Synthesis and fractionated crystallization of organic-inorganic hybrid composite materials from an amphiphilic polyethylene-block-poly (ethylene oxide) diblock copolymer

Mesostructurally ordered inorganic–organic hybrid composite materials were successfully synthesized by utilizing a low-molecular-weight amphiphilic polyethylene-block-poly(ethylene oxide) (PE–PEO) diblock copolymer as the directing agent. The hybrid composites were formed via the sol–gel reaction of inorganic precursor tetraethoxysilane (TEOS) in an acidic ethanol/water solution with various amounts of PE–PEO. In these composite materials, the hydrophobic PE block of the PE–PEO copolymer forms separate microphase on the nanoscales within the rigid matrix of silica network. The crystallization of the PE block is strictly restricted within the microphase by the rigid silica matrix and takes place through homogeneous nucleation under the nanoscale confinement environment.

Glass/carbon fibre hybrid composite laminates for structural applications in automotive vehicles

Light-weight structure is one of the keys to improve the fuel efficiency and reduce the environmental buden of transport vehicles (automotive and rail). While fibreglass composites have been increasingly used to replace steel in automotive industry, the adoption rate for carbon fibre composites which are much lighter, stronger and stiffere than glass fibre composites, remains low. The main reason is the high cost of carbon fibres. To further reduce vehicle weight without excessive cost increase, one technique is to incorporate carbon fibre reinforcement into glass fibre composites and innovative design by selectively reinforcing along the main load path. Glass/carbon woven fabrics with epoxy resin matrix were utilised for preparing hybrid composite laminates. The in-plane mechanical properties such as tensile and three-point-bending flexural properties were investigated for laminates with different carbon fibre volume and lay-up scheme. It is shown that hybrid composite laminates with 50% carbon fibre reinforcement provide the best flexural properties when the carbon layers are at the exterior, while the alternating carbon/glass lay-up provides the highest compressive strength.

Promoted water transport across graphene oxide-poly(amide) thin film composite membranes and their antibacterial activity

Hybrid composite membranes have great potential for desalination applications since water transport can be favorably promoted by selective diffusion at the interface between matrix and reinforcement materials. In this paper, graphene oxide nano-sheets were successfully incorporated across 200nm thick poly(amide) films by interfacial polymerization to form novel thin-film composite membranes. The impact of the graphene oxide on the morphology, chemistry, and surface charge of the ultra-thin poly(amide) layer, and the ability to desalinate seawater was investigated. The graphene oxide nano-sheets were found to be well dispersed across the composite membranes, leading to a lower membrane surface energy and an enhanced hydrophilicity. The iso-electric point of the samples, key to surface charge repulsion during desalination, was found to be consistently shifted to higher pH values with an increasing graphene oxide content. Compared to a pristine poly(amide) membrane, the pure water flux across the composite membranes with 0.12wt.% of graphene oxide was also found to increase by up to 80% from 0.122 to 0.219L·μm·m-2·h-1·bar-1 without significantly affecting salt selectivity. Furthermore, the inhibitory effects of the composite membrane on microbial growth were evaluated and the novel composite membranes exhibited superior anti-microbial activity and may act as a potential anti-fouling membrane material.

Souvenirs of the senses

CFRP-Steel hybrid retrofitting of steel-concrete composite structures

Carbon fiber reinforced polymer (CFRP) is found to be an effective material for the retrofitting of both reinforced concrete (RC) and steel structures. However, retrofitting such structures using CFRP alone is shown to exhibit a premature failure due to early de-bonding of the CFRP laminates from the hosting sur-faces. On the other hand, steel plates are also used separately for the steel and RC structures. However, steel plates usually add the self-weight to the structures whereas CFRP is known for its high strength to weight ra-tio. In the present study, the advantages of both steel plates and CFRP is used to form a hybrid retrofitting sys-tem that is able to withstand the existing load to prevent the failure of the structures. In order to improve the retrofitting efficiency of a steel-concrete composite structures, an experimental investigation is carried out to examine the use of effectiveness of CFRP-steel hybrid retrofitting system.

Recent advances of finite elements for laminated composite plates

A large amount of finite elements have been developed for finite element analysis of laminated composite plates. The laminated plate theories are reviewed and summarized in this paper. The focus of this review is on the recently developed laminated finite elements since 1990. The 2-D triangular and quadrilateral displacement-based and mixed/hybrid-based finite element models, which were developed based on the first-order shear deformation theories, the higher-order shear deformation theories, the zig-zag theories and the global-local higher-order deformation theories, and the layer-wise laminated plate theories are reviewed in this paper and also their related patents. Finally, some points on the development of the laminated finite elements are summarized.

Sulfur-impregnated, sandwich-type, hybrid carbon nanosheets with hierarchical porous structure for high-performance lithium-sulfur batteries

Sandwich-type hybrid carbon nanosheets (SCNMM) consisting of graphene and micro/mesoporous carbon layer are fabricated via a double template method using graphene oxide as the shape-directing agent and SiO2 nanoparticles as the mesoporous guide. The polypyrrole synthesized in situ on the graphene oxide sheets is used as a carbon precursor. The micro/mesoporous strcutures of the SCNMM are created by a carbonization process followed by HF solution etching and KOH treatment. Sulfur is impregnated into the hybrid carbon nanosheets to generate S@SCNMM composites for the cathode materials in Li-S secondary batteries. The microstructures and electrochemical performance of the as-prepared samples are investigated in detail. The hybrid carbon nanosheets, which have a thickness of about 10-25 nm, high surface area of 1588 m2 g-1, and broad pore size distribution of 0.8-6.0 nm, are highly interconnected to form a 3D hierarchical structure. The S@SCNMM sample with the sulfur content of 74 wt% exhibits excellent electrochemical performance, including large reversible capacity, good cycling stability and coulombic efficiency, and good rate capability, which is believed to be due to the structure of hybrid carbon materials with hierarchical porous structure, which have large specific surface area and pore volume.

Shape morphing in fibre reinforced composite beams containing NiTi

The present research investigates the design, activation and modelling of a new generation of hybrid materials; called shape memory alloy-composites. These hybrid materials exhibit reversible bending motion with a temperature change and have the potential to be employed in aerospace, automotive and robotic application.

Investigation of hybrid ion-exchange membranes reinforced with non-woven metal meshes for electro-dialysis applications

Salt and solvent permeations across ion-exchange membranes used in electro-dialysis are directly related to the membrane material structure and chemistry. Although primarily used for aqueous effluents desalination, electro-dialysis was recently shown to be a promising technology for industrial wastewater and co-solvent mixtures purification. The harsh working conditions imposed by these liquid effluents, including high suspended solids, require the development of more chemically and mechanically resistant membranes. In this study, commercial porous stainless steel media filters (240 μm thick) were used as a backbone to prepare hybrid ion-exchange membranes by casting ion-exchange materials within the porous metal structure. The surface of the metal reinforcements was modified by plasma treatment prior to sol-gel silane grafting to improve the interface between the metal and the ion-exchange resins. The morphology of novel hybrid materials and the interface between the metal fibers and the ion-exchange material have been characterized using techniques such as scanning electron microscopy and FTIR mapping. The thickness of the silane coating was found to lie between 1 and 2 μm while water contact angle tests performed on membrane surfaces and corrosion test behaviors revealed the formation of a thin passivating oxide layer on the material surfaces providing anchoring for the silane grafting and adequate surface energy for the proper incorporation of the ion-exchange material. The hybrid membranes desalination performance were then tested in a bench top electro-dialysis cell over a range of flow rate, current densities and salt concentration conditions to evaluate the ability of the novel hybrid materials to desalinate model streams. The performance of the hybrid membranes were benchmarked and critically compared against commercially available membranes (Selemion™). Although the salt transfer kinetics across the hybrid ion-exchange composite membranes were shown to be comparable to that of the commercial membranes, the low porosity of the stainless steel reinforcements, around 60%, was shown to impede absolute salt permeations. The hybrid ion-exchange membranes were however found to be competitive at low current density and low flow velocity desalination conditions.

Investigation of hybrid ion-exchange membranes reinforced with non-woven metal meshes for electro-dialysis applications

Salt and solvent permeations across ion-exchange membranes used in electro-dialysis are directly related to the membrane material structure and chemistry. Although primarily used for aqueous effluents desalination, electro-dialysis was recently shown to be a promising technology for industrial wastewater and co-solvent mixtures purification. The harsh working conditions imposed by these liquid effluents, including high suspended solids, require the development of more chemically and mechanically resistant membranes. In this study, commercial porous stainless steel media filters (240. μm thick) were used as a backbone to prepare hybrid ion-exchange membranes by casting ion-exchange materials within the porous metal structure. The surface of the metal reinforcements was modified by plasma treatment prior to sol-gel silane grafting to improve the interface between the metal and the ion-exchange resins. The morphology of novel hybrid materials and the interface between the metal fibers and the ion-exchange material have been characterized using techniques such as scanning electron microscopy and FTIR mapping. The thickness of the silane coating was found to lie between 1 and 2. μm while water contact angle tests performed on membrane surfaces and corrosion test behaviors revealed the formation of a thin passivating oxide layer on the material surfaces providing anchoring for the silane grafting and adequate surface energy for the proper incorporation of the ion-exchange material. The hybrid membranes desalination performance were then tested in a bench top electro-dialysis cell over a range of flow rate, current densities and salt concentration conditions to evaluate the ability of the novel hybrid materials to desalinate model streams. The performance of the hybrid membranes were benchmarked and critically compared against commercially available membranes (Selemion™). Although the salt transfer kinetics across the hybrid ion-exchange composite membranes were shown to be comparable to that of the commercial membranes, the low porosity of the stainless steel reinforcements, around 60%, was shown to impede absolute salt permeations. The hybrid ion-exchange membranes were however found to be competitive at low current density and low flow velocity desalination conditions.

Facile fabrication of superhydrophobic conductive graphite nanoplatelet/vapor-grown carbon fiber/polypropylene composite coatings

The fabrication of superhydrophobic surfaces with mechanical durability is challenging because the surface microstructure is easily damaged. Herein, we report superhydrophobic conductive graphite nanoplatelet (GNP)/vapor-grown carbon fiber (VGCF)/polypropylene (PP) composite coatings with mechanical durability by a hot-pressing method. The as-prepared GNP/VGCF/PP composite coatings showed water contact angle (WCA) above 150° and sliding angle (SA) less than 5°. The superhydrophobicity was improved with the increase of VGCF content in the hybrid GNP and VGCF fillers. The more VGCFs added in the GNP/VGCF/PP composite coating, the higher porosity on the surface was formed. Compared to the GNP/PP and VGCF/PP composite coatings, the GNP and VGCF hybrid fillers exhibited more remarkable synergistic effect on the electrical conductivity of the GNP/VGCF/PP composite coatings. The GNP/VGCF/PP composite coating with GNP:VGCF = 2:1 possessed a sheet resistance of 1 Ω/sq. After abrasion test, the rough microstructure of the GNP/VGCF/PP (2:1) composite coating was mostly restored and the composite coating retained superhydrophobicity, but not for the VGCF/PP composite coating. When the superhydrophobic surface is mechanically damaged with a loss of superhydrophobicity, it can be easily repaired by a simple way with adhesive tapes. Moreover, the oil-fouled composite surface can regenerate superhydrophobicity by wetting the surface with alcohol and subsequently burning off alcohol.

Multi-scale simulation using a hybrid mass-spring system and finite element model

Ply-scale finite element (FE) models are widely used to predict the performance of a composite structure based on material properties of individual plies. When simulating damage, these models neglect microscopic fracture processes which may have a significant effect on how a crack progresses within and between plies of a multidirectional laminate. To overcome this resolution limitation a multi-scale modelling technique is employed to simulate the effect micro-scale damage events have on the macro-scale response of a structure. The current paper discusses the development and validation of a hybrid mass-spring system and finite element modelling technique for multi-scale analysis. The model developed here is limited to elastic deformations; however, it is the first key step towards an efficient multi-scale damage model well suited to simulation of fracture in fibre reinforced composite materials. Various load cases have been simulated using the model developed here which show excellent accuracy compared to analytical and FE results. Future work is discussed, including extension of the model to incorporate damage modelling.