COMPOSITES SCIENCE AND ENGINEERING

Fabrication and impact performance analysis of carbon/Kevlar fiber hybrid 3D braided composites

WANG Xiaoming, WANG Xiaobo, CHENG Yanan, ZHANG Chen, QUAN Zhenzhen, ZHANG Hui, LIU Yong, SUN Houli, YU Jianyong

2024, 0(8): 5-10. DOI: 10.19936/j.cnki.2096-8000.20240828.001

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Hybrid is an effective way to improve the mechanical properties of composite materials. In this paper, based on the study of yarn motion path of three-dimensional (3D) braided prefabricated parts, the design and preparation methods of intralaminar hybrid and interlaminar hybrid 3D braided composites were presented. According to the above research, the intralaminar hybrid 3D braided composites were prepared, and the interlaminar hybrid (2 layers) and interlaminar hybrid (4 layers) 3D braided composites were prepared by resin co-curing method. The low-speed impact properties of the three hybrid 3D braided composites were tested. The results showed that hybrid mode was an important factor affecting the impact properties of 3D braided composites. Under in-plane impact and axial impact, the impact properties were as follows: interlaminar hybrid (4 layers) 3D braided composites > interlaminar hybrid (2 layers) 3D braided composites > intralaminar hybrid 3D braided composites. The research results in this paper can provide an effective and feasible way to optimize the properties of 3D braided composites.

Study on properties of epoxy modified benzoxazine resin for RTM technology

LI Jiamin, TAN Lina, JIANG Hanwei, FAN Ruyi, RAN Qichao

2024, 0(8): 11-16. DOI: 10.19936/j.cnki.2096-8000.20240828.002

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The development of composite industry requires special resin matrixes with good processing characteristic and high wet-heat resistance for RTM technology. In this paper, three kinds of epoxy resins with high heat resistance, E6110, AFG90 and AG80, were used to modify a diamine-type benzoxazine resin (DC-BOZ). The viscosity characteristics, gelation reaction, curing behavior, polymerization reaction, heat resistance, wet-heat resistance and thermal stability of the mixtures were compared. The results showed that the addition of epoxy resins reduced the viscosity of benzoxazine and extended the pot life. Among them, the viscosity of DC/E6110 was only 333 mPa·s after 10 h at 100 ℃, which meets the requirement of RTM process. The addition of epoxy resins affected the gelation time of the system and increased the curing peak temperature slightly. Epoxy resins can copolymerize with benzoxazine and increase the crosslinking densities of copolymerization systems, resulting in the significantly improvement of heat resistance, wet-heat resistance and thermal stability of the modified resin systems. Particularly, the glass transition temperature (T_g) of cured DC/E6110 was increased to 209 ℃ with an increase of 44 ℃ compared with the polybenzoxazine. In addition, the wet T_gs of all systems decreased, but the wet T_g of DC/E6110 still reached 189 ℃. A new resin matrix with low viscosity and good wet-heat resistance developed in this paper can be used to prepare large composite parts by RTM process.

Study on flame retardant properties and impact properties of flame retardant microcapsule modified glass fiber reinforced polymer composites

LING Xujie, CHEN Yinhong, LU Yizhou, FANG Yuan

2024, 0(8): 17-23. DOI: 10.19936/j.cnki.2096-8000.20240828.003

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In order to improve the flame retardancy properties of glass fiber reinforced polymer composites (GFRP), FR-PN@ETPTA flame retardant microcapsules prepared by microfluidic technology were used to modify epoxy resin based GFRP. The effects of FR-PN@ETPTA flame retardant microcapsules on the flame retardant properties, combustion performance and impact properties of GFRP were investigated by vertical combustion test, cone calorimetry test, and drop hammer test. The test results indicate that FR-PN@ETPTA flame retardant microcapsules can significantly improve the flame retardancy properties of GFRP. Compared with FR-PN flame retardant, GFRP composites with FR-PN@ETPTA flame retardant microcapsules show better combustion behavior, and the flame retardant effect is the best when the addition amount of FR-PN@ETPTA flame retardant microcapsules is 10wt%. On the other hand, the addition of FR-PN@ETPTA flame retardant microcapsules can effectively reduce the negative effect of flame retardants on the impact resistance of GFRP. In addition, GFRP composites with 10wt% FR-PN@ETPTA flame retardant microcapsules have the best impact resistance.

Research on gamma ray shielding performance of tungsten powder modified 3D spacer fabric composites

LIU Yushun, WEI Xiaolin, LIU Benben, GU Yizhuo

2024, 0(8): 24-31. DOI: 10.19936/j.cnki.2096-8000.20240828.004

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Nuclear energy generates ionizing radiation, such as X-rays and gamma rays, which require shielding materials for protection. Traditional X-ray and gamma ray shielding materials have drawbacks such as high weight, susceptibility to corrosion, toxicity, and low structural mechanical properties. Therefore, developing new composite with light weight, excellent radiation performance, and integrated structure/function is an important direction for the development of radiation protection technology. Based on densities and the theoretical calculation values of the mass attenuation coefficients of various tungsten containing powders, tungsten oxide was selected as the gamma ray shielding filler. Tungsten containing powders were used to modify epoxy resin and composite with glass fiber three-dimensional(3D)spacer fabric to form a fiber-reinforced composite with sandwich structure. The influence of different contents of tungsten oxide on the shielding ability of composite for ⁶⁰Co and ¹³⁷Cs gamma rays and their flattening performance was investigated. The experimental results show that tungsten oxide powder significantly improves the radiation shielding performance of composite, and the degree of improvement is similar to the theoretical calculation value. Under the same shielding rate, the weight of composite is significantly lower than that of iron. In addition, tungsten oxide also improves the compressive strength and modulus of the 3D spacer fabric composites.

Preparation and performance study of sizing treated carbon fiber/polypropylene composite molded by CF/PP fiber mat

MAO Jingqiao, HU Yiling, PANG You, YANG Yuqiu

2024, 0(8): 32-38. DOI: 10.19936/j.cnki.2096-8000.20240828.005

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Carbon fiber/thermoplastic resin matrix composites have a good prospect in the field of composites because of their excellent properties such as comprehensive performance, deformation resistance and recyclability. The interface, as the transition region between the two phases, plays a role in stress transfer and has an important influence on the mechanical properties of the composites. Sizing agent is a commonly used method to modify the surface of carbon fiber and improve the interfacial bonding ability. In this paper, a carbon fiber/polypropylene hybrid felt was sized and molded to prepare the composite. The effect of sizing uniformity and on the structure of the hybrid felt was analyzed by air permeability translucency test, and the effect of sizing on the mechanical properties of the composite was studied by tensile, bending and impact tests, and the mechanism of sizing agent action was analyzed. The results indicate that the tensile strength of the composites increased by 22.52%, the flexural strength by 7.57% and the impact strength by 39.07% after sizing.

Parametric design and optimization of composite wind turbine blade

JIN Xiangxiang, MA Yuanzhuo, ZHAO Zhenzhou, XU Bofeng, LI Hongshuang

2024, 0(8): 39-44. DOI: 10.19936/j.cnki.2096-8000.20240828.006

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Excessive wind turbine blade weight not only affects the structural performance of the blades, but also increases transportation, maintenance and other costs. In order to solve the problem of blade quality, a classic 1.5 MW composite wind turbine blade is selected, and different composite materials are laid in the spar cap, shear web, leading edge and trailing edge of the blade. Due to the laying thickness of the composite material decreases from the bladed root to tip, the failure location is mostly located at the bladed root. Therefore, about 1/3 of the distance from the bladed root was taken as the research object to simplify the problem, and the composite wind turbine blade model was constructed by ANSYS APDL parametric design in order to facilitate optimization. Considering the situation of falling into local optimum, subset simulation optimization method is selected for random optimization. The design variable is the shear web position, and the constraint function is that the blade displacement and the Tsai-Wu criterion are within a reasonable range under the limit load, with the goal of the smallest blade weight. Through the simulation optimization results of 30 sets of subsets, it shows that when the shear web position is about 29.4% and 53.3% of the chord length, compared with the deterministic design, the weight of blade is reduced by about 15.4%. The final results show that the optimization method is feasible in the optimization of wind turbine blade structure, and the optimization results have reference value for engineering design.

Research on resistance welding technology of carbon fiber reinforced polyaryl ether ketone thermoplastic composites

YE Lu, ZHANG Daijun, LI Jun, LI Fuping, CHEN Xiangbao

2024, 0(8): 45-52. DOI: 10.19936/j.cnki.2096-8000.20240828.007

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In this paper, the thermoplastic composite resistance welding technology using stainless steel wire mesh as resistance heating element was studied, and the influence of resistance welding process parameters such as material and specification of insulation film, welding power, welding time, welding pressure on welding quality was investigated, which disclosed the multiple correlation and restriction relationship between each parameter. Through process optimization, problems such as edge effect and current leakage in the welding process were solved, and 180 mm long weld with high quality was realized. The results show that when the insulating layer is 0.1 mm thick PEI film and the welding pressure is 2.0 MPa, the single lap shear strength of the welded sample reaches 40.5 MPa, which is higher than the intrinsic value of the material.

Parametric finite element modeling method for fiber reinforced composite bolted structures

WANG Haoda, ZHU Fuxian, HU Kejun, XU Xianyi

2024, 0(8): 53-61. DOI: 10.19936/j.cnki.2096-8000.20240828.008

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Finite element is an effective method for the strength analysis of bolted structure of fiber reinforced composites, in order to improve its efficiency of finite element modeling, the finite element parametric modeling method for fiber reinforced composite bolted structureswas studied based on ABAQUS analysis platform. According to the characteristic of bolted structure and the requirements of strength analysis of fiber reinforced composites bolted structure, the special GUI graphical parameter input interfaceswere developed by GUI plug-in, a kernel script program for finite element modeling of bolted structure was developed with Python, and a user damage subroutine for failure criterion and stiffness degradation was written in Fortran. A parametric finite element modeling and strength analysis platform for the bolted structure of fiber reinforced composites was established. Taking the three-nail bolted structure of carbon/glass hybrid composite and the ten-nail bolted structure of T800 carbon fiber composite as examples, the failure load and failure mode of the bolted structure were simulated and analyzed. Comparing with the experimental test results, the failure load error is about 3%, and the failure mode is same as experimental phenomenon. The research results show that the parametric finite element modeling and strength analysis platform can realize automatic modeling rapidly of various bolted structure of fiber reinforced composites with accurate and reliable analysis results, which provides an effective way for rapid strength analysis and engineering optimization design of fiber reinforced composites bolted structure.

Fatigue life calculation method of wind turbine blade based on piecewise linear mean stresses correction

XIE Lilai, HU Congliang, DONG Min, YANG Xiaohui, LIU Penghui

2024, 0(8): 62-69. DOI: 10.19936/j.cnki.2096-8000.20240828.009

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With the expansion of wind turbines, fatigue strength design has become one of the most critical factors in the large wind turbine blades design. The current calculation method for the blade fatigue life is mainly based on the simplified approach, which has many simplifications and assumptions and cannot predict the actual fatigue damage of wind turbine blades. Therefore, a more reasonable approach of fatigue life is needed. This paper proposes a suitable method for the fatigue life prediction of large wind turbine blades based on Goodman linear mean stresses correction theory and combined with multiple known fatigue S-N curves, which according to the piecewise linear mean stresses correction method mentioned in IEC 61400-5. With the widely used glass fiber pultrusion plate as the analysis object, the comparative analysis between the linear mean stresses correction and the piecewise linear mean stresses correction has been preformed. Finally through the analysis of the actual fatigue test damage and the spar cap fatigue strength of the blades, the conclusions come as follows: ① The fatigue performance of glass fiber pultrusion plate is not linear, and the fatigue performance predicted by the linear method based on a single fatigue S-N curve has a significant discrepancy with the test results. The piecewise linear CLD model based on multiple fatigue S-N curves is more suitable for describing the change of fatigue performance of glass fiber pultrusion plate, and the fatigue life prediction method based on piecewise linear mean stresses correction can better predict the actual fatigue damage of blades test; ② In the blade design, more attention should be paid to the fatigue strength of PS side of spar cap. It is suggested to calculate the fatigue strength of large wind turbine blades by using the piecewise linear mean stresses correction method based on multiple fatigue S-N curves to improve the reliability of blade fatigue design.

Life prediction method of wind turbine blade flapping fatigue test based on CLD model

FENG Xuebin, WANG Bowen, ZHANG Wenwei, DENG Hang, LIU Penghui

2024, 0(8): 70-74. DOI: 10.19936/j.cnki.2096-8000.20240828.010

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With the increasing length of wind turbine blades, the influence of blade weight and fixture weight on the blade during the flapping fatigue test can no longer be ignored. In this paper, taking the failure of the main beam of a 90 m-class blade waving fatigue experiment of Zhuzhou Times New Material Technology Co., Ltd., as the research object, the fatigue S-N curve of the main beam pultruded plate with different stress ratios was tested, and a new fatigue life prediction method for composite materials was proposed based on Goodman’s isotropic life diagram. By considering the effect of average stress on the fatigue life of the main beam, the article compares and analyzes the theoretical experimental prediction of damage and the actual fatigue experimental damage, and draws two important conclusions: ① The existing waving fatigue experimental load-equivalent method, which does not take into account the self-weight of the blade, can no longer reflect the actual loading of the blade; ② the Goodman fatigue life calculation method proposed in this paper can predict the fatigue experimental life of the blade more accurately by considering the mean value.

Layout optimization design on truss rib structure of civil aircraft center wing

LI Ming, FAN Weichao, SUN Qian, YANG Dongjin, JU Xiangwen, FANG Yaning, WU Ju

2024, 0(8): 75-83. DOI: 10.19936/j.cnki.2096-8000.20240828.011

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In the lightweight design process of civil aircraft center wing, the truss rib can be used to replace the traditional web rib. However, the research on truss rib structure the center wing lacks quantitative analysis currently, and reasonably arrange the connecting rod structure of truss ribs has become an important engineering issue. Therefore, in order to obtain the optimal structural efficiency of the truss rib, this article proposed 10 configurations of truss rib connecting rod structure with the same diameter. An optimization model is established using HyperSizer, with the minimum structural quality as the optimization objective, and the number of truss rib connecting rods and the connection method as the design variables. By comparing the internal force distribution and structural efficiency of different structure configurations, the influence law of the truss rib is obtained. The results show that when the number of truss rib is less than 9, the weight of the truss rib and the wing panel tend to converge, with a weight reduction of 16.1%. Meanwhile, when the connection scheme is adopted between the truss ribs and the front spar, the truss ribs can share the load borne by the web of front spar, reducing the weight of the front spar and improving the overall structural efficiency of the center wing.

Prediction model of bond strength between FRP bars and concrete based on PSO-RF neural network

YI Xiaoyuan

2024, 0(8): 84-90. DOI: 10.19936/j.cnki.2096-8000.20240828.012

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Compared with steel bars, FRP bars have excellent properties such as corrosion resistance, low magnetic properties and fatigue resistance, making their applications in unfavorable engineering environments more and more common. However, the current predictive models for the bond behavior between FRP bars and concrete exhibit limited applicability and low predictive accuracy. Therefore, this paper collected 170 sets of hinged beam test data. Utilizing particle swarm optimization (PSO) to enhance the random forest (RF)algorithm, a model for predicting the bond strength between FRP bars and concretewas developed. The PSO-RF model was compared with the RF model and five existing models, and the predictive performance of these models was evaluated using statistical indicators such as the coefficient of determination R² and the mean absolute error MAE. The PSO-RF model demonstrated an R² value of 0.939 6 and an MAE value of 1.014 3, which can provide a valuable reference for the applications of FRP bars in concrete. Compared with the existing models, the R² and MAE values of the PSO-RF model were improved by 141.9% and 81.3%, respectively. The results of the analysis on parameter importance within the model indicated that bond length and compressive strength of concrete are two significant factors influencing the model’s predictive outcomes, with importance coefficients of 22.35% and 18.3%, respectively.

Research on thermal expansion forming process of an ultra-short-range UAV and test verification

CHEN Lingfei, WANG Xuanbo, LIU Qichen, SHAO Zhenyu, WANG Zilong, ZHANG Hao

2024, 0(8): 91-96. DOI: 10.19936/j.cnki.2096-8000.20240828.013

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The structural design and integral forming process of an ultra-short-range UAV were studied. The aramid fiber prepreg was used as the raw material of the outer skin of the UAV components, the glass fiber prepreg was used as the raw material of the internal load-bearing beam structure of the UAV components, and the self-expanding polyurethane foam core was used as the sandwich material of the UAV components and a pressurized material during internal expanding molding. The fuselage, wing, vertical tail and flat tail were successfully prepared using this molding process, verifying the feasibility of the overall molding process for UAV components. Static tests were conducted on the UAV components, and the UAV passed the static test. The structural design of the UAV was reasonable and met the strength design requirements.

A review of liner damage and burst failure studies for vehicle mounted type Ⅳ high pressure hydrogen storage tanks

ZHANG Yikai, FENG Jiaji, GU Junfeng, SUN Xiujie, RUAN Shilun

2024, 0(8): 97-109. DOI: 10.19936/j.cnki.2096-8000.20240828.014

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High pressure hydrogen storage tank is the key equipment of hydrogen fuel cell vehicle. The application and popularization of hydrogen storage tank will be an important breakthrough for the commercial development of hydrogen energy vehicles, and type Ⅳ hydrogen storage tank is considered as one of the most potential energy storage equipment for hydrogen fuel cell passenger cars. This paper summarizes the latest research achievements on the liner damage and burst failure of type Ⅳ hydrogen storage tank, summarizes the common failure criteria according to the time sequence, and analyzes the failure mechanism and the factors causing the failure in detail. At the same time, the different damage models of type Ⅳ hydrogen tanks are compared, the shortcomings of the existing failure research of type Ⅳ hydrogen tanks are discussed, and the future development direction is prospected to help establish the quality evaluation system of type Ⅳ hydrogen tanks.

Detection technique progress of the residual stress in epoxy composites

RONG Yapeng, CHEN Yun, WANG Yaxiang, LI Tianhui, CHEN Rong, LI Jin

2024, 0(8): 110-118. DOI: 10.19936/j.cnki.2096-8000.20240828.015

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Epoxy composites are widely used in the core components of electrical equipment. However, the mismatch between the thermal and mechanical parameters of the reinforcement material and the resin matrix during the molding process can lead to significant residual stress, which directly affects the components’ mechanical properties and service life. Therefore, accurate and effective residual stress detection and characterization methods are of great significance for optimizing the component molding process and improving the reliability of electrical equipment. This paper first introduces the formation mechanism of residual stress in reinforced epoxy resin composites, summarizes the principle and application scope of several residual stress detection methods based on the curvature measurement method, delamination method, flexibility method, drilling method, photo-elasticity method, X-ray scattering techniques method, Raman spectroscopy method, optical fiber method, and acoustic-elasticity method, and discusses the research progress of residual stress affecting the mechanical properties of epoxy resin components. Finally, the residual stress detection methods for epoxy resin composite materials were prospected. The relevant summary in this article helps grasp the distribution law of residual stress in components and provides a reference for optimizing molding processes.

Review of prediction and prevention techniques for wind turbine blade icing

ZHANG Yingbo, SHAN Guanghua, WANG Fei, MA Haipeng, LIU Ruiqing, CHEN Hui

2024, 0(8): 119-128. DOI: 10.19936/j.cnki.2096-8000.20240828.016

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Wind turbines are prone to blade icing while in low temperature and humid environments, which seriously affects the safety and reliability of wind turbines seriously, and also affects power generation efficiency. This thesis is based on aircraft anti-icing coatings and low adhesion coatings technologies, elaborated from the detection and monitoring technology of blade icing, then focused on active deicing technologies such as liquid flow deicing, mechanical deicing, electric heating deicing and air-heating deicing. Through analyzed and compared different deicing technologies, it is concluded that electric heating deicing and air-heating deicing will be the main direction of research and application. Finally, it is recommended to considering the blade icing reduction ratio as affecting investment factor when in a new projects, and considering installing deicing systems when purchase wind turbines for the new project which blade icing reduction.

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