Assessment of mechanical strength of nano silica concrete (NSC) subjected to elevated temperatures

2019 ◽  
Vol 10 (1) ◽  
pp. 90-109 ◽  
Author(s):  
Hala Mohamed Elkady ◽  
Ahmed M. Yasien ◽  
Mohamed S. Elfeky ◽  
Mohamed E. Serag
Keyword(s):  
Elevated Temperature ◽  
Bond Strength ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Mechanical Tests ◽  
Nano Silica ◽  
Content Type ◽  
Post Exposure ◽  
Concrete Mix ◽  
Bond Strengths

Purpose This paper aims to inspect the effect of indirect elevated temperature on the mechanical performance of nano silica concrete (NSC). The effect on both compressive and bond strengths is studied. Pre- and post-exposure to elevated temperature ranges of 200 to 600°C is examined. A range covered by three percentages of 1.5, 3 and 4.5 per cent nano silica (NS) in concrete mixes is tested. Design/methodology/approach Pre-exposure mechanical tests (normal conditions – room temperature), using 3 per cent NS in the concrete mix, led to the highest increase in both compressive and bond strengths (43 per cent and 38.5 per cent, respectively), compared to the control mix without NS (based on 28-day results). It is worth noticing that adding NS to the concrete mixes does not have a significant effect on improving early-age strength. Besides, permeability tests are performed on NSC with different NS ratios. NS improved the concrete permeability for all tested percentages of NS. The maximum reduction is accompanied by the maximum percentage used (4.5 per cent NS in the NSC mix), reducing permeability to half the value of the concrete mix without NS. As for post-exposure to elevated-temperature mechanical tests, NSC with 1.5 per cent NS exhibited the lowest loss in strength owing to indirect heat exposure of 600°C; the residual compressive and bond strengths are 73 per cent and 35 per cent, respectively. Findings The dispersion technique of NS has a key role in NSC-distinguished mechanical performance with NSC having lower NS percentages. NS significantly improved bond strength. NS has a remarkable effect on elevated temperature endurance. The bond strength of NSC exposed to elevated temperatures suffered faster deterioration than compressive strength of the exposed NSC. Research limitations/implications A special scale factor needs to be investigated for the NSC. Originality/value Although a lot of effort is placed in evaluating the benefits of using nano materials in structural concrete, this paper presents one of the first outcomes of the thermal effects on concrete mixes with NS as a partial cement replacement.

scholarly journals Mechanical Performance Under Various Conditions of 3D Printed Polylactide Composites With Natural Fibers

2021 ◽  
Author(s):  
Karolina E. Mazur ◽  
Aleksandra Borucka ◽  
Paulina Kaczor ◽  
Szymon Gądek ◽  
Stanislaw Kuciel
Keyword(s):  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Natural Fibers ◽  
Crystallization Rate ◽  
Mechanical Tests ◽  
Hydrothermal Degradation ◽  
3D Printed ◽  
The Impact ◽  
Different Levels ◽  
Additive Methods

Abstract In the study, polylactide-based (PLA) composites modified with natural particles (wood, bamboo, and cork) and with different levels of infilling (100%, 80%, and 60%) obtained by additive methods were tested. The effect of type fiber, infill level and crystallization rate on the mechanical properties were investigated by using tensile, flexural, and impact tests. The materials were subjected to mechanical tests carried out at 23 and 80 °C. Furthermore, hydrothermal degradation was performed, and its effect on the properties was analyzed. The addition of natural fillers and different level of infilling result in a similar level of reduction in the properties. Composites made of PLA are more sensitive to high temperature than to water. The decrease in Young's modulus of PLA at 80 °C was 90%, while after 28 days of hydrodegradation ~ 9%. The addition of fibers reduced this decrease at elevated temperatures. Moreover, the impact strength has been improved by 50% for composites with cork particles and for other lignocellulosic composites remained at the same level as for resin.

Development of novel high Tg polyimide-based composites. Part II: Mechanical characterisation

2017 ◽  
Vol 52 (2) ◽  
pp. 261-274 ◽  
Author(s):  
Spyros Tsampas ◽  
Patrik Fernberg ◽  
Roberts Joffe
Keyword(s):  
Elevated Temperature ◽  
Composite System ◽  
Mechanical Performance ◽  
Mechanical Tests ◽  
Basic Material ◽  
Mechanical Characterisation ◽  
Short Beam ◽  
Fibre Treatment ◽  
Beam Shear ◽  
Fibre Matrix

In this study, the mechanical performance assessment of a newly developed carbon fibre-reinforced polyimide composite system T650/NEXIMID® MHT-R is presented. This system was subjected to a series of mechanical tests at ambient and elevated temperature (320℃) to determine basic material properties. Moreover, an additional test was conducted, using a T650/NEXIMID® MHT-R laminate in which the fibre sizing was thermally removed prior to laminate manufacturing, to investigate the effect of fibre treatment on mechanical performance. The experimental results indicated that the T650/NEXIMID® MHT-R composites along with exceptionally high Tg (360–420℃) exhibited competitive mechanical properties to other commercially available polyimide and epoxy-based systems. At elevated temperature, the fibre-dominated properties were not affected whilst the properties defined by matrix and fibre/matrix interface were degraded by approximately 20–30%. Finally, the fibre sizing removal did not affect the tensile and compressive strength, however, the shear strength obtained from short-beam shear test was deteriorated by approximately 15%.

scholarly journals Manifestation of Interactions of Nano-Silica in Silicone Rubber Investigated by Low-Frequency Dielectric Spectroscopy and Mechanical Tests

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 717 ◽  
Author(s):  
Chao Wu ◽  
Yanfeng Gao ◽  
Xidong Liang ◽  
Stanislaw M. Gubanski ◽  
Qian Wang ◽  
...  
Keyword(s):  
Silicone Rubber ◽  
Power Transmission ◽  
Mechanical Performance ◽  
Filler Content ◽  
Low Frequency ◽  
Mechanical Tests ◽  
Nano Silica ◽  
Rubber Composites ◽  
Rubber Composite ◽  
Surface Modified

Silicone rubber composites filled with nano-silica are currently widely used as high voltage insulating materials in power transmission and substation systems. We present a systematic study on the dielectric and mechanical performance of silicone rubber filled with surface modified and unmodified fumed nano-silica. The results indicate that the different interfaces between the silicone rubber and the two types of nano-silica introduce changes in their dielectric response when electrically stressed by a sinusoidal excitation in the frequency range of 10−4–1 Hz. The responses of pure silicone rubber and the composite filled with modified silica can be characterized by a paralleled combination of Maxwell-Wagner-Sillars interface polarization and DC conduction. In contrast, the silicone rubber composite with the unmodified nano-silica exhibits a quasi-DC (Q-DC) transport process. The mechanical properties of the composites (represented by their stress-strain characteristics) reveal an improvement in the mechanical strength with increasing filler content. Moreover, the strain level of the composite with a modified filler is improved.

Adhesives for increasing the bonding strength of in situ manufactured metal-composite joints

2020 ◽  
pp. 095440702096575
Author(s):  
Robert Thomas ◽  
Fabian Fischer ◽  
Maik Gude
Keyword(s):  
Bonding Strength ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Storage Conditions ◽  
Mechanical Tests ◽  
Metal Composite ◽  
Scanning Calorimetry ◽  
Lap Shear ◽  
Glass Fibre Reinforced ◽  
Metallic Parts

In this present work, the potential of metallic parts, locally reinforced with a continuous glass fibre reinforced thermoset material, pre-impregnated with an epoxy matrix (prepreg), was evaluated by differential scanning calorimetry (DSC), single-lap shear tests and 3-point bending tests of a metal-composite hybrid hat profile. This technology is evaluated regarding an automotive use case, the DSC experiments in combination with moulding trials have proven curing times below 30 s for a moulding temperature of 180°C. A bonding strength of 13.5 MPa was characterized for a co-cured fibre-reinforced plastic (frp) onto a metallic joining partner. By additionally introducing an epoxy glue film as a bonding agent, which is co-cured together with the frp, the bonding strength can be increased significantly up to 25.4 MPa at the expense of the curing time. The mechanical tests on the hybrid hat profile have shown an increase of energy absorption compared with non-reinforced hat profiles. Here, also an additional glue film extends the performance regarding a co-cured plastic reinforcement without glue film. The influence of the storage conditions of the uncured prepreg materials on the mechanical performance was evaluated by a simulated physical ageing at elevated temperatures, followed by a mechanical characterization of the bonding strength and part performance. Also the effect of different testing temperatures and testing velocities on the capability of the metal-composite hybrid part is illustrated.

Wear performance of Al-TiC composite at elevated temperature

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Eshan Agrawal ◽  
Vinod Tungikar
Keyword(s):  
Elevated Temperature ◽  
Wear Rate ◽  
Coefficient Of Friction ◽  
Elevated Temperatures ◽  
Centrifugal Casting ◽  
Wear Test ◽  
Heating Chamber ◽  
Wear Performance ◽  
Content Type ◽  
Pin On Disc

Purpose Aluminium matrix composites are subjected to wear as well as higher temperature applications such as pistons, cylinder heads and blocks for car engines. Therefore, it is important to evaluate the performance of aluminium metal matrix composite at elevated temperature. Design/methodology/approach In the present work wear performance of Al-TiC composite with 7.5% reinforcement of TiC powder is carried out at elevated temperature. The composite specimens are prepared with the help of centrifugal casting method to get the large segregation of reinforcement on the outer layer of the composite which is subjected to wear. Taguchi method is used for preparing design of experiments. Findings The wear test is performed on DUCOM pin on disc setup having the heating chamber facility. The results of wear test are analysed with the help of MINITAB 19 software. The results show that temperature has dominant effect on the wear rate. The mathematical model through regression is predicted for wear rate and coefficient of friction. The study of worn-out surface is performed with the help of scanning electron microscope. The micrographs show that the type of wear is changes from abrasive to severe wear and some delamination. Originality/value The experiments are conducted as per ASTM standards. The results give the mathematical equation for wear rate and coefficient of friction at elevated temperatures.

Dynamic Crush Test of Subcomponent Composite Front Frame Rails

2001 ◽  
Author(s):  
Thomas Brimhall ◽  
Hasetetsion G. Mariam
Keyword(s):  
Elevated Temperature ◽  
Bond Strength ◽  
Ambient Temperature ◽  
Energy Absorption ◽  
Elevated Temperatures ◽  
Peak Load ◽  
Absorbed Energy ◽  
Steel Rail ◽  
Composite Matrix ◽  
Lap Shear

Abstract Testing of components is a usual method to evaluate structures, joining methods, and materials prior to full scale testing. Ambient temperature dynamic crush testing was performed on steel and composite sub-component front frame rails to compare the energy absorption and evaluate crush behavior. The sub-component composite frame rails were fabricated from two parts, an upper and lower, and bonded using three adhesives: Ashland polyurethane, Lord epoxy, and 3M epoxy. Prior to the dynamic test of the rails, single lap shear coupon tests were performed at ambient temperature and elevated temperature, 135°C, to evaluate relative bond strength of these adhesives. Testing was performed at elevated temperature because adhesives used for structural bonding in automotive, specifically under-hood, applications can be subjected to elevated temperatures. All three adhesives tested showed reduced bond strength at elevated temperatures. At room temperature, the Ashland urethane and Lord epoxy adhesives were observed to have comparable higher bond strength with the composite-to-composite lap shear coupons compared to the 3M epoxy. However, the crush failure mode for the composite tubes was confined to the substrate and the mean crush load was independent of the adhesive used for fabrication. Progressive crushing of the rail specimens was observed for all specimens tested. The amount of energy absorbed and crush mode for each rail design depended on its structural and material characteristics. The steel specimen absorbed energy by localized buckling in an accordion crush mode. The composite specimens absorbed energy by fracturing the composite matrix, delamination, fracture of the reinforcement fibers, and friction between the fracture and crushing surfaces. The crushing process of the steel rail was initiated by fabricated corrugations in the rail comers at the front, or impact, end of the rail. The composite rail crush event was initiated with an aluminum plug trigger designed to cause the composite rail to split at the comers with fracture of the composite matrix and delamination of the composite plies. Glass fibers were observed to fracture primarily at the tube corners. Fiber fracture elsewhere was infrequent. Close examination of the bonded joint fracture surface showed extensive fiber tear-out indicating that the failure was in the composite, not the adhesive. Mean crush load for the steel rail was 60% higher than the average mean load for the composite rails. The peak load for the steel rail was 71% higher than the average peak load for the composite rails. Specific energy absorption (SEA) of the steel rail was calculated to be 6.34 kJ/kgm compared with an average of 10.5 kJ/kgm for the composite rails.

Application of a bionic ring structure on drill pipe surfaces to improve the performance of anti-corrosion coatings

2016 ◽  
Vol 63 (3) ◽  
pp. 177-183 ◽  
Author(s):  
Yunhai Ma ◽  
Hubiao Wang ◽  
Xin Zhang ◽  
Wenbo Shang ◽  
Jin Tong ◽  
...  
Keyword(s):  
Bond Strength ◽  
Drill Pipe ◽  
Ring Structure ◽  
Ring Groove ◽  
Content Type ◽  
Mechanical Adhesion ◽  
Wide Range ◽  
Bionic Structure ◽  
Bond Strengths ◽  
The Difference

Purpose Nature provides a wide range of structures with different functions, which can serve as a source of research concepts. Based on the bionics principle, a bionic structure was applied to drill pipe specimens to compare the bond strength of paint coatings with and without a bionic ring groove pattern machined on the substrate. Design/methodology/approach Using the Revetest Xpress Plus scratch tester, the bond strengths of the coatings on the drill pipe with and without the bionic structure were measured and the difference in bond strength was observed. Findings The critical scratch loads of the surface coatings were 12.77 and 5.4 N. Furthermore, the scratch curve from the plain sample had a larger fluctuation compared to the curve of the samples with bionic ring grooves. Originality/value This indicated that the application of a bionic pattern to the surface of the substrate could enhance the bond strength and the degree of mechanical adhesion between the coating and the surface of the drill pipe, which is beneficial for the anti-corrosion performance of the drill pipe.

Behavior of eccentrically loaded welded hollow spherical joints after elevated-temperature exposure

2018 ◽  
Vol 22 (6) ◽  
pp. 1352-1367 ◽  
Author(s):  
Jie Lu ◽  
Zhihua Chen ◽  
Hongbo Liu ◽  
Zimei Guo
Keyword(s):  
Finite Element ◽  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Lattice Structures ◽  
Spherical Joint ◽  
Load Bearing ◽  
Space Lattice ◽  
Temperature Exposure ◽  
Welded Hollow Spherical Joint

Welded hollow spherical joint is an extremely widely used connection pattern in space lattice structures. Understanding the behavior of the welded hollow spherical joint after elevated-temperature exposure is critical for the fire damage assessment of the entire space lattice structures. In this study, both experimental and numerical studies were conducted to reveal the mechanical behavior of eccentrically loaded welded hollow spherical joints subjected to eccentric loads after cooling from three elevated temperatures up to 1000°C, wherein two different methods were considered, namely, air and water cooling. Associate mechanical performance, such as load versus longitudinal displacement and load versus steel tube rotation responses, initial stiffness, load-bearing capacities, and strain development, were obtained and further analyzed. The results showed that the behavior of welded hollow spherical joints began to change when the exposure temperatures exceeded 600°C, with obvious reductions in both stiffness and strength. In addition, the influences of different cooling methods were significant. The joints cooled by water generally presented higher load-bearing capacities than those cooled by air. Furthermore, three-dimensional finite element analysis was conducted via ABAQUS software. After validating the finite element model against experimental results, parametric studies were performed and a practical formula was proposed to calculate the load-bearing capacity of welded hollow spherical joints subjected to eccentric load after elevated-temperature exposure.

Numerical and experimental studies on sustainable alkali activated concretes at elevated temperatures

2019 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Subhash Yaragal ◽  
Chethan Kumar B. ◽  
Manoj Uddavolu Abhinav
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Elevated Temperatures ◽  
Experimental Studies ◽  
Optimization Techniques ◽  
Gray Relational Analysis ◽  
Complete Replacement ◽  
Content Type ◽  
Alkali Activated

Purpose To reduce environmental impact caused by excessive use of ordinary Portland cement (OPC) and to mitigate scarcity of base materials such as natural coarse aggregate (NCA), industrial by-products can be carefully used as alternatives to OPC and NCA, in production of concrete. This paper aims to describe the performance of using ground granulated blast furnace slag (GGBS), fly ash (FA) as a complete replacement to OPC and ferrochrome slag (FCS) as replacement to NCA in production of novel FCS based alkali activated slag/fly ash concretes (AASFC) and evaluate their performance at elevated temperatures. Design/methodology/approach Two control factors with three levels each i.e. FA (0, 25 and 50 per cent by weight) and FCS (0, 50 and 100 per cent by volume) as a GGBS and NCA replacement, respectively, were adopted in AASFC mixtures. Further, AASFC mixture specimens were subjected to different levels of elevated temperature, i.e. 200°C, 400°C, 600°C and 800°C. Compressive strength and residual compressive strength were considered as responses. Three different optimization techniques i.e. gray relational analysis, technique for order preference by similarity to ideal solution and Desirability function approach were used to optimize AASFC mixtures subjected to elevated temperatures. Findings As FA replacement increases in FCS based AASFC mixtures, workability increases and compressive strength decreases. The introduction of FCS as replacement to NCA in AASFC mixture did not show any significant change in compressive strength under ambient condition. AASFC produced with 75 per cent GGBS, 25 per cent FA and 100 per cent FCS was found to have excellent elevated temperature enduring properties among all other AASFC mixtures studied. Originality/value Although several studies are available on using GGBS, FA and FCS in production of OPC-based concretes, present study reports the performance of novel FCS based AASFC mixtures subjected to elevated temperatures. Further, GGBS, FA and FCS used in the present investigation significantly reduces CO2 emission and environmental degradation associated with OPC production and NCA extraction, respectively.

Influence of elevated temperature on alkali-activated ground granulated blast furnace slag concrete

2019 ◽  
Vol 11 (2) ◽  
pp. 247-260
Author(s):  
Virendra Kumar ◽  
Amit Kumar ◽  
Brajkishor Prasad
Keyword(s):  
Blast Furnace ◽  
Elevated Temperature ◽  
Blast Furnace Slag ◽  
Elevated Temperatures ◽  
Experimental Result ◽  
Content Type ◽  
Granulated Blast Furnace Slag ◽  
New Type ◽  
Furnace Slag ◽  
Alkali Activated

Purpose This paper aims to present an experimental investigation on the performances of alkali-activated slag (AAS) concrete and Portland slag cement (PSC) concrete under the influence of elevated temperature. In the present study, the alkali-activated binder contains 85% of ground granulated blast furnace slag (GGBFS) and 15% of powder blended as chemical activators. Design/methodology/approach For the purpose, standard size of cube, cylinder and prism have been cast for a designed mix of concrete. The AAS concrete specimens were kept for water as well as air curing. After attaining the maturity of 28 days, the samples were first exposed to different elevated temperatures, i.e. 100°C, 200°C, 300°C, 400°C, 500°C, 600°C, 700°C and 800°C. Later on, the tests were conducted on these samples to find the change in weight and the residual strength of the concrete. Findings After 500°C exposure, a considerable amount of the strength loss has been observed for AAS concrete. It has been evaluated that the performance of AAS concrete is better than that of the PSC concrete at elevated temperature. Research limitations/implications The present research work is being applied on the material for which the experimental result has been obtained. Practical implications The author has tried to develop a new type of binder by using steel industry waste material and then tested at elevated temperature to sustain at high temperatures. Social implications This research may give a social impact for developing mass housing project with a lower cost than that of using a conventional binder, i.e. cement. Originality/value A new type of binder material is being developed.

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