Papers by Keyword: Hybrid Material

Abstract: Carbon nanotubes/alumina (CNTs/Al₂O₃) nanocomposites were prepared by the poly (dopamine) assisted chemical liquid phase deposition (CLPD). The poly (dopamine) layers were firstly coated on the CNTs surface uniformly by the self-oxidative polymerization of dopamine in mild aqueous solution and then the Al₂O₃ nanoparticles formed on the poly (dopamine) coated CNTs surface by the CLPD. The hydrophilic poly (dopamine) layers on the CNTs surface can improve the dispersion of CNTs in aqueous solution. Moreover, it can be used as a key linker between the CNTs and Al₂O₃ because of the nitrogen-containing group in poly (dopamine) could coordinate with Al³⁺ ions. The as-prepared poly (dopamine) coated CNTs and CNTs/Al₂O₃ nanohybrids were characterized by X-ray photoelectron spectroscopy (XPS), X-radial diffractometer (XRD) and high resolution transmission electron microscopy (HRTEM). These results showed that the poly (dopamine) layers were coated on the surface of CNTs uniformly, and the Al₂O₃ nanoparticles embellished with the poly (dopamine) coated CNTs surface. Compared with pristine NR composites, the thermal conductivity of the as-prepared NR/CNTs@Al₂O₃ composites increased 17%.

Abstract: Laser-structured metal surfaces in combination with thermoplastic compression mould processes allow intrinsic hybrid structures with high-strength connections. Suitable process parameters are still to be identified to provide optimised assembly parameters. Therefore, laser structures with different configurations are applied to steel sheets and compressed with textile reinforced thermoplastic composites to manufacture hybrid structures. Laser processing parameters, such as pulse duration or energy as well as laser scanning strategies and therefore structure dimensions are analysed.After manufacturing, specimens are extracted and characterized in single-lap shear tests comparing different configurations to identify boundary conditions for the laser structuring with optimal bonding characteristics.

Abstract: Failure of fiber reinforced polymers is a complex interaction of different microstructural mechanisms. In order to assign those mechanisms to the macroscopic material response, in-situ methods as acoustic emission can be applied. This allows for the detection of initiation and growth as well as for the localization of damage in mechanically loaded materials. In this study, mechanical material testing of continuous and discontinuous fiber reinforced polymers was coupled with acoustic emission. Results have shown that different failure mechanisms resulting from different reinforcement architectures can be distinguished due to their acoustic emission signal. Based on experimentally captured acoustic emission signals, machine learning algorithms were applied to differentiate various failure mechanisms. This offers the possibility to investigate damage of hybrid continuous-discontinuous Sheet Molding Compounds exposed to bending loads.

Abstract: Hybrid material systems are designed by the specific combination of different materials. As a result, expanded property profiles can be achieved, which would not be possible with monolithic material solutions. For lightweight, high strength and high rigidity, complex shaped structural components, which are used in the automotive industry and in aerospace, hybrid material systems offer an outstanding potential. A comprehensive understanding regarding the interaction of the individual components of the hybrid material is of great importance for a more efficient design of future structures. In this work, existing hybrid solutions for industrial applications and those, which are subject of current research, are analyzed and categorized first. Intrinsic and extrinsic material combinations are considered at different levels, ranging from hybrid laminates on shell level to complex hybrid structures on component level. Based on the situation analysis, different hybrid solutions are evaluated and compared considering the requirements of the automotive industry. Furthermore, the associated physical mechanisms which are responsible for the respective property profile are considered and explained systematically. The long-term objective of the work is to establish a methodology to derive the necessary physical mechanisms and, based on that, to derive optimal hybrid solutions for desired property profiles.

Abstract: Modern architecture is dominated by the tendency to design organically shaped filigree buildings. The resource and energy efficient construction of multifunctional buildings is as important as a broad variety of possible shapes. Multi-material support structures and shell constructions in lightweight design that also take over e. g. lighting and monitoring are needed for these purposes. Textile reinforced lightweight shell structures have been developed at Technische Universität Chemnitz within the scope of research projects. They consist of a hybrid material from carbon-fiber-reinforced concrete and glass-fiber-reinforced plastic. Thanks to the coupling of the positive material characteristics, the combination of two different composite materials results in a hybrid material with a total thickness of 15 mm, which has a high fatigue strength (XF4) and surface quality (exposed concrete). Furthermore, the hybrid is characterized by excellent compressive strength (120 MPa) and bending tensile strength (150 MPa), low susceptibility to corrosion and free formability. Therefore, it is highly suitable for thin-walled filigree lightweight shell structures. A research pavilion with a size of 4 x 4 x 3 m3 (l x w x h), made from textile reinforced lightweight shells, was built on the campus of TU Chemnitz, to test the theoretical investigations. Specially developed tensile sensors for the active lighting and determination of the elongations were integrated into the different layers. This aimed at an online-monitoring of the shell support structure.

Abstract: Trisilanolisobutyl polyhedral oligomeric silsesquioxane (TSI-POSS) with the humping semi-enclosed cage structure, was incorporated in concentrations of 7, 13 and 22 wt% into 4,4’-methylenebis (phenyl isocyanate) (MDI) and glycerol propoxylate to prepare TSI-POSS/PU hybrid composites, respectively. The polymer chain characteristics of these composites were investigated by wide angle X-ray scattering (WAXS) and molecular dynamics simulation approach. The results indicate that with TSI-POSS concentration increasing up to 22 wt% in hybrid composites, due to the humping semi-enclosed cage structure, distinct crystallite clusters are formed which lead to the micro-phase separation in composites. Meanwhile, the mobility of TSI-POSS cores and backbones in PU composites has been evaluated by the mean square displacement, which confirms that as the concentration of TSI-POSS increasing, the mobility of polymer chains are restricted apparently. Furthermore, it also indicates that the incorporation of TSI-POSS is as the rigid core in hybrid composites.

Abstract: Surface mechanical attrition treatment (SMAT) is an excellent method to get nanocrystalline and nanotwinned ultrafine crystalline steels from coarse-grained AISI 304 stainless steel. Due to their outstanding mechanical properties, they both appear to be relevant candidates for ballistic protection of marine engineering. Comparing their ballistic performance against coarse-grained steel, as well as identifying the effect of the hybridization with a carbon fiber–epoxy composite layer have been done by Jaime Frontan et al. Hybridization is proposed as a way to improve the nanocrystalline brittle properties in a similar way as is done with ceramics in other protection systems. Dur to the limit of experimental equipment, there are many results which are hardly got. In this paper, a numerical method with Johnson–Cook flow stress model, user material subroutine VUMAT and surface-based cohesive behaviour is presented.

Abstract: Trisilanolisobutyl polyhedral oligomeric silsesquioxane (TSI-POSS) with three hydroxyl functional groups pendent to a semi-enclosed cage, was incorporated in concentrations of 7, 13 and 22 wt% into 4,4'-methylenebis (phenyl isocyanate) (MDI) and glycerol propoxylate to prepare TSI-POSS/PU hybrid composites as a heavy linking node in backbone, respectively. The domain micro-structures of these composites were investigated by FTIR, wide angle X-ray scattering (WAXS) and molecular dynamics simulation approach. The results indicate that with TSI-POSS concentration increasing in hybrid composites, distinct crystallite clusters are formed which increase the volume of hard segments and lead to the micro-phase separation. Meanwhile, details of chain packing has been evaluated by radial distribution function, which shows that below 13wt% TSI-POSS concentration, the number of contacts between neighboring chains is decreased due to the humping semi-enclosed cage of TSI-POSS units. However, when TSI-POSS concentration is up to 22 wt%, the number of contacts is increased because the formation of crystallite cluster pulls neighboring chains closer to each other and significantly shortens their distance.

Abstract: A dedicated blanking test (DBT) was designed to measure the bonding shear strength of a metallic hybrid sample. To identify the required design parameters of the rig, a macro numerical model was developed using Abaqus Finite element (FE) package. Copper clad aluminum hybrid samples fabricated by an axi symmetric forward spiral composite extrusion (AFSCE) process were analyzed using the developed numerical model. The effect of the design parameters including sample thickness, blanking clearance and the die and punch fillet radii were determined to ensure a pure shear blanking along the interface. The numerical results showed that the sample thickness, clearance and fillet radii have a significant effect on the measured bond shear strength and the location of the failure. The required rig was designed and composite copper clad aluminum bonding shear strength was experimentally determined based on the numerical findings.

Abstract: Cerium oxide (CeO₂) or known as ceria were deposited on titanium dioxide, TiO₂, nanotubes by electrodeposition process as to produce hybrid materials that can generate photocurrent. The electrodeposition process is done by using 0.1 M cerium chloride mixed with 0.1 M ammonium acetate as ligands to promote stability complexes in a standard two electrode bath. Voltage and pH were controlled to ensure the most optimum condition of cerium oxide deposition. Samples were then annealed at different temperatures. Photocurrent results indicate that annealed sample at 450°C shows the best photocurrent due to high degree of anatase and cubic crystallinity.