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RISS 인기검색어
- 검색키워드
- 저자 : Mirzamohammadi, Sajjad (검색결과 5 건)
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Monitoring the required energy for the crack propagation of fiber-reinforced cementitious composite
Mirzamohammadi, Sajjad,Mazloom, Moosa Techno-Press 2021 Structural monitoring and maintenance Vol.8 No.3
In this paper, the results of experimental work on the required energy for the crack propagation (fracture energy), rupture modulus and compressive strength of fiber-reinforced cementitious composite (FRCC) with different types of fibers after exposure to 20℃, 100℃ and 300℃ are investigated. The experimental part of the work is divided into the following stages: the effects of sub-elevated temperatures and fiber types on the fracture and mechanical behaviors of FRCC; finding a relation between the fracture energy and mechanical properties of the specimens based on I-optimal design of response surface methodology (RSM-I-optimal). Specifically, the analysis of variance (ANOVA) was examined to evaluate the influences of compressive strength and rupture modulus on the required energy for the crack propagation. For this purpose, three monotype fiber reinforced mixes have been prepared. The utilized fibers were aramid, basalt and glass. Additionally, the predictive efficiency of the RSM model was studied based on the normalized goodness-of-fit statistics (Nash & Sutcliffe coefficient of efficiency, NSE). The main finding was that both compressive strength and rupture modulus had considerable influences on the fracture energy. However, the effect of rupture modulus was far greater than compressive strength. In terms of NSE value, the model predictive efficiency was good for fracture energy.
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Sajjad Mirzamohammadi,Masoud Soltani 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.4
High-performance fiber-reinforced cement composites (HPFRCC) are new materials created and used to repair, strengthen, and improve the performance of different structural parts. When exposed to tensile tension, these materials show acceptable strain-hardening. All of the countries of the globe currently seem to have a need for these building materials. This study aims to create a low-carbon HPFRCC (high ductility) that is made from materials that are readily available locally which has the right mechanical qualities, especially an increase in tensile strain capacity and environmental compatibility. In order to do this, the effects of fiber volume percent (0%, 0.5%, 1%, and 2%), and determining the appropriate level, filler type (limestone powder and silica sand), cement type (ordinary Portland cement, and limestone calcined clay cement or LC3), matrix hardness, and fiber type (ordinary and oxygen plasma treated polypropylene fiber) were explored. Fibers were subjected to oxygen plasma treatment at several powers and periods (50 W and 200 W, 30, 120, and 300 seconds). The influence of the above listed factors on the samples’ three-point bending and direct tensile strength test results has been examined. The results showed that replacing ordinary Portland cement (OPC) with limestone calcined clay cement (LC3) in mixtures reduces the compressive strength, and increases the tensile strain capacity of the samples. Furthermore, using oxygen plasma treatment method (power 200 W and time 300 seconds) enhances the bonding of fibers with the matrix surface; thus, the tensile strain capacity of samples increased on average up to 70%.
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Mazloom, Moosa,Mirzamohammadi, Sajjad Techno-Press 2021 Advances in computational design Vol.6 No.3
In this study, some models are developed to predict the fracture energy (G<sub>F</sub>), flexural strength (f<sub>t</sub>), splitting tensile strength (f<sub>spt</sub>), and compressive strength (f<sub>c</sub>) of fiber reinforced cementitious composites (FRCC) based on I-optimal design of response surface methodology (RSM-I-optimal). Indeed, the main aim of this paper is to predict the mentioned parameters of FRCC at different temperatures and the aspect ratios of fibers. For this purpose, the fracture energy and strength properties of FRCC reinforced with aramid, glass, basalt, and polypropylene (PP) fibers were obtained at 20℃, 100℃ and 300℃ temperatures and were used as experimental values by RSM. The analyses of variance (ANOVA), perturbation, three-dimensional, contour and normal of residual plots were studied to assess the impacts of independent parameters on the relationships. Furthermore, the predictive efficiency of the RSM models between observed and predicted values were examined based on the Nash & Sutcliffe coefficient of efficiency (NSE). In terms of NSE values, the models were exact enough for predicting the flexural, splitting tensile and compressive strengths as well as fracture energy.
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Mazloom, Moosa,Mirzamohammadi, Sajjad Techno-Press 2019 Advances in materials research Vol.8 No.2
In this study, thermal effects on the mechanical properties of cement mortars with some types of fibers is investigated. The replaced fibers were made of polypropylene (PP), aramid, glass and basalt. In other words, the main goal of this paper is to study the effects of different fibers on the mechanical properties of cement mortars after subjecting to normal and sub-elevated temperatures. The experimental tests used for investigating these effects were compressive, splitting tensile, and four-point bending tests at 20, 100 and $300^{\circ}C$, respectively. Moreover, the microstructures of the specimens in different temperatures were investigated using scanning electron microscope (SEM). Based on the experimental results, the negative effects of sub-elevated temperatures on four-point bending tests were much more than the others. Moreover, using the fibers with higher melting points could not improve the qualities of the samples in sub-elevated temperatures.
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Hossein Ebrahimnezhad-Khaljiri,Reza Eslami-Farsani,Sadegh Mirzamohammadi,Shabnam Arbab Chirani 한국섬유공학회 2022 Fibers and polymers Vol.23 No.10
The aim of this study is to assess the simultaneous effect of incorporating capsulated healing agent and silicananoparticles on the mechanical-healing behaviors of glass fibers/epoxy composites. To do so, the 14 wt.% capsulated epoxyhealing agent by urea-formaldehyde polymeric shell and the various percentage of silica nanoparticles (1, 3 and 5 wt.%) wereadded into the glass fibers-epoxy composites for studying the healing behavior under the tensile and flexural conditions. After the damaging and healing processes of composites, the maximum healing efficiency in flexural strength (110.7 %) wasseen in the composite containing 5 wt.% silica nanoparticles. But the highest healing efficiency in the tensile strength(64. 2%) belonged to the smart composite with 3 wt.% silica nanoparticles. The silica nanoparticles improved the recoverycapability of mechanical properties by changing the damage modes into the smart composites. Filling the micro-voids andreducing the effect of agglomerated nanoparticles by healing agent were the effective mechanisms, which improved themechanical recovery capability. The other observed phenomena by field emission scanning electron microscope wereimproving the adhesion between glass fibers and epoxy, creating the micro-voids by silica nanoparticles, wasting the crackpropagation energy by stick-slip method and reducing the flow ability of healing agent by silica nanoparticles.
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