Rongguo Wang

Super‐Stretchable Spring‐Like Carbon Nanotube Ropes

Spring-like carbon nanotube ropes consisting of perfectly arranged loops are fabricated by spinning single-walled nanotube films, and can sustain tensile strains as high as 285%.

Synthesis and characterization of a new hierarchical reinforcement by chemically grafting graphene oxide onto carbon fibers

We proposed a new hierarchical reinforcement consisting of graphene oxide (GO) and carbon fibers (CF). It was confirmed that GO was chemically grafted onto CF via poly(amido amine) dendrimers. The GO grafting significantly changes the surface configuration of CF. The new hierarchical reinforcement has the potential to be applied in high performance polymer matrix composites.

Preparation of MoO3 QDs through combining intercalation and thermal exfoliation

Lots of top-down approaches by weakening the van der Waals interaction between adjacent layers and breaking up the covalent chemical bonds in each layer have been reported to prepare QDs of layered materials due to the stacked structures. However, much attention has been focused on graphene and layered transition-metal dichalcogenides (TMDs), seldomly on layered transition-metal oxides (TMOs). Herein, a modified top-down method combining intercalation and thermal exfoliation is reported to prepare high-yield QDs of layered MoO3. Alkylamine was first intercalated into MoO3 layers to weaken the van der Waals forces. Then, the covalent bonds in each MoO3 layer were broken down under a sudden increase in gas pressure generated by the decomposition of alkylamines after rapid heating. These fractured particles were further incised to QDs by sonication. The as-prepared MoO3 QD dispersion showed a plasmon resonance after simulated solar light illumination. Surprisingly, their plasmon peak red shifted with an extended illumination time, which was different from the reported MoO3 nanosheets. This reported method is expected to extend to other QDs of layered materials providing that their bulk materials can also be intercalated.

Surface Modification of Poly(urea-formaldehyde) Microcapsules and the Effect on the Epoxy Composites Performance

The surfaces of poly(urea-formaldehyde) (PUF) were modified by γ -glycidoxypropyltrimethoxy silane (KH560) in order to improve the interfacial bonding between self-healing PUF microcapsules and epoxy matrix. The modification mechanism between PUF microcapsules and KH560 was studied. X-ray photoelectron spectra (XPS) analyses showed that the silane coupling agent molecular binds strongly to the surfaces of PUF microcapsules. Chemical bond (Si–O–C) and hydrogen bond were formed at interface by the reaction between Si–OH and the hydroxyl group of PUF microcapsules surface. The tensile and impact resistance tests revealed that strength and toughness of the composites was improved significantly. Furthermore, scanning electronic microscopy (SEM) photographs of the fractured surface confirmed that the silane coupling agent plays an important role in improving the interfacial performance between microcapsules and resin matrix.

Multiscale Carbon Nanotube-Carbon Fiber Reinforcement for Advanced Epoxy Composites with High Interfacial strength

In this study, carbon nanotubes were chemically grafted on carbon fibers using PAMAM functionalization. Single-fiber composites with the carbon nanotube/carbon fiber (CNT/CF) multi-scale reinforcement were fabricated to examine the influence of local nanotube reinforcement on load transfer at the fiber/matrix interface. Molecular simulations of the epoxy resin composites with a CNT/CF multi-scale reinforcement and an unsized CF were performed employing Materials Studio 4.0 software. Results show that the interfacial shearing strength (IFSS) of the CNT/CF composite is up to 116.98 MPa, an increment of 170% in comparison with that of the unsized T300 CF composite. The results of molecular simulations show that interaction energy of CNT/CF multi-scale composite is up to 929.83 kcal/mol, which is 2.7 times higher than that of the unsized one. This significant enhancement of interfacial shear strength can be attributed to two aspects: (i) Van der Waals binding and mechanical interlocking increase due to the CNTs addition, (ii) chemical bonding and surface wetting increase caused by the layer of PAMAM dendrimers.

Effect of thermal‐oxidative aging on carbon fibre‐bismaleimide composites

Purpose – The purpose of this paper is to investigate the effect of thermal‐oxidative aging at 150°C on the mechanical properties of carbon fibre reinforced bismaleimide composites.Design/methodology/approach – Composites specimens after thermo‐oxidative aging at 150°C for various times (up to 1,000 h) were investigated by scanning electron microscopy (SEM) for fracture morphology, Fourier transform infrared (FTIR) spectroscopy for chemical structures, and flexural strength test and inter‐laminar shear strength (ILSS) test for mechanical properties.Findings – The results indicated that the mechanical properties of carbon fibre/BMI composites were affected significantly by testing temperature rather than by aging time. SEM results showed that the good adhesion of fibre and matrix resulted in the better mechanical properties. The composites showed lower flexural strength and ILSS at 150°C due to the viscoelastic behaviour of matrix resin. The FTIR spectra confirmed the decomposition of crosslinked maleimide...

Dome Thickness Prediction of Composite Pressure Vessels by a Cubic Spline Function and Finite Element Analysis

Nowadays, finite element analysis (FEA) plays an important role in the design of composite pressure vessel. The more accurate finite element models are created, the more precise results could be obtained. In order to create the accurate finite element model for composite pressure vessels, a cubic spline function was developed to predict the dome thickness basing on the principle of total volume preservation of all bands at dome section. In the paper, the dome thickness of an arbitrary composite pressure vessel was forecasted by the cubic spline function and compared with the existing methods and actual measured values. The results show that the cubic spline function is more realistic than the other methods. Then the FEA considering the dome thickness pre-calculated by various methods was performed and compared with experimental data. The results further indicate that the cubic spline function could provide a more accurate model, which is approaching the real case.

A biomimetic, multifunctional, superhydrophobic graphene film with self-sensing and fast recovery properties for microdroplet transportation

Recently, multifunctional superhydrophobic surfaces with high adhesion behavior have attracted much attention for microdroplet transportation. Here, we report for the first time a multifunctional, rose-petal-like, superhydrophobic graphene film via the self-assembly of graphene oxide (GO) that has self-sensing and fast recovery properties for microdroplet transportation. This superhydrophobic film does not require a hydrophobic coating and has a micro-nanoscale hierarchical structure. Because of its structure, our biomimetic, superhydrophobic film has high adhesive force to water droplets and can be used as a medium for microdroplet transportation. In addition, because the film was constructed using pure graphene, it has excellent conductivity properties and an immediate response system is also built to detect potential damage. Moreover, owing to the gas sensing properties of graphene, our film has self-sensing properties where the resistance of the film increases gradually when water droplets are close to it. Whats more, the film has an ultra-fast Joule heating rate of 18 °C s−1. Based on these properties, the recovery time for the resistance of the film can be reduced by 57.7% for water droplet transportation. Therefore, our multifunctional, superhydrophobic graphene film can be used for smart microdroplet manipulation in the future.

Preparation and Characterization of Self-healing Polymeric Materials with Microencapsulated Epoxy and Imidazoline Derivatives Curing Agent

Binary self-healing system consisting of epoxy-containing microcapsules and latent curing agent based on anionic polymerization was investigated. When cracks propagated in the composites, the embedded microcapsules would be damaged and the epoxy healing agent would be released. The latent curing agent used in this study can be well dispersed in epoxy matrix during composites manufacturing, and hence activate the released epoxy wherever it is. As a result, self-healing of the cracked sites is successfully achieved through curing of the released epoxy healing agent. This paper also investigated the preparation and performance of microcapsules synthesized by situ polymerization. The mechanism of anionic chain polymerization between epoxy and curing agent was investigated. On the basis of this work, self-healing ability of the epoxy filled with the healing system was evaluated. It was found that the distribution of microcapsules and latent curing agent greatly influences the healing efficiency but not the stoichiometric composition, and the optimal weight ratio of microcapsules and curing agent 2MZ-AZINE are 15 wt.% and 2 wt.%, offering a ~83% healing efficiency.

Photothermal healing of a glass fiber reinforced composite interface by gold nanoparticles

The formation of microcracks especially in the interfacial region is a critical problem for fiber reinforced composites. Repairing the microcracks before catastrophic failure of the materials takes place is a promising solution to achieve long lifetime operation. In this context, a novel method is demonstrated for interfacial healing of glass fiber reinforced composites using the photothermal effect of gold nanoparticles (Au NPs). Au NPs were successfully dispersed into the interfacial region of a glass fiber reinforced composite. Once the interfacial damage occurred, a laser could be used to illuminate Au NPs to generate a large amount of heat through the photothermal effect. This would melt the resin and form mechanical interlocking between the fiber and PMMA to create a new interface. It has been confirmed by a micro bond test that the composite containing Au NPs has healing ability with a maximum healing efficiency of 98.5% under optimized conditions. The mechanism of the interfacial healing was also investigated and it is found that the density of Au NPs and irradiation intensity play key roles in the healing process.