Enhance high-temperature mechanical performance of a silicon-containing arylether arylacetylene resin with the aid of a terminal alkyne compound

2021 ◽  
Vol 28 (11) ◽  
Author(s):  
Gang Han ◽  
Jinsen Hou ◽  
Li Wan ◽  
Xufeng Hao ◽  
Xiaotian Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Mechanical Performance ◽  
Terminal Alkyne

scholarly journals Insight into the Mechanical Performance of the UHPC Repaired Cementitious Composite System after Exposure to High Temperatures

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4095
Author(s):  
Qing Chen ◽  
Zhiyuan Zhu ◽  
Rui Ma ◽  
Zhengwu Jiang ◽  
Yao Zhang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
High Temperatures ◽  
Bonding Strength ◽  
Composite System ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Interfacial Structure ◽  
Cementitious Composite ◽  
Average Percentage

In this paper, the mechanical performance of an ultra-high-performance concrete (UHPC) repaired cementitious composite system, including the old matrix and the new reinforcement (UHPC), under various high temperature levels (20 °C, 100 °C, 300 °C, and 500 °C) was studied. In this system, UHPC reinforced with different contents of steel fibers and polypropylene (PP) fibers was utilized. Moreover, the physical, compressive, bonding, and flexural behaviors of the UHPC repaired system after being exposed to different high temperatures were investigated. Meanwhile, X-ray diffraction (XRD), baseline evaluation test (BET), and scanning electron microscope (SEM) tests were conducted to analyze the effect of high temperature on the microstructural changes in a UHPC repaired cementitious composite system. Results indicate that the appearance of the bonded system changed, and its mass decreased slightly. The average percentage of residual mass of the system was 99.5%, 96%, and 94–95% at 100 °C, 300 °C, and 500 °C, respectively. The residual compressive strength, bonding strength, and flexural performance improved first and then deteriorated with the increase of temperature. When the temperature reached 500 °C, the compressive strength, bonding strength, and flexural strength decreased by about 20%, 30%, and 15% for the UHPC bonded system, respectively. Under high temperature, the original components of UHPC decreased and the pore structure deteriorated. The cumulative pore volume at 500 °C could reach more than three times that at room temperature (about 20 °C). The bonding showed obvious deterioration, and the interfacial structure became looser after exposure to high temperature.

An analysis of high-temperature microstructural stability and mechanical performance of the Hastelloy N-Hastelloy N Superalloy joint bonded with pure Ti

2018 ◽  
Vol 144 ◽  
pp. 72-85 ◽  
Author(s):  
Yanming He ◽  
Wenjian Zheng ◽  
Jianguo Yang ◽  
Dongdong Zhu ◽  
Xueshun Yang ◽  
...  
Keyword(s):  
High Temperature ◽  
Mechanical Performance ◽  
Microstructural Stability

Advanced wire bonding for high reliability and high temperature applications

2016 ◽  
Vol 2016 (1) ◽  
pp. 000214-000218
Author(s):  
M. Guyenot ◽  
M. Reinold ◽  
Y. Maniar ◽  
M. Rittner
Keyword(s):  
High Temperature ◽  
Band Gap ◽  
Mechanical Performance ◽  
High Reliability ◽  
Calculation Model ◽  
Basic Knowledge ◽  
Thermal Cycles ◽  
White Band ◽  
The Impact ◽  
Mission Profile

Abstract The next generation of switches for power electronic will be based on white band gap (WBG) semiconductor GaN or SiC. This materials supports higher switching current and high frequency. White band gap semiconductors enables higher application temperature. Certainly, high temperature capability is also to discuss in combination with high number of thermal cycles. For a frame module concept shows these paper a comparison of different joining techniques with the focus on the reliability issue on wire and ribbon bonding. Beside to the 1000 passive thermal cycles from −40°C to +125°C there are active thermals cycles for technology qualification required [3]. Depending on the application and mission profile a high thermal cycling capability is necessary. For this reason, new high temperature joining techniques for die attach, e.g. Silver sintering or diffusion soldering, were developed in the recent past [4]. All of this new joining techniques focusing on higher electrical, thermal and thermo-mechanical performance of power modules. By using an optimized metallization system for the WBG the numbers of thermal cycles can be increased and the maximum operating temperature advanced up to 300°C. In these new temperature regions silicon semiconductors will be substituted by WBG semiconductors. The present work shows an active power cycling capability of different wire and ribbon bonds and the failure mechanism will be discussed. A calculation model explained the reliability for the different wire diameter and the impact of bonding materials. This reliability calculation explain the thermo-mechanical effects and based on materials and geometry data and is not optimized for evidence. Through these physical background understanding more than 1.000.000 thermal cycles with a 150 K temperature swing from +30°C to +180°C are now possible. These is a the basic knowledge for a design for reliability based on current, mission profile and reliability optimization for future high end applications with wire or ribbon bonding technique.

High-temperature effect on the mechanical performance of screwed CFRPI–TC4 alloy joints repaired with metal inserts

2019 ◽  
Vol 54 (17) ◽  
pp. 2245-2260
Author(s):  
Yun-Tao Zhu ◽  
Jun-Jiang Xiong
Keyword(s):  
High Temperature ◽  
Carbon Fiber ◽  
Temperature Effect ◽  
Analytical Model ◽  
Joint Strength ◽  
Mechanical Performance ◽  
Joint Stiffness ◽  
Repair Efficiency ◽  
Strength And Stiffness ◽  
High Temperature Effect

This paper seeks to study high-temperature effect on mechanical performance of screwed single-lap carbon fiber-reinforced polyimide–TC4 titanium alloy joints repaired with metal inserts. Quasi-static tension tests were conducted at room temperature (RT) and 250℃ to determine the joint strength and stiffness of repaired joints with metal inserts. Based on the experimental results, high-temperature effect on joint strength and stiffness and insert repair efficiency were analyzed and discussed. A new analytical model was established to evaluate the effect of high temperature on joint stiffness. It is concluded that (1) joint strength and stiffness for all configurations are lower at 250℃ than that at RT, showing the expected detrimental effect of high temperature on joint strength and stiffness. The reductions in joint strength and stiffness depend on the joint configuration; (2) the repair efficiencies of embedded conical nut for joint strengths of protruding and countersunk head screw joints decrease, but those for joint stiffness increase at 250℃ as against at RT. Unlike the repair efficiencies of embedded conical nut, the repair efficiency of bushing for joint strength is slightly greater, but that for joint stiffness is less at 250℃ than at RT; and (3) the developed analytical model is capable of predicting the displacement of screwed single-lap carbon fiber-reinforced polyimide–TC4 joints at RT and high temperature, and there is good agreement between the experimental data and the predicted curves.

scholarly journals Experimental Study to Determine the Most Preferred Additive for Improving Asphalt Performance Using Polypropylene, Crumb Rubber, and Tafpack Super in Medium and High-Temperature Range

2019 ◽  
Vol 9 (8) ◽  
pp. 1567 ◽  
Author(s):  
Huang Xiaoming ◽  
Ismail Bakheit Eldouma
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Mechanical Performance ◽  
Asphalt Binder ◽  
Crumb Rubber ◽  
Asphalt Binders ◽  
Modified Bitumen ◽  
Asphalt Modification ◽  
Rotational Viscosity ◽  
Asphalt Performance

The overall objectives of this study were to determine the most appropriate additive for improving the physical properties and the medium- and high-temperature performances (mechanical performance) of asphalt binders. Three different types of modified binders were prepared: crumb rubber modifier (CRM), polypropylene (PP), and tafpack super (TPS), which had concentrations of 2%, 3%, 3.5%, and 4% by weight of asphalt binder, for each modifier. Their physical and rheological properties were evaluated by applying various tests such as ductility, rotational viscosity, toughness, and tenacity, as well as the dynamic shear rheometer (DSR) test. As a result, the physical properties of the modified bitumen binders were compared, as were the medium- and high-temperature performances (mechanical performance), which had temperatures of 58, 64, 70, 76, 82, and 88 °C, respectively. This was how the most appropriate modifier was determined. The results demonstrated that the asphalt binder properties significantly improved by utilizing CRM followed by PP and TPS modifiers. The increase in the rutting parameter (G*/sin(δ)) after asphalt modification indicated its excellent performance at both medium- and high-temperatures. Lastly, the CRM was determined as the most preferred additive because of its positive effect on the physical properties and enhancement of the medium- and high-temperature performance (mechanical performance).

Whisker-Reinforced Ceramic Matrix Composites

MRS Bulletin ◽  
1987 ◽  
Vol 12 (7) ◽  
pp. 66-72 ◽  
Author(s):  
J. Homeny ◽  
W.L. Vaughn
Keyword(s):  
High Temperature ◽  
Energy Dissipation ◽  
Mechanical Performance ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Matrix Composites ◽  
Mechanical Reliability ◽  
Interfacial Bond ◽  
High Fracture ◽  
The Matrix

Whisker-reinforced ceramic matrix composites have recently received a great deal of attention for applications as high temperature structural materials in, for example, advanced heat engines and high temperature energy conversion systems. For applications requiring mechanical reliability, the improvements that can be realized in fracture strength and fracture toughness are of great interest. Of particular importance for optimizing the mechanical reliability of these composites is the effect of the whisker/matrix interfacial characteristics on the strengthening and toughening mechanisms. Whisker reinforcements are primarily utilized to prevent catastrophic brittle failure by providing processes that dissipate energy during crack propagation. The degree of energy dissipation depends on the nature of the whisker/matrix interface, which can be controlled largely by the matrix chemistry, the whisker surface chemistry, and the processing parameters.It is generally believed that a strong interfacial bond results in a composite exhibiting brittle behavior. These composites usually have good fracture strengths but low fracture toughnesses. If the interfacial bond is weak, the composite will not fail in a catastrophic manner due to the activation of various energy dissipation processes. These latter composites tend to have high fracture toughnesses and low fracture strengths. Generally, the interface should be strong enough to transfer the load from the matrix to the whiskers, but weak enough to fail preferentially prior to failure. Thus, local damage occurs without catastrophic failure. It is therefore necessary to control the interfacial chemistry and bonding in order to optimize the overall mechanical performance of the composites.

Analysis of the Thermal-Hydraulic and Mechanical Performance of Intermediate Heat Exchangers Used in Systems With Very High Temperature Nuclear Reactors

2018 ◽  
Author(s):  
Raciel de la Torre Valdés ◽  
Juan Luis Francois Lacouture
Keyword(s):  
High Temperature ◽  
Heat Exchangers ◽  
Mechanical Performance ◽  
Nuclear Reactors ◽  
Optimized Design ◽  
Solid Region ◽  
Computational Fluid Dynamics Cfd ◽  
The One ◽  
Time Of Operation ◽  
Very High

Intermediate heat exchangers are one of the most critical devices in the safety of facilities with very high temperature nuclear reactors. In this application, the printed circuit heat exchanger (PCHE) design has been the one that has shown the greatest advantages in terms of heat transfer, compaction and structural strength. In this work, a thermal-hydraulic and mechanical model of the PCHE was developed using computational fluid dynamics (CFD) techniques and finite element methods, respectively. The CFD model was validated by comparison with experimental data and empirical correlations of Nusselt number and friction factor published by other authors. A methodology was proposed to evaluate the operation of the exchanger based on the analysis of capital and operating costs. As a relevant aspect of this methodology, the relationship between the maximum Von Misses stress in the structure and the time of operation was considered. In the structural calculations it was observed that increasing the temperature gradient between the channels caused by the increase of the mass flows of gases, causes the displacement of the solid region and the maximum stress increase. The Taguchi method was applied to identify the dimensions that have the greatest influence on the operation of the PCHE and to obtain an optimized design of the device.

Organic Hybrids for Circuit Assemblies – Initial environmental testing of a low cost alternative to ceramic substrate based assemblies

2018 ◽  
Vol 2018 (HiTEC) ◽  
pp. 000022-000027
Author(s):  
Martin Wickham ◽  
Kate Clayton ◽  
Ana Robador ◽  
Christine Thorogood
Keyword(s):  
High Temperature ◽  
Printed Circuit Board ◽  
Mechanical Performance ◽  
Low Cost ◽  
Mechanical Damage ◽  
Organic Matrix ◽  
Organic Substrate ◽  
Ceramic Substrate ◽  
Circuit Board ◽  
Environmental Testing

Abstract There are an increasing number of electronics applications in aerospace, automotive, shale/gas and power management, which are required to operate at or above 200 °C. Organic matrix reinforced substrates such as polyimide, have maximum operating temperatures in the region of 175 °C. Reliable operation of electronics at temperatures higher than this requires a combination of performance improvements in components, interconnects and substrates. Ceramic based substrate options are based on alumina substrates with printed inks fired at ~ 600 °C and can be costly, heavy and prone to mechanical damage. Printed circuit board (PCB) options are restricted to lower working temperatures of the organic resins and degradation of their conductive copper tracks through oxidation. This paper highlights earlier work undertaken by the authors and partners to understand the deficiencies of copper-clad PCB technology and details work to develop a low cost alternative to ceramic substrate based assemblies. The authors have investigated replacing the alumina substrates with high temperature engineering thermoplastics such as PEEK. The high temperature fired inks conventionally used in hybrid circuit manufacture have been replaced with screen-printable silicone based ink systems curing at 250 °C. The specially developed electrically conductive and dielectric inks were utilised to produce a multilayer system demonstrator with high temperature compatible components attached using a high temperature conductive adhesive. Such an assembly system has the potential to benefit from reductions in substrate cost and assembly weight. Energy cost associated with manufacture are significantly reduced. In addition the organic substrate is easier to machine and form into complex shapes and offers the possibility of integrating thermal management solutions. Environmental testing has been undertaken to determine the suitability of the system to operate for extended periods at 250 °C and the results of the electrical and mechanical performance for continuous ageing of test assemblies at 250 °C will be given.

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