to facilitate the design and manufacture of dielectric elastomer energy harvesters.

Effect of a linear monomer on the thermomechanical properties of epoxy shape-memory polymer

The effect of a linear monomer on thermomechanical properties and shape recovery behavior of an epoxy shape-memory polymer is studied. These shape-memory polymers are prepared from epoxy base resin, hardener and linear epoxy monomer. As the content of the linear monomer increases, the glass transition temperature (Tg) determined using differential scanning calorimetry ranges from 37 to 96 °C. A decrease in rubber modulus is seen from dynamic mechanical analysis for the polymers, which reveals decreasing crosslink density with increasing linear monomer content. Tensile test results show that the elongation at break and strength depends on the content of linear monomer at Tg or Tg−20 °C, while the linear monomer content has minor influence on elongation at break and strength at Tg+20 °C. Finally, investigation on shape recovery behavior reveals that full recovery can be observed for each polymer when the temperature is equal to or above Tg. Also, increasing the linear monomer content results in a decrease in both shape recovery ratio (below Tg) and shape recovery speed (at Tg). These results are interpreted in terms of various crosslink densities attributed to the increasing linear monomer content.

Carbon nanotube chains in a shape memory polymer/carbon black composite: To significantly reduce the electrical resistivity

Instead of individually aligned along the external electric field, the carbon nanotubes (CNTs) were electrically induced into aligned chains in a shape memory polymer (SMP)/carbon black (CB) composite, which would serve as long-distance conductive channels to bridge the CB aggregations. Compared with SMP composites with randomly filled CNTs, the electrical resistivity in those with chained CNTs was reduced for more than 100 times. The fabricated conductive SMP composites could be actuated by a low electrical power.

Optimization of superstructured fiber Bragg gratings for microwave photonic filters response

The microwave photonic responses of superstructured fiber Bragg gratings in combination with dispersive fiber are investigated theoretically and experimentally. The superstructured gratings are optimized, taking account of the spectral response of the broad-band source, erbium-doped fiber amplifier, and optical tunable filter to achieve a filter response with sidelobe suppression of more than 60 dB.

A new method for microwave generation and data transmission using DFB laser based on fiber Bragg gratings

A novel architecture for microwave/millimeter-wave signal generation and data modulation using a fiber-grating-based distributed feedback laser has been proposed in this letter. For demonstration, a 155.52-Mb/s data stream on a 16.9-GHz subcarrier has been transmitted and recovered successfully. It has been proved that this technology would be of benefit to future microwave data transmission systems

High performance microwave photonic response of superstructured fibre Bragg grating with designed apodisation function

The microwave photonic responses based on the superstructure fibre Bragg gratings with designed apodisation profile are investigated. The rejection level of more than 60 dB for a bandpass filtering response is demonstrated.