The Experts below are selected from a list of 1803 Experts worldwide ranked by ideXlab platform
Guofeng Tian - One of the best experts on this subject based on the ideXlab platform.
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Mechanical properties of hybrid composites reinforced by carbon Fiber and high-strength and high-modulus Polyimide Fiber
Polymer, 2020Co-Authors: Boyao Wang, Zhanwen Wang, Guofeng TianAbstract:Abstract High-strength and high-modulus Polyimide Fiber is a kind of high-performance organic Fiber rapidly developing in recent years. Taking advantage of its high strength and toughness and being combined with carbon Fiber, it is expected to make a balance between stiffness and toughness, so as to afford a kind of structural composite with high strength and toughness. In this study, a series of hybrid Fiber reinforced composites were prepared with high-strength and high-modulus PI Fiber and carbon Fiber as reinforcements. The effects of stacking sequence and hybrid ratio on the tensile, compressive and flexural properties and failure modes of the composites were systematically investigated. Experimental results showed that tensile, compressive and flexural properties of the hybrid composites were markedly improved compared with Polyimide Fiber composite, while failure strain and failure energy were superior to those of the carbon Fiber composites. The flexural properties were largely affected by the stacking sequence. Hybrid composites with carbon Fiber as the compressive side showed higher flexural strength, while the ones with carbon Fiber as both compressive side and tensile side had higher flexural modulus.
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Surface modification of Polyimide Fibers by oxygen plasma treatment and interfacial adhesion behavior of a Polyimide Fiber/epoxy composite
Science and Engineering of Composite Materials, 2017Co-Authors: Sun Xuyang, Bu Junfeng, Weiwei Liu, Hongqing Niu, Guofeng TianAbstract:AbstractOxygen plasma was used to enhance the surface behavior of Polyimide (PI) Fibers and PI Fiber-reinforced epoxy composites were prepared in our present work. The effects of plasma treating times on the surface properties of PI Fiber and the interfacial adhesion of PI Fiber/epoxy composites were investigated. Surface chemical composition, surface morphologies and surface free energy of the Fibers were characterized by X-ray photoelectron spectroscopy, scanning electron microscopy and dynamic contact angle analysis, respectively. The results suggest that some oxygen functional groups were introduced onto PI Fiber surfaces, and the surface roughness of Fibers was enhanced. Resultantly, the surface free energy of Fibers and the interfacial adhesion of composites were improved by the oxygen plasma treatment. The interlaminar shear strength of the composites increased to 70 MPa when the Fibers were treated for 10 min, which proved good interfacial adhesion properties.
Jianwen Xia - One of the best experts on this subject based on the ideXlab platform.
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highly mechanical strength and thermally conductive bismaleimide triazine composites reinforced by al2o3 Polyimide hybrid Fiber
Composites Part A-applied Science and Manufacturing, 2016Co-Authors: Jianwen Xia, Guoping Zhang, Xiaoliang Zeng, Fangfang Niu, Haipeng Yang, Rong Sun, Chingping WongAbstract:Abstract Bismaleimide–triazine (BT) resins have received a great deal of attention in microelectronics due to its excellent thermal stability and good retention of mechanical properties. Thereafter, developing BT based composites with high mechanical strength, thermal conductivity and dielectric property simultaneously are highly desirable. In this study, one hybrid Fiber of Al 2 O 3 nanoparticle (200 nm) supported on Polyimide Fiber (Al 2 O 3 @PI) with core–shell structure was introduced into BT resin to prepare promising Al 2 O 3 @PI–BT composite. The results indicated that the resultant composites possessed high Young’s modulus of 4.06 GPa, low dielectric constant (3.38–3.50, 100 kHz) and dielectric loss (0.0102–0.0107, 100 kHz). The Al 2 O 3 @PI hybrid film was also conductive to improve thermal stability ( T d5% up to 371 °C), in-plane thermal conductivity (increased by 295% compared to that of the pure BT resin). Furthermore, the Al 2 O 3 @PI–BT composite were employed to fabricate a printed circuit substrate, on which a frequency “flasher” circuit and electrical components worked well.
Nanliang Chen - One of the best experts on this subject based on the ideXlab platform.
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Interfacial properties of high failure strain Polyimide Fiber/epoxy composites analyzed by a modified single Fiber fragmentation test
Applied Surface Science, 2020Co-Authors: Lin Fangbing, Du Xiaodong, Jinhua Jiang, Nanliang ChenAbstract:Abstract Polyimide (PI) is one of the lightweight and high-performance materials, having great potential to be used as reinforcements for advanced composites. Quantitative evaluation of Fiber/matrix interface is critical in designing Fiber reinforced polymer composites. However, there is a lack of effect characterization methods to measure the interfacial shear strength (IFSS) of Polyimide Fiber (PIF) due to its high failure strain. In this study, a modified single Fiber fragmentation test (SFFT) was proposed to solve this problem. By employing Polyurethane (PU) resin as an additive in commercial epoxy resin, a transparent PU modified epoxy (PU-epoxy) resin is obtained. The PU-epoxy has a failure strain of 137.93%, which is much larger than 14.83% of the PIF, meeting the pre-requirement of SFFT. Oxygen plasma treatment is applied to modify surface properties of the PIF to improve its interfacial adhesion with epoxy. Statistical results show that a plasma-treated PIF for 4 mins achieves a 125.41% increase in IFSS compared with the pristine PIF. Meanwhile, a finite element model (FEM) is created to simulate and visualize stress distribution in Fiber, interface, and matrix during the SFFT.
Qinghua Zhang - One of the best experts on this subject based on the ideXlab platform.
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Structural evolution from poly(amic acid) to Polyimide Fibers during thermal imidization process
High Performance Polymers, 2018Co-Authors: Dianbo Zhang, Jie Dong, Feng Gan, Qinghua ZhangAbstract:In this study, poly(amic acid) (PAA) precursor Fiber was prepared via a two-step wet spinning method and subsequently heat-treated to obtain the Polyimide Fiber by thermal imidization. The structural evolution of the PAA precursor during the imidization was traced using various measurements. The imidization degree of the PAA Fibers treated at different temperatures was calculated by Fourier transform infrared analysis, and the cyclization reaction occurred accompanied by the decomplexation of the H-bonded N,N′-dimethylacetamide (DMAc). The thermogravimetry test illustrated that the residual solvent evaporation took place prior to imidization. Moreover, in situ wide-angle X-ray diffraction and small-angle X-ray scattering measurements were employed to investigate the development of the aggregation structure and microvoids in PAA Fibers. The results indicated that molecular chains were thermally extended during the thermal imidization, resulting in the increase of Hermans’ orientation factor and the increas...
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Principles and Application of Polyimide Fiber Bragg Gratings for Surface Strain Measurement
Applied Sciences, 2017Co-Authors: Yangyang Sun, Jianyong Liu, Wang Yuan, Qinghua Zhang, Duan Jianli, Zhenglin Zhang, Xiaodi Huang, Zewei YouAbstract:Although theoretical investigation has demonstrated that fewer strain transfer layers imply a greater strain transfer ratio, as well as increased accuracy, most researchers are still focused on investigating encapsulated Fiber Bragg gratings (FBGs) in surface strain measurements. This is because, in a traditional view, bare FBGs are too fragile to be mounted on the substrate for measuring surface strain. Polyimide FBGs may provide a better balance point between accuracy and protection. A new method to measure surface strain with Polyimide Fiber Bragg gratings is proposed. Bare Polyimide FBGs have a Polyimide coating, but like regular non-coated FBGs. This gives Polyimide FBGs a higher strain transfer ratio and response frequency. Bare Polyimide FBGs can be considered as uncoated FBGs. The coupling of the matrix material of Polyimide FBGs is improved as compared to FBGs without coating. In order to verify the capacity for surface strain measurement, Polyimide FBGs are mounted to obtain the surface strain of a concrete specimen with SM130-700 interrogator from Micron Optics Incorporation (MOI) with a sampling frequency maximum of 2000 Hz. The experiment demonstrates that Polyimide FBGs work well even in dynamic surface strain measurements such as explosion measurement. Validation experiment in this paper also proposed that fewer strain transfer layers can increase dynamic response frequency and coupling between FBG and substrate.
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Morphology Control of Polyimide Fibers by Phase Separation under Different Coagulation Bath Conditions
Materials Science Forum, 2014Co-Authors: Jie Dong, Chao Qing Yin, Zi Xin Zhang, Qinghua ZhangAbstract:In order to investigate the effects of the coagulation bath temperature and composition on the formation of Polyimide Fiber in wet spinning, theoretical ternary phase diagrams of water/NMP/PI system at two coagulation bath temperatures was investigated based on the extended Flory-Huggins theory. The cloud-points data of the system for more dilute PI terpolymer solutions were determined by cloud point titration, and the cloud point data for more concentrated PI terpolymer solutions were calculated by Boom's linearized cloud point curve correlation. The obtained diagrams showed that if the titration process constructed at a higher temperature, the meta-stable two-phase region in the ternary phase diagram increases, which is beneficial for the de-mixing of the filament via nucleation and growth mechanisms, resulting in a homogenous dense structure for PI Fiber.
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Polyimide Fibers prepared by dry-spinning process: imidization degree and mechanical properties
Journal of Materials Science, 2013Co-Authors: Xu Yuan, Shihua Wang, Qinghua ZhangAbstract:Polyimide Fibers were prepared by dry spinning a polyamic acid solution to get the precursor Fibers and then the precursor Fibers were transferred into the Polyimide Fiber by heat treatment. The imidization degree (ID) of the precursor Fibers obtained at various spinning conditions was investigated using FTIR and TGA analysis. As a result, the IDs of the precursor Fibers increased with elevating spinning temperature. Meanwhile, the IDs measured by FTIR and TGA were much higher than the values from our model prediction. The tensile strength of precursor Fibers exhibited a slight dependency on IDs. On the other hand, the complete imidization and hot stretching led to a great improvement in the mechanical properties. Subglass transition and glass transition of the stretched Polyimide Fibers were observed in DMA, and the activation energy of these transitions was 346 and 981 kJ mol−1, respectively.
Yen Wei - One of the best experts on this subject based on the ideXlab platform.
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A smart surface prepared using the switchable superhydrophobicity of neat electrospun intrinsically electroactive Polyimide Fiber mats
Soft Matter, 2011Co-Authors: Chang-jian Weng, Yu-sian Jhuo, Chi-hao Chang, Chun-fang Feng, Chi-wei Peng, Chung-feng Dai, Jui-ming Yeh, Yen WeiAbstract:An electroactive Polyimide Fiber (EPF) mat based on conjugated segments of electroactive amino-capped aniline trimer (ACAT) as a diamine and 4,4′-(4,4′-sopropylidenediphenoxy)-bis(phthalic anhydride) (BSAA) as a dianhydride was successfully prepared by electro-spin technology with electrochemical activity and dopable properties, which were similar to polyaniline. The degree of electrochemical activity and dopable properties can be tuned by varying the content of ACAT existing in the as-prepared electro-spun EPF mats. After doping with perfluorooctanesulfonic acid (PFOS), the water contact angle of EPF surface is increased from hydrophobicity at 133° to superhydrophobicity at 155°. It is interesting that the EPF mat undergoes a switchable process from superhydrophobicity to superhydrophilicity via doping with PFOS and de-doping with ammonium gas.