Improvement on Fatigue Performance of 3-D Orthogonal Woven Composite with Nanoclay Modification

Xiaoping Gao,Cong Wang,Wei Wu,Yonggui Li 한국섬유공학회 2021 Fibers and polymers Vol.22 No.1

3-D orthogonal woven composite (3DOWC) has attracted great interest in the industrial and energy fields, due totheir excellent mechanical properties. However, due to the poor bonding strength between fiber and epoxy, it’s mechanicalproperties, especially the fatigue behavior are critical for structural design in the practical applications. The nanoclaymodification composite reinforced with 3-D orthogonal woven fabric (3DOWF)/epoxy resin was fabricated using resininfusion under flexible tooling (RIFT). The quasi-static tensile and fatigue behavior of 3-D orthogonal woven composite(3DOWC) in 0 ° and 90 ° inclined to warp direction were evaluated and compared to the pristine one or composite materialnot modified with nanoclay. The fatigue behavior such as the S-N curves, stress-strain curves, stiffness degradation curvesand residual strength were also obtained. The results show that the tensile strength, modulus and the fatigue life wereimproved effectively due to nanoclay modification. However, the stiffness degradation of nanoclay addition in 90 ° directionwas decreased.

Working Condition Analysis and State Trend Prediction of Hydraulic Turbine Units

Xiaoping Jiang,Xiang Gao,Ziting Wang,Lele Wang 한국유체기계학회 2021 International journal of fluid machinery and syste Vol.14 No.3

Based on the pressure parameters of the turbine, the operation condition of the turbine is determined. Based on the input data, the operation condition of the turbine is predicted by the long short-term memory network. Firstly, the identification model of BP neural network method is established to identify the specific working conditions by using the historical values obtained in the practical engineering application. Then, according to the correlation between the measuring points, the multiple time series long short-term memory network prediction model (LSTM) is constructed, and the state trend of the hydraulic turbine unit under this condition is predicted. The corresponding punishment factors are calculated by using the prediction data of each measuring point and the threshold value of the prediction band, which are mapped into the radar chart Finally, an anomaly early warning system with flexible early warning rules based on equipment deviation index is proposed. Through the experimental analysis, the validity of the long short-term memory network prediction model and the radar graph model for calculating the deviation degree of the equipment is verified, and the advanced warning for the abnormal state of different acquisition points under different working conditions is realized, which provides a new method for the abnormal prediction and fault diagnosis of the hydraulic turbine.

Handling performance analysis and optimization of a vehicle with considering the influence of steering shaft parameters

Jin Gao,Xiaoping Qi 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.2

The structure of a steering system plays an important role in the vehicle’s handling performance. Considering the convenience of changing the structural parameters of the steering system, the phase angle of universal joints and the initial angle of steering shaft are selected as the structural parameters to be studied in this paper. The kinematics of the steering system and the dynamics of the whole vehicle are analyzed theoretically. The simulation study shows that the phase angle mainly influences the fluctuation of the steering ratio, the initial angle mainly influences the symmetry of the steering ratio. The transient and steady-state objective evaluation indexes vary with the phase angle and the initial angle at a period of 180°. Through optimization research, it is demonstrated that the handling performance of a vehicle can be improved in the direction of the desired level by matching the initial angle and phase angle.

Research on Influence of Matrix Component on the Mechanical Behavior of Multiaxial Warp-knitted Composites

Jiawei Chen,Xiaoping Gao,Ke Zhao,Wei Wu 한국섬유공학회 2022 Fibers and polymers Vol.23 No.11

The mass ratio of curing agent to epoxy resin is one of the important factors affecting the behavior of matrix andcomposites. In this paper, the solution of curing agent to epoxy resin with different mass ratio (0.25, 0.30, 0.35 and 0.40) wasselected as matrix, quadriaxial warp-knitted fabric was selected as reinforcement, and the composites were manufactured byapplying vacuum assisted film infusion. Then the tensile and bending behavior of the composites was experimentallyinvestigated, and the curing degree and failure mechanism of the composites were analyzed with respect to thethermodynamic properties and the microscopic failure morphologies. The optimal mass ratio was obtained by applyingnonlinear fitting and verified by experiment, and a mathematical model was derived to predict the relationship between thestrength and the mass ratio. The results showed that the thermal stability, curing degree, tensile and bending strength of thespecimens increase firstly and then decrease with increase of the mass ratio. According to the tensile and bending strengthresults, the optimum mass ratio were obtained as 0.31 and 0.33 by applying nonlinear fitting to the experiment data. Theresults could lay a theoretical foundation for optimizing the mass ratio of matrix components, and improve the strength ofcomposites.

Numerical Simulation of Tensile Behavior of 3D Orthogonal Woven Composites

Xiaori Yang,Xiaoping Gao,Yayun Ma 한국섬유공학회 2018 Fibers and polymers Vol.19 No.3

In this paper, the composite reinforced with three dimensional orthogonal woven fabric/epoxy resin was fabricated with vacuum assisted resin transfer model. The tensile behavior in 0 o and 90 o directions were experimentally executed. The tensile behavior of 3D orthogonal woven composite was numerical simulated based on the unit cell model and compared with the experimental result, the influence of crack damage and stress on fiber, resin and fiber/resin interface was analyzed. The maximum differences between experimental and simulated results are 3.23 % and 7.94 %. The verified model can be used to simulate the other static and dynamic mechanical properties and analyze the influence of the behavior of component material on the mechanical material properties of 3DOWC.

Mechanical Properties Improvement of Nanoclay Addition Epoxy 3D Orthogonal Woven Composite Material

Cong Wang,Xiaoping Gao,Yonggui Li 한국섬유공학회 2019 Fibers and polymers Vol.20 No.7

In this study, the influence of nanoclay on mechanical properties of epoxy/3D orthogonal glass fiber wovencomposite was studied. The DK2 polymer-grade organic nanoclay modification composite specimen reinforced with 3Dorthogonal woven fabric/epoxy was manufactured by means of Resin Infusion under Flexible Tooling (RIFT) process. Firstly, the modification mechanism with nanoclay was characterized by means of Fourier transform infrared spectroscopy(FT-IR), X-ray diffraction (XRD) and transmission electron microscope (TEM). Secondly, as far as the tensile behaviorbetween the fiber/matrix of the composite was concerned, the modification process was optimized by means of nonlinearleast square fitting. The results show that the bonding strength between the fiber and matrix was improved and thedelamination and debonding between fiber and matrix was retarded and shifted to cohesive failure of the matrix due to thenanoclay modification with respect to results from FT-IR, XRD and TEM. The tensile strength and modulus of compositewere increased by 23.32 % and 16.42 % respectively due to 3 of nanoclay addition. The contact angle also shows that thedispersion effect and wettability at this state. The tensile stress-strain curve was fitted by applying nonlinear fitting. It can beconcluded that there has a good modification effect with 3 wt% of nanoclay addition.

Modelling and Prediction of Stress Relaxation for Thermal Bonded Nonwoven Geotextiles

Shiyuan Sun,Xiaoping Gao,Chunhong Fu,Yudong Zhou,Xiaoying Wei,Jiaxin Li,Yiping Qiu 한국섬유공학회 2020 Fibers and polymers Vol.21 No.7

Stress relaxation experiments were performed on three types of thermal bonded nonwoven geotextiles in this studyto model and predict their stress relaxation behaviors. Four mechanical models, including the standard linear solid mechanicsmodel, Eyring’s model, the modified two-Maxwell-unit model and the modified three-Maxwell-unit model were used topredict stress values for 600 h based on 3 and 90 h experimental relaxation data. Results indicated that Eyring’s model and themodified three-Maxwell-unit model fitted the experimental results better than the other two. Estimation using modified three-Maxwell-unit model seemed to construct an upper bound while that using Eyring’s model form a lower bound for thecorresponding experimental data. In addition, predicted curves were much closer to the experimental curve when equationsof the two models were built with the 90 h experimental data than those data of 3 h. Thus, the prediction capability of the twomodels can be substantially improved by employing the data with longer time. In summary, the combination of the modifiedthree-Maxwell-unit model and Eyring’s model can well forcast the range of actual stress during stress relaxation experimentswith the longer term experimental data.

Experimental and Numerical Simulation of Resin Flowing in VARI Process

Geyi You,Xiaoping Gao,Jiawei Chen,Ke Zhao 한국섬유공학회 2023 Fibers and polymers Vol.24 No.8

In this paper, the flow characteristics of resin in vacuum-assisted forming (VARI) process were studied by experiments and numerical simulation. The position and time of resin flow front were recorded by high-speed camera and timer. The viscosity of resin, porosity and permeability of composites were tested. Based on Darcy’s law, the resin permeability model in composite molding was derived, and the permeability was obtained by nonlinear fitting. The unit cell model of plain fabric was established and the flow characteristics of four kinds of viscosity resins were simulated by finite volume method. The flow profile and filling time were compared between experimental and numerical simulation, and the error between the model and the experiment is less than 12%, which verifies the accuracy of the model and shows that the model can be used to predict the flow behavior of resin with different viscosities in composite molding.

Effect of Si/Al ratio on performance of Pt–Sn-based catalyst supported on ZSM-5 zeolite for n-butane conversion to light olefins

Zeeshan Nawaz,Shu Qing,Gao Jixian,Xiaoping Tang,Fei Wei 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.1

The performance of Pt–Sn-based catalyst, supported on ZSM-5 of different Si/Al ratios were investigated for simultaneous dehydrogenation and cracking of n-butane to produce light olefins. The catalysts were characterized by number of physio-chemical techniques including XRF, TEM, IR spectra, NH3-TPD and O2-pulse analysis. Increase in Si/Al ratio of zeolite support ZSM-5 significantly increased light olefin’s selectivity, while feed conversion decreases due to lower acidity of support. The results indicated that both the n-butane cracking and dehydrogenation activity to light olefin’s over Pt–Sn/ZSM-5 samples with increasing Si/Al ratios greatly enhanced catalytic performance. The catalysts were deactivated with time-on-stream due to the formation of carbon-containing deposits. A coke deposition was significantly related to catalyst activity, while at higher Si/Al ratio catalyst the coke precursors were depressed. These results suggested that the Pt–Sn/ZSM-5 catalyst of Si/Al ratio 300 is superior in achieving high total olefins selectivity (above 90 wt.%). The Pt–Sn/ZSM-5 also demonstrates resistance towards hydrothermal treatment, as analyzed through the three successive reaction-regeneration cycles.

China Consensus Document on Allergy Diagnostics

Chen Hao,Li Jing,Cheng Lei,Gao Zhongshan,Lin Xiaoping,Zhu Rongfei,Yang Lin,Tao Ailin,Hong Haiyu,Tang Wei,Guo Yinshi,Huang Huaiqiu,Sun Jinlyu,Lai He,Lei Cheng,Liu Guanghui,Xiang Li,Chen Zhuanggui,Ma Ha 대한천식알레르기학회 2021 Allergy, Asthma & Immunology Research Vol.13 No.2

The prevalence of allergic diseases has increased dramatically in recent years in China, affecting the quality of life in 40% of the population. The identification of allergens is the key to the diagnosis of allergic diseases. Presently, several methods of allergy diagnostics are available in China, but they have not been standardized. Additionally, cross-sensitization and co-sensitization make allergy diagnostics even more complicated. Based on 4 aspects of allergic disease (mechanism, diagnosis procedures, allergen detection in vivo and in vitro as well as the distribution map of the most important airborne allergens in China) and by referring to the consensus of the European Society of Allergy and Clinical Immunology, the World Allergy Organization, and the important literature on allergy diagnostics in China in recent years, we drafted this consensus of allergy diagnostics with Chinese characteristics. It aims to standardize the diagnostic methods of allergens and provides a reference for health care givers. The current document was prepared by a panel of experts from the main stream of professional allergy associations in China.