COMPOSITES SCIENCE AND ENGINEERING

Composite materials design for high-efficiency elastic wave mode conversion

WANG Tian, YANG Xiong-wei, CHAI Yi-jun, GENG Qian, LI Yue-ming

2021, 0(12): 5-11. DOI: 10.19936/j.cnki.2096-8000.20210727.031

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Composite materials are widely used in various fields for their excellent mechanical performances, while anisotropic metamaterials have significant engineering applications and scientific values for the extraordinary manipulation of elastic waves. By combining the anisotropy of composite materials and the requirements for extraordinary wave manipulation, a novel idea was proposed which could offer a new insight into the realization of integrated structure and function. Aimed at high-efficiency elastic wave mode conversion, which is expected to serve as the significant mechanism for vibration and noise reduction, the relation with composite monolayer plate fiber laying angles was studied based on transmodal Fabry-Perot interference(TFPI) theory and composite materials classical laminated plate theory. Then the design method of composite meta-structure for mode conversion was established, with which high-efficiency mode conversion was achieved as high as 89%. The results show that the design method proposed is effective for composite materials design for elastic wave mode conversion.

Acoustic target strength analysis of composite egg-shaped pressure hulls

WU Jian, ZHU Ting-guo, LI Hong-yun, WANG Wei-bo

2021, 0(12): 12-18. DOI: 10.19936/j.cnki.2096-8000.20211228.002

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In order to study acoustic target strength of underwater composite egg-shaped pressure hulls, the minimum thickness egg-shaped pressure hulls satisfying the strength and buckling condition are taken as research object. An acoustic-solid coupling model of egg-shaped pressure hull is established with finite element method. The influence of design parameters such as material type, egg-shaped coefficient, composite material thickness and winding angle on acoustic target strength is analyzed. Finally, acoustic target strength of egg-shaped pressure hull composed of composite material with metal head is analyzed. The results show that under the same shape conditions, the maximum acoustic target strength of composite egg-shaped pressure hulls is lower than that of titanium. When sound waves incident along the tip direction of egg-shaped pressure hull, medium and high frequency acoustic target strength is the lowest and it is inversely proportional to the egg-shaped coefficient. It is suggested that egg-shaped pressure shell should be arranged with the tip upward in deep sea.

Analysis of calculation method for ultimate stress and strain of FRP-confined seawater sea-sand concrete cylinders

LI Ben-ben, LI Peng-ju, ZHAN Yang

2021, 0(12): 19-24. DOI: 10.19936/j.cnki.2096-8000.20211228.003

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This paper investigates the applicability and prediction accuracy of three calculation models (Lim's model, Wei's model and Jiang's model) for ultimate stress and strain based on test database of FRP-confined seawater sea-sand concrete (SSC) cylinders. The analysis results show that the accuracy of the calculation model for predicting ultimate stress is generally higher than that of predicting ultimate strain. Among the three models for predicting ultimate stress, Lim's model and Jiang's model show similar high accuracy, with the average absolute error AAE equal to 10.7% and 11.0%, and the average mean of the ratio of the predicted value to the experimental value Mean equal to 104.3% and 105.8%. Compared with the experimental value, the predicted value of the Wei's model for ultimate stress is overall lower (Mean=81.0%), and the error is relatively large (AAE=19.6%). Among these three models, it is recommended to use Lim's model to predict the ultimate stress of FRP-confined SSC. At the same time, Jiang's model is also recommended because of similar prediction accuracy, easier computation with fewer formulas compared with Lim's model. Among the three calculation models for predicting the ultimate strain, Lim's model has the highest accuracy (AAE=27.8%, Mean=99.4%)while Wei's model and Jiang's model underestimate the ultimate strain of FRP-confined SSC, with Mean up to 74.5% and 52.2%, respectively. It is recommended to use Lim's model to predict the ultimate strain of FRP-confined SSC. To sum up, Lim's model is the best model among three calculation models for predicting the ultimate state of FRP-confined SSC since best accuracy has been achieved by Lim's model in both ultimate stress prediction and ultimate strain prediction.

Finite element analysis of stress concentration in tensile process of reinforced woven fabric

SUN Yi-wan, ZHANG Xue-wen, CAI Li-hai, SHAO Wei-guang, LIU Wen-yan

2021, 0(12): 25-33. DOI: 10.19936/j.cnki.2096-8000.20211228.004

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Woven fabric reinforcing layer is the pressure bearing framework material of lay-flat hose. During the stretching process of woven fabric, the mechanical efficiency of yarn will be reduced due to the stress concentration of warp and weft yarn at the intersection, resulting in the decrease of pressure bearing strength of lay-flat hose. Therefore, in this paper, firstly, the tensile properties of ring knitted twill fabric are studied by finite element tensile simulation and tensile test. Then, aiming at the problem of stress concentration at the intersection in the tensile process of woven fabric, the tensile process of twill fabric with different warp spacing and weft fineness is simulated by finite element simulation, and the stress distribution and stress concentration factor of yarn cross section at the intersection are calculated. The results show that the results of finite element tensile simulation are basically consistent with those of tensile test. Increasing the warp spacing, reducing the weft fineness and weft curl curvature can reduce the stress concentration at the intersection in the process of weft stretching, while the warp spacing, weft fineness and weft curl have no significant effect on the stress concentration at the intersection in the process of weft stretching.

Design and performance of embedded carbon nanopaper displacement sensor

HAN Cheng-lin, ZOU Ai-li, WANG Gong-dong, WANG Meng, LI Nan, LI Hua

2021, 0(12): 34-39. DOI: 10.19936/j.cnki.2096-8000.20211228.005

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In this paper, a new displacement sensor based on glass fiber reinforced composites (GFRP) and carbon nanopaper (BP) was developed based on the sensitivity of three-dimensional network structure of carbon nanopaper to bending stress and strain. Three displacement sensors with different thickness and embedded position were designed, and their performance was tested based on the three-point bending experimental platform to explore the influence of sensor thickness and embedded position on its sensing performance. The performance test results show that the resistance change rate of the new displacement sensor has a good quadratic fitting relationship with the displacement. Its sensitivity is mainly affected by the displacement range, sensor thickness and embedded position. The sensor has good repeatability. Experimental results show that when the sensor is thick and the carbon nanopaper is located below the neutral surface, the sensing performance is the best, and the controlled error is within the range of ±0.1 mm.

Failure behavior and influencing factors of volume characteristics of filament wound pressure vessel based on refined model

ZU Lei, JIN Shu-ming, ZHANG Qian, ZHANG Gui-ming, WU Qiao-guo

2021, 0(12): 40-47. DOI: 10.19936/j.cnki.2096-8000.20210528.031

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In this paper, the failure mechanism of filament wound pressure vessel was investigated by hydraulic burst test and numerical simulation analysis. The thickness of the winding layers measured by three-dimensional scanner was compared with that predicted by the cubic spline formula. A fine modeling method of the filament-wound pressure vessel was presented with the aid of the finite element software Abaqus and a Python script file. Each winding layer of the composite pressure vessel can be modeled intuitively and accurately by this method. The cohesive elements were employed to simulate the interlaminar damage of the winding layers. The progressive failure analysis of the composite layers based on the three-dimensional Hashin failure criteria and the stiffness degradation criteria was carried out, so as to predict precisely the burst pressure of the pressure vessel. Combined with the test results, the failure behavior of the filament wound pressure vessel was analyzed. Finally, based on the numerical model, the influencing factors of pressure vessel volume characteristics are analyzed. The results show that: ①The cubic spline method can accurately predict the thickness distribution of the domes based on the geodesic trajectories. ②The progressive damage method based on the Hashin failure criteria and the cohesive elements inserted two adjacent layers can accurately, comprehensively and intuitively predict the failure mode of the composite layers. ③The burst pressure of the pressure vessel by hydraulic test was 76 MPa, which was compared with finite element simulation result, and the error was 3.3%. The error between the displacement and strain results and the actual measured values is within 10%, indicating that it is reasonable to determine the burst pressure by the displacement mutation at the failure position. ④For type Ⅲ pressure vessel, the volume characteristic coefficient can be improved by increasing the design explosion pressure. The volume characteristics of pressure vessels with the same volume decrease with the increase of aspect ratio.

Research on deformation monitoring of CFRP plate using distributed optical fiber sensing technology

HE Jian-ping, SHEN Feng, ZHANG Shi-hai

2021, 0(12): 48-52. DOI: 10.19936/j.cnki.2096-8000.20211228.007

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Carbon fiber reinforced polymer (CFRP) has been widely used in supporting and strengthening structures due to its excellent tensile strength and corrosion resistance. In order to study the deformation characteristics of CFRP in service, distributed optical fiber sensors were placed on the CFRP plate to carry out deformation monitoring tests of CFRP plate under two working conditions of damage and non damage, and resistance strain gauges were placed on the CFRP plate for strain test comparison. The experimental results show that the distributed optical fiber sensor can effectively measure the strain information of the CFRP plate, and the measured strain is basically consistent with the finite element analysis value and the resistance strain gauge value. The continuous arrangement of the distributed optical fiber sensor is more realistic than the fixed-point arrangement to reflect the deformation of the CFRP plate.

Interlaminar properties of magnetically oriented carbon nanotubes-reinforced glass fiber/epoxy composites

HUANG Dong-hui, ZENG Shao-hua

2021, 0(12): 53-59. DOI: 10.19936/j.cnki.2096-8000.20211228.008

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To improve the interlaminar properties of glass fiber reinforced epoxy composites (GFRE), ferroferric oxide@multi-walled carbon nanotubes nanoparticles (Fe₃O₄@MWCNTs) were prepared by depositing Fe₃O₄ on the surface of MWCNTs based on the covalent bonding, and then such nanoparticles were dispersed in epoxy resin by three-roll grinding and ultrasound methods. The glass fiber/epoxy composites containing oriented MWCNTs were fabricated under a weak magnetic field. The results showed that MWCNTs were distributed along the flow direction of resins under a weak magnetic field, and MWCNTs and Fe₃O₄ could promote mutual co-dispersion in resins. MWCNTs with uniform orientation and dispersion could strengthen and toughen the interlaminar region of composites, and the improved mechanical and thermal properties of composites could be realized. Compared with pure GFRE, the interlaminar shear strength and work of fracture of composites containing oriented MWCNTs were increased by about 31% and 117%, respectively. The tensile and flexural properties and storage moduli were significantly improved, and the glass transition temperature was increased by about 7 ℃.

Experimental investigations on the failure behaviour of UHMWPE composite panel under the loading of fragments and blast

SU Luo-chuan, TIAN Li-zhi, YI Chen-hong, LIU Wen-jie, SHI Ya-qin

2021, 0(12): 60-65. DOI: 10.19936/j.cnki.2096-8000.20211228.009

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Due to the extremely high specific strength, the ultra-high molecular weight polyethylene (UHMWPE) fiber reinforced laminates are widely employed in protective armors. In this paper, the failure modes of UHMWPE laminate panel under explosive loading are experimentally investigated. Firstly, an explosive device that can simultaneously produce blast and fragments is designed. And then, the deformation and failure characteristics of the UHMWPE panel under the loading of the explosive device are gained and analyzed. The panel exhibits multiple failure modes, including the delamination, buckling, bubbling, fragments penetration and erosion. Based on the deformation characteristics, the failure progress of the UHMWPE laminate panel under explosive loading can be divided into four typical stages.

Optimization of forming process and supporting materials of domestic carbon fiber prepreg for radar antenna

SUN Kun, ZHAO Wen-zhong, ZHANG Chen-hui, LIU Ming-chang, LI Jian-wei, GAO Qi, XU Pei-lun

2021, 0(12): 66-72. DOI: 10.19936/j.cnki.2096-8000.20211228.010

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In order to realize the application of domestic developed carbon fiber/epoxy resin fabric prepreg in radar antenna, the forming process and key process parameters optimization of sandwich plate autoclave with new-developed carbon fiber prepreg as skin were studied. On this basis, six kinds of composite sandwich panels were prepared with newly prepared carbon fiber prepreg as skin, bonded with J-95 or SY-24C Ⅱ film, filled with J-47D or SY-P6 foam or not filled with foam. Through the test and analysis of plane tensile and bending mechanical properties, the supporting materials of the prepreg used in sandwich plate were optimized. The results of the study showed that the two-step autoclave forming process was used to form the sandwich board without foam or the sandwich board filled with J-47D foam and the three-step autoclave forming process was used to form the sandwich board filled with SY-P6 foam. In addition, the key process parameters, such as the rate of heating or cooling, the pressure timing, and the measures to improve the quality of sandwich panel, such as tooling assistance, were determined. The mechanical properties of six kinds of sandwich panels were tested and analyzed. It was found that SY-24C Ⅱ film had a better match with skin, honeycomb and foam, and compared with the two types of foam, the mechanical properties of the sandwich board filled with SY-P6 foam are obviously better. Therefore, SY-24C Ⅱ film and SY-P6 foam are determined as supporting materials for the manufacture of radar antenna.

Experimental study on mechanical properties of hybrid fiber rubber concrete based on orthogonal experiment

ZHU Peng-yu, WAN Hou-lin, ZHU Ye, GU Wen-hu

2021, 0(12): 73-77. DOI: 10.19936/j.cnki.2096-8000.20211228.011

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Orthogonal experiments were designed for hybrid fiber rubber concrete (HFRC), and its mechanical properties were tested and compared with ordinary concrete. The volume ratio of basalt fiber, polypropylene fiber and rubber volume ratio were analyzed for the impact of HFRC's compression and splitting strength. The results show that when the volume ratio of basalt fiber is 0.3%, the volume ratio of polypropylene fiber is 0.2%, and the volume ratio of rubber is 5%, the performance of HFRC is the best. Basalt fiber has an impact on the strength of HFRC and the strength of HFRC mixed with hybrid fiber has been greatly improved, which reflects a good fiber "positive hybrid effect". As the volume rate of rubber increases, the strength of HFRC gradually decreases. With the help of SEM microscopic analysis, the mechanism of fiber toughening and crack resistance of HFRC was discussed, and finally the strength of HFRC was modeled.

Application of composite materials protector in the subsea of offshore oil

SHI Jin-kun, LIU Hui, ZHANG Xi-wei, GUO Fei

2021, 0(12): 78-81. DOI: 10.19936/j.cnki.2096-8000.20211228.012

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With the rapid development of offshore oil and gas development, there are more and more underwater production facilities. At the same time, marine fishery fishing methods and fishing equipment are developing rapidly. The impact of fishing activities on these underwater facilities is becoming more and more obvious, and they are damaged by trawling and anchoring. And destruction accidents happen from time to time. In order to ensure the safe production of offshore oil and gas, underwater facilities need to be protected. Fiber-reinforced composite materials have the advantages of light weight, high strength, corrosion resistance, and difficulty in growing marine organisms. Therefore, the application of protective structures for marine oil and gas development underwater facilities has broad application prospects. This article mainly summarizes the application of this type of composite material protection structure, and compares and analyzes it with steel structure and cement briquette protection structure.

Size optimization design of composite wing for UAV

SHEN Hao-jie, CHEN Gang, XIA Yang

2021, 0(12): 82-88. DOI: 10.19936/j.cnki.2096-8000.20211228.013

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In order to deduce the structure weight and perform the properties of composite in the swept wing structure for UAV, the size optimization was conducted in the wing configuration with a double closed cell rectangular beam in the specific position. The composite wing adopted T800 carbon fiber woven clothes. Through commercial software MSC. Patran and Nastran, 89 variables, the thicknesses of 45° and 0° in different subareas and the widths of ribs were optimized to minimize the structure weight. The constraints of the optimized model included the strength and stiffness of the wing structure. The Tsai-Wu failure criterion was utilized to calculate the damage factors and determine the damage of composite structure. The optimized results satisfied the characteristics of force transmission within the main components of the swept wing, and met the strength, stiffness and weight requirements of the composite wing.

Microwave curing process and properties of T700/epoxy composites by wet filament lamination winding

LI Meng-ying, XIAO Jun, HUAN Da-jun, WANG Xing-bang, YANG Xiao, JIAO Yang

2021, 0(12): 89-94. DOI: 10.19936/j.cnki.2096-8000.20211228.014

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In this paper, the rapid manufacturing of large-size solid rocket motor shell is the research background. Aiming at the problems of long curing cycle and high production cost in traditional heat curing, a layered microwave pre-curing process is proposed to shorten the manufacturing cycle and maintain excellent performance. With the help of differential scanning calorimeter, based on the curing degree, combined with the shell winding law and microwave absorption efficiency, the layered winding element of [90°₂/±20°] was selected. Considering the influence of heat conduction and microwave effect on the curing degree of the wound layer, a microwave pre-curing process with heating rate of 5 ℃/min and rising from room temperature to 90 ℃ was determined. The post-treatment was heat curing by holding at 160 ℃ for 1 h. Microwave curing and heat curing composite laminates and NOL rings were prepared. When the preparation time of samples cured by microwave (regardless of cooling time) is nearly half shorter than that of samples cured by heat, the mechanical properties of samples cured by microwave and heat are basically the same. Because of the bulk heating characteristics of microwave curing, it can achieve the mechanical properties equivalent to that of the heat cured samples in a short time.

Research on process of T300 carbon fiber/BMP370 polyimide composites and its properties

LIANG Heng-liang, ZHOU Hong-fei, SUN Ke-han

2021, 0(12): 95-98. DOI: 10.19936/j.cnki.2096-8000.20211228.015

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The BMP370 polyimide of high-temperature resistant PMR-15 model is a new third-generation polyimide resin. The composites curing process of the BMP370 and the T300 carbon fiber includes the amidation, the imidization and the cure cross-linking reaction. The volatiles content and the vacuum control during the curing is studied particularly. The mechanical, high-temperature mechanical and physical properties of laminates are analyzed. The development direction used in model application was proposed.

Preliminary research on induction welding process of CF/PPS coupons

WANG Hong-en, YANG Yang, QIAN Ying, ZHOU Jian-feng, ZHU Shu

2021, 0(12): 99-105. DOI: 10.19936/j.cnki.2096-8000.20211228.016

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This paper studied the temperature history and distributions at key positions during induction welding of thermoplastic composites. Carbon fiber reinforced poly(phenylene sulfide) (CF/PPS) coupons were fabricated, with in-situ thermocouple monitoring. Effects of welding parameters on surface morphology were explored, along with fundamental influences from air cooling and sustaining press. We further evaluated single-lap-shear strength and compared with data from hot pressing. Finally, some approaches were suggested for processing improvements.

Study on the mechanism of the honeycomb node cracking in sandwich structure

LIU Zhi-jie, SUN Zhen-ping, ZHAO Ying-nan, CAI Yu-jin, XU Heng-yuan, WEN You-yi

2021, 0(12): 106-113. DOI: 10.19936/j.cnki.2096-8000.20211228.017

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The aramid honeycomb node cracking occurred in high temperature and high pressure when the honeycomb sandwich was processed by secondary bonding. The typical sandwich samples were produced and the honeycomb node cracking was observed and detected by ultrasonic C-scan and X-ray. In order to analyze and study the mechanism of the honeycomb node cracking, the article induced the forces analysis of the core grid, and the stress suffered on the node was computed by the theoretical arithmetic and finite element simulation respectively. The results indicated that the node cracking started from the seam of the node under the dual action of the compression stress and the core grid pressure difference, and the core grid pressure difference was the key factor which effected the node damage stress. In addition, the honeycomb node peel strength was tested and compared with the node damage stress. After the honeycomb joint cracking happened, the bending instability of the honeycomb core grid walls was initiated under compression stress easily. At last, some suggestions were given to avoid the honeycomb node cracking.

Design and development of an efficient and adaptive grinding head system for a new type of wind turbine blade automatic grinding robot

YAN Chen, CHEN Xiao-liang, LI Guo-liang, LI Cheng-liang

2021, 0(12): 114-119. DOI: 10.19936/j.cnki.2096-8000.20211228.018

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With the rapid development of China's wind power generation industry, wind turbine blades, as the key core components of the whole fan, are becoming larger and lighter. With the increasing size of wind turbine blades, the difficulty of grinding operations in the production process is also increasing. At present, the blade grinding process in wind power blade manufacturing enterprises is still carried out by manually adding auxiliary climbing tooling. The whole process needs a large number of workers, and has low grinding efficiency, unstable grinding quality, high dust concentration in the working environment, and serious safety risks. In this case, the development of wind turbine blade automatic grinding robot has become the same goal of each wind turbine blade production enterprises. This paper mainly discusses a new kind of automatic grinding robot equipment for wind turbine blades. The equipment mainly includes omnidirectional AGV car, lifting platform, efficient adaptive grinding head, Kuka long arm downward type manipulator, efficient explosion-proof dust collector, integrated control unit and sensing control system, etc. In the equipment composition of wind turbine blade automatic grinding robot, omnidirectional AGV and Kuka manipulator are all standard spare parts, which are introduced here. This paper mainly describes the self-developed efficient adaptive grinding head and automatic grinding control method in detail. The application and promotion of wind turbine blade automatic grinding robot can effectively reduce the number of workers in the blade production and grinding process, enhance the grinding efficiency, stabilize the grinding quality, improve the working environment of the process, and have a positive effect on promoting the intelligent level of the blade manufacturing industry.

A review about drilling of CFRP

ZHANG Yue-xin, YANG Ming-jun, LIU Geng, WANG Chong-jie

2021, 0(12): 120-128. DOI: 10.19936/j.cnki.2096-8000.20211228.019

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Carbon fiber reinforced plastic(CFRP) composites are widely used in aero engine nacelles for its exellent mechanical properties. The material inevitably requires a lot of connection, but it is a brittle material and anisotropic. After drilling, the stress concentration of the material will have a certain of defects. In order to explore the impact of drilling on the quality of the hole, a lot of researches have been carried out on its drilling process at home and abroad, its process includes three phenomen i.e., a chip formation mechanism, drilling force, drilling heat. Based on the research results from all over the world, this article comprehensively summarizes the drilling mechanism of CFRP, explains the types of defects in the hole after drilling and the development of the drilling process of carbon fiber composite materials.

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