COMPOSITES SCIENCE AND ENGINEERING

STUDY ON EDGEWISE COMPRESSION PERFORMANCE OF HONEYCOMB SANDWICH STRUCTURE WITH SCRATCH DAMAGE

ZHOU Chun-ping, LIU Wu-shuai, WANG Xuan, CAO Yang-li

2019, 0(7): 5-10.

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The progressive damage analysis model of honeycomb sandwich structure with plain braided panel is established. The lateral strength and failure mode of honeycomb sandwich structure with scratch damage on one side panel are studied. The results are compared with the experiments to verify the correctness of the model. Considering the high material nonlinearity of the model, ABAQUS/Explicit solver is used to simulate the quasi-static lateral compression of honeycomb sandwich structure. By compiling VUMAT subroutine, failure criteria and stiffness degradation models of panel and core are set respectively, and cohesion model is used to simulate the adhesive layer to complete progressive damage analysis of honeycomb sandwich structure subjected to lateral compression. The results show that the buckling behavior of the unilateral plate without damage will occur when the failure occurs, which will increase the stress outside the honeycomb core surface and lead to the damage of the honeycomb core. The longitudinal compression failure of fiber and the longitudinal shear failure of the fiber-matrix will occur on one side plate with surface scratches, and the failure will extend from the vicinity of the scratch area to both sides along the scratch direction.

THE INVERSE DESIGN FOR COMPOSITE LAMINATES BASED ON RANDOM UNCERTAINTY

SONG Shu-fang, WANG Zhuo-qun

2019, 0(7): 11-15.

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The inverse design is a novel modern design method, and it can provide strong theoretical support for the composite design. In this paper, the structural mechanical behaviors of composite laminates are considered as deterministic and uncertainty responses, respectively. On the basis of the finite element method (FEM) or experimental data, the advanced Group Method of Data Handling-Neural Network (GMDH-NN) algorithm is used to construct the relationship between input variables and output responses, and the genetic algorithm (GA) is employed in the optimization process of inverse simulation for the composite laminates. Furthermore, several examples are given to show that the presented methods are reliable and feasible in application to gain the elastic constants, which is of great significance in practical engineering.

NUMERICAL SIMULATION FOR MECHANICAL BEHAVIOR OF N330 CARBON BLACK FILLED RUBBER COMPOSITES

LI Qing, YANG Xiao-xiang

2019, 0(7): 16-20.

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Stress-strain behavior test curves of four different volume fraction of N330 carbon black filled natural rubber composites have been obtained by mechanical test. Microstructural features of carbon black filled rubber composite has been gotten through scanning electron microscope observation. Two-dimensional Representative Volume Elements containing multi-particles with different size random distribution have been established, and the macromechanical properties of the carbon black filled rubber composites have been studied and analyzed by the micromechanical nonlinear finite element method. The research shows that the prediction results with 7 percent filler content on the stress-strain behavior are higher than experimental results. The prediction results with 15 and 25 percent filler content are consistent well with the experimental results, until the certain strain are lower gradually than the experimental results. And it demonstrates that the two-dimensional model can be used for simulation analysis of stress-strain behavior of the carbon black filler particle reinforced rubber matrix composites.

STUDY ON THE TENSILE DAMAGE EVOLUTION BEHAVIOR OF THREE DIMENSIONAL FIVE DIRECTIONAL CARBON FIBER BRAIDED COMPOSITES

HAN Kang-ning, LI Xiao-tong, QIN Reng, ZHOU Wei

2019, 0(7): 21-27.

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In order to reveal the damage evolution rule and the effect of the damage mode on the properties of the composites under different fiber volume fraction, combined with the Acoustic Emission (AE), Digital Image Correlation (DIC) and Infrared Thermography (IT) complementary monitoring technology, the tensile mechanical properties of the composites were tested and the AE signals under tensile load and the surface strain field and temperature field information during the damage process were obtained dynamically. The results show that, with the increase of fiber volume fraction, the failure load and fracture strength of carbon fiber three-dimensional five-direction composite material increase, the relative energy increase, and the AE signal grows faster per unit time. Obvious strain concentration occurs in the interlaced area of yarn, forming a serrated strain concentration belt. With the continuous increase of tensile load, the surface temperature of the composite specimen increases continuously, and the specimen has obvious temperature characterization at the moment of failure, which is consistent with the failure characterization of strain field instability. Therefore, the combination of AE, DIC and IT complementary detection technology can effectively monitor the damage evolution process of fiber three-dimensional five-directional braid composite materials, providing reference for the structural health detection.

RESEARCH ON THE PROPERTIES OF 2D MULTIAXIAL WARP-KNITTED CARBON FIBER COMPOSITES

LIU Ming-fan, ZHANG Peng, CHENG Yong-qi

2019, 0(7): 28-33.

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In this paper, three kinds of multiaxial warp-knitted carbon fiber composites were prepared by the same process. The impact, compression and friction characteristics of carbon fiber composites with different weaving methods were studied. The results show that the three-axis (±45°/90°) carbon fiber composite show outstanding impact properties. Compared with the two-axis (±45°) composite, the three-axis impact strength is increased by 90%. While compared with the four-axis (-45°/0°/+45°/90°) composite, the three-axis impact strength is increased by 45%. Compression strength of two-axial (±45°), three-axial (±45°/90°) and four-axial (-45°/0°/+45°/90°) carbon fiber composites are increased with the increase of weaving angle. Compared with the four axis and the two axis, the compression strength increases by 125.7%. Temperature has a direct effect on the friction properties of composites. Compared with plain weave carbon fiber composites at room temperature, the friction coefficient of multiaxial warp-knitting carbon fiber composites is lower and the friction stability is higher. With the increase of the test temperature, the friction coefficient of composites decreases first and then increases. When the temperature is 150 ℃, the friction coefficient of composite reaches its minimum value.

NUMERICAL STUDY AND EXPERIMENT OF COMPOSITE STRINGER ON COMPRESSIVE PROPERTY

YE Ti, YUE Yuan

2019, 0(7): 34-38.

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Based on the progressive damage analysis, compressive property of composite stringer was studied with the 3D HASHIN criterion and nonlinear stiffness degradation method. By coding the user-defined material subroutine (UMAT), the application of failure criterion and stiffness degradation method were implemented in ABAQUS. With different sizes and lay-ups into consideration, three dimensional finite element models were built to analyze the compressive property and the failure process, and experimental verification was made simultaneously. For configuration 1,the result of finite element analysis was 247 kN, which agreed well with the experimental result 257 kN, verifying the reliability of the model.

STUDY ON BEARING CAPACITY OF CARBON FIBER REINFORCED ALUMINUM ALLOY LAMINATE BASED ON ABAQUS

YIN Xue-zhi, HUANG Ya-xin, LIN Yuan

2019, 0(7): 39-47.

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In order to study the influence of different aluminum alloy grades and layers on the load-bearing performance of carbon fiber aluminum alloy laminates, this paper taked carbon fiber reinforced aluminum alloy laminates as the research background, and four groups of 3/2 type carbon fiber aluminum alloy specimens composed of two kinds of aluminum alloy materials 2024-T3 and 7075-T6 and two kinds of carbon fiber prepreg layer structure [0/90/0] and [45/0/-45] were taken as research objects, the method of modeling and analysis of ABAQUS software was used. The results show that: The initial stiffness and ultimate load of the four groups of specimens are not different, but there are obvious differences in the ultimate displacements, the ultimate displacements of the specimens with 2024-T3 aluminum alloy are larger than those with 7075-T6 aluminum alloy. The ultimate displacement of specimens with [45/0/-45] layer structure is larger than that with [0/90/0] layer structure. The surface strain of four groups of aluminum alloys is symmetrical distribution, the strain of aluminum alloy with 2024-T3 is obviously larger than that with aluminum alloy 7075-T6, and the strain level of short edge in loading area is obviously higher than that of long edge. There is a clear sequence of damage in the material layer of the specimen, the 0 degree fiber fracture occurs first, the 90 degree fiber second, and the 45 degree fiber finally, 7075-T6 aluminum alloy fracture occurs after fiber fracture, and 2024-T3 aluminum alloy fracture occurs in fiber fracture process. In addition, the finite element analysis is in good agreement with the test, and the ultimate load and the main failure mode are consistent with the test results.

MODE EQUAL STIFFNESS VERIFICATION BASED ON STIFFNESS DESIGN OF CFRP

HOU Peng-fei, YANG Yi, TANG Jian-ping

2019, 0(7): 48-54.

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Equal stiffness verification is an important basis for material replacement of various engineering structures. In this paper, an efficient and reliable equal stiffness verification method is obtained by designing and verifying the stiffness of carbon fiber-reinforced plastics (CFRP) replace steel shape tubes. Firstly, by the theoretical calculation, the deformation of the shape tube structure in different loading conditions is obtained, the influencing factors and degree of deformation are analyzed. Then, according to the theoretical deformation of the shape tube and the equal stiffness design principles, equal stiffness carbon fiber-reinforced plastics (CFRP) shape tube and steel shape tube are obtained. Finally, an efficient and reliable equal stiffness verification method, i.e., the modal verification method, is proposed. According to the theoretical derivation, the verification conditions of equal stiffness are used to verify the stiffness of CFRP shape tube and steel shape tube which have met the equal stiffness requirement. The results show that the CFRP shape tube and the steel shape tube satisfy the stiffness verification conditions, and the effectiveness of the method is verified. Compared with the previous multi-case loading verification method, main advantages of the equal stiffness mode verification method are as follows: ① The analysis process is simpler, which only includes the modal analysis of replacement parts and original parts, and this can greatly improve the verification efficiency; ② The validity of this method is not limited by the loaded condition of the structure, and it can be applied in the equal stiffness verification of variable-loading structure; ③ The verification results, which are based on the theory of the stiffness matrix, are more reliable, and the all-round equal stiffness verification can be obtained.

DEVELOPMENT OF WATER-SOLUBLE CORE MOLD FOR RTM MOLDING

LI Yi-jie, CHEN Li

2019, 0(7): 55-59.

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In order to develop novel hollow composite materials, a new type of skin-core structure of water-soluble core mold was prepared by using sand with different particle size, and the surface roughness of the core mold was studied by its formability, mechanical properties, water-soluble collapsibility and particle size. The results show that the skin-core structure of water-soluble core mold has good formability, high strength, and good water-soluble collapsibility while ensuring surface precision. It combines the advantages of small particle size, light weight and large particle size, and high temperature resistance. The Teflon film successfully prevented the resin from immersing in the core mold in the composite. The gradient particle size water-soluble core mold process can well meet the requirements of the core mold with large aspect ratio, and provides a new idea for the preparation of shaped parts with small opening and large aspect ratio.

EFFECTS OF THE INGREDIENTS IN SIZING AGENT ON THE CARBON FIBER SURFACE PROPERTIES

HANG Chuan-wei, QIAN Hong-chuan, XU Niu-niu, HE Zhou-wen

2019, 0(7): 60-64.

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Three main components of the sizing agent, i.e., biphenyl A epoxy resin, vinyl ester resin and ether emulsifier for carbon fiber, were comparatively studied on the physical properties such as the surface properties, fuzz weight, splitting rate, hardness, water absorption rate, surface energy and the interlaminar shear strength of the composite (ILSS). Bisphenol A epoxy resin helps to improve fiber surface condition and improve fiber strand integrity. The ether emulsifier helps to reduce the fuzz weight and improve the splitting rate of the fiber. The vinyl ester resin can improve the strand integrity and hardness of the fiber. The rank of total surface energy is epoxy resin>ether emulsifier> vinyl ester resin. The rank of water absorption rate is epoxy resin<vinyl ester resin<ether emulsifier. The water absorption of different components in the sizing agent was not the main influencing factor on the interlaminar shear strength of the carbon fiber composite.

STUDY ON VARI FORMING PROCESS OF COMPOSITE FOAM SANDWICH STRUCTURE

DONG Qing-hai, DANG Lei, YUAN Chong-xin, LIU Chen-xiao

2019, 0(7): 65-68.

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The characteristics of the foam sandwich structure of lightweight, high strength composite materials are widely used in aerospace ships rail transit wind power and other fields. This paper has carried out VARI molding process of preparation of sandwich structure, studies the double guide network note glue single bubble slot foam slot punch punch injecting process design such as the effect of the preparation of sandwich structure, technical requirements for different parts of the sandwich structure, provides the process forming in different ways, and introduces a kind of method which can directly observe the approach of resin flow state.

STUDY ON BEARING LOAD OF GLASS FIBREBOARD PRE-BURIED BY HONEYCOMB SANDWICH STRUCTURE

ZHAO Xia-jun, LOU Cheng-fei, ZHANG Wei

2019, 0(7): 69-72.

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Honeycomb sandwich structure is a typical composite structure, but the joints and joints of honeycomb sandwich structure are the weak points in the structure. In this paper, for the sandwich structure of carbon fiber panel and Nomex honeycomb, the embedded glass fibreboard plate is used as the force transmission joint to study the bearing performance at the joint of the sandwich structure. The results show that the pre-embedded glass fibreboard can effectively improve the bearing strength of the sandwich structure, and the bearing load increases linearly with the increase of glass fibreboard diameter. Non-destructive testing found the the peeling of glass fibreboard with the panel/honeycomb, indicating that the glass fibreboard and the binder are the medium through which the load is transmitted to the surrounding honeycomb and panel. Attention should be paid to the matching relation between the connecting piece and the embedded part in actual use. Generally, it is suitable for the embedded part of bolt NAS6303-8 (diameter of bolt 4.8 mm) with glass fibreboard diameter of 20 mm, and it is suitable for the embedded part of bolt NAS6304-8 (diameter of bolt 6.4 mm) with glass fibreboard diameter of 30 mm.

RESEARCH ON DIGITAL RADIOGRAPHIC DETECTION TECHNOLOGY OF POROUS C/SiC COMPOSITES

JIANG Bai-hong, YU Shi-zhang, GAO Xiao-jin, DONG Jia-ju

2019, 0(7): 73-77.

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The two digital imaging techniques of CR and DR were studied for porous C/SiC composite plate components. The reference block for evaluating the digital photographic quality of porous composites was designed, and the influence of the parameters such as tube voltage and exposure amount on the test results was studied. The results show that the parameters such as tube voltage and exposure amount can affect the detection effect of CR and DR, and the groove and hole-type reference block can be used to characterize the quality of X-ray digital detection image, which provides a basis for optimizing the parameters of X-ray inspection of composite components.

EFFECT OF SURFACE TREATMENT ON INTERFACIAL PROPERTIES OF QUARTZ FIBER REINFORCED PAA RESIN COMPOSITES

MIAO Chun-hui, ZHAI Quan-sheng, ZHANG Chen-qian, YE Hong-jun

2019, 0(7): 78-84.

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In this paper, the surface sizing agent was removed by ablation method, and the surface grafting coupling agent was used to treat the quartz fiber with different surface treatment. Composite laminates were fabricated using different quartz fiber/PAA resin systems. The bending, interlaminar shear and compression properties were tested. The fiber infiltration, mechanical properties and cross-section morphology were compared by comparing different surface treatments. The effects of different surface treatment methods on the interfacial bonding properties of quartz fiber and PAA resin were investigated. The results show that the fiber of the sizing agent is removed, the capillary pressure value is reduced, the wetting ability of the resin to the fiber is reduced, and the wetting angle of the PAA resin and the quartz fiber is increased. The interface bonding force is lowered, and the mechanical properties of the composite material are lowered after curing. Moreover, the fiber on the fracture surface of the composite material is smooth and the resin has less adhesion. With the Wolla modified fiber, the capillary pressure value increases and the resin′s ability to infiltrate the fiber increases. At the same time, the wetting angle of PAA resin and quartz fiber is reduced, the interfacial bonding performance of quartz fiber and PAA resin is effectively improved, the mechanical properties of the composite material are improved, and the resin adhering to the fracture surface of the composite material is obviously increased.

STRESS ANALYSIS AND VERIFICATION TEST OF COMPOSITE FUSELAGE PANEL MECHANICALLY FASTENING

ZHANG Xu, WANG Hou-bing, YU Zhen-bo, HU Hai-wei

2019, 0(7): 85-91.

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A static test was designed to verify the composite fuselage panels mechanically-fastening design and analysis method. Stress analysis was carried out by experience formula and finite element modeling respectively. As shown by the test results, the mechanically fastening design can sustain the limited load and ultimate load. The theoretical strain complies with the test strain. Load ratio carried by the fasteners calculated by test data is in line with the experience data. The damage load level in the test was higher than the predicted level given by theoretical analysis, demonstrating that the selected method is rational and conservative.

STUDY ON DESIGN METHOD OF WIDE-BAND WAVE-ABSORBING HONEYCOMB SANDWICH COMPOSITES

LI Song-ming, WU Si-bao, YUAN Wei, LU Hai-jun

2019, 0(7): 92-97.

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In this paper, a simulation calculation model of electrical properties of wave-absorbing honeycomb and honeycomb sandwich structural wave-absorbing composites with good computational accuracy was established. By the simulation calculation model, the effects of wave-absorbing honeycomb and microwave-transparent skin on electrical properties of honeycomb sandwich structural wave-absorbing composites were studied. The wide-band electrical properties of honeycomb sandwich structural wave-absorbing composites were optimized. The results show thatwave-absorbing properties of honeycomb sandwich structural wave-absorbing composites were first improved and then decreased with the increase of the dielectric properties of wave-absorbing honeycomb. While the dielectric properties of wave-absorbing honeycomb increased to the optimum balance of the electromagnetic matching and attenuation characteristics of the wave-absorbing honeycomb, the wave-absorbing properties were optimal. As the honeycomb height increased, the wave-absorbing properties at low frequency(1 GHz~2 GHz) were improved. And, the wave-absorbing properties at high frequency(8 GHz~18 GHz) improved firstly and then tended to be stable and no longer improved continuously. For the same microwave-transparent material, microwave-transparent skin with 1 mm thickness can meet both the requirements of wide-band electrical properties and bearing performance. With the reasonable design of gradient electrical structure, optimizing wide-band electrical properties of honeycomb sandwich structural wave-absorbing composites can be realized. The optimized honeycomb sandwich structural wave-absorbing composite has a high wide-band wave-absorbing property in the frequency range of 1 GHz~18 GHz.

APPLICATION OF HONEYCOMB SANDWICH STRUCTURE COMPOSITE TO AUTOMOBILE EXTERIOR PARTS

WANG Yong-hong

2019, 0(7): 98-102.

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In recent years, in order to realize energy conservation and emission reduction, lightweight has been the research direction and theme in the automobile industry. This paper aims to discuss how to develop a low-cost lightweight technology solution for automobile exterior. In this paper, through the study for product material structure mechanics, combine auto exterior parts’ force analysis, make sure the direction of the product structure design, and then choose the reasonable process and material with corresponding characteristics, under the premise to guarantee the basic strength and rigidity properties, the object is to investigate how to realize the light-weight effect. The technology involved in this paper mainly makes use of grade A-class quality surface characteristics of SMC material and good weathering and chemical resistance, to be used as the outer skin of multilayer material, SMC can also be designed for different thickness according to the needs of different position structural strength. Then we select multi-layer honeycomb sandwich structure as backside reinforcement part, which choose honeycomb hollow material as core material, glass fiber reinforce and polyurethane foam as reinforcement layer, so that the backside reinforcement combined with the light-weight, high strength, high stiffness characteristics of honeycomb sandwich structure, so can reach to light-weight, high strength, high stiffness of large automotive exterior accessories. Examples prove that by using this lightweight process of car exterior parts, the weight loss of SMC process products with the same stiffness is reduced to 40%~50%. In addition, this paper also elaborates the production process of the lightweight technology and the technical key points of the technology structure.

STUDY ON VIBRATION AND ACOUSTIC CHARACTERISTICS OF FOAM SANDWICH COMPOSITE REINFORCED STRUCTURE

TIAN Xu-jun, HU Gang-yi, HUANG Guo-bing

2019, 0(7): 103-108.

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In order to investigate the vibration and acoustic effect of foam sandwich composite reinforced structure in engineering application, a comparative test of vibration modes in air was carried out for the foam sandwich composite reinforced structure and the steel structure. The test results show that, compared the steel structure, the first three-order natural frequencies are twice higher for sandwich composite reinforced structure, and the foam sandwich composite reinforced structure can reduce the weight of the structure and improve the stiffness of the whole structure. Based on the layerwise theory, the modal test of the foam sandwich composite reinforced structure was simulated, the simulation results were consistent with the test results, which verified the accuracy of the simulation method. On this basis, the modal and frequency response of foam sandwich composite reinforced structure in air and fluid medium are simulated, and the effect of the size of reinforcement on the natural frequency of reinforced foam sandwich composite structure are analyzed, which can provide reference for engineering application.

A REVIEW OF AXIAL COMPRESSION PERFORMANCE OF FRP REINFORCED MASONRY COLUMNS

LEI Zhen, GUO Hong-bo, BAI Liu, TAN Peng-xiang

2019, 0(7): 109-115.

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Fiber reinforced composite (FRP) reinforcement technology is widely used in masonry structure reinforcement and rehabilitation. A large number of studies have shown that FRP can significantly improve the brittleness, bearing capacity and ductility of the masonry components. This paper reviews and summarizes the research and theoretical analysis on the axial compression test of FRP reinforced masonry column, introduces the research on the axial compression performance of FRP reinforced brick column, and sorts out the calculation formulas of the effective constraint area of different section types of masonry brick column. The calculation formula of the bearing capacity and ultimate strength of FRP reinforced brick column are summarized as well as the theoretical model of FRP reinforced brick column. Finally, the defects and blanks are put forward to provide reference for future research according to the current research status of FRP reinforced masonry brick column.

PROGRESS OF STUDY ON SEISMIC PERFORMANCE OF ECC STRUCTURES

GONG Hong-wei, JIANG Shi-yong, FEI Wei, CHEN Jin

2019, 0(7): 116-124.

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Under earthquake actions, the reinforced concrete structure is prone to damage because of concrete spalling or progressive collapse. Engineered cementitious composite (ECC) has many advantages, such as good toughness, excellent deformation performance, strain hardening and multiple cracks development. Using ECC to replace concrete can meet the structure seismic performance requirements. From the perspectives of experiment, theory and finite element analysis, the tensile behavior of ECC and the seismic behavior of ECC beams, columns, joints and frames are introduced. Researches at home and abroad have shown that ECC component has many fine cracks under low-cycle reciprocating loads. Compared with concrete structures, deformation, ductility and energy dissipation ability of ECC structures are greatly improved. And ECC structures or members can also avoid shear failure if its stirrups are reduced. Under earthquake actions, the ECC structure is much less damaged than the concrete structure.

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