Showing papers by "Jinsong Leng published in 2018"
TL;DR: In this paper, the authors investigated the low-velocity impact responses of hybrid carbon/glass fiber reinforced polymer composites and found that a hybrid composite with surface carbon fiber layers would help minimize the risk of damage, in terms of the size of damage and deflection subject to an impact load.
Abstract: Hybrid Composites, made of two different types of high strength fibre cushioned with a relatively low strength matrix to meet specific strength requirements, have been recognized as modern materials for many engineering applications. They are lightweight and low cost as compared with using a single type of fibre to make structural components, which may be over-strength and not cost-competitive. Carbon fibre is extremely strong, contributing to a thin, light but strong structure. To a certain extent, it is too costly and induces a problem of structural instability due to the decrease of second moment of inertia as compared with the use of traditional metals for designing a structure. Hybrid composites are able to minimize aforementioned problems with a low cost solution to meet the requirements. However, the design of materials and structures becomes a key challenge on how to fully utilize the benefits of these fibre to make a structure strong enough to withstand different loads imposed on it. This project aims at experimentally investigating the low-velocity impact responses of hybrid carbon/glass fibre reinforced polymer composites. It was found that a hybrid composite with surface carbon fibre layers would help minimize the risk of damage, in terms of the size of damage and deflection subject to an impact load. However, failures by impactor penetration were observed on some samples. Severe damages were found on samples with surface glass fibre layers and carbon fibre in core. Images captured by the thermography technique demonstrated that localized damages (delamination) existed within plies in a failed sample, which normally cannot be detected by using traditional visual inspection techniques.
99 citations
TL;DR: In this paper, a shape recovery progression of 4D printed laminated Miura-origami tessellations and tubes under compressive load-induced unfolding and folding was investigated.
Abstract: Four-dimensionally (4D) printed origami structures have great potential for applications in actuators and reconfigurable devices by taking the advantages of 3D printing technology and shape memory polymers. This study focuses on the shape recovery progression of 4D printed laminated Miura-origami tessellations and tubes under compressive load-induced unfolding and folding. Recovery forces of the specimens are characterized by dynamic mechanical analysis (DMA) experiments. The shape recovery behavior and recovery force are significantly influenced by the shape recovery temperature and loading pattern. The high shape recovery capability of the specimens are signified by the shape recovery ratio of over 94% and volume changes of up to 289%. Lastly, the actuator application of a 4D printed laminated Miura-origami structure has been demonstrated.
82 citations
TL;DR: In this article, an integrative hinge fabricated by carbon fiber reinforced shape memory epoxy composites in the sequence of material selection, structure design and manufacture, material and structure experiments, and application is presented.
71 citations
TL;DR: A conductive shape memory polylactic acid (PLA) microfiber membrane was synthesized by combining electrospinning with chemical vapor polymerization and the low surface temperature is compatible with potential applications in many fields.
Abstract: Conductive shape memory polymers as a class of functional materials play a significant role in sensors and actuators. A high conductivity and a high response speed are needed in practical applications. In this work, a conductive shape memory polylactic acid (PLA) microfiber membrane was synthesized by combining electrospinning with chemical vapor polymerization. The shape memory PLA was electrospun into microfibers with different diameters, and a conductive polypyrrole (PPy) coating was applied to the PLA microfiber membranes using vapor polymerization. The conductivity of the microfiber membrane was investigated as a function of different experimental parameters: FeCl3 concentration, PPy evaporation time, and PPy temperature. The maximum conductivity of the membrane prepared in a sub-zero environment is 0.5 S/cm, which can sustain a heat-generating electric current sufficient to trigger the electro-actuated behaviors of the membrane within 2 s at 30 V. Thermographic imaging was used to assess the uniform...
43 citations
TL;DR: In this article, a thermoviscoelastic constitutive model incorporating uncoupled structure and stress relaxation is proposed to capture the material behavior for thermally induced amorphous shape memory polymers.
28 citations
TL;DR: In this paper, the effect of UV light exposure on thermomechanical properties and shape memory effect (SME) of the Styrene-based SMP and its Glass fibre shape memory polymer composites (SMPC) was investigated.
25 citations
TL;DR: In this article, a series of foldable buckypaper/polyacrylonitrile (BP/PAN) composite films were developed in a facile strategy based on electrospun and vacuum pressurized filtration methods.
Abstract: Herein, a series of foldable buckypaper/polyacrylonitrile (BP/PAN) composite films were developed in a facile strategy. This strategy was based on electrospun and vacuum pressurized filtration methods. The composite film had better mechanical properties than pristine BP via interface reinforcing, but not deprived of excellent conductivity. The maximum tensile strength and elongation at break of BP/PAN films were 1.45 and 11.65 times than pristine BP, respectively. Moreover, BP/PAN film had higher electromagnetic interference (EMI) shielding effectiveness (63.7–65 dB) in the Ku band (12–18 GHz) than pristine BP (34.3–42.9 dB), due to interfaces forming between PAN fibers and CNTs. The BP/PAN composite as a promising EMI shielding material could be utilized in military and civil applications, such as flexible antenna, EMI shielding clothes and soft portable electronic products.
24 citations
TL;DR: In this paper, a multi-branch thermoviscoelastic model based on fractional derivatives is proposed for the prediction of temperature-dependent free recovery behaviors of amorphous shape memory polymers (SMPs).
24 citations
TL;DR: In this article, a theoretical model of DE balloon, incorporating stiffening and damping effect, is developed, and numerical results, such as stretch-time curves, phase diagrams and Poincare maps, are presented to study the influence of stiffening on its dynamic performance.
Abstract: Dielectric elastomer (DE) balloon is a new type of actuator that can be used as high frequency pumps or loudspeakers. In this paper, a theoretical model of DE balloon, incorporating stiffening and damping effect, is developed. The numerical results, such as stretch–time curves, phase diagrams and Poincare maps, are presented to study the influence of stiffening and damping on its dynamic performance. Taking the damping effect into account, the DE balloon can reach the equilibrium state after attenuation when subject to an instantaneous constant voltage; subject to a ramping voltage, the dynamic response presents three obvious stages: steady deformation, snap-through or snap-back, and damped oscillation. Due to the strain stiffening, the DE balloon may have two different stable equilibrium states and each has its own natural frequency. With small perturbation energy, the DE balloon can oscillate steadily around the two equilibrium states and resonate at multiple excitation frequencies. With large perturbation energy, the steady oscillation may transform into chaos. The damping force, however, changes no matter steady or chaotic oscillation into a constant periodic oscillation, and also determines the oscillation position.
24 citations
TL;DR: In this article, a low colored and transparent shape memory copolyimide (SMcoPI) was obtained by suppressing the charge transfer complex interactions, and the optical transmittance of the synthesized SMcoPI film could reach at ∼86% at the wavelength of 450 nm.
21 citations
TL;DR: In this article, the authors investigated the behavior of delamination crack under applied axial quasi-static tensile load in glass fiber reinforced composite materials and found that the observed delamination damage propagation was in good agreement with FEA simulation results.
TL;DR: In this paper, a simple approach was used to fabricate ESMPs with the aim of improving their overall properties by introducing crosslinked carboxylic nitrile-butadiene nanorubber (CNBNR) into the ESMP network.
Abstract: Epoxy-based shape-memory polymers (ESMPs) are a type of the most promising engineering smart polymers. However, their inherent brittleness limits their applications. Existing modification approaches are either based on complicated chemical reactions or done at the cost of the thermal properties of the ESMPs. In this study, a simple approach was used to fabricate ESMPs with the aim of improving their overall properties by introducing crosslinked carboxylic nitrile–butadiene nanorubber (CNBNR) into the ESMP network. The results show that the toughness of the CNBNR–ESMP nanocomposites greatly improved at both room temperature and the glass-transition temperature (Tg) over that of the pure ESMP. Meanwhile, the increase in the toughness did not negatively affect other macroscopic properties. The CNBNR–ESMP nanocomposites presented improved thermal properties with a Tg in a stable range around 100 °C, enhanced thermal stabilities, and superior shape-memory performance in terms of the shape-fixing ratio, shape-recovery ratio, shape-recovery time, and repeatability of shape-memory cycles. The combined property improvements and the simplicity of the manufacturing process demonstrated that the CNBNR–ESMP nanocomposites are desirable candidates for large-scale applications in the engineering field as smart structural materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45780.
TL;DR: In this article, the authors fabricated nanocomposites consisting of epoxy-based shape memory polymer (ESMP) matrix and carbon nanofillers, which are all efficient microwave absorbing materials that can transform microwaves into heat energy.
Abstract: This study fabricated nanocomposites consisting of epoxy-based shape memory polymer (ESMP) matrix and carbon nanofillers. The nanofillers include zero-dimensional carbon black, one-dimensional multiwalled carbon nanotubes, two-dimensional (2D) graphene nanoplatelets, and three-dimensional (3D) functionalized graphene sheets, which are all efficient microwave-absorbing materials that can transform microwaves into heat energy. As a result, the temperatures of the nanocomposites increased more rapidly than pristine ESMP in microwaves. The functionalized graphene sheets were found to transform the microwaves into heat more efficiently than the other nanofillers. Possible microwave propagation paths in the nanocomposites were proposed. Moreover, the nanocomposites displayed significantly higher mechanical strengths than pristine ESMP. The low cost and strong nanocomposites with fast microwave responses may be applied as actuators or deployable devices in medical treatments. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45676.
TL;DR: In this paper, a broadband magnetic E-shape piezoelectric energy harvester with wide frequency bandwidth was described, based on a nonlinear electromechanical model.
Abstract: We describe in this work a broadband magnetic E-shape piezoelectric energy harvester with wide frequency bandwidth. We develop first a nonlinear electromechanical model of the harvester based on th...
TL;DR: In this article, a shape memory light-induced microfluidic technology is applied in preprogrammed micro-fluidic chip based on shape memory gold nanoparticles/poly (vinyl alcohol) nanocomposites.
Abstract: A shape memory light-induced microfluidic technology is applied in preprogrammed microfluidic chip based on shape memory gold nanoparticles/poly (vinyl alcohol) nanocomposites. The shape memory gold nanoparticles/poly (vinyl alcohol) nanocomposites display excellent light-induced shape memory property with recovery ratio of nearly 100% in visible light. The crosslinked network of light-induced shape memory gold nanoparticles/poly (vinyl alcohol) nanocomposites forms by aldol reaction, esterification, and/or hydrogen bonding of poly (vinyl alcohol), glutaraldehyde, and gold nanoparticles. The light-induced shape memory mechanism of shape memory gold nanoparticles/poly (vinyl alcohol) nanocomposites is based on photothermal effect of gold nanoparticles and shape memory effect of poly (vinyl alcohol)based shape memory polymer (SMP). In this report, a light-induced microfluidic microvalve is demonstrated based on the shape memory gold nanoparticles/poly (vinyl alcohol) nanocomposites. This research presents demonstration of the shape memory light-induced intelligent microfluidic chip. The light-induced SMP microfluidic microvalve would yield practical, physical, and technological advantages for disposable integrated microfluidic chip laboratories.
TL;DR: In this paper, a carbon nanotube filled silicone elastomer (SE) as DE composite and modeled its Mullins effect using the pseudo-elastic theory was combined to predict the idealized electromechanical softening behavior.
Abstract: Dielectric elastomer (DE) is a promising electroactive polymer. As DE material, rubbers are often filled with functional particles to improve their electromechanical performance. However, the filled particles also bring stress softening, which is known as Mullins effect. In this paper, we prepared the carbon nanotube filled silicone elastomer (SE) as DE composite and modeled its Mullins effect using the pseudo-elastic theory. Then, the thermodynamics of DE was combined to predict the idealized electromechanical softening behavior. Two cases are considered: linear dielectric and saturated dielectric. For linear dielectric with an initial force, “residual strain” will appear after every voltage-controlled cycle, and instability may be eliminated in reloading. For saturated dielectric, the material response changes a lot after saturation, which also affects the subsequent softening behavior. At last, viscoelasticity was further incorporated to account for rate-dependent softening deformation, and we also carried out some simple electromechanical experiments on VHB 4910 to explore its softening behavior. This work may lead to a better understanding of the softening behavior in DEs undergoing electromechanical coupling situations.
TL;DR: In this article, a shape memory polymer (SMP) mandrel with good shape retainability and recoverability was synthesized and examined by uniaxial tensile test and dynamic mechanical analysis test.
TL;DR: In this paper, the effects of γ-radiation on chemical structure, optical transmittance, shape memory behavior, thermomechanical property, thermal stability, and mechanical properties were investigated.
17 Jul 2018
TL;DR: The applications of SMP micro/nanofiber membranes in the brackets of bone tissue, bone tissue repair, nerve scaffolds and cell culture research, and analysis other structures used in the biomedical field are discussed.
Abstract: As a class of smart materials, shape memory polymers (SMPs) can remember the temporary shape and return to the original shape under the condition of the external stimuli. The shape memory micro/nanofibers prepared by electrospinning technology possess a three-dimensional structure which is similar to the natural extracellular matrix. Therefore, it shows great application prospect in the biomedical field, especially in tissue engineering. Moreover, shape memory micro/nanofiber membranes bring more and more opportunities for the rapid development of personalized and smart biomedical devices. This paper reviews of SMP micro/nanofiber membranes, including preparation, structure, morphology and driving methods. We also summarize the applications of SMP micro/nanofiber membranes in the brackets of bone tissue, bone tissue repair, nerve scaffolds and cell culture research. Furthermore, analysis other structures used in the biomedical field are discussed. Finally, we conclude the challenges and the perspectives of SMPs in the future.
TL;DR: In this article, the full-field displacement and strain of disc, beam and ring structures based on SMP and its composites were investigated by digital speckle correlation method, which is important for the comprehensive study of mechanical behavior and fabrication of SMP composites.
TL;DR: In this article, a facile strategy for cross-linked carbon nanotube film (CL-CNF) was carried out via self-assembly of CNTs, which was achieved based on esterification and acylation reactions of functional CNT.
TL;DR: In this article, a type of biocompatible composite foam with shape-memory property has been developed on the basis of cross-linked poly(ε-caprolactone) (PCL) and silk fibrin (SF).
Abstract: As we know, shape-memory foams with porous feature are better suited for a certain application compared with their solid counterparts, especially in tissue engineering, drug delivery, filtration, etc. In this study, a type of biocompatible composite foam with shape-memory property has been developed on the basis of biocompatible materials cross-linked poly(ε-caprolactone) (PCL) and silk fibrin (SF). Solid-state foaming method was used to fabricate the composite shape-memory foam. Hierarchical cellular foam with micropore on the cellular wall was observed. To optimize pore morphology, the relationship between cross-linking agent content/reinforcement filler content and PCL matrix was investigated. Excellent shape-recovery property (>97.6%) and shape-fixing property (>98%) have been achieved for PCL foam. For composite foams, SF addition is not too much effective on their shape-memory property by varying SF content. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46767.
02 Feb 2018
TL;DR: In this article, the shape memory properties of a carbon fiber reinforced shape memory epoxy composite have been investigated, such as tensile strength, Young's modulus, impact energy and hardness.
Abstract: In this study, the thermo-mechanical behaviour, shape memory characteristic and the mechanical properties such as tensile strength, Young’s modulus, impact energy and hardness of the carbon fibre reinforced shape memory epoxy composite have been investigated.