COMPOSITES SCIENCE AND ENGINEERING

DESIGN OF CUSTOMIZED DEVELOPMENT FOR WIND TURBINE BLADE BASED ON THE MATLAB AND SOLIDWORKS

ZHANG Hai-ying, ZHU Shui-qin

2014, 0(4): 4-7.

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In view of the complexity of the wind turbine syndrome design and the difficultyin modeling, according to the Wilson design process, using Wilson algorithm for 15kW fan blade aerodynamic shape parameters calculation, the optimization function fmincon of Matlab software was used to optimize the blade element chord length and torsion angle. A universal program was developed for small wind turbine blade aerodynamic configuration. Dy loading the design results directly into SolidWorks, the wind wheel 3D modeling cpulaberealized inis simplifies a large number of data conversion and storage process, solves the problem of data transmission between Matlab and SolidWorks, enhances the precision and efficiency of the design wind turbine blade.

NONLINEAR VIBRATION ANALYSIS OF PIEZOELECTRIC FGM PLATE UNDER STRONG ELECTRIC FIELDS BY SPLINE FINITE POINT METHOD

LI Shuang-bei, HUANG Jun, GU Chun-xia, HUANG Xian-zhi

2014, 0(4): 8-12.

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In the strong electric field, the natural frequency of piezoelectric FGM plate cannot be accurately solved based on the linear constitutive equations. For this, a dynamic analysis model that considering the nonlinear piezoelectric constitutive relation is established by using the spline finite point method (SFPM) in this paper, and the impact of the nonlinear piezoelectric effect to the natural frequency is discussed in the environment of strong electric. Numerical results show that natural frequency of piezoelectric FGM plate has large deviation between nonlinear and linear results in strong electric field. And, nonlinear effects can't be ignored in this case. Owing to the special material properties of FGM, different control on the natural frequency can be obtained with different applying ways of the electric. The analysis modal based on the SPFM is accurate and reliable. Moreover, it is simple to make the input and easy to deal with the boundary conditions.

INFLUENCE OF GLASS FIBER ON THE CURE CHARACTERISTIC OF EPOXY RESIN PREPREG

LUO Li, TANG Qing-ru

2014, 0(4): 13-17.

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The curing kinetics of glass fiber/epoxy resin prepreg were investigated by dynamic differential scanning calorimetry (DSC). The curing characteristic temperatures were obtained by analyzing the DSC profile and cure temperatures were calculated by liner fitting and extrapolating method. The curing degree curve was plotted according to reaction heat of t (ΔH_t) and total reaction heat (ΔH₀) . The activation energy (E) and frequency factor (A) were calculated using Kissinger method while the reaction order (n) was calculated by Crane equation. The results showed that glass fiber led to increasing theoretical gelling temperature, curing temperature and postprocessing temperature. Also, glass fiber increased the activation energy. Moreover, glass fiber did not bring about the change of reaction order. Consequently, it was concluded that glass fiber had no obvious effect on the curing reaction mechanism while restrained the curing reaction.

FABRICATION AND PERFORMANCE OF LAUNCHING TUBE OF STAINLESS STEEL-COMPOSITE

LUO Han

2014, 0(4): 18-22.

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Aiming at the defect of launching tube for rockets, a program has been proposed in which the stainless steel wasused as inner lining to prevent ablation of wake flame and the composite wasused as outer lining to guarantee strength and rigidity. And, thorough the research of sample performance, along with rockets launching, this program has been proved to meet the operating requirements sample parameters as follows: tensile strength 220MPa, tensile module 23.7GPa, compression intensity 153MPa, flexural strength 330MPa and layer trimming 24MPa.

RESEARCH ON HEAT RESISTANCE OF VECTRAN FIBER

DU Yi-jun, JIANG Jin-hua, CHEN Nan-liang

2014, 0(4): 23-26.

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Vectran fiber was subjected to heat treatments at different temperature to find out its heat resistance. The impact of temperature on the fiber′s tensile property and weight loss was investigated. The surface and chemical structure of the fiber were studied. The result shows that the heat resistance of Vectran fiber is good. Its tensile strength starts decreasing at about 250℃. The SEM photos suggest that strips would appear on the surface of Vectran fiber after being treated, and the depth of the stripes would increase by the higher temperature; it can be seen from the ATR-FTIR spectra that 1725cm^-1 and 1110cm^-1 are weaken by the high temperature, which attribute to C=O and C-O. The DSC shows that Vectran′s melting-point raises a little because of heat treatment. The reason mightbe that the high temperature maycause the movement of the end of the molecular chain, which lead the molecular tighter and shorter.

EXPERIMENTAL STUDY ON BULKING DEFECTS EFFECTING ON COMPRESSION BEHAVIOR OF THICK FRP LAMINATES

XU Song-jian, SUN Qi-li, WANG Jia-ji, FENG Peng

2014, 0(4): 27-31.

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FRP(fiber reinforced polymer) materials made from VARTM (Vacuum-Assisted Resin Transfer Molding) could be manufactured with various bulking defects. This article employs thick-slab FRP members which was manufactured by steel molds of high precision to derive the load-displacement curve of normal specimen and bulking specimen under compression. The experiment shows that the compression capacity of bulking members is merely 66.4% of the normal specimen, with the axial cracks occurring near the outward resin part. With FEM methods, a strength criterion of Mises stress of resin is derived and testified.

EFFECT OF THICKNESS VARIATION OF THEIR LINERS ON FATIGUE PERFORMANCE OF HOOP-WRAPPED COMPOSITE CYLINDERS

LI Qing-wan, DENG Gui-de, LING Xiang, LI Wei

2014, 0(4): 32-36.

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Actual thickness of the liners of hoop-wrapped composite cylinders may have a deviation of 0 ~ +30% affected by the thickness variation of seamless steel tubes for cylinders. The variation of the actual thickness of the liner has an influence on the autofrettage effect of the composite cylinders, and may affect the anti-fatigue performance of the cylinders. Finite element method was used to analyze the stress of glass fiber hoop-wrapped composite cylinders with steel liners with different thickness. Numerical results show that hoop pre-stress on liners decreases under the same autofrettage pressure, and the mean hoop stress on liners increases during working process, which weakens the fatigue resistance of the composite cylinders; but the alternating stress amplitude decreases during working process, which improves the anti-fatigue performance of the cylinders. Therefore, both Goodman and SWT equations taking the effect of mean stress into account were utilized to calculate equivalent alternating stress amplitude. The equivalent alternating stress amplitude on the liners from the two methods both decreases slightly as the thickness of the liners increases, which indicates that the combined action of the two can improve the anti-fatigue performance of the composite cylinders slightly. So the positive thickness variation of the liners does not decrease the fatigue resistance of hoop-wrapped composite cylinders.

WIND TURBINE BLADE DAMAGE IDENTIFICATION BASED ON HARMONIC WAVELET PACKET AND SUPPORT VECTOR MACHINE

RAO Jin-gen, GU Gui-mei

2014, 0(4): 37-41.

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In order to solve the wind turbine blade damage type identification problem, a new approach for acoustic emission (AE) source type identification based on harmonic wavelet packet (HWP)and support vector machine is proposed. The type of blade damage was distinguished by SVM which was built by using the energy as the feature vectors for the support vector machine classifier, where the energy was extracted in different frequency bands from the acoustic emission generated by the blades after a four-level decomposition of HWP.In recognition of the blade for damage, the AE signals were decomposed using harmonic wavelet packet and daubechies wavelet packet and compared with each other. The results show that good recognition results could be obtained using HWP and SVM combined method.

BENDING FATIGUE BEHAVIOR OF 3D BRAIDED COMPOSITE T-BEAM

ZHANG Zhong-wei, YAN Jing

2014, 0(4): 42-45.

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This paper reports the three-point bending fatigue behaviors of four-step 3D braided composite T-beam manufactured by four-step braiding technology and vacuum assisted resin transfer molding (VARTM). The fatigue failure of the braided composite T-beam under different stress levels have been represented to explain the fatigue behaviors.The quasi-static three-point bending tests were conducted on the MTS 810.23 material tester system, and the fatigue tests with the sinusoidal wave loading of frequency of 3 Hz and stress ratio (R) value of 0.1 were implemented on the same system. The S-N curve, stress-displacement curves and the max and min deflections curves based on experimental data were used for analysis, and the load cysles of three-point fatigue test under stress level of 50% was found tobe over 5×10⁵ times. The fiber breakage on the web is the main damage mode which leads the ultimate failure of the 3D braided composite T-beam according to the damage morphologies.

TOUGHENING OF EPOXY USING BITUMEN AS MODIFIER

XU Yan, LI Wei

2014, 0(4): 46-50.

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This article describes the toughening effect on epoxy using bitumen as the modifier. Impact properties,tensile properties and thermal properties with different bitumen contents were analyzed. With the addition of only 2% bitumen to epoxy, maximum improvements of 120% were obtained for impact energy. The addition of bitumen had no significant effect on tensile properties of epoxy. FTIR result showed that there was no chemical reaction between epoxy and bitumen. DSC analysis of the hybrid showed that the Tg of epoxy decreases significantly after 2% bitumen.

THE APPLICATION OF HIGH MODULUS GLASS UD FABRIC IN WIND TURBINE BLADE

YAN Wen-juan, TAO Sheng-jin, JI Xiang

2014, 0(4): 51-53.

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This paper analyzed the structure of a MW-class wind turbine blade. The effects of E glass UD fabric and high modulus glass UD fabric on the blade weight, stiffness, frequency and normal stress safety factor were analyzed. The results showed that using high modulus glass UD fabric could reduce the weight of blade spar caps significantly and increase the safety, while the stiffness is basically retained.

CHARACTERIZATION OF CONTINUOUS CARBON FIBER REINFORCED POLYPHENYLENE SULFIDE(PPS) PIPES BY FILAMENT WINDING PROCESS

GUO Bing-bing, WANG Lian-yu, ZHOU Chun-hua, ZHOU Xiao-dong

2014, 0(4): 54-57.

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In this paper, continuous carbon fiber reinforced PPS pipes were fabricated by an own-designed filament winding machine and its relative performances were examined. According to ASTM D792 and D2344, voidage and ILSS of composites were measured. Meanwhile, the other characteristics (crystallinity, density water absorption ratio) of composites pipes were studied. The results showed that the voids mainly located between the carbon fiber. The presence of voids had an effect on the pipe ILSS and the ILSS deceased with the increasing of void content through the research. The ILSS of composites were 33.25MPa and 27.54MPa with 0.04% and 0.05% of the void volume fractions, respectively. At different temperatures for the heat treatment of materials, a conclusion could be drawn that the ILSS of composites increased with the growing of the heat treatment temperature. The influence of ambient temperature was also studied in a similar way and the ILSS of composites decreased as it increasing. Soaking in boiling water for 8 h, the water absorption ratio of composites was only 0.66%. The composite pipe has low water absorption ratio. The thermoplastic composites winding machine can produce thermoplastic composite pipe with excellent performance.

GEOMETRICAL METHOD FOR EXPANDED PLANAR MILLING OF HONEYCOMB CORE MATERIAL WITH CHANGING THICKNESS FOR RADOME

LI Xing-de, ZHOU Chun-ping, WANG Min, QIU Jin-hao

2014, 0(4): 58-61.

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Changing thickness honeycomb core material for high performance broadband radome is conventionally machined by multiple degree machining systems on three dimensional molds, which needs a lot of time and costs and is less flexible. In this article, the radome surface was cut into a set of narrow strips of surfaces, then discretize each narrow strip of surface into a clustered of adjacent triangle planes. Afterwards the present work utilizes the in-plane flexibility of honeycomb material and apply the mathematical expansion methods and equal-area micro-transforming methods to expand the three dimensional surface into a corresponding planar pattern. This process creates a corresponding planar point for each three dimensional points. Thus, the changing thickness honeycomb core material that is widely used for modern broad-band radomes can be machined on a conventional three-degree freedom machine instead of on a complex four-degree freedom machine that needs expansive cutting molds or cost elongated time. This lowers the requirement on the machinery and machining fixtures and increases the flexibility for the honeycomb material machining in time of repair and maintenance.

INVESTIGATION OF THE FATIGUE PROPERTY OF THE EPOXY STRUCTURE ADHESIVE USED FOR WIND POWER BLADE

PENG Xing-cai, ZHANG Li-ping, XIE Xiang-fu, ZHANG Li-li

2014, 0(4): 62-64.

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This study give out the fatigue property of the epoxy structure adhesive used for wind power blade. According to ISO 9664:1995, the tensile shear fatigue character was tested periodicity vibration with the parameter of 30Hz frequency, τ_m=0.35τ_R mean stress, 2.0≤τ_a≤3.0 stress amplitude. The fatigue stress limit was calculated from the S-N curves obtained in the above test. In addition, we still studied thickness of the adhesive layer, proportion of flexibilizer, broken pattern of sample and other factors that would affect the fatigue property. The result shows that the fatigue property of the epoxy adhesive is very important to wind power blade's design performance and service life.

STUDY ON THE PROPERTIES OF FIBER REINFORCNED POLYMERS (FRP) USED IN THE POWER TRANSMISSION POLES --INFLUENCES OF THE RESIN SYSTEMS ON THE PROPERTIES OF FRP

ZHOU Bai-jie, WU Xiong, HU Qian

2014, 0(4): 65-71.

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According to the essential requirements on the fiber reinforced polymer materials (FRP) used in the power transmission poles or towers, two kinds of FRP materials based on polyurethane resins (vinyl modified polyurethane resin, VPU & two-component polyurethane, TPU) were studied. Simultaneously, FRP material prepared by high-functional epoxy resin was tested as a comparison (all samples were prepared by pultrusion method). EP-FRP material exhibited the best mechanical and electrical insulation properties, but its UV aging resistance and the fire resistance properties were limited. Therefore, it cannot be used directly in the outdoor environments. The insulation, corrosion resistance and aging resistance behaviors of VPU-FRP material were good enough. Also, it had the best hydrophobicity. However, the transverse properties of VPU-FRP should be improved further. The combination properties of TPU-FRP materials turned to have better properties, which was the suitable material for the power transmission poles.

INVESTIGATION OF LONG-TERM PERFORMANCE OF GLASS FIBER REINFORCED PLASTIC UNDER CONSTANT LOAD

ZHU Si-rong, HUANG Qian-wen, CHEN Jian-zhong

2014, 0(4): 72-75.

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Glass fiber reinforced plastics has been widely applied in various engineering areas for several decades. Both the domestic and foreign have carried out extensive research, but few on the longtermproperties of glass fiber reinforced plastics. The current domestic design is basically based on the initial performance reduction according to certain safety coefficient. The safety of this kind of design method needs further research. From the perspective of viscoelastic analysis, this paper designs the experiment scheme on the basis of theoretical research. And, though concrete experiment, the relationshipe of the strength of different layer spread angle of glass fiber reinforced plastic under certain stress level with the keeping time was measured. Based on the experimental data processing, the long-term performance of retained strength and its relation with the time was deduced,proving the accuracy of the conclusion by combining with the relevant specification.

PROGRESS OF SMA SMART STRUCTURES IN SHAPE CONTROL

XU Liang-liang, YUAN Guo-qin

2014, 0(4): 76-80.

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Shape memory alloy (SMA) has some special properties different from common metal. It can produce big recovery force during the recovery process once it was prestrained. We may embed SMA into structures and utilize the shape recovery force to change the shape. Thus, the structures can meet different requirements in different service conditions. Many scholars have carried out researches on smart beam structures, smart wings and blades, smart inlet, variable chevron, and variable nozzle. This paper reviews the progress of SMA in shape control, and puts forward some critical issues needing to be solved in engineering applications in future.

THE APPLICATION OF NONDESTRUCTIVE TESTING TECHNIQUES FOR COMPOSITES WIND TURBINE BLADE

SUN jiu-liang

2014, 0(4): 81-84.

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As the amount of wind turbine installed increasing, more and more blades are operating, and blade maintenance becomes very important. This paper introduced several methods of nondestructive testing (NDT) for composites. The Ultrasonic test was introduced in detail. In the end, it is concluded that the Ultrasonic test is proper for semi-manufactures on workshop and on-site damage forecast.

PROGRESS IN PEREABILITY OF NATURAL FIBER FOR LIQUID COMPOSITES MOULDING

CAI Jing, ZHU Ying-dan, QIN Yong-li, FAN Xin-yu

2014, 0(4): 85-90.

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Natural fiber composites have been widely used in transportation and construction industry due to their high performance, low cost, and recyclability. Permeability of natural fiber fabric has a significant impact on the accuracy of LCM flow simulation, which will give useful guidance for parameter optimization, mold design and quality control. This review introduces measurement theory and equipment used for natural fiber. The effects of many factors on natural fiber permeability are discussed in details. Also, the difference of permeability between natural fiber and glass fiber is highlighted and the research directions of natural fiber permeability are pointed out.

THE NON-DESTRUCTIVE TEST OF FIBER-REINFORCED COMPOSITES

WANG Bao-rui, DING Xin-jing

2014, 0(4): 91-94.

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In this paper, the type and reasons of defects were reviewed according to the characteristics of the fiber-reinforced composites. The testing methods for composite products were summarized on the basis of the technigues of acoustics, ray, optics, thermo, etc. The basic principles, application scope and merits and demerits of the different detective methods were analyzed.

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