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Hoang Van Tho,Young Jin Yum(염영진) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
Carbon fillers like multiwalled carbon nanotubes (MWCNT or CNT) and graphene oxide (GO) etc. have superlative mechanical and physical properties. They are widely applied in composite materials with high potential to increase mechanical properties of matrix. The dispersion of nano fillers is the key to evaluate bonding properties of Unsaturated Polyester Resin (UPR). Tensile specimens were fabricated by cast molding with the difference types of nano carbon fillers dispersed by stirring and sonication technique. 0.1 wt.% of MWCNT or GO separately and both of them were mixed with UPR. As the result, Young’s modulus increased significantly due to the appearance of nano fillers in all cases. On the other hand, the mixture of CNT and UPR showed the highest tensile strength and fracture strain. However, the mixture of GO with UPR showed no good effect on ultimate strength and GO combined with CNT also showed the same behavior. Moreover, higher of nano filler ratio, smaller fracture strain of mixture was shown. Scanning electron microscope (SEM) was used as the evidence to evaluate the strength effect of nano particles at the fracture surface of specimens based on their dispersion in UPR.
Hoang Van Tho,Young Jin Yum 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
Fiber-reinforced plastics (FRP) are applied widely in many fields including ship building that is made of glass fiber (both Mat and Woven) and unsaturated polyester. Because of the behavior of matrix and reinforcement, hardener ratio, making condition, configuration of shape and stacking sequence, etc the deformation of FRP product can be considerable. Furthermore, the deformation affects the strength and aesthetics of product. Thus, experimental investigation and evaluation of deformation of laminated composite structures are necessary. In this study, glass fiber reinforced laminates of three shapes (flat shape, L-shape and curve shape) were fabricated to evaluate the deformation of samples having various stacking sequences and fiber volume fractions. The experimental results show that deformations of FRP specimens strongly depend on the stacking sequences and fiber volume fractions.
Van-Tho Hoang,이대성,남영우,권진회 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.2
A numerical study was conducted to investigate the tensile behavior of carbon fiber-reinforced polymer (CFRP) scarf-repaired structures with different scarf ratios (1/5, 1/10, 1/20, and 1/30) using two approaches associated with the finite element method (FEM): the damage zone model (DZM) and cohesive zone model (CZM). The experimental data of CFRP laminates with the stacking sequence [45/ − 45/ − 45/0/90/0/45/ − 45/90/0]S, an over-ply layer (additional ply covering the outermost layer of the scarf-patch-repaired structure), and four different scarf ratios were obtained and analyzed. First, an empirical formula was established to describe the mathematical relationship and correlation between the failure load and scarf angle. Subsequently, the strength recovery rate was calculated to evaluate the mechanical performance of the scarf-repaired structures with different scarf ratios. Finally, the experimental data were used to verify the numerical results. The experimental and numerical results exhibited good agreement with each other. The effect of the scarf angle of scarf-patch-repaired composite laminates on the selection of the reference sample in the DZM method and the cohesive parameters in the CZM method were discussed as well.
Van-Tho Hoang,염영진 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.4
Multi-walled carbon nanotubes (MWCNTs) were mixed with Unsaturated polyester resin (UPR) using the stir method at high temperatures. The mixing temperature and hardener ratio were optimized based on compression properties and the exothermic temperature. In the experiment, 60 °C and 1 wt.% of Methyl ethyl ketone peroxide (MEKP) were chosen for the mixing condition and catalyst concentration, respectively. MWCNTs with different weight fractions (0.05, 0.1, 0.2 and 0.3 wt.%) were dispersed to investigate the effect of MWCNTs on tensile properties of the UPR, and it was found that 0.1 wt.% of MWCNTs showed the best performance in this range of fiber weight fraction due to a higher strength (42.14 %), modulus (14.33 %) and fracture strain (37.17 %) than pure UPR. The state of dispersion and arrangement of fibers were examined by a Field emission Scanning electron microscope (FE-SEM) according to fracture surfaces. Similarly, the FE-SEM also showed better results with 0.1 wt.% of MWCNTs mixed in the UPR.
Dinh Pham Van,Takeshi Fujiwara,Bach Leu Tho,Pham Phu Song Toan,Giang Hoang Minh 대한환경공학회 2020 Environmental Engineering Research Vol.25 No.1
With benefits to the human health, environment, economy, and energy, anaerobic digestion (AD) systems have attracted remarkable attention within the scientific community. Anaerobic digestion system is created from (bio)reactors to perform a series of bi-metabolism steps including hydrolysis/acidogenesis, acetogenesis, and methanogenesis. By considering the physical separation of the digestion steps above, AD systems can be classified into single-stage (all digestion steps in one reactor) and multi-stage (digestion steps in various reactors). Operation of the AD systems does not only depend on the type of digestion system but also relies on the interaction among growth factors (temperature, pH, and nutrients), the type of reactor, and operating parameters (retention time, organic loading rate). However, these interactions were often reviewed inadequately for the single-stage digestion systems. Therefore, this paper aims to provide a comprehensive review of both single-stage and multi-stage systems as well as the influence of the growth factors, operating conditions, and the type of reactor on them. From those points, the advantages, disadvantages, and application range of each system are well understood.