COMPOSITES SCIENCE AND ENGINEERING

EFFECT OF SURFACE TREATMENT ON THE PROPERTIES OF VECTRAN REINFORCED MEMBRANE

DING Lei, CHEN Nan-liang, WANG Jin-xi, LI Bei-bei

2020, 0(11): 5-11.

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In order to enhance the interfacial adhesion between Vectran fibers and water-based polyurethane, the effects of tensile properties and peeling properties of Vectran reinforced membrane materials were investigated by alkali treatment and plasma treatment on Vectran fibers. The effects of surface treatment on the surface morphology and wettability of Vectran fibers were analyzed by scanning electron microscope and contact angle surface property tester. The research results show that both alkaline treatment and plasma treatment can effectively improve the interface properties of Vectran fibers, but they have different degrees of damage to the mechanical properties of Vectran reinforced membrane materials. Among them, the peel strength of Vectran reinforced membrane increased by 70.67% after being treated with 20 mol/L alkali solution for 120 min on base fabric. After 120 min treatment with 10 mol/L alkali solution, the reinforced membrane peel strength increased by 29.19%, and after 6 min with plasma treatment, the reinforced membrane peel strength increased by 13.50%. But tensile strength of the Vectran reinforced membrane materials had been reduced by 89.99% after 120 min treatment with 20 mol/L alkali solution on base fabric. The reinforced membrane tensile strength was reduced by 19.02% after 120 min treatment with 10 mol/L alkali solution, and the reinforced membrane tensile strength was reduced by 4.38% after 6 min of plasma treatment.

ANALYSIS ON MECHANICAL CHARACTERISTIC OF COMPOSITE SANDWICH PLATE IN PLATE-CONE RETICULATED SHELL

DENG Yu-chen, WANG Xing

2020, 0(11): 12-18.

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For application of composite sandwich panels in the plate-cone reticulated shell, the mechanical characteristics are studied. The overall performance of the structure was analyzed based on ANSYS software, and the local buckling capacity of the composite sandwich plate was analyzed in consideration of the local buckling influencing factors. The comparative analysis of the ordinary plate-cone reticulated shell is also made. The results reveal that the structure has a large overall stiffness. Compared with ordinary plate-cone reticulated shell, it has the same static law and the composite sandwich plate has a good strength reserve. The influence factors of local buckling of sandwich plate are analyzed and some important conclusions are obtained, and it also has more advantages than ordinary plate-cone reticulated shell in terms of mechanical characteristic.

TEST OF MOISTURE ABSORPTION BEHAVIOR AND FINITE ELEMENT SIMULATION OF PLAIN WEAVE COMPOSITE MATERIALS

ZHANG Xian-feng, GUAN Guo-yang

2020, 0(11): 19-25.

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The moisture absorption curve of a plain weave composite was measured experimentally, and a moisture-absorbing finite element model containing the plain weave microstructure was established. Through this model, the effects of random offset, the angle ratio of the laminate lay-up and the fiber volume in the fiber bundle on moisture absorption were studied. The investigation shows that the moisture absorption behavior of the plain weave composite laminate is in accordance with Fick's law in general. The FEA results agrees well with the test. A random offset of the layup position has an effect on the balanced moisture content. The angle ratio of composite lay-up has a slight effect on the balanced moisture content, but it has no significant effect on the exposure time before banlance.The fiber content in the fiber bundle of plain weave composite material increases, which makes it easier to reach the moisture absorption balance, but the equilibrium moisture absorption rate and the moisture absorption rate decrease.

THE EFFECT OF THERMAL RESISTANCE IN COMPOSITE CURING PROCESS

WANG Ya-peng, HUANG Qi-zhong, YIN Shuang-shuang, HE Jing

2020, 0(11): 26-31.

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The quality of composite parts is largely depended on the cross-linking reaction of polymer matrix which is affected by the curing temperature. The manufacturing process of composites shows that the thermal resistance between the interface of the dies and the products of composites and the auxiliary materials is assignable, which affects the temperature distribution of composites. There is an improved element model which defines a variable thermal contact conductance parameter between the contact surfaces, which can help to better investigate the effect of thermal resistance on composite parts curing. The numerical analysis and experimental results show that, compared with the traditional model, the new model brings more accuracy prediction with the same computing resource.

EFFECT OF WATERBORNE EPOXY SIZING AGENT ON PROPERTIES OF CARBON FIBER COMPOSITES

CHAI Jin, KONG Hai-juan, ZHANG Xin-yi, YU Mu-huo

2020, 0(11): 32-36.

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A kind of aqueous epoxy resin sizing agent was made by the reaction of phthalic anhydride, polyethylene glycol 2000 and epoxy resin E51. Carbon fiber epoxy resin composite material was prepared by the way of vacuum bag molding process. The properties of the carbon fiber epoxy composites after sizing were estimated by thermal stability, the free energy of the contact angle surface, the surface and composite material section morphology, and interlaminar shear strength (ILSS). The results show that carbon fibers were successfully modified by sizing agent, the decomposition temperature of the sizing agent is about 300 ℃; the contact angle with water decreased from 71.4° to 65.1°, and the surface free energy increased from 32.2 mN/m to 38.9 mN/m; the interlaminar shear strength of the epoxy resin composite reached a maximum value (88.6 MPa) at sizing agent mass fraction of 6wt%, which increased by 10.3% compared with the unsized carbon fiber (80.3 MPa).

SIMULATION AND EXPERIMENTAL STUDY ON CURRENT DISTRIBUTION CHARACTERISTICS OF CARBON FIBER COMPOSITES

RUAN Wei, DUAN Ze-min, SI Xiao-liang, LI Zhi-bao

2020, 0(11): 37-41.

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The electrical conductivity of carbon fiber composites (CFRP) is anisotropic, which has different current distribution characteristics from traditional metal materials in lightning injection. With a multiphysics electromagnetic simulation software, a CFRP reduced lightening current injection model is established to explore the current distribution characteristics of CFRP. Based on the current density simulation results, a current injection test is performed to collect current waveforms in different directions. The results show that for the CFRP board which is unprotected, the current peak along the surface fiber arrangement direction is greater than the surface vertical and thickness direction when injected with a waveform with a smaller peak current. The current waveform in all directions is close to the injection waveform, and the peak current increases linearly with the peak value of the injection current. Under the protection of copper mesh, the current peak in the thickness direction of the CFRP board is much smaller than in other directions on the surface. The aluminum board shows that the current peak in the thickness direction is greater than in other directions on the surface.

RESEARCH ON CUTTING FORCE AND HOLE QUALITY DURING THE DRILLING OF KFRP COMPOSITES

GONG Wen-dong, LIN Yu-liang, LI Ying

2020, 0(11): 42-48.

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KFRP composites have strong toughness which are therefore difficult to be processed. Different kinds of plates are used to investigate the efforts for the hole quality, and then single factor experiments are conducted to investigate the cutting force and hole quality in different working conditions. The cutting force, the tearing area and the fuzzing area are presented to analysis the cutting process and characterize the hole quality. The experimental results indicated that the plates can improve the hole quality, and the aluminum plates have the best efforts. There are close influences of feed speed and spindle speed on the cutting force and hole quality. The cutting force decreases with the spindle speed, and increases with the feed speed. The feed speed has a greater impact. Decreasing the axial cutting force can reduce the tearing and fuzzing area. The inside walls of the hole will be burned under low feed speed and high spindle speed working conditions.

RESEARCH ON STRUCTURE DESIGN OF COMPOSITE PRESSURE HULLS FOR DEEP SEA

WANG Peng-fei, JIANG Ya-bin, SONG Jiang, TAN Zhi-duo

2020, 0(11): 49-53.

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Compared with metallic materials, composite materials have higher specific strength and specific modulus. According to equipment from the United States and other underwater technology powerhouses. Carbon fiber composite materials are an important way to make pressure-resistant cabins for water gliders. However, at present, there is no mature design method and specification for composite pressure tanks in China. Therefore, this paper takes an underwater 1000 m class composite pressure tank as an example, estimates its wall thickness using empirical formulas, and then uses ANSYS finite element analysis software. The strength check and stability analysis of the pressure-resistant tanks were performed, and finally the composite pressure-resistant tanks were verified by external pressure performance tests. It is found that the failure mode of thin-walled cylindrical composite pressure-resistant tanks is instability. The design should focus on the critical external pressure strength at the time of instability. The empirical formula used formula used in this paper can be used for thin-walled composite pressure-resistant tanks engineering application design.

EFFECT OF STRESS RATIO ON FATIGUE PROPERTIES OF T700 CARBON FIBER COMPOSITES BASED ON DIC

WANG Fu-sheng, OUYANG Jun-jie, KONG Fan-qi, DI Ze-kun

2020, 0(11): 54-60.

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Under fatigue cycle loads with different stress ratios, digital image correlation (DIC) is used to investigate the damage modes and processes of carbon fiber laminates. Using Instron8803 electro-hydraulic servo fatigue machine to perform fatigue tests on composite laminates, and DIC technology to collect information during the damage process, combined with micro failure morphology, the fatigue failure modes of composite materials were analyzed. The fatigue life of composite laminate was affected by the stress ratio under the condition of tensile-tension fatigue loading. The smaller the stress ratio, the shorter the fatigue life, and the fatigue life of the sample decreased from 6×10⁵ to 6×10³ when the stress ratio decreased from 0.6 to 0. The DIC technique was used to analyze the layered damage of the laminate in the thickness (Z) direction, and a width (Y) strain contour was obtained. Comparing the micro-morphology of fatigue failure and tensile failure, it was found that the delamination damage appeared on the fatigue fracture obviously, the resin matrix between layers failed, and the fiber in the layer was pulled out.

THE RESEARCH AND DEVELOPMENT OF COMPOSITE TAIL BOOM FOR AN UNMANNED AERIAL VEHICLE (UAV)

GUAN Xin, WANG Hong-yu, XU Ting, WU Hai-sheng

2020, 0(11): 61-65.

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Aiming at the main technical specifications for tail boom of a type of twin-boom UAV, the composite tail boom product is designed and manufactured: A variable elliptical cross-section tapered tail boom is designed, and a high specific strength carbon fiber composite is used. The design status of the tail boom is determined through the finite element simulation. In order to mold the product, the low-cost rubbing-winding process is creatively adopted,and the product passes the 2.5 g static test. The composite tail boom product in this paper meets the comprehensive requirements of light weight, high performance and low cost.

THE CLEARANCE SIZE OF BLADE WEBS WAS MEASURED BASED ON 3D LASER SCANNING TECHNOLOGY

LIU Xiao-bin, ZHU Kun, MAO Yi-mei, GAO Yan-hui

2020, 0(11): 66-70.

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The thickness prediction of the adhesive layer on the blade web is usually made by pressing the plasticine during the blade trial closing process. The thickness of the plasticine measured is the thickness of the adhesive layer on the web. In this paper, a measurement method is proposed to scan the shape of blade skin and web by means of three-dimensional laser scanning technology, and to obtain the mold closing die by simulating the mold closing mode, and to measure the die closing clearance of the blade web. In this paper, the three-dimensional laser scanning is used to measure the closing clearance of the blade web, and the measured data are compared with the data of the plasticine pressed by the trial closing die. The 3D laser scanning measurement can be used as a method to measure the clamping gap of the blade web to achieve the trial-free clamping measurement. This paper analyzes the main factors affecting the measurement accuracy.

A NEW TYPE OF POLYMER RIGID FOAM

ZHOU Dian, ZHANG Chao, ZHANG Rui, ZHU Ye

2020, 0(11): 71-75.

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This present paper documents a study on a new type of interpenetrating polymer network rigid foam Atlas HPE. A series of tests were performed on the new type of foam, which includes quasi-static mechanical tests, fatigue test, resin absorption test and dimension stability test. We further conduct a comparative study for Atlas HPE with the existing conventional PVC and PET foams. The results show that Atlas HPE foam has excellent fatigue resistance, and the sandwich structure made of it can withstand 2 million cycles of loading under the condition that the maximum dynamic load is 50% of the static shear strength. Besides, resin absorption per square meter of Atlas HPE is 1.287 kg, and the volume change rate after 120 ℃ high-temperature treatment is only 0.81%. Its resin absorption performance and dimension stability are both better than PVC and PET foams, revealing that the foam is of great physical performance. Therefore, the core material made of Atlas HPE can be applied to various load-bearing sandwich composite structures.

EXPERIMENTAL STUDY ON SHEARING OF FIBER WINDING AUTOMATIC CUTTING/HANGING MECHANISM

TIAN Hui-fang, ZHANG Yang, WU Ying-feng, WANG Sen

2020, 0(11): 76-80.

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In view of the relatively low degree of automation of the auxiliary equipment for fiber winding, this paper designs an automatic cutting/hanging mechanism, and experimentally explores the shearing effect of the key picking and cutting module. Using glass fiber and epoxy resin applied in industrial production as experimental materials, the effects of fiber number, slip distance, tension, and shear speed on the minimum cutting force were tested under dry yarn and dipped state, respectively, and compared. The fracture morphology of the tow was analyzed to reflect the cutting effect. The experimental results show that the minimum cutting force increases almost linearly with the increase of the number of fibers, which decreases with the increase of the slip distance and tends to be gentle, decreases with the increase of tension, and increases with the increase of shear speed. Under the same conditions, the minimum cutting force required for the glass fiber tow in the dipping state is smaller, and the fracture morphology is better.

THE RESEARCH OF CONFORMITY INSPECTION OF THE CIVIL AIRCRAFT COMPOSITE MATERIAL STRUCTURES

YU Tao, WEI Ran, CHEN Xi

2020, 0(11): 81-86.

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A study was performed in the conformity inspection of the composite material structures based on the existing airworthiness regulations and the in-field inspection experiences. A practical method was built based on three key factors including conformity of material, process and product quality, expecting to provide guidance for the conformity inspection of civil aircraft composite material structures.

TOUGHTENING MODIFICATION OF VINYL ESTER RESIN BY POLYURETHANE ACRYLATE

BAI Guo-dong, LIU Ye, GUAN Yong, JIANG Xian-long

2020, 0(11): 87-92.

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In order to improve the toughness and expand the application of vinyl ester resin, polyurethane acrylates(PUA)were synthesized by polycondensation of diphenylmethane diisocyanate (MDI), polypropylene glycol (PPG) and hydroxyethyl methacrylate, and then blended with vinyl ester resin. Modified vinyl ester resin containing polyurethane acrylate blocks was synthesized by radical copolymerization under the action of initiator. The effects of addition of different urethane acrylates on the mechanical properties of the modified resins were investigated. The results show that the urethane acrylate can effectively improve the tougheness of the vinyl ester resin. When MDI∶PPG=3∶2 and the polyurethane acrylate is added at 15%, the tensile strength is 56.3 MPa, the elongation at break is 22.5%, the notched impact strength is 2.56 kJ/m². Elongation at break and impact strength are 2.45 times and 2.29 times of the unmodified resin, respectively. The comprehensive mechanical properties are the best. The elongation at break of optical fiber reinforced core prepared by pultrusion process using modified resin as matrix resin increases by 21.5%, and the high temperature bending performance is improved.

EFFECT OF AUTOMATIC PLACEMENT PROCESS PARAMETERS ON PROCESS PERFORMANCE OF DRY FIBER PREFORMS

LIU Shu-cheng, LI Lin-xiu, PAN Li-jian, NING Bo

2020, 0(11): 93-101.

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Compared to the prepreg/autoclave process usually used in aerospace, the automatic placement of dry fiber/liquid molding can manufacture the same composite materials, as measured by fiber volume content and good mechanical properties, but at a lower cost. The preforms are made of dry fiber tows with heating and pressing by Automatic Fiber Placement (AFP) machine, and their permeability, fiber volume contents and compression characteristics have a great influence on the properties of the composite materials. In this paper, the preforms of different interlayer structures were prepared by adjusting the temperature and pressure of the dry fiber tow within the automatic placement technology. The influence of the automatic placement process parameters on the performance of the preforms was studied. The results show that at a constantly held pressure, as the temperature increases, the thickness and permeability of the preforms decrease, and their deformation resistance and fiber volume content increase. The volume content is 58.45% at 175 ℃. Also, at a constantly held temperature, as the pressure increases, the thickness, permeability, fiber volume content and deformation resistance of the preforms have the same changing trend as increasing temperature, and the volume content is 55.39% at 0.2 MPa. This is mainly related to physical/chemical changes of dry fiber surface with the styling agent and the flow guiding fiber.

STUDY ON THE LOW-SPEED IMPACT PERFORMANCE AND RESIDUAL STRENGTH AFTER IMPACT OF COMPOSITE SANDWICH STRUCTURE WITH DIFFERENT LAYUP

SUN Zi-heng, WANG Ji-hui, NI Ai-qing, CHEN Hong-da

2020, 0(11): 102-110.

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In this paper, three kinds of carbon fiber sandwich structures with different layup face sheets were prepared by using carbon fiber plain weave prepreg, unidirectional prepreg and Balsa. The low-speed impact with impact energy of 5 J, 15 J, 25 J, 35 J, 45 J and post-impact compression test of these three composite sandwich structures were carried out to study the effect of different laminate types on the low-speed impact properties and residual compressive strength of sandwich panels. The results indicate that stacking parameters can prominently influence the damage failure modes of composites sandwich structure when subjected to low-speed impact and post-impact compression. The low-speed impact damage area, pit depth, damage area, impact response curve and the compressive strength reduction ratio after impact of the three sandwich panels were remarkably different. Among the three laying methods, the specimens of unidirectional carbon fiber prepreg with quasi isotropic layer exhibit high impact load resistance.

STUDY ON THE INFLUENCE OF MOLDING TECHNOLOGY ON THE PERFORMANCE OF POLYURETHANE SLEEPER

WEI Jian-guo, LI Shuai-qi, MA Duan-ren, LIU Jia

2020, 0(11): 111-115.

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In this paper, the effects of yarn arrangement, curing temperature, curing time and other factors on the compressive properties and the pull-out strength of spikes of fiber-reinforced polyurethane synthetic sleepers are studied. It is shown that the density of yarn arrangement 1 is the closest to the design value, its compressive strength and modulus of compression are superior to other yarn arrangement methods, and its pull-out strength is the highest and its uniformity is the best. At about 55 ℃~63 ℃, the curing time is in the range of 55 ℃~63 ℃. The mechanical properties of the product are better after 60 minutes, the compressive strength is about 110 MPa, and the pull-out strength (ø22) of the spike is more than 55 kN.

MULTI-SCALE INTERFACE SIMULATION RESEARCH AND DEVELOPMENT OF FIBER REINFORCED RESIN COMPOSITES

LI Chong-rui, GAO Cong, SHI Peng-cheng, YAN Chun

2020, 0(11): 116-122.

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Nowadays, fiber reinforced resin matrix composites are widely applied in various industries as lightweight structural materials, and the design and research of interface have also attracted people's widespread attention as the Achilles' heel of composite materials. The traditional experimental characterization methods are difficult to explain the complex equilibrium/non-equilibrium interface interaction mechanism, but computer simulation technology shows strong superiority in the visualization of interface interaction mechanisms and the description of quantitative structure-activity relationship (QSAR). In this paper, the modeling methodology and the mechanism of interface of fiber reinforced resin composites and its effect on mechanical properties, thermodynamic properties and kinetic properties of materials are in hierarchical order, including perspectives from microscale, macroscale, and cross-scale, and this article proposes the guiding significance of computer simulation technology for cross-scale constitutive parameters, nonlinear friction dissipation mechanisms, high strengthening and toughening mechanisms, and high-throughput prediction and screening which represent the trends in future development of high-performance composites.

PROGRESS IN HELICAL MILLING HOLES FOR CARBON FIBER REINFORCED POLYMER

FANG Chun-ping, ZHAO Jin-ze, YE Zheng-mao, GUO An-ru

2020, 0(11): 123-128.

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In order to solve the problem of fracture, burr and delamination of carbon fiber reinforced polymer (CFRP) with the traditional drilling method, recently, helical milling technology plays a significant role in studying hole-making of carbon fiber reinforced composites. And it has been more widely used in aircraft and aerospcace industries. This paper reviews the progress of helical milling in maching process of CFRP by analysizing and summarizing the current research status in the aspects of cutting force, surface quality and cutting tool at home and abroad. A preliminary prospect on the future development direction of the helical milling about CFRP was given.

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