• Computers and Concrete
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• v.27 no.2
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• pp.131-141
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• 2021

This paper aims at investigating the capability of different FRP/concrete interface models to predict the effect of carbon nanotubes on the flexural behavior of RC beams strengthened with CFRP. Three different interfacial bond models are proposed to simulate the adhesion between CFRP composites and concrete, namely: full bond, nonlinear spring element, and cohesive zone model. 3D Nonlinear finite element model is developed then validated using experimental work conducted by the authors in a previous investigation. Cohesive zone model (CZM) has the best agreement with the experimental results in terms of load-deflection response. CZM is the only bond model that accurately predicted the cracks patterns and failure mode of the strengthened RC beams. The FE model is then expanded to predict the effect of bond strength on the flexural capacity of RC beams strengthened with externally bonded CNTs modified CFRP composites using CZM bond model. The results reveal that the flexural capacity of the strengthened beams increases with increasing the bond strength value. However, only 23% and 22% of the CFRP stress and strain capacity; in the case of full bond; can be utilized before failure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.6
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• pp.53-60
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• 2019

The purpose of this study is to evaluate the degree of improvement in strengths by mixing blast-furnace slag and fly ash in polymer cement mortar(PCM). The test specimens are prepared with EVA polymer dispersion, two types of Admixtures (blast-furnace slag and fly ash), five kinds of polymer-cement ratios (0, 5, 10, 15 and 20%), and six kinds of admixtures (0, 3, 5, 10, 15 and 20%). Plain cement mortar is also made for comparison. From the test results, the flowing of PCM is greatly improved with the mixing of the admixtures, and strengths of PCM compared to ordinary cement mortar are also improved due to a decrease in water cement ratio. In addition, the strength characteristics of PCM by admixtures are greatly improved in flexural strength with fly ash compared to other strengths. It is apparent that the optimum mix proportions with polymer-cement ratio of 10% or more, admixture contents 5 to 10% of flay ash for flexural strength improvement of EVA-cement mortar are recommended in this study.

• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.496-501
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• 2007

The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases. Also, this quality of polymer modified cement strongly depend on weather condition. To overcome this problem, polymer-modified cement based on rapid setting cement mortars were prepared by varying polymer/cement mass ratio (P/C) with a constant water/cement mass ratio of 0.5. The effect of polymer on the hydration of this polymer cement is studied on different curing temperature. The results showed that the polymer mortar which is modified with rapid setting cement have superior physical strength properties on independent curing temperature. In addition the PIC ratio, the compressive strength, flexural strength, tensile strength and adhesion strength of mortar is enhances and polymer-modified cement based on rapid setting cement is more beneficial to the improvement of the mortar properties in jobsite.

• Journal of Adhesion and Interface
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• v.15 no.1
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• pp.9-13
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• 2014

The purpose of this work is to investigate the specific gravity, thermal, and mechanical property changes of polypropylene (PP)/mica composites before and after solid-state extrusion. On increasing the filler content, the specific gravity of the composites increased. The specific gravity of the oriented specimen containing filler in PP matrix is found to be much smaller than that of pre-specimen due to the formation of more microvoids. The presence of microvoids in the case of oriented composite specimen significantly affected the tensile and flexural properties of the composites. Both flexural strength and modulus of the composites showed maxima when the mica contents was 10 wt%, regardless of the orientation via solid state extrusion.

• Journal of Adhesion and Interface
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• v.7 no.2
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• pp.26-31
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• 2006

In order to effectively improve interfacial adhesion strength between polypropylene (PP) and jute fiber, we particularly incorporated maleic anhydride grafted PP (MAPP) into the matrix through the environment-friendly process without an additional method of process and had better mechanical performances by providing the alignment into the natural fiber than those of the conventional fabrication technology such as an extrusion or injection molding. We also proposed hot pressing method which applied relatively low shear to the composites and confirmed the chemical bonds among the functional groups of MAPP and jute using FT-IR approach. The concentration of MAPP for maximum tensile strength and modulus was optimized at 3 wt%. Flexural properties had no noticeable tendency to increase with MAPP contents compared to tensile strength, which could probably be explained by the degree in wetting of PP/MAPP matrix.

• Elastomers and Composites
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• v.46 no.2
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• pp.125-131
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• 2011

The effects of chopped kenaf fiber concentration on mechanical property of polypropylene (PP) composite are investigated. The addition of kenaf increased the tensile strength, flexural modulus, impact strength, specific gravity, and HDT, while decreased the elongation%, flexural strength, and melt flow index. The increase of mechanical properties is due to increased surface area contacting between fiber and polymer matrix and fiber-fiber interaction. Volatile extractives in the kenaf seemed to decrease the interfacial adhesion between kenaf surface and PP.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.573-578
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• 1998

Recently, the Carbon Fiber Sheet(CFS) is widely used to strengthen the RC beams. But the behaviour of the RC beams which is strengthened with the CFS is not clearly defined yet. So, in this study we experimented with simply supported RC beams strengthened with the CFS, under monotonic loads. We included three parameters in this experiment which are the number of the sheets, the length of the sheets, and the existence of the anchor bolts. We investigated the strength effect of the RC beams by adhesion of the CFS, and the strengthening effect of CFS as to the respective parameters.

• Journal of Integrative Natural Science
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• v.12 no.2
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• pp.29-34
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• 2019

In dental resin cement studies, viscosity is also an important factor in the adhesion of tooth defects and implants. This study used BisGMA and HPMA as the main ingredients, triethylene glycol dimethacrylate (TEGDMA) as a diluent, and benzoyl peroxide (BPO) as a photoinitiator. The physical properties of graphene oxide used as an additive for functionality were evaluated, and its use as a dental resin cement material was investigated.The rupture strength has the tendency to increase along with the increase of the ratio of graphene oxide that was added, which seemed to reflect the effect of the high strength property of graphene oxide. The flexural strength also has the tendency to increase when about 0.5% of graphene oxide was added the same as the increase of rupture strength.When graphene oxide was added, according to viscosity use, the utilization as high-quality dental resin cements will increase.

• Restorative Dentistry and Endodontics
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• v.44 no.4
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• pp.45.1-45.10
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• 2019

Objectives: Self-adhesive resin cements contain functional monomers that enable them to adhere to the tooth structure without a separate adhesive or etchant. One of the most stable functional monomers used for chemical bonding to calcium in hydroxyapatite is 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP). The aim of this study was to evaluate the influence of the10-MDP concentration on the bond strength and physical properties of self-adhesive resin cements. Materials and Methods: We used experimental resin cements containing 3 different concentrations of 10-MDP: 3.3 wt% (RC1), 6.6 wt% (RC2), or 9.9 wt% (RC3). The micro-tensile bond strength of each resin cement to dentin and a hybrid resin block (Estenia C&B, Kuraray Noritake Dental) was measured, and the fractured surface morphology was analyzed. Further, the flexural strength of the resin cements was measured using the three-point bending test. The water sorption and solubility of the cements following 30 days of immersion in water were measured. Results: The bond strength of RC2 was significantly higher than that of RC1. There was no significant difference between the bond strength of RC2 and that of RC3. The water sorption of RC3 was higher than that of any other cement. There were no significant differences in the three-point bending strength or water solubility among all three types of cements. Conclusions: Within the limitations of this study, it is suggested that 6.6 wt% 10-MDP showed superior properties than 3.3 wt% or 9.9 wt% 10-MDP in self-adhesive resin cement.

• Journal of Adhesion and Interface
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• v.10 no.2
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• pp.106-112
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• 2009

In the present work, novel biocomposites made with biodegradable Lyocell woven fabrics and poly (butylene succinate) were successfully fabricated for the first time. Lyocell/poly(butylene succinate) biocomposites with different fiber loadings of 0, 30, 40, 50 and 60 wt% were prepared by compression molding with a sheet interleaving manner. The effect of Lyocell fabric loading on the interlaminar shear strength, tensile and flexural properties, heat deflection temperature, thermal expansion behavior, and thermal stability of the biocomposites was investigated. The properties strongly depended on the fabric loading and the results were consistent with each other. It was demonstrated that the Lyocell fabrics played a remarkable role in improving the properties of poly(butylene succinate) resin by incorporating the fabrics into the resin. The greatest inter-laminar, tensile, flexural and thermal properties of the biocomposites were obtained with Lyocell fabrics of 50% by weight.