Influence Of High Temperature Exposure Research Articles

The influence of high temperature exposure on the tensile and cracking behavior of crimped-textile reinforced mortar composites (TRMs)

The use of textile reinforced mortar/concrete composites (TRM) in strengthening applications and new constructions necessitates understanding its behavior after exposure to high temperatures. Therefore, in this study, the residual tensile and cracking behavior of carbon based TRMs was studied. A total of 96 TRM samples were tested in the temperature range of 25–450 °C. The main parameters studied were the textile crimp, textile orientation, textile coating, multiple textile layers and hybrid reinforcement. The hybrid TRM was formed with a combination of uncoated and styrene butadiene (SBR) coated textile layers. This study served as one of the first experimental campaigns to use digital image correlation (DIC) for understanding the residual crack opening behavior of TRMs. The results demonstrated that the properties of the TRMs were noticeably influenced by temperature exposure of 450 °C. Unlike the uncoated or hybrid textile TRMs, the SBR coated textile TRMs demonstrated curvature and cracking after 450 °C exposure. The study showed that the load aligned crimped yarn TRMs were always associated with larger deformation irrespective of the exposure temperature. The crack openings also increased significantly after exposure to 450 °C. Whereas the presence of heat formed cracks caused higher initial rate of crack openings. The evolution in the crack spacing with increasing temperature fluctuated due to the possible relative degradation of cracking strength vs interfacial mortar textile bonding. Finally, the proposed empirical equation showed a good fit to the residual average crack opening vs. stress relations.

Optimizing Cement Asphalt Mortar Mixtures for Bridge Expansion Joints in Tropical Climates: Performance and Durability Assessment

In this study, the suitability of various Cement Asphalt Mortar (CAM) mixtures for bridge expansion joint applications in tropical climates was quantitatively assessed. A comprehensive analysis encompassed key properties, including mixing stability, flowability, unconfined compressive strength, expansion characteristics, and resistance to acidic and alkali environments. The influence of high-temperature exposure on unconfined compressive strength and the microstructural features were also examined. The results revealed a discernible trend: lower cement content, in conjunction with anionic Asphalt Emulsion (AE) or epoxy resin, significantly enhanced mixing stability and flowability while contributing to improved unconfined compressive strength and chemical degradation resistance. Notably, epoxy resin emerged as a valuable component in mitigating high-temperature-induced strength reduction, indicating potential promise for CAM mixture design. SEM analysis visually supported these findings by highlighting the microstructural distinctions among CAM mixtures. Quantitatively, the findings indicated that CAM mixtures with a 25% cement content and 75% anionic AE exhibited an 11% improvement in mixing stability, along with a 13% enhancement in flowability, relative to the control mixture with 100% cement. Additionally, CAM mixtures incorporating epoxy resin (at various percentages) with anionic AE exhibited a significant 15% resistance to high-temperature-induced UCS reduction, surpassing other mixtures. The SEM micrographs visually confirmed the superior microstructural connectivity achieved with epoxy resin, further validating the observed enhancements. These quantitative results offer a robust foundation for tailoring CAM mixture compositions to optimize their suitability for rigorous infrastructure projects in tropical climates.

Influence of high-temperature exposure on the properties of gypsum-plastic waste composites: Thermophysical and microstructural analysis

Gypsum plasters are a versatile material with a wide range of applications due to their fireproof, thermal, hygroscopic, and acoustic properties. They are commonly used as a coating material to provide passive protection to structural components. Moreover, the construction sector recognizes the potential for gypsum material to address the issue of plastic waste by offering a recycling solution. However, it is crucial to consider the effect of polymeric waste aggregates on the behavior of the gypsum matrix against fire. To address this issue, this study aims to evaluate the impact of high temperature exposure on the microstructural and thermal properties of gypsum composites containing plastic waste. The study compares two different residues, crushed polypropylene (PP) sourced from disposable coffee capsules and nylon (PA6) fibres obtained from discarded fishing nets, with the reference material as partial replacements of the gypsum matrix. The samples are exposed to different high-temperature conditions, including service temperatures (23 ± 2 °C, 150 °C, and 300 °C) and fire temperatures (1000 °C). The physical, thermal, and chemical properties of the new composites are analyzed based on TGA and XRD analysis, and SEM and micro-CT methods to evaluate the effect of plastic residues on the microstructural properties of the gypsum matrix. Additionally, the cracking patterns induced by 1000 °C exposure are compared. The study finds that the nature of the gypsum matrix remains largely unchanged after plastic waste addition. However, the low cohesion degree of the interface transition zone (ITZ) between the products of different hydration is a critical feature that must be considered during the heating process. It could significantly affect the mechanical performance of the new composites. Furthermore, it is worth noting that the inclusion of PA6 fibres in the gypsum matrix improves the cracking performance after exposure to fire temperature. This is a result of better heat spread by microcracking generated after fibres melted. In conclusion, this study highlights the potential of using plastic waste as a partial replacement of gypsum matrix in construction applications. However, it is crucial to consider the impact of high temperature exposure on the mechanical performance of the new composites. Further research is needed to optimize the composition and processing parameters of the new composites to ensure their mechanical stability under fire conditions.

Influence of high temperature exposure on compressive strength and microstructure of ultra-high performance geopolymer concrete with waste glass and ceramic

This research evaluates the effect of high temperatures up to 800 °C on the compressive strength and microstructure of the developed ultra-high performance geopolymer concrete (UHPGC) containing waste glass (WG) and ceramic (WC). Fine aggregate was partially substituted with WG and WC in the range of 7.5–22.5% by vol. Samples were heated in the range of 200–800 °C at a heating rate of 5 °C/min for 1.5 h. The visual appearance, mass loss, residual compressive strength, and microscopic investigation of UHPGC mixtures were investigated. The outcomes of the experiments demonstrated that the residual strength of UHPGC containing WG varied from 98% to 97%, 59%–63%, and 27%–32% after being subjected to 300, 600, and 800 °C, respectively. While WC samples had residual strengths varying from 86% to 83%, 51%–45%, and 24%–18%, respectively. Therefore, compressive strength deteriorates more slowly with an increase in WG than WC. Microscopy experiments showed that WC pore structure expanded with temperature, notably above 600 °C, while WG had less pore structure and enhanced residual strength. Finally, the incorporation of WG is more effective in UHPGC thermal stability up to 800 °C than WC. Thermogravimetric analysis (TGA) results revealed that the mixtures containing 22.5% WG maintained about 95% of its weight, while the mixtures incorporating 22.5% WC lost 8% of their weight. It is concluded that WG could be implemented as an eco-friendly material with desirable properties at high temperatures.

Long-term thermal ageing of the 2219-T851 and the 2050-T84 Al-Cu alloys

In this study, the influence of high temperature exposure on mechanical properties as well as on the microstructures of two Al-Cu alloys, has been investigated. Driven by an industrial will to use structural aluminium at higher temperature than usually stated, this work is focused on the characterization of the evolution of two commercial alloys, the 2219-T851 and the 2050-T84, induced by an ageing treatment of 1000 h at 200 °C. Careful TEM observations confirm the importance of the nanoscale precipitation and that the precipitate size and distribution strongly influence the mechanical properties of the studied alloys. Results unexpectedly show that the θ′−Al2Cu precipitates are more stable in time than the T1−Al2CuLi precipitates at this temperature. Regarding the mechanical properties related to ageing, it follows that the 2219-T851 alloy presents a reduced drop with time of its tensile test curves compared to the 2050-T84, thus a limited, and at least less pronounced, temperature dependence. For an industrial application on structural part, 2219-T851 alloy then appears to be a good candidate for long-term structural applications at intermediate temperatures.

Influence of high temperature exposure on the mechanical performance of double-lap adhesive joints between glass and aluminium adherends

The present paper illustrates an experimental investigation on double-lap adhesive joints between glass and aluminium adherends. Four different commercial structural adhesives (three epoxies and one urethane) are selected for tensile tests on adhesive joints subjected to different loading conditions (i.e. quasi-static and cyclic) and high temperature exposures (85 °C). The main objective is to verify the mechanical performance and the applicability of the joint in the field of civil engineering.The results show - after curing under laboratory conditions (20 ± 1 °C/50 ± 5% RH) - a good adhesion between the tested materials. A suitable mechanical behaviour for the assembly of building components with adhesive technology is observed. The first epoxy adhesive shows the best performance both in terms of stiffness and ultimate load, which is due to a better and complete catalysis of the two components of the epoxy adhesive. Exposure to a heating (85 °C) and cooling (20 °C) cycle shows a positive effect on the mechanical performance of the joints. An increase in stiffness and ultimate loads is observed for the first and second epoxy and urethane adhesives. Cyclic loading/unloading tests performed after each heating (85 °C) and cooling (20 °C) process - up to ten repetitions - show a nonlinear trend of displacements and stiffnesses. However, at the end of each loading/unloading cycle, an increase in the ductility of the joint is observed. Moreover, a short exposure of the joints to high temperatures (85 °C) leads to an improvement in the failure modes: mixed failure modes are observed, with CF and GF failure rates coexisting with adhesive failures. Prolonged exposure to high temperatures has a negative effect on the failure modes of the joints and leads to an increase in the percentage of adhesive failures.

Influence of High-Temperature Exposure on the Microstructure of ATI 718Plus Superalloy Studied by Electron Microscopy and Tomography Techniques

The changes in ATI® 718Plus™ (718Plus) superalloy microstructure after high-temperature long-term exposure (850 °C/4000 h/air) were characterized by two- and three-dimensional imaging techniques. The 718Plus microstructure consists of a γ-matrix strengthened by coherent γ′-phase and plate-like η-phase at grain boundaries. The η-phase analysis showed the presence of δ-phase stacking faults within it, along with fluctuations of chemical composition within these defects. Applied thermal exposure resulted in an increased amount of δ-, η-phases and formation of topologically close-packed phases. One of them was identified by electron diffraction as trigonal μ-phase. However, the difference in size and morphology revealed via tomographic reconstruction indicates that the formation of other topologically close-packed phases is possible. The μ-phase was enriched in Mo, Co, Fe and Cr, which causes their depletion in the γ-matrix and may detrimentally affect the superalloy mechanical properties.

Influence of High Temperature Exposure on the Thermal and Optical Properties of Thermal Oil-Based Solar Nanofluids

Influence of High Temperature Exposure on the Thermal and Optical Properties of Thermal Oil-Based Solar Nanofluids

Acoustic Emission behavior of thermally damaged Self-Compacting High Strength Fiber Reinforced Concrete

This paper investigates the effect of high temperature on two different Self-Compacting (SC) cementitious composites. SC-High Strength (SCHSC) and Fiber-Reinforced Concrete (SCHSFRC) samples were tested in three-point bending after having been exposed to high temperature at 300 and 600 °C. Besides the conventional force-displacement response, Acoustic Emission (AE) activity was monitored during the bending tests with the aim to investigate the possible correlation between the fracture behavior, the rate of AEs and the influence of high temperature exposure. The tests clearly pointed out the effects of heat exposure. More specifically, SCHSC specimens showed a significant decay in mechanical properties as a result of thermal treatments. Then, a lower degradation was observed for the SCHSFRC after heat exposure at 300 °C, whereas the specimens exposed to 600 °C exhibited a tougher response than the corresponding SCHSC. The results showed that the effect of fibers played a beneficial role in bridging the expansion of heat-induced cracks developed in the concrete matrix during the exposure of specimens at high temperature. This bridging effect of fibers was observed also in terms of the AE activity: much less AE events were systematically registered for SCHSFRC specimens with respect to SCHSC ones, for a given value of the imposed Crack-Mouth-Opening-Displacement (CMOD). Therefore, AE measurements confirm their potential in scrutinizing the damage level in cementitious composites.

Influence of high temperature exposure on the adhesion of a micro-composite refractory enamel to a Ni–18Cr–12W superalloy

A new micro-composite refractory enamel (MCRE) was designed to play a multifunctional protective role (thermal barrier coating, corrosive and erosive protection) for the hot working parts made of EI868 superalloy sheets i.e. burning chambers, fire tubes, volets, eclises, etc. The effect of the isothermal heating at elevates temperature (800 °C, 900 °C) were, for the first time, investigate for MCRE/EI868 couple. The adhesion strength has shown an enhancement of about 100% when the couple was heated at 800 °C or at 900 °C for 10 h compared with the unexposed one. SEM-EDS, OM, XRD, EDP-XRFS and SDAR-OES investigations support a chemical bonding mechanism between MCRE and EI868 substrate via a transient interface layer. Elemental EDS distributions show that the Cr selective oxidation is responsible for the formation of the transient layer. The XRD measurements can be correlated with the contribution of the spinellic transformation of the SiO2, Cr2O3, NiO to the adhesion enhancement. The most important result reported herein is the adhesion strength enhancement of the MCRE coatings to the EI868 supperalloy by isothermal treatment. Accordingly, the MCRE behaves as a self-healing coating. Noteworthy, the working lifetime of the MCRE-EI868 couple can be significantly enhanced if an optimum pre-treatment is applied before it comes into service.

Residual Mechanical Properties of Hybrid Fiber Reinforced HPC Exposed to High Temperatures

The effect of high temperature load on mechanical properties and porosity of a newly designed Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is studied. The hybrid reinforcement of UHPFRC is based on a mixture of polypropylene and steel fibers. In order to identify influence of high temperature exposure on UHPFRC, its residual mechanical parameters such as compressive strength, flexural strength and Young’s modulus of elasticity are accessed. Moreover, residual bulk density, matrix density and total open porosity are examined and related to the monitored structural changes. Simultaneous Thermal Analysis (STA) is employed in order to describe transformation processes during high temperature loading. The conducted tests provide practical information for controlled regulation of water vapor transport in a low permeable cementitious composite in order to decrease risk of spalling.

The Influence of High Temperature Exposure on the Wear of Selected HVOF Sprayed Coatings

The influence of high temperature exposure on the mechanical and wear properties of selected HVOF sprayed CrC and No/Co – based alloy coatings were tested. Comparison of as-sprayed and 600°C/116 h annealed coatings’ microhardness, cohesive strength, abrasive and adhesive wear resistance showed that the Co-based Stellite 6 coating’s wear properties were deteriorated by heat exlosure despite of the increase of its hardness and cohesive strength. The heat exposure was found to be beneficial for both mechanical and wear properties of NiCrBSi self-fluxing coating. On the contrary, mechanical properties of Cr3C2-NiCr coating slightly decreased, while its wear resistance slightly increased as a result of high temperature exposure.

521 しゃ熱コーティング材のトップコートヤング率に及ぼす高温曝露の影響

521 しゃ熱コーティング材のトップコートヤング率に及ぼす高温曝露の影響

OM4 bend insensitive multi-mode fibers’ usefulness for MCM integration

► The influence of high temperature exposure on OM4 fibers’ mechanical properties. ► Researching OM4 class fibers for use in innovative Optical Multi Chip Module. ► The influence of bending at a very small radius, up to 2 mm, on MM fibers. For future generations of electronic systems, a severe bottleneck is expected on the interconnection level and the use of optical interconnection is considered as one of the most promising solutions in this matter. Recent progress in fiber development resulted in new generation of optical fibers that are bend insensitive. This makes them ideal for Multi Chip Module (MCM) application. This paper focuses on OM4 bend insensitive multi-mode fibers’ usefulness for MCM integration, particularly the investigation of MM fiber loss is presented, which is influenced by bend diameter and the fiber's mechanical performance under influence of high temperature (400 °C–1000 °C adequate to MCM production process).

555 しゃ熱コーティング材のトップコートヤング率に及ぼす高温曝露の影響(材料力学II,学術講演)

555 しゃ熱コーティング材のトップコートヤング率に及ぼす高温曝露の影響(材料力学II,学術講演)

751 しゃ熱コーティング材の熱伝導率及び気孔率におよぼす高温曝露の影響(材料力学III)

751 しゃ熱コーティング材の熱伝導率及び気孔率におよぼす高温曝露の影響(材料力学III)

752 しゃ熱コーティング材のトップコートヤング率に及ぼす高温曝露の影響(材料力学III)

752 しゃ熱コーティング材のトップコートヤング率に及ぼす高温曝露の影響(材料力学III)

120 しゃ熱コーティング材のトップコートヤング率に及ぼす高温曝露の影響(コーティング・溶射・薄膜プロセス(2),ものづくりにおける基礎研究と先端技術の融合)

120 しゃ熱コーティング材のトップコートヤング率に及ぼす高温曝露の影響(コーティング・溶射・薄膜プロセス(2),ものづくりにおける基礎研究と先端技術の融合)

119 しゃ熱コーティング材の熱伝導率及び気孔率におよぼす高温曝露の影響(コーティング・溶射・薄膜プロセス(2),ものづくりにおける基礎研究と先端技術の融合)

119 しゃ熱コーティング材の熱伝導率及び気孔率におよぼす高温曝露の影響(コーティング・溶射・薄膜プロセス(2),ものづくりにおける基礎研究と先端技術の融合)

The influence of high temperature exposure to air on the damage to 3D-C/SiC composites

The influence of high temperature exposure to air on the damage to 3D-C/SiC composites