Papers by Keyword: Reinforcement

Abstract: This study examined the performance of an unpaved road reinforced with a triaxial geogrid built on a soft clay subgrade. The test setup featured a fully instrumented unpaved road model comprising a 0.2-m-thick crushed rock base supported by a 0.8-m-thick soft clay subgrade. The triaxial geogrid was positioned between the base and subgrade layers. Plate bearing tests were performed following ASTM standards. The thickness of the triaxial geogrid-reinforced base layer played a critical role in determining the unpaved road model’s ultimate bearing capacity and failure modes. Results showed that the reinforced model with a base layer of 0.2 m thick exhibited the highest bearing capacity compared with the unreinforced model, with an enhancement factor of 1.44. Furthermore, the reinforced section outperformed the unreinforced one, even with a reduced base thickness of 0.15 m. This suggests that triaxial geogrid reinforcement offers a viable solution for enhancing the sustainability of unpaved road construction on weak subgrades.

Abstract: Compared with traditional shielded metal arc welding and semi-automatic welding, fully automatic welding has the advantages of fast welding speed, high welding quality as well as a high qualification rate on the premise of ensuring the comprehensive performance of the girth weld joint. Meanwhile, the proportion of welding defects also changed from porosity and slag inclusion to lack of fusion. Therefore, from the view of the macroscopic and dynamic evolution behavior, the paper aims to reveal the influence of the coupling of weld-pass morphology and molten-pool flow on the formation of lack of fusion using macroscopic metallographic observation and high-speed photography. The results indicate that the weld morphology is prone to convex reinforcement and larger penetration depth in the 6 o’clock direction of the pipeline girth weld under the reference parameters. The excessive reinforcement of the pass to be welded is one of the sufficient conditions for the formation of a lack of side fusion in the 6 o’clock direction. Excessive reinforcement could lead to welding arc heat mainly used to melt the raised weld metal to be welded, which results in insufficient heat flow to both sides of the molten pool metal. Furthermore, due to the larger curvature radius at the groove and the increase of the surface tension of the molten pool with lower relative temperature, the flow resistance of the molten pool increases and the fluidity decreases.

Abstract: In today's automotive, aerospace, and high-temperature applications, there is a pressing demand for lightweight, high-strength materials. Meeting these industry requirements necessitates the development of such materials through rigorous research efforts. This study is focused on synthesizing, characterizing, and exploring the mechanical and tribological properties of forged AA7075-based Hybrid Metal Matrix Composites (HMMCs) reinforced with TiB₂ (titanium boride) and ZrO₂ (zirconium oxide) particles. The composites were subjected to hot forging, and comprehensive analyses were conducted to assess their microstructural features, elemental composition, and phase distribution. Mechanical properties were evaluated to gauge the enhancements achieved by incorporating TiB₂ and ZrO₂ reinforcements. Tribological behavior was examined using a tribotester under diverse conditions to elucidate the influence of these particles on wear resistance and frictional characteristics, thereby shedding light on potential applications in demanding tribological environments. This investigation incorporates varying percentages of ZrO₂ (zirconium dioxide) by weight (4% and 6%) and TiB₂ particles at 5% by weight into an AA7075 matrix alloy to synthesize a composite material. Scanning Electron Microscope (SEM) micrographs illustrate the uniform distribution of ZrO₂ and TiB₂ particles achievable through the stir casting and grain refinement after the forging process. Experimental results demonstrate that the addition of ZrO₂ and TiB₂ particles enhances the hardness and tensile strength of the AA7075/ZrO₂/TiB₂ composite compared to the base matrix material, with the AA7075/5%TiB₂/4%ZrO₂ composite exhibiting the highest hardness and strength among all variants. At the same time, tribological evaluations underscored enhanced wear resistance and frictional performance, indicating suitability for applications where tribological stability and mechanical strength are paramount. This investigation contributes valuable insights to developing advanced MMCs for high-performance engineering applications, demonstrating that the forging technique facilitates fine grain refinement, enhancing the abovementioned properties. Furthermore, the study identifies notable property improvements achieved through the forging process.

Abstract: A series of styrene–acrylonitrile (SAN) copolymer nanoparticles were prepared by grafting styrene–acrylonitrile from both aggregated silica and colloidally dispersed silica nanoparticles using atom-transfer radical polymerisation (ATRP). Cross-linking and macroscopic gelation were minimised by using a miniemulsion system. The thermal and mechanical behavior of composites were made from PSAN aggregated silica nanoparticles or colloidally dispersed silica has been examined by Differential scanning calorimetry (DSC) and Dynamic mechanical thermal analysis (DMTA). The filler particles increased the rubbery modulus above the T_g of PSAN considerably and led to a temperature-independent plateau of the modulus between 130 and 240 °C similar to that normally observed for crosslinked amorphous polymers. Covalent attachment of PSAN to the silica nanoparticles, by grafting the polymer from the surface of the silica using atom-transfer radical polymerization (ATRP), gave rise to hybrid materials with a comparable elastic plateau. While neat PSAN started to flow and deform irreversibly above 120 °C, the new silica nanoparticle–polymer hybrid materials proved stable up to 240 °C, which was more than 120 °C above the T_g of the polymer. Aggregated silica nanoparticles displayed more affect compared to colloidally dispersed silica.

Abstract: Calcium carbonate (CaCO₃) and silica are two types of additives for rubber. Through the implementation of a typical semi-efficient (Semi-EV) vulcanisation formulation, those additives were added separately into the compound of natural rubber (NR). The CaCO₃ or silica was added as the reinforcing filler and, incorporated into NR at a constant concentration i.e., 30 parts per hundred NR (phr). It was found that the CaCO₃ or silica have successfully provided an increase in mechanical properties including a greater tensibility (tensile strength) and abrasion resistance of the compound of NR. However, as hydrophilic fillers, the CaCO₃ or silica is hard to disperse homogeneously and hence, lauryl alcohol was used to improve their dispersion degrees. It was combined into the NR compound with varied concentrations such as 1, 3, 5 and 7 phr. Therefore, the effect of lauryl alcohol concentration on the processing and reinforcement properties of CaCO₃ or silica-filled NR was investigated. It could be found that lauryl alcohol has increased the rate coefficient of vulcanisation (Rv) of the CaCO₃ or silica-filled-NR. The greater the lauryl alcohol concentration; the greater the Rv value, tensile strength, and abrasion resistance. Overall, lauryl alcohol has a successful function as a plasticizing agent which increased the reinforcement effects of the fillers on NR through the increasing of crosslink density of CaCO₃-NR or silica-NR especially at the 5 phr of addition.

Abstract: In order to enhance diverse composites and foster sustainable development, it is essential to use strategic measures. Microcrystalline cellulose (MCC) has the desirable characteristics of being both renewable and biodegradable. The characteristics above provide MCC with a favorable option for enhancing the structural integrity of composite materials. This study examines the literature on using MCC as a composite reinforcement to identify its primary characteristics. This evaluation explores the properties and potential future advancements of the naturally derived materials under investigation. This work comprehensively reviews scientific publications to guide future research efforts. Based on empirical investigations, using MCC as a composite reinforcement has enhanced various mechanical and tribological characteristics. This study provides a comprehensive reference for implementing sustainable MCC as a composite reinforcement.

Abstract: Building industry is an important player that consumes a significant part of raw materials and energy. With regard to construction industry sustainable development and design requirements there is a space for innovative solutions, where one of the possibility include the use of high-strength concrete. The paper deals with the substantial description and detailed evaluation of the testing of reinforced high strength concrete beam which was exposed to three point loading test. Large scale experiment was complemented with material diagnosis of selected mechanical properties using destructive and non-destructive methods. Non-destructive methods were used to verify compressive strength and dynamic modulus of elasticity. Destructive compressive strength testing was applied on cylinder samples prepared with core drilling and determined values were compared with non- destructive testing. Measured data will be used for future advanced non-linear modelling.

Abstract: The paper deals with the problem of stress in the connection detail of vertical supporting structures with a flat slab and possible methods for its analysis. It mainly focuses on the problem of non-axial connection of columns and walls, which is typical for today's architectural designs. The parametric study compares the effect of the distance of the connected vertical support structures on reinforcement in the discontinuity region. Three different computational methods are used to stress analysis of this region - linear Finite Elements Method in SCIA Engineer software, 2D Strut-and-Tie Model and 2D non-linear Finite Elements Method in IDEA StatiCa software. The conclusion of the study is a comparison of the accuracy of different calculation methods and also a comparison of the solved design variants in terms of shear and bending stress and specific form of reinforcement.

Abstract: Lignocellulosic biomass, such as sorghum stalk fiber, has received a lot of interest as reinforcement in polymer composites because of its renewable nature, low cost, and potential environmental benefits. This is due to crystalline cellulose fibrils embedded in hemicellulose, lignin, wax, and other impurities in the lignocellulosic fiber. As a result, treatment to remove non-cellulosic components, expose cellulose fibrils, and improve the adhesion with polymer matrices is critical for their usage as reinforcement in polymer composites. This study investigates the effects of environmentally friendly steam treatment on sorghum stalk fiber's structural and morphological properties. Sorghum stalk fiber was subjected to steam treatment conditions at different durations. Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and sessile drop tests were used to examine the structural and morphological changes generated by steam treatment. It was observed that the steam treatment of sorghum fiber was successful in eliminating part of the amorphous lignin and hemicellulose components as well as contaminants such as wax, causing the crystallinity ratio to rise. Defibrillation also occurs, and the fiber surface becomes rougher. Due to the rough fiber surface and the space created by defibrillation, the polymer matrix can penetrate the fiber and increase its adhesion by a mechanical interlocking mechanism.

Abstract: The development of road and highway networks sometimes involves passing through compressible soils of poor quality. Given their mechanical properties as foundation soils, these soils are characterized by low short-term shear strength, expressed by undrained cohesion, which increases during soil consolidation, and are also characterized by significant compressibility, resulting in large-scale settlements when a load is applied to them. Nowadays, there are reinforcement methods that make it possible to execute these structures while limiting the risks of instability. This study consists of the numerical analysis of a light-weight embankment of a highway section built on soft soils. Two reinforcement methods are investigated to support the embankment layers and reduce settlement. Interest is given to the behavior of the soils in place before and after the installation of the adopted reinforcement. The analysis is carried out in such a way as to show the importance of the complete consolidation of the soils in place in the long term, which makes it possible to take into account the dissipation of the pore pressures.