Table of Content

28 February 2017, Volume 0 Issue 2

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BASIC STUDY

FINITE ELEMENT ANALYSIS ON BENDING FATIGUE RESISTANCE PERFORMANCE OF ANGLE-INTERLOCK COMPOSITE MODEL

FENG Gu-yu,CAO Hai-jian, QIAN Kun

2017, 0(2):  5-9. 

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3D angle-interlock composite model was created by PRO/E 5.0 mapping software, bending fatigue resistance performance of the 3D composite model was predicted and analyzed with the help of finite element software ANSYS. Based on the results of static analysis, fatigue tool was added to analyze the fatigue resistance performance. That was analyzed by cloud picture of life and damage of fiber and resin. Results showed that maximum stress was located in the areas nearby the testing tool; earlier damage happened at these areas under the cyclic loading that was not enough to break the composite directly; waft fiber parallel with the testing directioned occur more serious damage.

EXPERIMENTAL STUDY ON INTERFACE PERFORMANCE OF GFRP COMPOSITE SANDWICH COLUMN WITH WOOD-PLASTIC COMPOSITE CORE

LENG Yuan, QI Yu-jun, LIU Wei-qing, FANG Hai

2017, 0(2):  10-14. 

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Fibre reinforced polymer (FRP) composite sandwich column which composed of FRP sheets and wood-plastic composite (WPC) core were manufactured using vacuum infusion molding process with wood-plastic composite, alkali-free glass fiber bundle and unsaturated resin. The effects of the WPC core on load-bearing capacity, the failure mode and load-strain curve were investigated using axial compressive tests. The results showed that a failure of axial strength and transverse cracks occurs in the composite sandwich column under axial pressure. The ultimate bearing capacity of the composite sandwich column under axial pressure is related to section size of the column, which is raised with the size. In addition, the lateral deformations of the composite sandwich column is greatly constrained by FRP, so the ductility can be improved. A formula of ultimate bearing capacity of the composite sandwich column was deduced and the predictions of the formula agree well with the test data when the value is 0.3.

EFFECTS OF REPAIR ANGLES ON THE TEMPERATURE AND THERMAL STRESS OF COMPOSITE PATCHES DURING CURING PROCESS

TANG Qing-ru, TIAN Qiu-shi, PANG Jie, CHEN Shu-xian

2017, 0(2):  15-20. 

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The physical and mathematical models of composite patches during curing process are established using finite element analysis. The temperature field and the thermal stress field of resin matrix composite patches in different repair angles are simulated during curing process. The effects of repair angles on temperature, curing degree and thermal stress of patches are studied. The results show that, the smaller the repair angles are, the larger of the temperature peak and the thermal stress at the center of patch, and the faster of the curing rate will be. At decentered point of patch, the curing rate is faster, the thermal stress is smaller for small repair angles than that for larger one, and the repair angles have important effect on the value of the thermal stress. Based on the comprehensive analysis, it can be concluded that, within the scope of the repair angles, the repair angles is smaller, the repair quality of composite patches is better. The research results provide the good numerical basis for the actual repair.

RESEARCH ON OPTIMAL PARAMETERS OF ULTRASONIC PHASED ARRAY DETECTION OF DRILLING-INDUCED DELAMINATION IN COMPOSITE LAMINATES

WEN Jiao-ling, LU Chao, HE Fang-cheng, LIN Jun-ming

2017, 0(2):  21-25. 

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In the drilling machining process of aeronautical carbon fiber composite laminate, layer defect is one of the most serious detections, which effects the connection of assembly and its using life. Ultrasonic phased array is widely used in detecting aeronautical composite defects because of its efficiency, flexiblity, intuitive display and so on. Aiming at improving the detection rate and imaging quality of drilling-induced delamination in composite laminates, this article mainly studied the effects of aperture, focal length and pulse width on results of detecting imaging by controlling variate method, then obtained the regular pattern of parameter changing and the most suitable install of each parameter. When the number of elements was too small, the focus beam length was too short. So it affects the detection rate of stratified defects and makes the defect information seriously distorted. With the number of elements under the same circumstances, the maximum amplitude of defect increased and then decreased with the depth of focus increasing. When the pulse width of the element excitation was about half of the center frequency, detection effect was optimal. This paper supplies reference to the following detection and study of drilling-induced delamination in composite laminates.

TENSILE STRENGTH IMPROVEMENT OF SINGLE BOLT DOUBLE SHEARING BY VARIABLE STIFFNESS PLACEMENT

NIU Xue-juan, YANG Tao, LI Yang

2017, 0(2):  26-31. 

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The variable stiffness placement along the direction of the maximum principal stress can enhance the strength of composite laminate. By focusing on the area around the hole, the optimization objective is defined as the minimization of the directional difference between the velocity vectors at the cells in the flow field and the maximum principal stress obtained by the FE. Based on this optimization objective, the optimum parameters of the flow field are calculated. Then the tape paths on the variable-stiffness ply are determined, what are consistent with the direction distribution of the maximum principal stress as far as possible. The comparative experiments of the laminates show that the average ultimate tensile strength of the variable stiffness laminates was increased. Moreover, the declining of the load bearing capability of the variable stiffness laminates is slowing when the tensile load exceeds the ultimate strength, which reduces the occurrence rate of instantaneous failure.

A FORECASTING METHOD FOR THE TRANSVERSE ELASTIC MODULUS OF MONODIRECTIONAL BASALT FIBER COMPOSITE MATERIAL

LI Zu-zhan, HAO Zhi-ming, JIA Bin, LI Pan

2017, 0(2):  32-37. 

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According to the arrangement of fiber in monodirectional basalt fiber composite material, with consideration of geometric symmetry and introducing of the strain coordination hypothesis, a rectangular representative volume element is proposed. Then the transverse elastic modulus of monodirectional basalt fiber composite material can be derived according to the arrangement of fiber and matrix material in the representative volume element. The comparison of the calculated results with the experimental results and other similar theoretical results shows that the representative volume element method can well predict the transverse elastic modulus of monodirectional basalt fiber composite material.

ANALYSIS ON THE EFFECT OF EULER-BERNOULLI BEAM MODEL AND TIMOSHENKO BEAM MODEL ON DAMAGE IDENTIFICATION BASED ON MODAL STRAIN ENERGY METHOD

YUE Shi-yan, YANG Zhen-zhen, XIE Feng , HUANG Li-xin

2017, 0(2):  38-43. 

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With the change of span-depth ratio of functionally graded (FG) beam from small (thick beam) to large (thin beam), the effect of shear deformation on the beam deformation decrease. In order to analyze the deformation of the beam accurately, Timoshenko beam model is used for the thick beam with small span-depth ratio and Euler-Bernoulli beam model is used for thin beam large span-depth ratio. In this paper, free vibration is calculated based on the two beam models by a finite element method (FEM) to further analysis on the difference between element stiffness matrix, mass matrix and modal mode. Numerical examples are given to analyze the effect of those differences on the damage identification index. The damage indices of Timoshenko beam model are better than those of Euler-Bernoulli beam model in thick beam, while the damage indices of Euler-Bernoulli beam model are better than those of Timoshenko beam model in thin beam (for example l/h=25).

RESEARCH ON FINITE ELEMENT MODELING OF ROOT CONNECTION BASED ON ANSYS

TANG Jin-qian, LU Xiao-feng, ZHANG Deng-gang, LI Cheng-liang

2017, 0(2):  44-47. 

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Different finite element modeling approaches of root connection for wind turbine blades were studied in this paper. The computed results of the stress level in the connection bolts obtained by two different modeling methods, namely the full-scaled and 1/N scaled FE models, were compared with the results calculated by the theoretical analysis. Hence the theoretical results were calculated first and then the full-scaled and 1/N scaled FE model were modeled and analyzed. The comparison shows that the difference between the theoretical results and the two FEM results is very small, illustrating that both of the two modeling approaches are acceptable in terms of obtaining reasonable results. Further study also shows that the full-scaled model is closer to the reality, but setting up the 1/N scaled model requires less modeling work and is therefore more efficient.

CURE KINETICS AND TTT-DIAGRAM OF THE BA9913 RESIN

ZHANG Chen-qian, CHEN Wei, GUAN Zhi-dong, YE Hong-jun

2017, 0(2):  48-53. 

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In this paper, the cure kinetic parameters of the toughed epoxy resin (BA9913) were gained by dynamic DSC analysis based on the phenomenological model. Also, the phenomenological model of BA9913 resin was established. The curing degree of BA9913 were determined under different heating time at 100 ℃. Then, the relationship between curing degree and heating time of BA9913 resin was investigated with Dibenedetto equation based on the tested data, and the equation of glass transition temperature and curing time were obtained. The relationship between conversion at gelation and glass transition temperature of BA9913 resin was also obtained by shear modulus testing method. Then, the time-temperature-transition (TTT) diagram was presented based on the above results. Two kinds of T300/BA9913 composites under different isothermal time were manufactured by the guide of the TTT diagram. The internal quality, basic mechanical property and glass transition temperature of them were studied. The result show that the curing curve of T300/BA9913 now in use could be further optimized.

APPLICATION RESEARCH

STUDY ON THE FIBER DISTRIBUTION OF EPOXY SHEET MOLDING COMPOUND IN THE PROCESS OF COMPRESSION MOLDING

XU Jiao-jiao , LI Jian, HUANG Zhi-xiong

2017, 0(2):  54-59. 

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The fiber flowing and distribution of epoxy sheet molding compound(ESMC) have great effect on the properties of ESMC parts. In this article, the relationships between raw materials, viscosity of ESMC sheets, molding parameters etc. and fiber distribution were systematically studied by measuring the fiber content of ESMC parts. The results showed that when the fiber content of ESMC was 24%, the length of fibers was 24 mm, the size of filler was 45 μm, the viscosity of ESMC sheets was 5 × 10³ Pa·s, the layering area was 60% and the velocity of mould closing was 1 mm/s, indicating a better fiber distribution of ESMC parts.

EXPERIMENTAL STUDY ON THE SENSING CHARACTERISTICS OF CFRP TENDONS BASED ON THE PIEZORESISTIVITY

LIANG Ge, LIU Rong-gui, XU Zhao-hui, XIE gui-hua

2017, 0(2):  60-63. 

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In this paper, it aims to study the relationship between the CFRP tendons resistance changing rate and the strain in different strain stages. The relationship formula of the resistance changing rate and the strain has been derived, which is based on the sensing principle of CFRP. Then, the initial resistance and volt-ampere characteristic curves of the samples were obtained from the axial tensile test on three bunches of CFRP tendons, which includes its resistance-strain behavior, the initial resistance and volt-ampere characteristic curves. Through studying the changing rate of resistance of the samples which varies with the strain in three different strain stages, the CFRP tendons sensitivity of the initial stage was obtained by linear fitting. Results show that: when the strain is less than 0.8%, the resistance changing rate changes rapidly with the strain, and shows a good linear relationship; when the strain varies from 0.8% to 2.4%, the changing speed comes lower; and when the strain is higher than 2.4%, the changing rate of resistance increases sharply, which leads to the specimen destroyed.

RESEARCH ON THE BENDING CAPABILITY OF COMPOSITE FIBER REINFORCED PLASTIC TUBE WITH RECTANGULAR CROSS SECTION

YUAN Wei, HU Ye-fa, ZHANG Jin-guang

2017, 0(2):  64-68. 

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According to the bending capability of rectangular cross section(RCS) tube made of carbon fiber reinforced plastic(CFRP), five different layer schemes of the tubes were designed. The finite element software Abaqus was used to analysis the three point bending test, and the strain of the middle position on the bottom surface was obtained. Then, the three point bending test was carried out on the universal testing machine, and the strain of the middle position on the bottom surface was obtained by using FBG sensor. The load-strain curve of the 5 schemes was fitted, the load-strain curve and bending stiffness were obtained. It is found that the experimental results are in good agreement with the analysis results. The results show that the higher the ratio of 0 degrees, the better of the bending performance.

INFLUENCE OF QUARTZ FIBER′S DEWAXING ON THE QUARTZ/CYANATE ESTER COMPOSITES′ PROPERTIES

SHI Pei-luo, WANG Fei, PANG Jin-cheng, LING Hui

2017, 0(2):  69-71. 

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Dewaxing of quartz fiber weave was done by surface treatment at high temperature, and quartz/cyanate ester prepregs as well as the composites were produced. Properties of prepregs and composites, with and without dewaxing, were compared. It was found that the processability of prepregs was improved by dewaxing, the composites′ dielectric properties remained the same, and the mechanical properties were improved significantly with flexural strength increased by 31% and interlaminar shear strength increased by 16%. The interface adhesion of composites was improved by dewaxing of quartz fibers.

FORMATION AND TEST METHODS OF THE THERMO-RESIDUAL STRESSES OF THE THERMOPLASTIC POLYMER MATRIX COMPOSITES

WANG Chang-chun, YUE Guang-quan, ZHANG Jia-zhen, LIU Jian-guang

2017, 0(2):  72-75. 

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Fiber reinforced thermoplastic composites have wide application in aircraft structure for the excellent comprehensive advantages of the high toughness, long material storage period and short molding cycle, which have been regarded as the promising advanced aeronautical structure materials. The thermo-residual stresses will be produced in the molding processes of high processing temperature and cooling rates. The stresses caused by the mismatch in coefficients of the thermal expansion, anisotropy of the adjacent fabrics layers and thermal gradient distribution of the thermoplastic composite during the cooling process will play an important role in the mechanical properties of thermoplastic composites, which must be taken into consideration in the design of composite parts. It is beneficial to recognize the formation causes and development of the thermo-residual stresses to effectively control the residual stress level of the thermoplastic parts. The mechanism of thermo-residual stresses formation was firstly analyzed in three different levels in present study, i.e. constituent materials level, lamination plate′s level and the structure parts level. Moreover, testing methods of the thermo-residual stresses of the thermoplastic composites based on the previous literatures were also introduced. The advantages and disadvantages of these methods were evaluated as well.

RESEARCH ON THE TECHNOLOGY OF SINGLE-SIDED TWO NEEDLES STITCHING EQUIPMENT FOR COMPOSITES PREFORM

PAN Jie, WEN Li-wei, XIAO Jun, HUANG Xiao-chuan

2017, 0(2):  76-81. 

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Stitching technique can effectively improve inter-laminar strength of composite materials and their damage tolerance. The integral structure can be prepared by the stitching joint. Based on the working principle of industrial sewing machine. We established two needles stroke relationship through researching the cooperative relationship between a conventional needle and a catcher-needle in the process of forming coil. And we designed the cam-crank link mechanism to realize the two needles cooperation movement. The single-sided two needles stitching head and three axis linkage platform are combined to stitch preform. We explored the effect of the angle between the two needles on coil forming. The study shows that it can form the coil probability up to 90% when the angle between the two needles is 45° to 60°. It makes the probability of the formation of the coil reduced when the angle between the two needles is too large or small. The experiment verified the rationality of the structural design of the single-side two needles stitching equipment. This paper provides a theoretical basis for the optimization of the equipment.

THE SIMULATION OF X-RAY IMAGING DETECTION OF DEFECTS IN CARBON FIBER RESIN MATRIX COMPOSITE MATERIAL

WANG Cong-ke, DONG Fang-xu, ZHAO Fu-bao, FAN Li-mei

2017, 0(2):  82-87. 

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Using CIVA simulation software to simulate the X-ray imaging detection results of the carbon fiber resin matrix composite material under different voltages, different currents, different focal spot sizes, the optimal X-ray process parameters are obtained. Then the X-ray cone-beam computed tomography imaging under the optimal X-ray process parameters was simulated. Comparing the X-ray cone-beam computed tomography imaging test results of the carbon fiber resin matrix composite material with lamination defects and simulation results, the two results coincided well. Meanwhile, the X-ray cone-beam computed tomography imaging test results of the actual carbon fiber resin matrix composite material demonstrate the feasibility and reliability of the optimal X-ray process parameters.

EFFECTS OF DIFFERENT MIXING METHODS ON MECHANICAL PROPERTIES OF BASALT FIBER REINFORCED CONCRETE AFTER HIGH TEMPERATURE

GUO Rui-jin, BI Zhong, WANG Fu, WANG Pan-le

2017, 0(2):  88-92. 

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In this study, the effects of two different fibers (cement slurry wrapped fiber, direct incorporation) on the compressive strength and tensile strength of reinforced coarse aggregate concrete were studied under different basalt fiber volume (0%, 0.1%, 0.15%, 0.2%) and high temperature(20 ℃, 200 ℃, 400 ℃, 600 ℃). The strength ratio of the indirect mixing method was higher than that of the direct mixing method, but the variable was different and the range of the increase was different. When the temperature was kept constant, the increase amplitude of compressive strength is increased with the increase of fiber content, and the maximum is 0.2%. The increase amplitude of splitting tensile strength is decreased with the increase of fiber content, and the maximum is 0.1%. When the dosage is constant, the increasing range of compressive strength shows the trend of the broken line with the change of temperature. It presented an upward trend between 20 ℃ and 200 ℃, tended to be gentle between 200 ℃ and 400 ℃, and rose again between 400 ℃ and 600 ℃. The splitting tensile strength is basically unchanged with the increased amplitude between 20 ℃ and 200 ℃, but presented a trend of sharp decline after 200 ℃.    

REVIEW

THE REVIEW RESEARCH PROGRESS OF METALLIZING TECHNOLOGY ON FIBER-REINFORCED RESIN COMPOSITE SURFACE

DONG Xiao-yang, GUO Jin-hai

2017, 0(2):  93-99. 

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In this paper, research progress of metallizing technology on fiber-reinforced resin composite surface was reviewed. The fiber and the resin metalizing method before composited, and the uncured composite metallizing technology were introduced. In addition, the composite metallzing method was also introduced after cured. The advantage and disadvantage of the metallizing were expressed on different state. Combined with the demanding of aviation and aerospace field on the fiber-reinforced resin composite, the applicability of the different metallizing technology on aerospace field were analyzed.