COMPOSITES SCIENCE AND ENGINEERING

EFFECTS OF BFRP LATERAL CONFINEMENT ON BOND BEHAVIORBETWEEN GFRP RIBBED BARS AND CONCRETE

WANG Yan-lei, WANG Mi-feng, ZHANG Xue, XU Qing-feng

2020, 0(4): 5-12.

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A total of 36 pull-out specimens were tested to evaluate the bond behavior between GFRP ribbed bars and BFRP-confined concrete. Test parameters included BFRP layers (0 ply, 1 ply, 2 plies and 3 plies) and the concrete cover to bar diameter ratio c/d (1.6, 2.2 and 3.0). The test results indicated that the typical failure mode of the specimens was changed from brittle splitting failure to ductile pull-out failure due to the lateral confinement of BFRP. The bond strength and the corresponding slip as well as confining stress were increased with the increasing number of BFRP layers. Based on the same BFRP confinement, normalized bond strength was increased with the increase of c/d, while the confining stress corresponding to bond strength was increased exponentially with the deceasing c/d. A logarithmical relationship was observed between the increment of normalized bond strength and the confining stress of BFRP corresponding to the bond strength.

PROGRESSIVE DAMAGE ANALYSIS OF OMEGA STIFFENEDCOMPOSITE PANELS WITH DIFFERENT ORIENTED NOTCH

YU Fen, AN Bo-ning, LIU Wu-shuai, GUO Tuo

2020, 0(4): 13-18.

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It is of great significance to study the load-bearing strength and failure modes of omega stiffened composite panels with different oriented notches under axial compressive loads. By compiling VUMAT subroutine, the selected three-dimensional Hashin failure criterion and stiffness degradation mode were added to the progressive damage model analysis. Firstly, the displacement-load curve, out-of-plane displacement and failure mode of the 0° notch model were studied, and the results were compared with the experimental results and the literature to verify the correctness of the model, and the effect of different oriented notches on stiffened panels was further studied. The results show that the stiffened panel model with 90° notch has the strongest bearing capacity under axial compression, followed by 45° notch model and 0° notch model. The fiber compression failure of 0° notch model appears at the lower side of the model, 45° and 90° notch model appears at both sides of the notch, and the failure of the three models extends vertically with the load.

EFFECT OF IMPACT ANGLE ON THE LOW-VELOCITY IMPACT PERFORMANCEOF ALUMINUM HONEYCOMB SANDWICH PLATE

XIE Xin, DUAN Yue-chen, QI Jia-qi

2020, 0(4): 19-27.

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In order to study the effect of impact angle on the low-velocity impact performance of aluminum honeycomb sandwich plate, a finite element model of aluminum honeycomb sandwich plate subjected to low-velocity impact was established in ABAQUS with reference to the literature experiment process. The simulation results were compared with the literature experiment results to verify the reliability of the model. The effects of impact angle on damage and energy absorption of sandwich plate, maximum contact force and contact time between impactor and top face-sheet, the tangential slip-stick state between impactor and top face-sheet were investigated. The results show that with the increase of impact angle, the maximum damage depth of the aluminum honeycomb sandwich plate decreases, the deformation of the top face-sheet decreases, and the buckling of the honeycomb core element along the sliding direction of the impactor increases. But its damage decreases, and the bottom face-sheet almost not deforms. Besides, the maximum contact force decreases, the contact time between impactor and top face-sheet increases. Also, the absorbed energy by total sandwich plate decreases, absorbed energy by every component of plate decreases slowly. But the trend that top face-sheet is larger than honeycomb core than bottom face-sheet is always maintained. In addition, the slip time increases, the stick time decreases first and then increases. The proportion of stick time decreases first and then increases rapidly, and the proportion of stick time is the smallest at 45°.

SURFACE MODIFICATION BASALT AND ITS SOLVENT-FREE HEAVY ANTICORROSIVE COMPOSITE COATINGS

YANG Zhong-jia, QIAO Cai-xia, GU Yi-zhuo, LI Min

2020, 0(4): 28-34.

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Basalt flake is a new kind of environmental protection material, which has a broad application prospect in improving the performance of anticorrosive coatings. The basic performance parameters such as thickness, composition, crystallinity and micromorphology of basalt scales were characterized in this paper. Basalt scales were modified with silane coupling agent kh-550. Basalt scales treated with silane coupling agent were added to epoxy resin E51 to prepare heavy anticorrosive coating. The effects of addition amount and particle size of the scales on wear resistance, hardness, water absorption and alkali corrosion resistance of the coating were studied. The test results show that the surface hardness of the coating with basalt scales increases greatly. The particle size and content of basalt scales have coupling effect on coating properties. It is found that basalt scale mass fraction of 6%, size between 60 and 80 mesh produce the best wear resistance coating. With the increase of scale content, the water absorption of coating decreases. In the aspect of alkali corrosion resistance, the alkali corrosion resistance of the coating increases with the decrease of the size of the scale, and then decreases with the increase of the scale content. The alkali corrosion resistance of the coating is the strongest when the mass fraction of the basalt scale is 9%.

EFFECT OF ANGULAR RADIUS SIZE AND SANDBLASTING PROCESS ON FAILURESTRENGTH OF T-SHAPED PLATE JOINTS OF COMPOSITE SHIPS

CHEN Ying-hao, GUO Ming-en, DING Lei, DAI Jian-jun

2020, 0(4): 35-38.

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T-plate joints of composite components are widely used in naval structures, which are the weak parts of the mechanical properties of naval structures. The effects of structure size and manufacturing process on the failure strength and deformation of joints were studied experimentally. The failure strength of T-joint increases with the increase of the turning radius, and decreases when the radius exceeds R50 mm. The failure load and displacement of sandblasted specimens are 2.1 and 2.16 times higher than those of non-sandblasted specimens. When the air pressure reaches 0.6 MPa and the injection time is 100 s, the failure strength increases slowly.

STUDY ON TENSION-TENSION FATIGUE PERFORMANCE FOR CARBON/GLASSHYBRIDIZED FABRIC REINFORCED COMPOSITES

XU Jing-wei, GU Ai-juan

2020, 0(4): 39-45.

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Fiber hybridization is an effective solution to achieve a completive material with balanced price and properties. Glass/carbon hybridized fabric (GCHF) is the typical example. Fatigue performance is one of the key material parameters of composites for engineering applications. In this paper, the material for spar caps manufacturing of wind blade were used as research subject. Four different carbon ratio uni-directional GCHF were chosen to make hybrid composites, and both static and fatigue test (R=0.1) were carried out. Moreover, pure glass and pure carbon were also tested for comparison. It was demonstrated that high-cycle fatigue of GCHF reinforced composites correspond to the linear rule of mixtures well, but low-cycle fatigue is relatively worse. Based on the experimental study, a fast way of GCHF reinforced composites fatigue properties prediction has been achieved.

SCANNING AND IMAGING OF GFRP PLATES BY AIR-COUPLED ULTRASONIC LAMB WAVE

CHANG Jun-jie, WAN Tao-lei, WU Jun, ZENG Xue-feng

2020, 0(4): 46-52.

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Aiming at the Air-coupled ultrasonic Lamb wave, a probability imaging method independent of signal velocity was used to study the multiple types of defects in Glass Fiber Reinforced Plate (GFRP). Firstly, the single mode Lamb waves are excited and received on the same side of the GFRP with an air-coupled probe, and the probe is scanned in two orthogonal directions. Then, we intercept the direct defect signal received by each scanning path and carry out Fast Fourier Transform (FFT). After obtaining the energy in the frequency domain, the relative difference between the energy in the frequency domain and the reference signal is defined as the energy damage factor. Finally, the energy damage factors of each scanning path were combined with the probability damage principle to conduct imaging of different types of defects, and the imaging results were compared with the results of air-coupled C-Scan. The results show that the imaging method based on the air-coupled Lamb wave can effectively localize and quantify multiple types of defects in GFRP.

PREPARATION AND MECHANICAL PROPERTIES OF TAEKIFYING-TOUGHENING CARBONFIBER COMPOSITES BY COPOLYESTER NON-WOVEN VEILS

KANG Shao-fu, LI Jin,QU Li, MA Peng

2020, 0(4): 53-59.

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Aiming at the problems of lower fiber volume content, difficult to control thickness and poorer interlaminar toughness of fiber reinforced composites prepared by Vacuum Assisted Resin Infusion process(VARI), the non-woven copolyesterveils were introduced into the preforms of carbon fiber fabric and then they were pretreated by hot-pressing process in the vacuum bag. Finally, carbon fiber/epoxy composite laminates were prepared by VARI process. The changes of composite thickness, short-beam shear strength, three-point bending behavior and ModeⅠ interlaminar fracture toughness were studied by comparison of the composite laminates before and after modification. The results showed that the thickness of the modified laminate decreased, the fiber volume content increased from 57.9% to 62.2%, the G_ⅠC value of interlaminar fracture toughness increased by 144.7%, and the shear strength and bending performance were basically equal to the unmodified laminate. The significant increase of ModeⅠ interlaminar fracture toughness of the modified composites were mainly based on the following three mechanisms. The first is the fiber bridging between interlaminar fracture surfaces. The second is the dispersion of thermoplastic particles at interlayer interface which hinders the crack propagation. The third is that the interfacial phases need to dissipate additional fracture energy due to shear plastic deformation.

THE SPRINGBACK STUDY OF I SHAPE STRINGER MANUFACTURED BY X850 PREPREG

GAO Long-fei, XU Peng, WANG Shi-jie, LUAN Ying-wei

2020, 0(4): 60-64.

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The springback of I shape stringer manufactured by X850 prepreg is studied with simulation method in order to establish an accurate simulation model. Temperature falling period is the key point in the simulation model. In order to find suitable simulation model boundary condition, element size and discrete method are analyzed. Through parameter sensitivity analysis, the key parameter can be found. Then the simulation model is calibrated by adjusting the key parameter. The results show that the simulation results are different when choosing different element sizes and discrete methods. The 2 mm element size and monolayer discrete method are the best choice taking into account simulation accuracy and compute cost. The simulation model can perfect predict springback direction when the part size is small and temperature is homogeneous. Simulation accuracy can be improved by adjusting sensitive parameter. The calibrated model is verified by other projects, the difference between simulation result and measuring result is within 8%.

THE PREPARATION OF PSI-CONTAINING BENZOXAZINE AND ITS INFLUENCE ONTHE PROPERTIES OF BISMALEIMIDE ESTER RESIN SYSTEM

JIA Yuan, LIU Zhen, SHI Rui-feng, YANG Ju-xiang

2020, 0(4): 65-71.

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In order to improve the poor toughness and heat resistance of bismaleimide (BMI) resin, benzoxazine monomer (BOZ) containing polysiloxane (PSi-BOZ) was synthesized via a chemical method, the hyperbranched polysiloxane with amino terminal groups (PSi-NH₂) and the phenol were chosen as the raw materials. The PSi-BOZ was then used as modification system to add into BMI, and PSi-BOZ/BMI composite with excellent comprehensive performance and good manufacturability was obtained. The influence of the addition of PSi-BOZ on the curing reaction kinetics and impact strength of BMI were also studied. This study is aiming to provide an idea for the development of new BMI resin materials.

RESEARCH ON THE TECHNOLOGY OF STRUCTURE DESIGNAND FORMING OF ULTRA-LIGHT COMPOSITE WING

WANG Kai, XIONG Chen-xi, HE Qiang

2020, 0(4): 72-78.

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The paper seeks to address the techniques of structural design, technological design, product manufacturing and mechanical properties of the wing with given shape and size. By using finite element analysis software, the static analysis of composite wing was carried out, the main bearing structure was extracted, and the internal skeleton structure was designed. A structural scheme of "I-beam+thin skin+variable thickness" was put forward. Through the design of carbon fiber composite material and polymethacryl imide (PMI) foam, the structure of the wing was realized. The design idea of die for complex shape parts was studied, and the central wing box and wing die were designed. The process flow of wing forming was designed by molding process and co-bonding. Through this method, the wing was manufactured successfully and the mechanical properties were tested. Finally, the surface quality and shape size of the prepared wing meet the requirements, and the design and manufacture of the wing with light weight and heavy load ratio are realized. The rationality and validity of the structure design and forming method are proved.

EVALUATING THE REASONABLE TEMPERATURE RISE TIME OF COMPOSITE INSULATIONPILLAR CORE HEAT ENGINE TEST FROM THE PERSPECTIVE OF HEAT TRANSFER

XING Zhao-liang, ZHANG Zhuo, YUAN Jin, ZHAO Wei-sheng

2020, 0(4): 79-83.

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As the diameter of the core of the composite post insulator for UHV applications continues to increase, the rationality of the temperature rise retention time of the existing standard heat engine test is worth discussing. In this paper, the thermal conductivity of the composite insulating pillar core is estimated by equivalently simulating the heat transfer pattern in the composite. Using the finite element simulation method, the mathematical model of the composite insulating pillar core was established by ANSYS software, and the estimated thermal conductivity and thermal test environment conditions were input to simulate the internal temperature change process of the pillar core. We set the type test, set the monitoring point in different thickness positions inside the pillar core, and record the curve of the internal temperature of the core with time under the uniform heating state in real time. The test result shows that the internal height of the pillar core reaches (50±5) ℃, which is 62800 s, which is much larger than the thermal test time of 43200 s. The existing test methods have defects. The simulation temperature and the actual temperature rise error of the product are 6.2687%, 6.5026%, and 5.5696%, respectively. The simulation results are of good accuracy.

RESEARCH ON CFRP PROPELLER FORMING PROCESS OF EMBEDDED FBG SENSOR

LU Zhong-yin, DING Guo-ping, ZHANG Yi-xuan, LI Wen-hu

2020, 0(4): 84-89.

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In this paper, a CFRP propeller with a split metal embedded blade structure embedded in an FBG sensor is designed. The structure is a composite of metal embedded parts and carbon fiber materials, compared with pure composite propeller blades and blades. The root strength is higher and the placement of the blade carbon fiber prepreg is facilitated during the forming process. Using ANSYS ICEM software and 3D printing technology, 11 different three-layer solid model of the blade thickness were obtained, and the paving template of different carbon fiber layers was obtained, and the shape and size were closer to the theoretical design. The preparation of the pre-embedded FBG sensor is completed by the molding process, and the cause of the damage of the pre-embedded FBG sensor is analyzed. It can be known that the composite structural member is prepared by the molding process, and the fiber is required to be taken out and protected by the slotting method. Where the fiber may be bent or subjected to large shear forces, increasing its chamfer or fillet would prevent fiber damage.

INFLUENCE OF LAYUP STRUCTURES ON SOUND INSULATION OF COMPOSITE LAMINATES

TIAN Hong-lei, WANG Ming, CAI Ji-jie, SUN Hao

2020, 0(4): 90-95.

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In order to design a kind of composite material with excellent sound insulation performance for rail vehicles and other transportation vehicles, the autoclave process was employed to prepare this composite material with a sandwich structure laminates. Performance of sound insulation of this composite structure was effectively controlled with a design of the laminated structure, thickness and damping layer. The results show that the sound insulation performance can be effectively improved with an increase in thickness and density of composite materials. The utilization of a damping layer makes the impedance mismatch at the internal interface of the composite structure, which results in that the sound waves are easily reflected at the interface, and the increase in sound energy further step consumption effectively improves the sound insulation performance either. With the structural design, the weight of the composite material was not only reduced but the sound insulation performance was improved. Finally, it makes this composite laminated structure material meet the sound insulation requirements of the high-end transportation field.

PREPARATION AND PROPERTIES OF CERAMICIZABLE PDMSMODIFIED POLYURETHANE FOAM COMPOSITES

OU Yun, SHI Min-xian, YAO Ya-lin, HUANG Zhi-xiong

2020, 0(4): 96-100.

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Rigid polyurethane foam has low density, low thermal conductivity and excellent thermal insulation properties, but its heat resistance is poor which needs to be improved to meet the application requirements. In this paper, the ceramicizable RPUF modified polyurethane foam composite was prepared by using hard polyurethane foam (RPUF) as matrix, hydroxyl silicone oil (PDMS) as modified additive, low melting point glass powder, talc powder and kaolin as ceramicable filler. And, the effects of kaolin on the compressive strength, thermal conductivity and ablative properties at high temperature of the ceramicizable PDMS modified polyurethane foam composites were studied. The results show that with the increase of kaolin content, the density of the material increases, the thermal conductivity increases, and the compressive strength increases. The SEM results show that a ceramic continuous phase structure is formed on the surface of the material after ablation at 800 ℃. XRD analysis indicates that the newly formed ceramic phase was α-quartz and orthorhombic manganese. Therefore, the addition of the inorganic filler effectively improves the heat resistance of the rigid polyurethane foam.

PREPARATION AND APPLICATION STUDY OF MODIFIED PHASECHANGE MICROCAPSULE IN THERMAL CONTROL FIELD

WANG Rui-jie, LI Hui, JIN Zhao-guo, JI Xu-yang

2020, 0(4): 101-105.

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Permeability and the lower-thermal conductivity of phase change materials (PCMs) affects the control thermal application. According to the requirement of thermal control of spacecraft, this paper introduces a series of optimization techniques about the preparation of n-octadecane microcapsules by insitu polymerization, summarizes the mehods of improving the thermal conductivity about low temperature PCMs microcapsules, demonstrates the application of PCMs microcapsules composites in the field of space thermal control, and projects the direction of PCMs microcapsules materials in the future.

EFFECT OF STRINGER FLANGE TAPER ON SKIN WRINKLE IN CO-BONDING PROCESS

XUE Xiang-chen, WANG Ben, YU Tian-qi, HU Jiang-bo

2020, 0(4): 106-111.

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In the process of forming a composite stiffened panel, there is a process of curing the stringer and then co-bonding with the uncured skin. This process requires to reduce the wrinkle of the skin at the edge of the stringer flange. In order to optimize the manufacturing process of the panel and improve the process stability of the product, the method of manufacturing the panel by tapering the flange of the stringer is explored. By sampling the wrinkle section and measuring the geometrical dimensions of the wrinkles by microscopic observation, the trend of wrinkling of the skin after different tapering angles was explored. The results show that the skin wrinkle can be significantly reduced after tapering the edge of the stringer, and the sharper the tapser is, the smaller the wrinkles are. According to the actual situation, after selecting a specific angle to chamfer the stringer flange, the amplitude of the skin wrinkle can be effectively controlled while simplifying the manufacturing process.

DEVELOPMENT AND APPLICATION OF BY-PASS DUCT CASINGMADE OF RESIN MATRIX COMPOSITE

ZHAO Kai, LIU Peng-fei, LIU Bo-lang, YI Kai

2020, 0(4): 112-116.

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In order to meet the goal of engine weight reduction, the development of by-pass duct casing made of resin matrix composite was carried out. According to the operation requirements, the structural design process is described from the aspects of connection form, material selection, ply principle and structural design. The verification of design scheme is carried out through the simulation analysis. Based on the development scheme, the prototyping and manufacturing process is introduced from the aspects of mould design, shell forming, machining forming and non-destructive inspection. According to the ground test, it is concluded that the by-pass duct casing under development meets the requirements of engine operation.

STUDY ON CONNECTION PERFORMANCE OF WIRE THREAD INSERTOF CARBON FIBER REINFORCED PLASTICS (CFRP)

LI Zhe, LI Jian-fang, SHEN Deng-xiong, WAN Qing

2020, 0(4): 117-120.

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The structure parts of carbon fiber reinforced plastics (CFRP) were widely used in the aerospace field. Usually, the mechanical connection method of screwing or riveting was employed after processing through-hole of structure parts. This method increased the connection weight and connection complexity of the structure parts. However, the mechanical connection method for itself threaded hole of CFRP structure parts had the problems of poor wear resistance, poor load bearing capacity, low connection strength, easy thread breakage and poor fatigue resistance and so on, which greatly limited the connection application of CFRP threaded hole. In recent years, the connection method of wire thread insert had appeared in the mechanical connection of CFRP structure parts, which partially improved the connection strength of CFRP threaded hole. In this paper, to analyse the connection performance of MT700 CFRP with the wire thread insert, based on the principle analysis of wire thread insert, the repeated disassembly test and the pulling-out load strength test, the connection performance of wire thread insert and the failure type of CFRP threaded hole were analyzed in detail. The results show that compared with the CFRP threaded hole without wire thread insert, the CFRP threaded hole with wire thread insert can significantly enhance the load bearing connection performance and wear resistance, improve the pulling-out force by 26% and stability, reduce the damage risk of the threaded hole, as well as expand the connection application range of CFRP threaded hole.

STUDY ON MOULD DESIGN OF INTEGRATED MOLDING PROCESS OF AIR RUDDER

ZHU Kun, LU Dong-bin, GAO Ting, WANG Dan

2020, 0(4): 121-124.

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This paper studied a mould project, and the mould was made to manufacture a composite air rudder by RTM process. The air rudder was prepared with a skin/rudder core structure, for which the skin was composite, and the rudder core was metal. By analyze the air rudder, the mould was designed to be a fission mould. To solve those problems such as how to position the air rudder core with the skin and mould-assembling mechanism, a new RTM mould has been designed in the paper, which contains optimized location mechanism and mould-assembling mechanism. Then, modal analysis was done to obtain the most reasonable injections and outlets. When a injection was set up in the surface of the skin, this mould project can avoid the phenomenon of lack of resin. An air rudder was manufactured with preferbly boundary dimension. By those works, this paper provides a mould project and fulfils the integrated manufacture of the air rudder.

THE RESEARCH ON MOLDING TECHNOLOGY OF CYLINDRICALSPIRAL ELEMENT IN COMPOSITE MATERIAL

LI Qi-hui, GUO Jun-gang

2020, 0(4): 125-128.

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The molding technology of cylindrical element is introduced from material selection, process plan, mold design and process control. Experimental results show that the method of using the high performance glass fiber composite material and combining autoclave curing technology and CNC technology can realize the processing and manufacturing of spiral element. The element has the characteristics of high machining accuracy and mechanical properties. Meanwhile, it also shows the good electric and vibration performance.

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