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Development of oxide based diffusion barrier coatings for CFC components applied in modern furnaces

Kirsten BOBZIN, Lidong ZHAO, Thomas SCHLAEFER, Thomas WARDA

《机械工程前沿(英文)》 2011年 第6卷 第4期   页码 392-396 doi: 10.1007/s11465-011-0241-z

摘要:

Carbon fibre reinforced carbon (CFC) materials show a high potential for usage in furnaces as sample carriers for example, which is due to their excellent thermal stability compared to steel carriers. Only their tendency to react with different metals at high temperatures by C-diffusion is a disadvantage, which can be solved by application of diffusion barriers. In order to enable the utilization of CFC-carriers for e.g. brazing furnaces, within the frame of this study thermally sprayed diffusion barrier coatings were developed. Coatings of mullite and ZrO2-7%βY2O3 (YSZ) were prepared by air plasma spraying (APS). The coatings were investigated in terms of their microstructure and thermal shock behaviour. In order to prove the suitability of the coatings for the application in brazing furnaces, the wettability of the coating surfaces by a Ni-based brazing alloy was investigated. The results showed that both mullite and YSZ could be deposited on CFC substrates with a bond coat of W or SiC. Both coatings exhibited good thermal shock behaviour and an excellent non-wetting behaviour against the used Ni-based braze alloy.

关键词: diffusion barrier coatings     carbon fibre reinforced carbon (CFC)     plasma spraying     microstructure     furnace    

Studies of fiber-matrix debonding

Navneet DRONAMRAJU,Johannes SOLASS,Jörg HILDEBRAND

《结构与土木工程前沿(英文)》 2015年 第9卷 第4期   页码 448-456 doi: 10.1007/s11709-015-0316-8

摘要: In this paper, the debonding of a single fiber-matrix system of carbon fiber reinforced composite (CFRP) AS4/Epson 828 material is studied using Cohesive Zone Model (CZM). The effect of parameters namely, maximum tangential contact stress, tangential slip distance and artificial damping coefficient on the debonding length at the interface of the fiber-matrix is analyzed. Contact elements used in the CZM are coupled based on a bilinear stress-strain curve. Load is applied on the matrix, tangential to the interface. Hence, debonding is observed primarily in Mode II. Wide range of values are considered to study the inter-dependency of the parameters and its effect on debonding length. Out of the three parameters mentioned, artificial damping coefficient and tangential slip distance significantly affect debonding length. A thorough investigation is recommended for case wise interface debonding analysis, to estimate the optimal parametric values while using CZM.

关键词: single fibre     cohesive zone model     interface debonding     carbon fiber reinforced composite (CFRP)    

高强度纤维的低成本化开发新路

回显权

《中国工程科学》 2007年 第9卷 第11期   页码 132-136

摘要:

为增强玻璃纤维的工作强度,使它达到碳纤维的水平,提出了新生态预浸复合改性技术,以一种永 久保持新生态提高强度的方法达到此目的。

关键词: 玻璃纤维     新生态强度     高性能复合材料     低成本化    

Deflection behavior of a prestressed concrete beam reinforced with carbon fibers at elevated temperatures

Mohammed FARUQI, Mohammed Sheroz KHAN

《结构与土木工程前沿(英文)》 2019年 第13卷 第1期   页码 81-91 doi: 10.1007/s11709-018-0468-4

摘要: Fiber reinforced polymer(FRP) have unique advantages like high strength to weight ratio, excellent corrosion resistance, improving deformability and cost effectiveness. These advantages have gained wide acceptance in civil engineering applications. FRP tendons for prestressing applications are emerging as one of the most promising technologies in the civil engineering industry. However, the behavior of such members under the influence of elevated temperatures is still unknown. The knowledge and application of this could lead to a cost effective and practical considerations in fire safety design. Therefore, this study examines the deflection behavior of the carbon fiber reinforced polymer(CFRP) prestressed concrete beam at elevated temperatures. In this article, an analytical model is developed which integrates the temperature dependent changes of effective modulus of FRP in predicting the deflection behavior of CFRP prestressed concrete beams within the range of practical temperatures. This model is compared with a finite element mode (FEM) of a simply supported concrete beam prestressed with CFRP subjected to practical elevated temperatures. In addition, comparison is also made with an indirect reference to the real behavior of the material. The results of the model correlated reasonably with the finite element model and the real behavior. Finally, a practical application is provided.

关键词: FRP     CFRP     concrete     elevated temperatures     deflections     prestress    

Strengthening mechanisms in carbon nanotube reinforced bioglass composites

Jing ZHANG, Chengchang JIA, Zhizhong JIA, Jillian LADEGARD, Yanhong GU, Junhui NIE

《化学科学与工程前沿(英文)》 2012年 第6卷 第2期   页码 126-131 doi: 10.1007/s11705-012-1279-0

摘要: Carbon nanotube reinforced bioglass composites have been successfully synthesized by two comparative sintering techniques, i.e., spark plasma sintering (SPS) and conventional compaction and sinteirng. The composites show improved mechanical properties, with SPS technique substantially better than conventional compact and sintering approach. Using SPS, compared with the 45S5Bioglass matrix, the maximum flexural strength and fracture toughness increased by 159% and 105%, respectively. Enhanced strength and toughness are attributed to the interfacial bonding and bridging effects between the carbon nanotubes and bioglass powders during crack propagations.

关键词: 45S5Bioglass     multi-wall carbon nanotubes     biocomposite     mechanical properties     sintering    

Experimental and numerical investigations of the compressive behavior of carbon fiber-reinforced polymer-strengthened

Peng DENG, Boyi YANG, Xiulong CHEN, Yan LIU

《结构与土木工程前沿(英文)》 2020年 第14卷 第5期   页码 1215-1231 doi: 10.1007/s11709-020-0663-y

摘要: A method for strengthening damaged tubular steel T-joints under axial compression by wrapping them with carbon fiber-reinforced polymer (CFRP) sheets was proposed and evaluated. The influence of the CFRP strengthening on the failure mode and load capacity of T-joints with different degrees of damage was investigated using experiments and finite element analyses. Five T-joints were physically tested: one bare joint to obtain the peak load and corresponding displacement ( ), two reinforced joints to provide a reference, and two pre-damaged then retrofitted joints to serve as the primary research objects. The ratio of the pre-loaded specimen chord displacement to the value of was considered to be the degree of damage of the two retrofitted joints, and was set to 0.80 and 1.20. The results demonstrate that the maximum capacity of the retrofitted specimen was increased by 0.83%–15.06% over the corresponding unreinforced specimens. However, the capacity of the retrofitted specimen was 2.51%–22.77% lesser compared with that of the directly reinforced specimens. Next, 111 numerical analysis models (0.63≤ ≤0.76, 9.70≤ ≤16.92) were established to parametrically evaluate the effects of different geometric and strengthening parameters on the load capacity of strengthened tubular T-joints under different degrees of damage. The numerical analysis results revealed that the development of equivalent plastic strain at the selected measuring points was moderated by strengthening with CFRP wrapping, and indicated the optimal CFRP strengthening thickness and wrapping orientation according to tubular T-joint parameters. Finally, reasonable equations for calculating the load capacity of CFRP-strengthened joints were proposed and demonstrated to provide accurate results. The findings of this study can be used to inform improved CFRP strengthening of damaged tubular steel structures.

关键词: tubular T-joint     carbon fiber-reinforced polymer     degree of damage     numerical analysis     equivalent plastic strain    

Consumption of carbon fiber plates in the reinforced concrete beams strengthened with CFPs

BU Liangtao, SHI Chuxian, SONG Li

《结构与土木工程前沿(英文)》 2007年 第1卷 第4期   页码 393-398 doi: 10.1007/s11709-007-0053-8

摘要: Four-point bending flexural tests were conducted to one full-size reinforced concrete (RC) beam and three full-size RC beams strengthened with carbon fiber plates (CFPs). The experimental results showed that the consumption of CFP

关键词: flexural     full-size     Four-point     consumption     experimental    

Experimental study on fire protection methods of reinforced concrete beams strengthened with carbon fiberreinforced polymer

HU Kexu, HE Guisheng, LU Fan

《结构与土木工程前沿(英文)》 2007年 第1卷 第4期   页码 399-404 doi: 10.1007/s11709-007-0054-7

摘要: In this paper, two reinforced concrete (RC) beams strengthened with carbon fiber reinforced polymer (CFRP) and attached with thick-painted fire resistant coating were tested for fire resistance following the standard fire testing procedures. The experimental results show that the specimen pasted with the insulated layer of 50 mm in thickness could resist fire for 2.5 h. It is also demonstrated that the steel wire mesh embedded in the insulated layer can effectively prevent it from cracking and eroding under firing.

关键词: polymer     insulated     resistant     CFRP     resistance    

Axial compression tests and numerical simulation of steel reinforced recycled concrete short columnsconfined by carbon fiber reinforced plastics strips

Hui MA; Fangda LIU; Yanan WU; Xin A; Yanli ZHAO

《结构与土木工程前沿(英文)》 2022年 第16卷 第7期   页码 817-842 doi: 10.1007/s11709-022-0844-y

摘要: To research the axial compression behavior of steel reinforced recycled concrete (SRRC) short columns confined by carbon fiber reinforced plastics (CFRP) strips, nine scaled specimens of SRRC short columns were fabricated and tested under axial compression loading. Subsequently, the failure process and failure modes were observed, and load-displacement curves as well as the strain of various materials were analyzed. The effects on the substitution percentage of recycled coarse aggregate (RCA), width of CFRP strips, spacing of CFRP strips and strength of recycled aggregate concrete (RAC) on the axial compression properties of columns were also analyzed in the experimental investigation. Furthermore, the finite element model of columns which can consider the adverse influence of RCA and the constraint effect of CFRP strips was founded by ABAQUS software and the nonlinear parameter analysis of columns was also implemented in this study. The results show that the first to reach the yield state was the profile steel in the columns, then the longitudinal rebars and stirrups yielded successively, and finally RAC was crushed as well as the CFRP strips was also broken. The replacement rate of RCA has little effect on the columns, and with the substitution rate of RCA from 0 to 100%, the bearing capacity of columns decreased by only 4.8%. Increasing the CFRP strips width or decreasing the CFRP strips spacing could enhance the axial bearing capacity of columns, the maximum increase was 10.5% or 11.4%, and the ductility of columns was significantly enhanced. Obviously, CFRP strips are conducive to enhance the axial bearing capacity and deformation capacity of columns. On this basis, considering the restraint effect of CFRP strips and the adverse effects of RCA, the revised formulas for calculating the axial bearing capacity of SRRC short columns confined by CFRP strips were proposed.

关键词: steel reinforced recycled concrete     CFRP strips     short columns     axial compression behavior     recycled aggregate concrete    

A deep feed-forward neural network for damage detection in functionally graded carbon nanotube-reinforced

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1453-1479 doi: 10.1007/s11709-021-0767-z

摘要: This paper proposes a new Deep Feed-forward Neural Network (DFNN) approach for damage detection in functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates. In the proposed approach, the DFNN model is developed based on a data set containing 20 000 samples of damage scenarios, obtained via finite element (FE) simulation, of the FG-CNTRC plates. The elemental modal kinetic energy (MKE) values, calculated from natural frequencies and translational nodal displacements of the structures, are utilized as input of the DFNN model while the damage locations and corresponding severities are considered as output. The state-of-the art Exponential Linear Units (ELU) activation function and the Adamax algorithm are employed to train the DFNN model. Additionally, in order to enhance the performance of the DFNN model, the mini-batch and early-stopping techniques are applied to the training process. A trial-and-error procedure is implemented to determine suitable parameters of the network such as the number of hidden layers and the number of neurons in each layer. The accuracy and capability of the proposed DFNN model are illustrated through two distinct configurations of the CNT-fibers constituting the FG-CNTRC plates including uniform distribution (UD) and functionally graded-V distribution (FG-VD). Furthermore, the performance and stability of the DFNN model with the consideration of noise effects on the input data are also investigated. Obtained results indicate that the proposed DFNN model is able to give sufficiently accurate damage detection outcomes for the FG-CNTRC plates for both cases of noise-free and noise-influenced data.

关键词: damage detection     deep feed-forward neural networks     functionally graded carbon nanotube-reinforced composite plates     modal kinetic energy    

Multiscale model of micro curing residual stress evolution in carbon fiber-reinforced thermoset polymer

Xinyu HUI, Yingjie XU, Weihong ZHANG

《机械工程前沿(英文)》 2020年 第15卷 第3期   页码 475-483 doi: 10.1007/s11465-020-0590-6

摘要: In this study, the micro curing residual stresses of carbon fiber-reinforced thermoset polymer (CFRP) composites are evaluated using a multiscale modeling method. A thermochemical coupling model is developed at the macroscale level to obtain the distributions of temperature and degree of cure. Meanwhile, a representative volume element model of the composites is established at the microscale level. By introducing the information from the macroscale perspective, the curing residual stresses are calculated using the microscale model. The evolution of curing residual stresses reveals the interaction mechanism of fiber, matrix, and interphase period during the curing process. Results show that the curing residual stresses mostly present a tensile state in the matrix and a compressive state in the fiber. Furthermore, the curing residual stresses at different locations in the composites are calculated and discussed. Simulation results provide an important guideline for the analysis and design of CFRP composite structures.

关键词: CFRP     curing residual stress     multiscale modeling     finite element method    

Strengthening of reinforced concrete beams using fiber-reinforced cementitious matrix systems fabricated

《结构与土木工程前沿(英文)》   页码 1100-1116 doi: 10.1007/s11709-023-0967-9

摘要: The performance of a new fiber-reinforced cementitious matrix (FRCM) system developed using custom-designed mortar and fabrics is investigated in this study. The behavior of this system is evaluated in terms of both the flexural and shear strengthening of reinforced concrete beams. Eight beams are designed to assess the effectiveness of the FRCM system in terms of flexural strengthening, and four specimens are designed to investigate their shear behavior. The parameters investigated for flexural strengthening are the number of layers, span/depth ratio, and the strengthening method. Unlike previous studies, custom fabrics with similar axial stiffness are used in all strengthening methods in this study. In the shear-strengthened specimens, the effects of the span/depth ratio and strengthening system type (fiber-reinforced polymer (FRP) or FRCM) are investigated. The proposed FRCM system exhibits desirable flexural and shear strengthening for enhancing the load capacity, provides sufficient bonding with the substrate, and prevents premature failure modes. Considering the similar axial stiffness of fabrics used in both FRCM and FRP systems and the higher load capacity of specimens strengthened by the former, cement-based mortar performs better than epoxy.

关键词: fiber-reinforced cementitious matrix     flexural strengthening     shear strengthening     carbon fiber-reinforced polymer     shear span    

Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

《结构与土木工程前沿(英文)》 2021年 第15卷 第6期   页码 1426-1440 doi: 10.1007/s11709-021-0783-z

摘要: The ultra-high-performance concrete (UHPC) and fiber-reinforced polymer (FRP) are well-accepted high-performance materials in the field of civil engineering. The combination of these advanced materials could contribute to improvement of structural performance and corrosion resistance. Unfortunately, only limited studies are available for shear behavior of UHPC beams reinforced with FRP bars, and few suggestions exist for prediction methods for shear capacity. This paper presents an experimental investigation on the shear behavior of UHPC beams reinforced with glass FRP (GFRP) and prestressed with external carbon FRP (CFRP) tendons. The failure mode of all specimens with various shear span to depth ratios from 1.7 to 4.5 was diagonal tension failure. The shear span to depth ratio had a significant influence on the shear capacity, and the effective prestressing stress affected the crack propagation. The experimental results were then applied to evaluate the equations given in different codes/recommendations for FRP-reinforced concrete structures or UHPC structures. The comparison results indicate that NF P 18-710 and JSCE CES82 could appropriately estimate shear capacity of the slender specimens with a shear span to depth ratio of 4.5. Further, a new shear design equation was proposed to take into account the effect of the shear span to depth ratio and the steel fiber content on shear capacity.

关键词: beam     external prestressing     ultra-high-performance concrete     fiber-reinforced polymers     shear behavior     design equation    

Graphene-reinforced metal-organic frameworks derived cobalt sulfide/carbon nanocomposites as efficient

《化学科学与工程前沿(英文)》 2021年 第15卷 第6期   页码 1487-1499 doi: 10.1007/s11705-021-2085-3

摘要: Developing cost-effective electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is vital in energy conversion and storage applications. Herein, we report a simple method for the synthesis of graphene-reinforced CoS/C nanocomposites and the evaluation of their electrocatalytic performance for typical electrocatalytic reactions. Nanocomposites of CoS embedded in N, S co-doped porous carbon and graphene (CoS@C/Graphene) were generated via simultaneous sulfurization and carbonization of one-pot synthesized graphite oxide-ZIF-67 precursors. The obtained CoS@C/Graphene nanocomposites were characterized by X-ray diffraction, Raman spectroscopy, thermogravimetric analysis-mass spectroscopy, scanning electronic microscopy, transmission electronic microscopy, X-ray photoelectron spectroscopy and gas sorption. It is found that CoS nanoparticles homogenously dispersed in the in situ formed N, S co-doped porous carbon/graphene matrix. The CoS@C/10Graphene composite not only shows excellent electrocatalytic activity toward ORR with high onset potential of 0.89 V, four-electron pathway and superior durability of maintaining 98% of current after continuously running for around 5 h, but also exhibits good performance for OER and HER, due to the improved electrical conductivity, increased catalytic active sites and connectivity between the electrocatalytic active CoS and the carbon matrix. This work offers a new approach for the development of novel multifunctional nanocomposites for the next generation of energy conversion and storage applications.

关键词: MOF derivative     graphene     electrocatalyst     oxygen reduction reaction     oxygen evolution reaction     hydrogen evolution reaction    

Nonlinear dynamic analysis of functionally graded carbon nanotube-reinforced composite plates using MISQ20

《结构与土木工程前沿(英文)》   页码 1072-1085 doi: 10.1007/s11709-023-0951-4

摘要: The main objective of this study is to further extend the mixed integration smoothed quadrilateral element with 20 unknowns of displacement (MISQ20) to investigate the nonlinear dynamic responses of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates with four types of carbon nanotube distributions. The smooth finite element method is used to enhance the accuracy of the Q4 element and avoid shear locking without using any shear correction factors. This method yields accurate results even if the element exhibits a concave quadrilateral shape and reduces the error when the element meshing is rough. Additionally, the element stiffness matrix is established by integrating the boundary of the smoothing domains. The motion equation of the FG-CNTRC plates is solved by adapting the Newmark method combined with the Newton–Raphson algorithm. Subsequently, the calculation program is coded in the MATLAB software and verified by comparing it with other published solutions. Finally, the effects of the input parameters on the nonlinear vibration of the plates are investigated.

关键词: carbon nanotube     MISQ20     FG-CNTRC plate     nonlinear vibration     nonlinear dynamic analysis     SFEM    

标题 作者 时间 类型 操作

Development of oxide based diffusion barrier coatings for CFC components applied in modern furnaces

Kirsten BOBZIN, Lidong ZHAO, Thomas SCHLAEFER, Thomas WARDA

期刊论文

Studies of fiber-matrix debonding

Navneet DRONAMRAJU,Johannes SOLASS,Jörg HILDEBRAND

期刊论文

高强度纤维的低成本化开发新路

回显权

期刊论文

Deflection behavior of a prestressed concrete beam reinforced with carbon fibers at elevated temperatures

Mohammed FARUQI, Mohammed Sheroz KHAN

期刊论文

Strengthening mechanisms in carbon nanotube reinforced bioglass composites

Jing ZHANG, Chengchang JIA, Zhizhong JIA, Jillian LADEGARD, Yanhong GU, Junhui NIE

期刊论文

Experimental and numerical investigations of the compressive behavior of carbon fiber-reinforced polymer-strengthened

Peng DENG, Boyi YANG, Xiulong CHEN, Yan LIU

期刊论文

Consumption of carbon fiber plates in the reinforced concrete beams strengthened with CFPs

BU Liangtao, SHI Chuxian, SONG Li

期刊论文

Experimental study on fire protection methods of reinforced concrete beams strengthened with carbon fiberreinforced polymer

HU Kexu, HE Guisheng, LU Fan

期刊论文

Axial compression tests and numerical simulation of steel reinforced recycled concrete short columnsconfined by carbon fiber reinforced plastics strips

Hui MA; Fangda LIU; Yanan WU; Xin A; Yanli ZHAO

期刊论文

A deep feed-forward neural network for damage detection in functionally graded carbon nanotube-reinforced

期刊论文

Multiscale model of micro curing residual stress evolution in carbon fiber-reinforced thermoset polymer

Xinyu HUI, Yingjie XU, Weihong ZHANG

期刊论文

Strengthening of reinforced concrete beams using fiber-reinforced cementitious matrix systems fabricated

期刊论文

Shear behavior of ultra-high-performance concrete beams prestressed with external carbon fiber-reinforced

期刊论文

Graphene-reinforced metal-organic frameworks derived cobalt sulfide/carbon nanocomposites as efficient

期刊论文

Nonlinear dynamic analysis of functionally graded carbon nanotube-reinforced composite plates using MISQ20

期刊论文