COMPOSITES SCIENCE AND ENGINEERING

PLY OPTIMIZATION OF COMPOSITE MATERIALS FOR THE BLADE IN WIND TURBINE

FENG Xiao-bing, HUANG Hai, WANG Wei

2013, 0(3): 3-7.

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This paper presents optimized design based on genetic algorithm about FRP blade of large-scale wind turbine. First we must grasp the theory of mechanics and can use numerical analysis method. So after researching elasticity theory and improved genetic algorithm on monolayer and multilayer composite material,reference a number of layup rules,aiming at four different directions to optimize. The result shows that there are many advantages in using dealing with disperse problem,and proved this method is reliable and feasible.

BASED ON VIRTUAL CRACK CLOSE TECHNIQUE THE CALCULATION OF STRAIN ENERGY RELEASE RATE FOR COMPOSITE MATERIAL

CHEN Yu-liang, CHENG Chen, WAN Shui, JIANG Zheng-wen

2013, 0(3): 8-12.

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Compulation of the strain energy release rate for composite material,based on the virtual close technique,is studied. During the calculation in the finite element,in order to reduce the processing workload,the spring element is applied at the tip of the crack. In practical applications,with Combin14 spring elements are being adopted to establish the finite element model,the solving process and post process are linked,so the the energy release rate can be calculated quickly. Then,this technique is applied to calculate the strain energy release rate for composite material,and the technique is taken to do numerical simulation experiment. Comparing the numerical results and theoretical values,it shows that the calculated values of the strain strain energy release rate are well with the theoretical values. This numerical analysis method is an efficient and accurate numerical analysis method.

AN APPLICABLE STIFFNESS MODEL OF RC BEAMS STRENGTHENED WITH FRP SHEETS

LIN Xin-yan, MENG Hai-ping, YANG Jian-hui, ZHU Xiao-jing

2013, 0(3): 13-17.

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In order to predict the deformability of RC beams strengthened with FRP sheets,an applicable stiffness model is drawn based on stiffness analysis method. In this model,the contributions of FRP to stiffness are considered by introducing two parameters β and λ which denote the reduction of steel strain in tension and concrete strain in crush due to the application of FRP,respectively. The midspan deflections given by this proposed model are compared and shown to agree well with the results from the experimental study. The results show that the stiffness of beam is improved with the increase of FRP amount,and that the proposed stiffness model is simple and practical and has satisfying precision,so it can work as a reference for engineering design.

EXPERIMENTAL STUDY ON TENSILE STRENGTH OF CFRP PLATE BONDED WITH MOC AFTER HIGH TEMPERATURE

XU Ming, HAN Chun-lei, CHEN Zhong-fan

2013, 0(3): 18-21.

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In consideration the problem that currently the softening point of resin adhesive used in strengthening concrete structure with carbon fiber reinforced polymer(CFRP) sheets is too low,an inorganic adhesive,magnesium oxychloride cement(MOC) was invented. Based on the tensile test of 60 CFRP plates heated at the high temperature ranging 20 ~ 400℃,the fire behavior of CFRP plate (2,4,6,8 layers) was investigated. The test results show that the CFRP plate bonded with MOC has the same tensile strength with the CFRP plate bonded with epoxy adhesive; the tensile strength of CFRP plate after 300℃ remain 70% of CFRP plate at 20℃ and the tensile strength of CFRP plate after 400℃ will only 35% of CFRP plate at 20℃. There is a trend of drop for the elastic modulus with the increase of temperature.

RESEARCH ON THE RESINS FOR HIGH TEMPERATURE CARBON FIBER COMPOSITE IN POWER TRANSMISSION AND DISTRIBUTION

LIU Hui, CHEN Xin, WANG Ying-nan, YANG Chang-long

2013, 0(3): 22-25.

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The winding performance of carbon fiber reinforced composites core conductor depends on the toughness of resin system. In this paper,the resin system that is used in carbon fiber reinforced composites core of high temperature resistance was studied. The experimental results showed that: 4,4'-diaminodiphenylmethane epoxy resin could meet the requirement of high temperature resistance. To further improve the safe reliability of the conductor, a polymer of core-shell structure was used to toughen the resin system and the winding performance was further enhanced. The results of pultrusion test and comprehensive performance test showed that the resin formula in this study could meet the technical requirements of pultrusion and the 40D winding performance.

ANALYSIS OF VISCOSITY AND THIXOTROPY ABOUT THE STRUCTURAL ADHESIVE UTILIZED IN WIND TURBINE BLADES

TAN Juan-juan, JIA Zhi-yuan, SONG Qiu-xiang

2013, 0(3): 26-29.

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The application of the structural adhesive is flourishing in wind power generation. The structural adhesive is a key component and has been widely applied in the production, assembly and parts manufacturing of the wind turbine blades. So it is extremely important to guarantee the quality of wind turbine blades based on an effective evaluation about the rheology of the structural adhesives. Since the viscosity and thixotropy are the two extremely important characterizations of rheology, the effect of different testing conditions on the viscosity and thixotropy has been summarized through carrying out a series of testing, and furthermore, the way of evaluating the thixotropy about the structural adhesives utilizing thixotropic loop has been proposed. A series of analyses show that the thixotropy of the structural adhesive can be qualitatively and quantitatively evaluated through the way of thixotropic loop.

STRUCTURAL PARAMETERS INFLUENCE ON THE MODE METHOD TO DETECT DEBONDING DEFECTS

AI Chun-an, PENG Jiong, XU Zhi-gao, LI Jian

2013, 0(3): 30-33.

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This paper regards metal /composite materials structure with debonding as a research object,the finite element method is used to study the influence of composite thickness on the natural frequencies,modal shapes,flexibility matrix to detect structure debonding defects. The results show that: As the thickness increases,the rate of change of the natural frequencies, the modal shape of debonding region and the flexibility matrix of debonding region all appear a increasing and then decreasing trend,when the thickness of composite materials is 5mm,the rate of them are the maximum; On different composite thickness conditon,the flexibility matrix used to detect small area debonding is feasible. The results of this paper provides theoretical guidance for experimental detecting the debonding defects of solid rocket motor nozzle structure based on the modal method in next step.

MECHANISM RESEARCH ON BASALT FIBER WITH PLASMA GRAFTED TREATMENT

LI Wei-na, SHEN Shi-jie, MA Chun-mei

2013, 0(3): 34-38.

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The aim of this study was to explore the mechanism of basalt fiber after plasma grafted with maleic anhydride. Three different fibers were treated including basalt fiber,basalt fiber dealt with KH550 and basalt fiber dealt with KH570. The plasma graft of maleic anhydride on the surface of basalt fiber was generated and confirmed by FTIR,XPS. The morphology of the grafted fiber surface was observed with SEM. It is concluded that maleic anhydride was successfully grafted on three kinds of basalt fiber surface and COOR group was introduced on the fiber.O/C was increased after plasma grafted treatment and the largest increasement was on fiber that was treated with KH570,which was from 0. 74 to 1. 139.

THE CLIMBING DRUM PEEL BEHAVIOR OF STITCHED FOAM-CORE SANDWICH COMPOSITES

PAN Li-jian, LIU Wei-ping, CHEN Ping, QI Fang-fang

2013, 0(3): 39-42.

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The stitched foam core sandwich composites with different parameter under three stitch formation lockstitch,stuffing stitch and double chain stitch were produced. And the climbing drum peel tests were performed.The experimental results show that the peel load of unstitched sandwich composites increased to a peak value and then drove to stabilization,while the peel load of stitched foam-core sandwich composites increased to a peak value and then varies in sine-shaped mode. The average value of the max peel load increased remarkably by stitching.The average value of the max peel load of stitched foam-core sandwich composites increased to 1. 6 ~ 4. 7 times of that unstitched. The peel load of the stitched foam-core sandwich composites with different stitch formation was different under the same stitch parameters. The greater of stitch density and stitch diameter was,the greater of the peel load was under the same stitch formation.

STUDY ON MECHANICAL PROPERTIES OF SINGLE FIBERS REINFORCED SHOTCRETE OF HIGH PERFORMANCE

LI Yan-fei, YANG Jian-hui, DING Peng, ZHAO Hong-bing

2013, 0(3): 43-46.

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The collapse phenomenon of tunnel in construction process is closely related with the quality of shotcrete,so high strength and toughness on the shotcrete of good performance is one of the research contents of need in the construction of the underground engineering. The experiments of single steel fiber,polypropylene fiber,macrosynthetic fiber reinforced shotcrete on the compressive strength and flexural strength are researched in this paper,which are compared with the mechanical properties of common shotcrete,which shows that the compressive strength,flexural strength,flexural compression ratio of fiber shotcrete with appropriate dosage are obviously improved than common shotcrete; strength and flexural compression ratio of macro-synthetic fibers reinforced shotcrete are the best,whose content is 0. 3%. So steel fiberss and polypropylene fiber can be completely replaced by the macro-synthetic fibers in project application with its excellent price-lim,good dispersion and weak corrosion etc.

INFLUENCE FROM STIFFNESS OF LONGITUDINAL RESTRAINT ON STRUCTURAL BEHAVIOURS OF CONCRETE BRIDGE DECK SLABS REINFORCED WITH GFRP BARS WITH ARCHING ACTION

LI Chun-hong, ZHENG Yu, WEI De-min

2013, 0(3): 47-52.

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When concrete bridge deck slabs were restrained by components aside,arching action existed and restraint force acted at arching feet in longitudinal direction of slabs. In order to investigate the influence from various stiffness of restraint on slabs' structural behaviours,six slabs with rotational restraint and longitudinal restraint at both ends were loaded until failed. It showed that as stiffness of restraint rose,restraint force increased,which enhanced the compressive area and reduced strains of GFRP bars. As a result,development of deflection at central span and cracks was slowed down,and serviceability and ultimate bearing capacity of slabs were both improved.Base on the former research,influence from longitudinal restraint on height of compressive area was quantified and restraint force was deduced. The estimated restraint forces were close to test results. And the conclusion was drawn that when proportion of restraint stiffness to compressive stiffness of slab in longitudinal direction was 0. 25 to 2. 00,longitudinal restraint would obviously improve structural behaviours of slab.

SIMULATION STUDY ON THE MECHANICAL PROPERTIES OF THE COMPOSITE COMPONENTS OF TWO-WAY STRETCH METAL

ZHANG En-xue, SUN Yin-bao

2013, 0(3): 53-57.

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Composite is widely used in the aviation industry. It's very important to predict the performance of the critical region by analysis or experiment. Even in the modern aircraft structures metallic joint are needed,and the analysis of the hybrid structures is a key problem. During the elements level of " Building Block" tests,we analyzed the hybrid joint of composite-metal structures by ANSYS finite element software. In the model,we calculated the biaxial tension behavior of the joint,and taken into account the residual curing stress of composite parts. It is found that the specimen warped,and the residual transformation of the joint region is 0. 67mm. when the structure is under ultimate strain,the interlaminar strain is 0. 022mm.

STUDY OF INTERFACIAL PERFORMANCE OF T800 /TDE85 COMPOSITE

ZHANG Lin, ZHENG Li, CHI Bo

2013, 0(3): 58-61.

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On account of its low density and high performance as well as high module,carbon fiber reinforced plastic materials have been used broadly in the aerospace field,the properties of which are dependent on the interface between carbon fiber and resin matrix. For this reason,to discuss the interface performance is extremely significant. Experiments studied T800 /TDE85,comparing to T300 and CCF300 carbon fibers. The surface element concentrations, surface functional groups of fibers were examined by X-ray photoelectron spectroscopy (XPS) . XPS spectra indicates that changes take place in the amount,structure and chemical environment of functional group,and formation of the physical and chemical effect in the interface. By the DCT21 measuring apparatus,we tested the dynamic contact angle between carbon fiber and TDE85 epoxy resin. The result reveals that TDE85 epoxy resin can wet the carbon fiber well. On that basis,with the microdebonding experiments,we characterized the interfacial shear strength of the composites,microdebonding outcome shows that interface shear strength of T800 /TDE85 is 79. 7MPa,which is higher 21% and 24% respectively than T300 /TDE85,CCF300 /TDE85.

THE OPTIMIZATION OF AUTO-FROTTAGE PRESSURE WITH THE CNG COMPOSITE WOUND CYLINDERS

GUO Ya-fang

2013, 0(3): 62-65.

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Facing the deteriorating environment and the depletion of oil resources,as a typical application of the clean energy,the use of CNG cylinders increase year by year,and CNG vehicles are used more widely gradually in the country. CNG-2 cylinders are made up of the metal liner and the outer layer of high strength fiber reinforced composite material composition. They have been widely used because of their light weight,high strength and safety and reliability. In the process of using,it appears some failures and explosion,which results in more and more attention to the safety analysis and research into cylinders. This paper takes CNG-2 cylinders as the research object, describes the optimization process of the auto-frottage pressure using ANSYS.

RESEARCH ON THE INFLUENCE FACTORS OF THE BEARING CAPACITY FOR BONDED-BOLTED HYBRID JOINTS

YUAN Hui, LIU Peng-fei, ZHAO Qi-lin, MA Yu

2013, 0(3): 66-71.

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Theoretical and experimental analyses were performed on the effects of the adhesive layer thickness, the bolt location and the bolt rigidity on bearing capacity of bonded-bolted hybrid joints with bonded-bolted deformation harmony. The valid range of the calculation formula for bearing capacity was discussed. It is founded that the varying of the related geometrical and mechanic parameters influence the failure mode and the bearing capacity and the current calculation method is limited.

PROPERTIES ＆ APPLICATION RESEARCH ON NEW-TYPE WATER SOLUBLE MOLD MATERIAL

MA Li

2013, 0(3): 72-75.

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A new-type of water soluble material,which trade mark is Aquacore^TM,has been investigated. The properties investigated include density,linear expansion ratio,compressive strength and compressive creep ratio. The results show that the density is about 0. 47g /cm³,mean linear thermal expansion coefficient is 1. 17 × 10 ^–6 /℃,compressive strength is 2. 40MPa under 190℃,compressive creep ratio is less than 1. 5%. In the meantime, application research has been conducted. With water soluble mold,a CFRP double-peak corrugated part has been fabricated. The influences of roughness and de-mould method on product have been studied. The test results show that finished surface roughness of water soluble mold R_a is 1. 2,the roughness of product's marble surface R_ais 3. 4. Temperature ＆ water used during de-molding have little effect on product. The moisture absorption of product is 0. 98%. It is shown that the water soluble mold is especially suitable for complex structural parts and those parts which are hard to de-mold.

NDT FOR THE MW WIND TURBINE'S ROTOR BLADE

XU Yang, LIU Wei-sheng, QIAO Guang-hui

2013, 0(3): 76-79.

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Since it's difficult to detect the defect of the big rotor blade visually,especially the exact position and size. Through UT and Shearography's combination,the relative thick glass fiber laminate and bonding area used UT,and for the sandwich structure used Shearography. Through the different devices' combination we can get the detection for the whole blade,further we can do the test for the rotor blade in operation at the wind farm that to guarantee the wind turbine's good operation.

MECHANICAL ANALYSIS OF COMPOSITE WRAPPED CYLINDERS UNDER RANDOM VIBRATION ENVIRONMENT

CHEN Li, REN Ming-fa, SUN Dong-sheng

2013, 0(3): 80-83.

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The stress of a composite overwrapped pressure vessel (COPV) fixed on supports was investigated under a random vibration environment. The fatigue life of the COPV was evaluated by combining the Three Interval Method and Miner criterion. Based on the object of the longest fatigue life of liner,the belt spacing of the COPV is optimized,and a solution for quickly determining the belt spacing is proposed.

CRACK PREVENTING TECHNOLOGY OF THE LARGE L/D RATIO CASE MANDREL

ZHANG Sheng-li, HAN Jian-ping, CHENG Yong, YANG Jie

2013, 0(3): 84-88.

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Study on crack causes of the large L /D ratio case mandrel. The measures of avoid crack have been constituted. The better effects have been obtained. The leading conclusions are enumerated as follows. They are favorable to reduce the mandrel's weight and to improve the mandrel's rigidity that the mandrel's framework adopts the truss structure,and the parts and the assemblies adopt the hollowly structure of rib and lightweight material. That use improving plaster on the mandrel's surface,the ability of the mandrel avoiding transmutation is toned up; the cracks do not appear easily.

FINITE ELEMENT ANALYSIS OF VEHICLE-MOUNTED COMPOSITE CONCRETE MIXING DRUM CYLINDER

LIU Yong, LIU Wei-sheng, QIAO Guang-hui, CHEN Liang-shi

2013, 0(3): 89-92.

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The vehicle-mounted composite concrete mixing drum has some excellent performances such as light quality,good anticorrosion property,good insulation,long life and high plasticity etc,which has been widely applied abroad. However,the research about vehicle-mounted composite concrete mixing drum is still lags behind in our country,and no relevant enterprises and institutions engaged in the product research and development. For this reason,the finite element model of vehicle-mounted composite concrete mixing drum cylinder was builded by using ANSYS software,and the stiffness and strength of composite mixing drum cylinder under self-weight of mixing drum and weight load of concrete material were also calculated and analysed. This article aims to analysed the security and rationality of the application of composite mixing drum on concrete truck.

A STUDY OF THE DISTRIBUTION OF VASCULAR BUNDLE IN A NATURAL BAMBOO TUBE

SHANG Xin-long, MAO Teng-fei, GUAN Xin, WANG Peng-ren

2013, 0(3): 93-96.

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A natural bamboo possesses excellent mechanical properties due to its special structure. With help of observing and measuring instrument,this paper gained the relationship between the thickness of culm wall of bamboo and the equivalent radius,determined the volume percentage of the vascular bundle,the diameter and average distance of the vascular bundle along the radical direction of the bamboo tube. A model was proposed to describe the distribution of the vascular bundle in radial direction.

STUDY ON THE ADHESIVE BEHAVIOR OF THE COMPOSITES OF 5228A RESIN HONEYCOMB SANDWICH STRUCTURE WITHOUT ADHESIVE FILM

WANG Zhen-lin

2013, 0(3): 97-101.

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In this paper,the composites of honeycomb sandwich structure without adhesive film was prepared, the high resin content 5228A prepreg was used as the adhesive layer. The adhesive behavior of composites with the molding pressure and the resin content in the adhesive film was analyzed through ultrasonic nondestructive testing, microstructure of cross-section and the drum peel strength. It was concluded that the 5228A resin with a controllable rheological properties was applicable to the preparation of the composites of honeycomb sandwich structure without adhesive film; the 5228A prepreg had a good process performance. The internal quality of the composites was excellent. The adhesive behavior between the skinning and the cellular was excellent. The drum peel strength of the composites improved as the increasing of the molding pressure and the glued layer resin content.

THE STUDY OF DIFFERENCE BETWEEN REPAIRING TECHNIQUES OF ADHESIVELY BONDING AND VARI

HOU Xue-jie, LI Hua, SHI Jun-hu, LIN Ming

2013, 0(3): 102-105.

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Because of some partly damage,there are many repairing works in the process of wind turbine blade's transportation,assembly and service. In this paper,two scarf patch repair techniques,adhesively bonding repair and VARI(vacuum assistant resin infusion) repair,are designed. And the differences between these two methods are discussed. The results show that,tensile strength and shear strength of adhesively bonding method can remain about 80% after repairing,and VARI method can reach above 90%.

THE RESEARCH OF MODIFIED VINYL ESTER RESIN SYSTEM FORMING PROCESS AND PROPERTIES IN RTM

ZHAO Wei-sheng, SUN Chao-ming, WANG Wen-jing, PENG Yu-gang

2013, 0(3): 106-108.

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Preparing three kinds of vinyl ester resin for RTM,named R-1,R-2,R-3. studying their curing reaction characteristics,process characteristics and mechanical properties of resin-cast body. Three kinds of resin systems under the low viscosity at room temperature (25℃) ,respectively 350mPa·s,80mPa·s,70mPa·s,The viscosity of a certain temperature is the below of 500mPa·s,and has a longer period of application,in line with the requirements of RTM injection process. Analysis of the mechanical properties of resin cast body,the bending strength of up to 110. 05MPa,the impact strength of up to 12. 27kJ /m² . R-3 for the final selection of the best overall performance resin system.

PROGRESS IN RESEARCH OF THE CREEP BEHAVIOR OF RESIN COMPOSITES

LIU Peng-fei, ZHAO Qi-lin, WANG Jing-quan

2013, 0(3): 109-117.

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Creep at room temperature is considered as a major limitation to the more extensive use of resin composites. This paper provided an overview of the progress in research of the creep behavior of resin composites. Effects of the creep of fiber and resin,temperature,external stress and the material properties on the creep of resin composites were investigated and the mechanism of creep was probed in this paper. The models popularly used to predicate the creep of resin composites and their valid ranges were analyzed,and the prospect of creep of resin composites was given finally.

PROGRESS IN EPOXY RESIN OF HIGH-TEMPERATURE RESISTANCE

LIU Xiao-bei, WANG Xiao-jie, HUI Xue-mei

2013, 0(3): 118-121.

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In this paper,the methods of improving the heat resistance of epoxy resin were summarized. One way is to introduce new structures by epoxy resin or curing agent,such as multifunctional structure,aromatic structure and liquid crystal epoxy resin. The other way is to modify the epoxy resin by blend or copolymerization with other materials,like thermoplastic polymer,silicone,nanocomposites and so on. Besides,some problems on the current study and the main direction of development were pointed out at the same time.

RESEARCH PROGRESS IN TEST TECHNOLOGY OF LARGE-SCALE COMPOSITE COMPONENT

YANG Jie-biao, ZHANG Lin-wen, HU Zhong-yong

2013, 0(3): 122-126.

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This paper introduces the research progress,the standards and the equipments of common nondestructive testing methods for the large-scale composite component. And points out that with development of the large-scale composite component applied in various areas,the test technology will attract more and more attention.

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