COMPOSITES SCIENCE AND ENGINEERING

Development and experimental research on CFRP bonded joints plug-in

ZHANG Jinguang, LI Yiwen, WEN Xianglong, OUYANG Yujia, MENG You

2023, 0(2): 5-13. DOI: 10.19936/j.cnki.2096-8000.20230228.001

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Adhesive bonding is the most important way to connect carbon fiber reinforced plastic (CFRP) drive shaft with other components. Due to the uncertainty of bonding strength, it has become a common choice to study the rationality of adhesive layer design by using finite element software. In this study, the failure criterion, stiffness balance design criterion and shear strength design method of adhesive joint have been studied. Meanwhile, in order to improve the efficiency of finite element analysis of similar CFRP-metal adhesive joints, the parameter optimization plug-in is developed by using the Python programming language interface provided by ABAQUS software. The plug-in provides automatic pre-and post-processing function for finite element analysis of CFRP-metal bonded joints, the optimization function of stiffness balance design criterion and shear strength design method of adhesive joint is realized. Finally, the accuracy and reliability of the simulation plug-in are verified through experiments.

Multi-scale mechanical properties analysis of three-dimensional four-direction braided composites considering pore defects based on improved three-cell model

ZHANG Huai, LI Cheng, LIU Le, GONG Guilin

2023, 0(2): 14-23. DOI: 10.19936/j.cnki.2096-8000.20230228.002

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Hole defects inevitably occur in the manufacturing process of braided composites, which directly affect the mechanical properties of braided composites. Based on the open source software TexGen^[1], parametric modeling of the inner cell, face cell and corner cell of braided composites was carried out. In the face cell and corner cell models, the deviation of yarn trajectory in space and the extrusion deformation when subjected to the tightening process are considered. The random function is used to introduce pore units into the matrix of microscopic model at micro scale to simulate dry spots in fiber bundles, and pore units are introduced into the matrix of tri-cell model at micro scale to simulate pores between fiber bundle. On macro scale, a macroscopic homogeneous model with inner cell, face cell and corner cell is established to forecast the macroscopic elastic constants. The results show that: ① The porosity has different effects on the elastic constants of the three types of microcellular models; ② The influence of dry spot pores in fiber bundles on macroscopic elastic properties is greater than that between fiber bundles. With the increase of dry spot porosity P_m, the longitudinal Poisson’s ratio is reduced, while with the increase of porosity P_n between fiber bundles, the longitudinal Poisson’s ratio presents the increasing trend.

Research on test and bearing capacity calculation model of two-way RC slabs strengthened with textile reinforced mortar

LI Yongzhang, WU Di

2023, 0(2): 24-33. DOI: 10.19936/j.cnki.2096-8000.20230228.003

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To study the effect of textile reinforced mortar (TRM) on the flexural capacity of two-way reinforced concrete (RC) slab, three two-way RC slabs under monotonic loading distributed at four points were tested. And the influence of different strengthening techniques on the flexural capacity and bending deformation capacity of the two-way RC slab was studied. It was concluded that the application of TRM to strengthen the two-way RC slab can effectively improve its flexural capacity and bending deformation capacity. Compared with the unreinforced test plates, the flexural capacity and energy absorption of the two strengthened plates are increased by 54.2% and 43.8%, 75.5% and 49.1% respectively. Compared with the unreinforced test plates, the post-cracking stiffness of the test plates are increased by 145.2% and 83.4% with and without interfacial agent, which shows that the application of interface agent for interface treatment can improve the adhesion between the strengthening layer and the old structure, thus preventing the initiation and development of cracks between the new and old interfaces. Based on the theory of plastic hinge lines, a simple calculation formula for the flexural capacity of the two-way RC slab strengthened with TRM was proposed, which provided the reference for the application of TRM for strengthening projects.

Analysis of interpolating element-free Galerkin scaled boundary method for fracture problems in orthotropic materials

WANG Juan, CHEN Yang, XIAO Shucong

2023, 0(2): 34-38. DOI: 10.19936/j.cnki.2096-8000.20230228.004

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The interpolating element-free Galerkin scaled boundary method is a semi-analytical numerical method which combines the advantages of the scaled boundary method and the element-free Galerkin method under the framework of improved interpolating moving least-squares method. By introducing the scaled boundary coordinate system, this method only needs to perform numerical discretization on the boundary of the computational domain and solve the problem by using the analytical method in the radial direction, which has considerable accuracy and efficiency in analyzing the fracture problem of isotropic materials. In order to make full use of the virtues of this method and improve its service ability, the interpolating element-free Galerkin scaled boundary method is proposed to study the fracture of orthotropic materials. Finally, two numerical examples of different crack forms are used to certify the effectiveness and precision of the method.

Research on carbon fiber paving of control arm based on multi-objective optimization

KANG Yuanchun, LIU Junfeng

2023, 0(2): 39-43. DOI: 10.19936/j.cnki.2096-8000.20230228.005

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In order to obtain the lightweight carbon fiber control arm and determine the optimal carbon fiber laying angle, the moving least square method fitting response surface combined with multi-objective optimization method is adopted. Firstly, when the steel control arm is replaced by carbon fiber composite, the thickness of carbon fiber composite is determined based on the approximate relationship of equal stiffness. In order to further improve the performance of carbon fiber composite control arm, Hammerley test and moving least square method are combined to fit the relationship between ply angle and stiffness performance of control arm. Based on the fitted response surface, the multi-objective optimization method is used to determine the best carbon fiber ply angle scheme. Compared with the original steel control arm, the weight of the carbon fiber control arm is reduced by 32.7%, and the stiffness and strength performance meet the requirements.

Finite element analysis of the flexural fatigue performance of reinforced concrete beams reinforced with externally bonded prestressed CFRP sheets

ZHANG Zhimei, YANG Yang

2023, 0(2): 44-53. DOI: 10.19936/j.cnki.2096-8000.20230228.006

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To investigate the flexural performance of reinforced concrete beams reinforced with externally bonded prestressed CFRP sheets under fatigue loading, in this paper, the fatigue damage of concrete, steel bar and CFRP during fatigue loading is taken into account comprehensively and the fatigue constitutive model of each material is established. Fatigue cumulative damage failure full process numerical analysis method is adopted and the ABAQUS software is used to model and analyze the reinforced concrete beam reinforced with prestressed CFRP sheet. The influence of concrete strength, fatigue load amplitude and CFRP prestress level on the flexural performance of the reinforced beam under fatigue load is studied respectively. The results of the analysis show that increasing the strength of concrete, increasing the prestressing level of the CFRP and reducing the load amplitude can increase the residual bearing capacity of reinforced beams after fatigue loading and reduce the strain of concrete, steel bar and CFRP to improve the force and deformation performance of the reinforced beam. Increasing the level of CFRP prestressing can effectively increase the strength utilisation of CFRP and give full play to its high strength properties.

Dynamic modeling investigation of a composite blade

SHAO Song, YING Xucheng

2023, 0(2): 54-59. DOI: 10.19936/j.cnki.2096-8000.20230228.007

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When a helicopter rotor works,the composite blade undergo large nonlinear extension, bending, twisting deflection,the traditionally moderate beam theory can’t satisfy the necessity of the composite blade dynamic analysis. In this paper, based on geometrically exact rotating beam theory, the composite blade dynamic model is presented with the mixed variational formulation. The deformation and natural frequency of the composite beam are solved numerically and compared with Minguet’s experimental data of composite large deflection beam, and the dynamic response of the rotating composite blade is also calculated to compare the result of Dymore software.The results show that the composite blade dynamic model can accurately predicte the dynamic behaviors of the composite blade with structure coupling. The effectiveness of the model is verified.

Modeling method and performance evaluation of filament-wound hydrogen storage cylinder with layer-by-layer renewal

ZHANG Guiming, SONG Chunyu, ZU Lei, ZHANG Qian, CHEN Shijun, FU Jianhui, LI Debao, GENG Hongbo

2023, 0(2): 60-66. DOI: 10.19936/j.cnki.2096-8000.20230228.008

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In this paper, a layer-by-layer updating modeling method for filament-wound hydrogen storage cylinder based on 3D laser scanning system and ABAQUS is presented. By programming in Python, the geometric data obtained from the 3D scanner are fitted by non-uniform Rational B spline, and combined with the winding angle generated by the winding software to generate the finite element model in ABAQUS. The validity of the finite element model was verified by comparing the results of hydraulic blasting test with Hashin criterion, and the failure mechanism of filament-wound hydrogen storage cylinders was explored. The results show that, the blasting pressure and strain response predicted by the finite element model are within 5% of the test results, and the predicted blasting location and failure mode are consistent with the test results.

Investigation of tension stiffening effect in fiber concrete beam reinforced with FRP bars based on macroscopic model

AN Ru, LI Yuankang, CHEN Guoxiong, FU Shihua

2023, 0(2): 67-74. DOI: 10.19936/j.cnki.2096-8000.20230228.009

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Adding fiber in concrete can effectively decrease the crack width of FRP reinforced concrete beams and improve the ductility of the beams. In this study, combined with the tensile constitutive relation of fiber reinforced concrete, a weakening coefficient was introduced to describe the stiffness of fiber reinforced concrete after cracking, and a three-dimensional finite element model was established to reflect the tension stiffening effect of fiber reinforced concrete beam reinforced with FRP bars. The simulated load-displacement curves were consistent with the experimental results under different fiber contents and different reinforcement ratios. In addition, the crack patterns obtained by the finite element analysis were in good agreement with the experimental results. With the decrease of the weakening coefficient, the crack propagation slows down, the number of cracks increases and the width decreases under the ultimate load. The study also shows that the weakening coefficient decreases linearly with the increase of the characteristic parameter of fiber content, and the slope was weakly affected by the reinforcement ratio, while the intercept was significantly affected by the reinforcement ratio.

Experimental study on corrosion degradation of basalt fiber concrete under combined salt erosion and drying-wetting coupling action

WANG Cheng, LI Xitong, GE Guanghua, RONG Zebin, LI Zhenyi, XUE Shan

2023, 0(2): 75-83. DOI: 10.19936/j.cnki.2096-8000.20230228.010

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In order to explore the corrosion and deterioration law of basalt fiber concrete under the coupling effect of compound salt solution and dry-wet cycle, the macro-microscopic corrosion degradation tests of basalt fiber concrete specimens with different volume contents (0%, 0.1%, 0.2%, 0.3%) were carried out, under the combined action of composite salt solution (NaCl+MgSO₄+Na₂SO₄) with different concentrations (clean water, reference concentration, 5 times reference concentration, 10 times reference concentration) and dry-wet cycles. The results show that the addition of basalt fiber improves the salt corrosion resistance of concrete, and when the content of basalt fiber is 0.3%, the relative dynamic elastic modulus of the specimen has the smallest fluctuation and the most stable performance. Concrete corrosion products are mainly ettringite (AFt) and gypsum under the action of combined salt solution corrosion. The corrosion products increase continuously with the increase of the number of drying and wetting cycles, and the specimen is finally destroyed by the combined action of physical and chemical corrosion. According to the microstructure and composition analysis of corrosion products in different corrosion ages, it is found that adding basalt fiber reduces the consumption rate of Ca(OH)₂ in concrete, and the content of corrosion products decreases correspondingly, and the ability of concrete to resist compound salt erosion is enhanced. The results can provide scientific basis for the engineering application of basalt fiber concrete in the saline soil area of Southern Xinjiang.

Investigation of the viscoelastic behavior in the hot press-forming process of uncured prepreg laminates

LI Zhefu, LIU Weiping, SUN Baozhong, YUE Guangquan, TAN Yuan, ZHANG Jian

2023, 0(2): 84-93. DOI: 10.19936/j.cnki.2096-8000.20221228.031

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In the pre-forming process of uncured prepreg laminates with hot press, pressure is an important parameter that affects the performance and quality of the final product. In this study, the compression and relaxation viscoelastic behaviors of uncured prepreg laminates were investigated in different fiber orientation, displacements, velocities, and thicknesses. The results show that the power law model could accurately describe the compression behaviors of prepreg. The generalized Maxwell viscoelastic model and the fractional viscoelastic model could describe the relaxation behaviors of prepreg, respectively. The theoretical fitting curves match very well with experimental data at each condition and the R-squared value is greater than 0.96. Compared with the generalized Maxwell model, the fractional viscoelastic model requires fewer parameters and has more definite physical significance, which is more suitable for describing the viscoelastic deformation behaviors of prepreg in the process of hot press-forming.

Nondestructive testing and evaluation of carbon fiber reinforced polymer laminates with inclusions

HU Yefa, MENG You, ZHANG Jinguang, DENG Wei, XU Shengfeng

2023, 0(2): 94-100. DOI: 10.19936/j.cnki.2096-8000.20230228.012

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In the field of nondestructive testing and evaluation(NDT&E)of carbon fiber reinforced polymer(CFRP), phased array ultrasonic testing technique(PAUT)was usually used to detect the size and location of defects. Furthermore, wavelet packet transform and BP neural network were used to identify the type of defects. In this paper, three different types of CFRP laminates which contain defects such as teflon, CFRP sheet and plastic paper were made. Then, PAUT was used to detect these CFRP laminates with inclusions. The size and location of defects were evaluated from B and C scanning images, and the type of defects were evaluated from the A scan signals. The recognition rate could reach 90.9% in three types of defects. However, if only CFRP sheet and plastic paper were recognized, and the recognition rate could reach 100%.

Crane telescopic boom CFRP lightweight material friction wear test study

XU Shengfeng, HU Yefa, ZHANG Jinguang, YANG Ji, YUAN Chunhui, MENG You

2023, 0(2): 101-106. DOI: 10.19936/j.cnki.2096-8000.20230228.013

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In order to explore the difference between the friction and wear properties of carbon fiber composite crane jib and traditional steel crane jib, the two materials and four commonly used polyethylene (PE), polyoxymethylene (POM), MC nylon and MCS nylon were measured by experimental methods to obtain several friction and wear performance parameters between the crane sliders. The results show that the friction coefficient, friction coefficient fluctuation, and the difference between the dynamic and static friction coefficients between the carbon fiber composite material and the four sliders are smaller than those of the steel represented by GCR15, but the wear rate of the carbon fiber composite material is greater than that of the steel, and is about two times more.

Application of composites automated fiber placement technology in aircraft integral fuselage panel

TANG Shanshan, HE Daliang, WANG Xianfeng, XU Xiaowei, XUE Ke, YU Jingjing

2023, 0(2): 107-114. DOI: 10.19936/j.cnki.2096-8000.20230228.014

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The amount of composite materials used in aircraft has become one of the important symbols to measure the advances of aircraft. With the increase of aircraft tonnage and the rapid development of composite manufacturing technology, the aircraft composite parts are moving towards the direction of large-scale, integration and automation. It is difficult to meet the increasing technical and quality demands of parts by traditional manual laying. This paper introduced the present manufacturing situation and development prospect of automated fiber placement technology for composite component, and the application of automated fiber placement technology for composite component in the integral fuselage panel of aircraft is described in detail. According to the structural characteristics of fuselage barrel section,the trajectory planning methods of various angles are analyzed. What’s more, the direction and the placement ability of trajectory are studied. Through the finite element simulation and laying experiment, the optimal laying process parameters are determined. Finally, the automatic manufacturing of fuselage barrel skin is realized by using automated fiber placement.

Experimental study on shear performance of BFRP bars concrete beams with regional constraints

QI Gongcheng, JIANG Jitong, GAO Yu, DU Derun, DONG Kun, YANG Song

2023, 0(2): 115-121. DOI: 10.19936/j.cnki.2096-8000.20230228.015

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FRP bars can effectively solve the corrosion problem of steel reinforcement in ordinary concrete beams, but the shear failure of FRP-reinforced concrete beam is brittle failure and the shear ductility is small. In this paper, the regional restraint technology is applied to BFRP-reinforced concrete beams, and BFRP-reinforced stirrups are used to restrain the concrete in the shear compression zone. Through the shear comparative test of one blank beam and four restrained beams, the influence laws of spiral stirrup ratio and shear span ratio of restrained spiral stirrups on the ultimate load, failure mode and ductility of the beam are studied. The research shows that the shear ductility of the beam analyzed by equivalent energy method and displacement ductility coefficient method has been significantly improved, and the addition of regional confined stirrups changes the failure mode of the beam, and the shear bearing capacity decreases with the increase of shear span ratio.

Stress concentration at the hole edge of open-hole glass fiber reinforced pultrusion plate

LU Xiaofeng, LI Zhanying, YANG Yurong, XU Jun

2023, 0(2): 122-125. DOI: 10.19936/j.cnki.2096-8000.20230228.016

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In order to predict the stress concentration effect of open-hole glass fiber reinforced pultrusion plate in wind turbine blade, the tension behaviors for different hole diameters are studied by test, theoretical analysis and finite element analysis. First, the tensile strength of glass fiber pultrusion plates with different hole diameters are tested. Then, the analytical expression of stress concentration coefficient for open-hole plate under average stress criteria is presented. After that, the finite element models of open-hole pultrusion plate are established in commercial finite element software ANSYS. The effect of mesh size on the stress distribution for hole edge is studied. Finally, the results using different methods are compared and discussed. It is found that as the diameter of open hole increases, the stress concentration coefficient of the open-hole plate will increase and the strength will decrease. The experiment results of stress concentration factor are smaller than the theoretical values. The deviation of stress distribution and stress concentration coefficient at the hole edge obtained by finite element solution and analytical solution is small, and the deviation of stress concentration coefficient is less than 3%.

Research progress of the vibration performance of fiber reinforced resin matrix composite laminates

ZHOU Chen, CHEN Mingda, YANG Jian, ZHANG Xiongjun, ZHU Yingdan

2023, 0(2): 126-132. DOI: 10.19936/j.cnki.2096-8000.20230228.017

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Fiber reinforced resin matrix composites are increasingly used in various fields and they are the key strategic materials related to national defense security and economic development. The vibration of composites can lead to undesirable effects in practical applications. It is of great significance to study its vibration mechanism and optimize its vibration performance to improve the application of composites. In this paper, the basic principles of vibration analysis of composites are firstly introduced. Then, several mathematical analysis methods for obtaining the natural frequencies and forced responses of composites are discussed. Furthermore, various structural and material parameters influencing natural frequencies are analyzed. In addition, the research methods on the vibration of variable stiffness composites are reviewed. Finally, some future research directions on the vibration performance of composites are also discussed.

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