COMPOSITES SCIENCE AND ENGINEERING

INFLUENCE OF THERMAL BOUNDARY CONDITIONS ON CURE PROCESS OF COMPOSITES LAMINATE

TANG Qing-ru, BAO Zheng-tao, CHEN Shu-xian

2019, 0(4): 5-11.

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In order to reduce peak temperature of the thermosetting resin matrix composites and optimize the temperature field distribution during the process of curing based on hot bonder, three optimization methods of thermal conditions are proposed, i.e., isothermal boundary conditions, convective heat transfer boundary conditions and a aluminum mould are set respectively on the top surface of laminated plate. The degree of cure and temperature field distribution above three conditions are calculated by the finite element method, and compared with traditional method. The calculation results show that compared with existing methods, the optimization method can reduce the peak of temperature and optimize the temperature field distribution of laminated plates. The peak temperature drops the most on isothermal boundary conditions, while it drops the least on convective heat transfer boundary conditions. The temperature gradient of laminated plates in parallel to the mold surface is relatively uniform with good thermal conductivity of aluminum when aluminum mold are set on the top surface of laminated plate.

EXPERIMENTAL STUDY ON FATIGUE DAMAGE DETECTION BASED ON NONLINEAR ULTRASONIC

ZHANG Fa-you, LI Cheng, TIE Ying, YIN Zhen-hua

2019, 0(4): 12-16.

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The fatigue testing and nonlinear ultrasonic testing are carried out on the complete aluminum plates, the aluminum plates containing the hole and the aluminum plates repaired with the composite patches. The amplitudes of fundamental ultrasonic and the second harmonic of the three sets of specimens under different fatigue cycles areextracted. The relative second-order ultrasonic nonlinear coefficients are obtained, and the graph of the relative second-order ultrasonic nonlinear coefficient with the fatigue cycles is fitted to study the corresponding relationship between the relative second-order ultrasonic nonlinear coefficients and the fatigue damage process. The results show that with the increase of fatigue cycles, the second-order ultrasonic nonlinear coefficients of the three sets of specimens show a slow rise first, then rise rapidly and reach the peak value, and finally decrease, which is consistent with the process of dislocation and crack generation and propagation during fatigue damage. At the same time, it is found that the pore damage will aggravate the transition of microcracks to macroscopic cracks, while repairing pore damage with composite patches can slow crack propagation.

THE ANALYSIS OF PARAMETRIC AND REINFORCEMENT COEFFICIENT ABOUT H-SECTION STEEL BEAMS REINFORCED BY PRESTRESSED CFRP PLATES

DONG Shi-er, MA Meng-liang, WANG Yi-heng

2019, 0(4): 17-24.

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Sticking carbon fiber reinforced composite material is a new reinforcement method. Compared with the traditional reinforcement material, it has the characteristics of light weight and high strength. However, the strength utilization ratio of strengthened by common CFRP is low. Therefore, some scholars put forward the method reinforced by prestressed CFRP plates. In view of the present study, no concrete formula for stiffness of composite beams after reinforcement is given. Therefore, to study the effect of design parameters on H-section steel beam stiffness reinforced by prestressed CFRP plates, the finite element software ABAQUS was used to calculate the multi components under four-points-loading. The influence of CFRP plate length, thickness, width, modulus of elasticity and prestress level on the strengthening performance were analyzed. 0n this basis, the reinforcement coefficient was introduced. Combining with the calculation formula of the mid-span deformation on simple supported beam, the calculation formula for steel beam reinforced by prestressed CFRP plate was given. Afterwards, the calculation results of simplified calculation formula of reinforcement coefficient were compared with the results calculated by ABAQUS. The results show that length, width, thickness and prestress size of the CFRP plate have a significant influence on stiffness of reinforced steel beam. Meanwhile, the elastic modulus of CFRP plate has little effect on the stiffness of steel beam, and the simplified formula of strengthening coefficient has certain applicability and accuracy.

IN-SITU POLYMERIZABLE THERMOPLASTIC EPOXY RESIN AND THE PROPERTIES OF ITS COMPOSITES

ZOU Jun-jie, WANG Jun, CHEN Xi

2019, 0(4): 25-30.

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In this paper, a novel thermoplastic epoxy composite was prepared by impregnating a reinforcing material with a mixture of epoxy resin, bismaleimide resin and monoamine. By immersing the cured resin in an organic solvent, it was found that the resin was dissolved in the solvent, indicating that the resin matrix was not crosslinked. The curing system of the resin system was studied by differential scanning calorimetry (DSC) and infrared spectroscopy (FTIR). The heat resistance of the system was studied by DSC and synchronous thermal analyzer. The mechanical properties of the composites were studied by using an electronic universal material testing machine. The results showed that the best curing system was 70 ℃/1 h+120 ℃/2 h+150 ℃/5 h+170 ℃/2 h. The addition of bismaleimide resin could effectively improve the glass transition temperature of the system. When the content reached 10%, the T_g could reach 90 ℃ and the glass transition temperature was increased by 36% compared to the system in which no bismaleimide resin was added.

STUDY ON THE TENSION-TENSION FATIGUE PROPERTIES OF T700/MTM46 COMPOSITE LAMINATES UNDER HIGH STRESS LEVEL

WANG Yu-qian, LIU Zhan, DU Jin-qiang

2019, 0(4): 31-36.

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Tension-tension fatigue properties of T700/MTM46 composite laminates under high stress level were studied in this paper. Static tensile properties were investigated to obtain the ultimate tensile strength, modulus and failure strains. The static index has small scatter and the static failure modes are mainly characterized by the brittle fracture in a small region. Fatigue stress levels were determined by the ultimate tensile strength. Then the tension-tension fatigue tests were conducted. The scatter of fatigue life in each stress level is relatively large, which do not show clear trend with the change of the stress level. Fatigue failure modes of composite laminates are mainly serious delamination through the whole gauge length. The higher the stress level is, the more serious the stiffness decreases. Moreover, the normalized stiffness degradation curves exhibit three obvious stages characterized by "Quick-Slow-Quick" trend. The damages in fatigue loading initiate from 90° plies and show the most serious damage. Damages in 0° plies during fatigue loading appear latest. However, the fiber breakage in 0° plies indicates the coming catastrophic fatigue failure.

FEASIBILITY RESEARCH OF ×× EPOXY ADHESIVE USED FOR REPAIRING THE INNER SURFACE OF AERO-ENGINE OUTER CULVERT CASING

YOU Yan-yu, WU Mao-qing, ZHAO Hong-qi, LI Zhan-shan

2019, 0(4): 37-42.

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The high working temperature on the internal surface of aero-engine outer culvert casing and the influence of complex environmental factors are the difficulties in the repair of the outer culvert casing at present. This paper mainly used ×× epoxy resin as repair adhesive, and the typical specimen with damage depth of 0.5mm are prepared. Through the heat resistance, vibration resistance and mechanical properties of the typical specimen, the feasibility of ×× epoxy adhesive applied to the inner surface repair of aero-engine outer culvert casing was studied. The results show that specimen has no obvious change under 230 ℃ and 280 ℃ high temperature environment and it meets aero-engine outer culvert casing heat resistance requirements. The average strain value of each strain point in vibration experiment is less than 50 με, and the results show that adhesive and composite are in good bonding state after the test. The tensile strength of reparative specimens are similar to the undamaged specimen, and the fatigue strength was slightly decreased, but the results show that both of them meet the requirements of aero-engine outer culvert casing.

PREPARATION AND PROPERTIES ANALYSIS OF GRAPHENE/POLYIMIDE FILM

ZHAO Si-mei

2019, 0(4): 43-46.

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The graphene inorganic filler was polymerized with PAA by in situ polymerization and formed chemical bonds at the phase interface. Graphene and polyimide composite film was made using gradual temperature curing. The research results show that graphene and polyimide composite film had excellent comprehensive performance when w (graphene) was 1.0% in PI through analysis of the structure, microstructure, thermal stability, mechanical properties and electrical conductivity.

THE THEORETICAL DESIGN OF HOT-AIR HEATING ANTI-ICING SYSTEM AND APPLICATION IN ENGINEERING PRACTICE

HOU Bin-bin, YANG Wen-tao, ZHOU Jun-jie

2019, 0(4): 47-51.

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Based on the principle of hot-air heating method, a anti-icing thermodynamics computational model is established for MW wind turbine blades. The model is used to calculate the time for melting ice attached on composite surface. The results show good agreements between the mathematical model and FEA. Then a hot-air heating anti-icing system designed by means of FEA, is equipped in a 2 MW wind turbine. The test in wind-farm shows that, in -10 ℃ environment, ice on the surface of blades starts to be melt in 45 minutes. This system could be applied to anti-icing of wind turbine blades.

PERFORMANCE OF FIBER REINFORCED PLASTIC EXHAUST INNER TUBE UNDER HIGH TEMPERATURE CONDITIONS

TUBE UNDER HIGH TEMPERATURE CONDITIONS WANG Tao, ZHANG Hai-peng, HOU Rui-gang, HE Zhi-chao

2019, 0(4): 52-57.

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Fiber reinforced plastic (FRP) exhaust inner tube is widely used in new coal-fired power plants. In this paper, according to the actual temperature condition design experiment of coal-fired power plant,the changes of appearance, quality, rubber content and mechanical properties of FRP exhaust inner tube in 90 ℃, 135 ℃, 180 ℃ under high temperature conditions were studied in this paper. By comparing the mechanical properties of vinyl ester resin under different temperature conditions and scanning electron microscope (SEM), the analysis results of the cross section of the FRP smoke inner barrel were studied, the change tendency and reason of mechanical properties of FRP smoke inner tube at elevated temperature are discussed emphatically. The results show that the color of the FRP exhaust inner tube is deepened with the increasing of temperature, and the sample is almost carbonized and black at 180 ℃, and the change of mass and rubber content is caused by the quality change of the resin matrix. The result is that the quality and the glue content decrease with the increase of the cycle length and the temperature, and the mechanical properties are similar with vinyl ester resin, and the trend of the increase in the first time is decreased. The mechanical properties of 60 d are best under 135 ℃, which is around the glass transition temperature (T_g). At a temperature of 180 ℃, which is much higher than that of the glass transition temperature, the mechanical properties of the material decreased significantly at the later stage, but it remained about 80% of the strength retention rate.

DISCUSSION ON THE APPLICATION OF PFMEA IN THE BONDING PROCESS OF OFF-SHORE BLADE

ZHAO Li-yan, LIU Yan, XU You-mu, JIANG Yue

2019, 0(4): 58-61.

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During the early design development stage of off-shore blade, fully identify potential failures, draw up and validate control measure is an important measure to design development blade. This paper introduced the samples of PFMEA applications on off-shore blade design and development. By analyzing the potential failure causes, it is found that the bonding adhesive shape design and bonding interface treatment was the root cause of the adhesive voids, bubbles and other defects in the TE bonding area. Through the NDT (Non-destructive testing), the reliability of the bonding adhesive shape and bonding interface treatment were verified, which effectively control the risk of product development.

COMPOSITE MATERIAL B-BASIS ALLOWABLE SIMULATION BASED ON SMALL SAMPLE PHYSICAL TESTS

ZHAO Hui, ZHANG Li-tong, ZHANG Jia-xin

2019, 0(4): 62-66.

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Composite materials are extremely difficult to study due to their complexity, process and manufacturing defects, resulting in great dispersion of materials. The current traditional methods rely on a large number of tests and require extremely high manpower, time and material costs. Using the simulation method, the B-basis allowable of five mechanical properties such as longitudinal tensile, transverse tensile, longitudinal compression, transverse compression and in-plane shear of a carbon fiber composite used in the actual engineering of the institute were calculated and analyzed. The difference between the test and the simulation. The longitudinal compressive strength with large error between the experimental calculation and the simulation results was analyzed, and the transverse tensile strength of the uncalculated test was analyzed. The calculation error is controlled at 5% and the cost is saved.

AUTOMATED MANUFACTURING PROCESS STUDY OF COMPOSITE RADIUS FILLERS

YAN Chao, AN Shen-shen, SU Jia-zhi

2019, 0(4): 67-70.

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Radius fillers are indispensible part of filling material used in triangle area of composite beam and rib structure. To optimize manufacturing process, improve quality and enhance automatic level, the process study of material configuration, molding temperature and material filling quantity have been done to explore the influence of different process on quality of radius filler. The results show that the radius filler is of size stability and good appearance quality when the material filling quantity is 102%, molding temperature is 100 ℃, the material configuration is 6.35 mm×6 ply. Automated fiber placement and pultrusion process should be used to produce the radius filler of omega stringer reinforced panel. The skin and stringer can be assembled very well when the optimized process is used, and the triangle area of panel is smooth and of high quality.

RESEARCH ON RESIN CRYSTALLIZATION PROBLEM OF EPOXY-ESTOLIDE SYSTEM ACCELERATED BY 2,4-EMI

LU Wu-gang, WU Xiao-ping

2019, 0(4): 71-74.

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With the use of a kind of epoxy resin glue, a kind of adhesive half-solid matter appeared on the inside surface of resin barrel where was the resin surface, which was called crystallization. In order to solve the crystallization problem of resin matrix, consulting related reference was done in the paper, and related test research was developed at the same time. The results show that, the reason for the resin crystallization was that some unnecessary chemical reaction happened between MeTHPA and 2,4-EMI, which produced a kind of acid amides and carboxylic acid. They could not dissolve in the resin system and thus produce a kind of crystallization chemical substance. The crystallization phenomenon can be avoided effectively when make-up process was modified, namely the 2,4-EMI was added to epoxy resin first, and then preliminary mixture was done, then MeTHPA and assistant agent was added sequentially.

PREPARATION AND PERFORMANCE STUDY OF THE RADOME FOR FY-4 SATELLITE

PANG Zeng-kai, LI Yun-fei, LIU Yi-duo, LIU Li-li

2019, 0(4): 75-78.

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This paper mainly introduced a large size and high-performance radar radome for FY-4 satellite. The radome was a foam sandwich structure, using free E glass cloth, unsaturated polyester resin, polyurethane foam and surface coating system. The radome was prepared by hand lay-up molding and vacuum infusion process technology at room temperature to solidify. Structure calculation for the radome was analyzed in 67 m/s wind load, with a maximum deformation of 50 mm. Before the foam and skin forming, the surface treatment of foam was used to improve the interface bonding performance. The forming process was of high efficiency and good surface quality. The mechanical properties were excellent with the tensile strength of 0.35 MPa, the bending strength of 28.3 MPa, the shear strength of 320 kPa and the lateral pressure strength of 60.8 MPa. The electrical performance of the radome was good, and the dielectric loss in the L/S/C band was between 0.1 dB and 0.6 dB.

THE PERFORMANCE RESEARCH OF CARBON FIBRE-WINDING COMPOSITE CURED WITH ELECTRON-BEAM

ZHANG Shi-jie, WANG Ru-min, BAO Jian-wen, LI Ye

2019, 0(4): 79-83.

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The processing property, curing parameter, mechanical property and heat-resisting property of electron-beam cured resin systerm were investigated which were combined with the winding-forming process of pressure vessel. The pressure vessel of T700 carbon fibre composite material was prepared firstly with the adoption of electron beam curing technology interiorly which passed the hydroburst pressure experimental verification. The result of expriment indicates that the electron-beam cured expoxy system (EB-1) possesses better processing property and mechanical property. Its heat-resistant quality is excellent and up to 191.4 ℃. The tensile strength of NOL ring is 2020 MPa, which is made of T700 carbon fibre/EB-1 composite material cured with electron beam, and its interlaminar shear strength is 68.9 MPa; The characterization factor (PV/W_c) of the prepared Φ150 mm pressure vessel has reached 44 km which currently achieved the level of the same type of thermo-curing composite material, while the cure period is only the 1/15 of thermo-curing composite material.

DESIGN AND ANALYSIS OF GRINDING SYSTEM FOR GLASS FIBER REINFORCED PLASTIC LINING

TIAN Hui-fang, DING Hao, ZHANG Zhi-yong

2019, 0(4): 84-89.

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GFRP tanks are being widely used due to their own advantages. Among them, the surface of the lining of the FRP tank is polished, and many enterprises in China still stay in the stage of artificial grinding. In order to avoid the drawbacks of manual grinding, this paper designs a set of GFRP lining grinding system and introduces it from the mechanical structure and control structure. In order to ensure the rationality of the design and avoid excessive deformation of the grinding system during the working process, the finite element software workbench is used to carry out the static analysis of the grinding frame, the resonance, fatigue and other phenomena that may occur during the grinding process, the hazard caused by forced vibration, modal analysis of the main components of the grinding system to verify the design implementability. Since the grinding speed, working pressure and other parameters have a significant influence on the grinding amount during the grinding process, the surface material removal amount analysis based on the Preston equation provides theoretical support for the parameter setting of the grinding process to achieve high efficiency and reliability for the system.

CURRENT STATUS AND PROSPECTS OF GFRP ANCHOR RESEARCH

ZHENG Chen, BAI Xiao-yu, ZHANG Ming-yi, KUANG Zheng

2019, 0(4): 90-99.

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Anchor anchoring is a very important field in civil engineering, and the bolt is greatly concerned as its core structure. Compared with traditional steel anchors, glass fiber reinforced polymer (GFRP) anchors have better tensile strength and are less prone to be rusted, which can reduce engineering costs to a certain extent and is used in more and more projects. In this paper, the development history of GFRP anchors and the research progress of mechanical properties are briefly introduced. The shortcomings in the research of GFRP anchors are discussed, and the future development of GFRP anchors is proposed.

PROGRESS IN SELF-SENSING CONDECTIVE POLYMER MATRIX COMPOSITE

ZHAO Yue, YAN Chun, CHEN Gang, CHEN Ming-da

2019, 0(4): 100-105.

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Polymer matrix composites have been widely applied in many fileds due to their excellent properties. However, the internal cracks or defects of composites can easily lead to material failure. Early warning of material damage and real-time monitoring during its service can effectively improve their serving security. In this paper, the principle of self-sensing conductive polymer matrix composites is introduced and the research progress of polymer matrix composites with different reinforcements is analyzed. Furthermore, the research directions of in-situ monitoring of polymer matrix composites are pointed out.

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