Abstract: This article delineates the characterization of the 3D printed MR elastomer through a forced vibration technique in the squeeze mode of operation. An anisotropic hybrid magnetorheological (MR) elastomer is developed via 3D printing. The 3D printed MR elastomer consists of three different materials; magnetic particles, magnetic particles carrier fluid, and an elastomer. MR fluid filaments are encapsulated layer-by-layer within the elastomer matrix using a 3D printer. When a moderately strong magnetic field is applied, the 3D printed MR elastomer changes its elastic and damping properties. The hybrid 3D printed MR elastomer also shows an anisotropic behavior when the direction of the magnetic field is changed with respect to the orientation of the printed filaments. The relative MR effect is higher when the applied magnetic field is parallel to the orientation of the printed filaments. The maximum change in the stiffness is observed to be 65.2% when a magnetic field of 500 mT is applied to the MR elastomer system. This result shows that the new method, 3D printing could produce anisotropic hybrid MR elastomers or possibly other types.
Abstract: Extrusion-based 3D concrete printing is analogous to fused deposition modeling method, which extrudes cementitious materials from a nozzle to build a complex concrete structure layer-by-layer without the use of expensive formwork. This study aims to investigate the influence of type of fiber on inter-layer bond strength and flexural strength of extrusion-based 3D printed geopolymer. An extrudable fly ash-based geopolymer composition previously developed by the authors was reinforced by three types of fibers, namely polyvinyl alcohol (PVA), polypropylene (PP) and polyphenylene benzobisoxazole (PBO) fibers. Control geopolymer specimens with no fiber were also 3D printed for comparison purposes. The results indicated that the incorporation of fibers reduced the inter-layer bond strength of 3D printed geopolymer. This pattern was true regardless of the type of fiber. On the other hand, the flexural strength of 3D printed fiber-reinforced geopolymer mixtures was substantially higher than that of the 3D printed geopolymer with no fiber. The rate of increase in the flexural strength depended on the type of fiber. The flexural failures of the specimens were due to the tensile failure of the bottom layer, rather than the shear failure of the interfaces.
Abstract: The nanosilver particles are attractive in the research field of nanotechnology due to one of their applications as an effective antibacterial agent. The main objective of the current research is to inhibit the bacterial growth in the molasses to decrease the rate of total sugar degradation caused by contaminated bacteria. The polypropylene masterbatch containing with AgNPs (PP/AgNPs) was prepared and tested against contaminated bacterial species identified in molasse. The percentage of bacterial inhibition was calculated by observing the viability of bacteria cultures by using spread plate technique after treated with PP/AgNPs masterbatch in batch experiment. The concentrations of nanoparticles in masterbatch were varied to be 200, 500, 1000, 1200 and 1500 ppm. At 1500 ppm, the compromised antibacterial activities were observed in all tested bacterial species with 2-h-long exposure time. The results in this study could be further applied to fit in operation of molasse use in industrial scale in various application, including bioethanol production.
Abstract: Polymer nanocomposites based on carbon nanotubes attract a great deal of attention recently due to their excellent performance. The dispersion state of CNTs embedded in the matrix is the primary and key issue to realize the potential of the nanocomposite. Here, this paper considers how the boiling point of solvent affects the performance of the nanocomposite when the ultrasonication dispersion method is employed. It is found that solvent with a low boiling point is conducive to save evaporation time so that CNTs can maintain the homogenous dispersion state as much as possible after ultrasonication. Therefore, the stretchability and tensile strength can be improved, while the electrical conductivity has an obvious enhancement as well.
Abstract: Powder-based 3D concrete printing (3DCP) process is highly suitable for producing building components and interior structures that can be later assembled on site. The accuracy and strength of 3D printed concrete components heavily rely on printing parameters, among which the binder saturation is the most decisive parameter. This paper reports the effects of binder saturation level on linear dimensional accuracy and compressive strength of 3D printed geopolymer. A geopolymer composition suitable for the powder-based 3DCP process previously developed by the authors was used in this study. 20 mm cubic specimens were printed with five binder saturation levels (75%, 100%, 125%, 150% and 170%). The results indicated that the increase in binder saturation level resulted in significant increase in compressive strengths of both green and post-processed samples in both directions. Nevertheless, the rate of increase in compressive strength of green samples was significantly higher than the post-processed samples. On the other hand, the increase in binder saturation level significantly reduced the linear dimensional accuracy of green samples in all directions. Nonetheless, the rate of reduction in linear dimensional accuracy in Z-direction was lower than the other two directions.
Abstract: Due to a reduced structural weight, composite parts offer the possibility to increase the eco-efficiency of any mobility devices during their lifetime. Due to the mold-based production of composite parts, their surfaces are contaminated with release agent residues (e.g. silicones). Thus, the adhesion of the part’s surface is lowered, which prevent structural adhesive bonding of untreated parts. To enable this joining technology and guarantee a sufficient adhesion during part’s lifetime, a surface pre-treatment prior to the bonding process has to be performed. A laser treatment shows a high potential for an integration in an industrial process chain, but unfortunately, common laser sources lower this potential due to high investment costs (excimer laser) or the risk of causing material damage (lasers emitting in the range of 1 μm wavelength). To solve this challenge, laser radiation at 3 μm wavelength, which has several advantages (high absorption within epoxy resin, less thermal interaction concluding less risk to cause delaminations and the possibility to be guided through a fiber) was generated by frequency conversion of an industrial ND:YAG laser (at 1064 nm) and applied to the composite. The results show a good and sensitive treatment of the surface, resulting in high bonding strengths and providing a robust pre-treatment method.
Abstract: In this paper, phenolic resin-based composite materials were prepared using glass fiber instead of asbestos for the oil driller brake friction materials, and its impact performance and friction and wear properties were investigated, and compared with performance of asbestos containing material. The results showed that the impact strength of glass fiber reinforced material were higher than that of asbestos reinforced material. When the friction speeds were constant, the friction coefficient of asbestos reinforced material changed in the range of 0.308~0.4302, and the glass fiber reinforced material was 0.308~0.425.The glass fiber can replace asbestos as a reinforced material for oil driller brake friction materials.
Abstract: In comparison to monolithic composite structures, tailored multi-material structures offer high potential considering lightweight design approaches in combination with cost efficient manufacturing processes. Roll forming enables flexible large scale production of hybrid structures, due to the continuous manufacturing process as well as high degree of automation. The multi-material structures consist of steel sheets which are selectively reinforced by unidirectional carbon fibre reinforced thermoplastics (CFR-TP). In view of minimizing process steps and decreasing cycle times, both materials are joined by fusion bonding. Therefore, CFR-TP is heated above melting temperature of thermoplastic matrix and joined to the steel surface under defined pressure and time. However, joining of both materials within a continuous process is still challenging due to a lack in terms of process comprehension. Consequently, multi-material specimens were manufactured depending on various process parameters as temperature of either material or processing speed and tested mechanically by floating roller peel test for the evaluation of the adhesion between both materials. Furthermore, viscosity of matrix was determined and investigations of CFR-TP interface were performed by Fourier transform infrared spectroscopy. The results show the requirement of a defined CFR-TP temperature and the change in crystalline structure of the matrix in dependency of the processing.