COMPOSITES SCIENCE AND ENGINEERING

Angle optimization analysis of variable stiffness laminates based on ant colony algorithm

ZHANG Guiming, SHEN Zhiqiang, ZU Lei, WANG Huabi, ZHANG Qian, XIA Xianzhao, GENG Hongbo, PAN Jie, ZOU Liqing

2023, 0(1): 5-15. DOI: 10.19936/j.cnki.2096-8000.20230128.001

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In order to perform stiffness analysis of variable stiffness composite laminates, a discrete unitisation of the laminate vibration equation was carried out based on the differential quadrature method (DQM) in this study, which can facilitate frequency analysis. Meanwhile, the fundamental frequency is an essential research parameter of vibration. The ant colony algorithm (ACA) is used in conjunction with DQM to generate the initial angle randomly by the ACA to improve the frequency values calculated by DQM in the evolutionary iteration process. The results show that the evolutionary iteration process of ACA can optimize the selection of the beginning and termination angles of the pavement very well. Through updating the pheromone generation by generation and improving the ACA appropriately to achieve the final angle convergence, the optimal pavement start and end angles are found to be [<38°|62.75°>,<90°|72°>,<0°|5°>,<0°|5°>]_S. Moreover, the corresponding frequency value is 11.712 57 Hz. Also, the data statistics show that the initial angles are mainly concentrated around 0°, 38°and 90°, and the termination angles are loosely distributed but mainly concentrated around 10°~90°.

Multi-scale analysis and comparison of low-speed impact of carbon fiber plain and twill woven composite materials

LIU Le, SHI Jianwei, YANG Jingjing, LI Cheng

2023, 0(1): 16-25. DOI: 10.19936/j.cnki.2096-8000.20230128.002

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To explore the impact response of the plain and twill woven composites, a multi-scale framework was constructed to analyze and compare. First, the mesoscale representative volume element (RVE) of plain and twill woven composites were established to explore their mechanical properties, then locally homogeneous the mesoscale representative volume element(RVE) of pain and twill woven composites were transformed into equivalent cross lamination (equivalent cross-ply laminate, ECPL) model. Finally, the ECPL model of both was expanded into a macroscopic low-speed impact model, with numerical simulations at 6 J impact energy and compared with the experimental results. The results show that the impact time curves of plain and twill woven composite are similar to the experiments, verifying the effectiveness of the macroscopic model. The impact peak of twill woven composite, impact shock time and energy absorption are higher than the plain woven composite.

Study on structural design and drawing performance of new partially potted inserts in honeycomb sandwich structure

CUI Haonan, WEN Liwei, ZHAO Cong

2023, 0(1): 26-33. DOI: 10.19936/j.cnki.2096-8000.20220328.031

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The structure of traditional inserts in honeycomb sandwich panels are usually I-shaped, which requires manual injection of potting materials until the potting materials fills honeycomb core, resulting in low accuracy, low efficiency and large overall weight. In order to reduce weight and adapt to automatic assembly, a new hat-shaped partially potted insert was designed, an automatic assembly platform of inserts was built, and the process verification of automatic assembly of inserts was completed. The filling state of potting materials with different numbers of flow orifices was analyzed by industrial CT system. With the help of tensile testing machine, the tensile tests perpendicular to the panel were carried out on the new hat-shaped partially potted inserts with different numbers of flow orifices and different amounts of potting materials injection and the traditional I-shaped full potted inserts filled with 100% potting materials. The results show that the more the number of flow orifices on the side of the new hat-shaped partially potted insert, the more uniform the distribution of potting materials in the honeycomb core, and the better the tensile properties of the inserts. And the increase of the amount of potting materials injection can significantly improve the drawing capacity of the inserts, and the corresponding total mass of the structure will also improve rapidly. However, when the amount of potting materials is too large, the excess potting materials will flow to the bottom of the honeycomb core, so that the increase of drawing capacity is not obvious. Compared with the traditional I-shaped full potted inserts, the maximum drawing capacity of the new hat-shaped partially potted inserts is reduced, but the reduction is small, in which the G08-P04 is only reduced by 9.5%, while the structural weight can be reduced by 65.2%, which is more suitable for the requirements of low-load and light-weight structural plate. The work done in this paper can provide reference for weight reduction design and automatic assembly of inserts in honeycomb sandwich panels.

Thickness analysis at the jagged boundary of the inserted layer in the inserted-layer reinforced composite member

ZHANG Haotian, WANG Xianfeng, GAO Tiancheng, YE Fan

2023, 0(1): 34-43. DOI: 10.19936/j.cnki.2096-8000.20230128.004

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In order to calculate the thickness of the layers containing the inserted layer, this paper first introduces the concept and representation of the boundary residual to quantitatively evaluate the size of the triangular region of the jagged boundary. Then, by discretizing the centerline of the inserted layer trajectory, the distance from the endpoint of the trajectory centerline along the tangential direction to the inserted layer boundary is calculated, so that the boundary residuals in different cases can be calculated. And at the same time, the triangular area generated at the boundary is divided and quantified by using the boundary residuals to lay the foundation for the calculation of the thickness distribution of the single-layer pavement. Finally, the thickness at the apex of the triangular surface sheet is obtained by meshing the surface of the core mold and the surface assignment of the inner and outer triangular areas and the laydown defect area in each layer of the pavement, and the average value of the thickness at the three apex locations of the triangular surface sheet is obtained as the overall thickness of the triangular surface sheet, so that the thickness analysis of the pavement as a whole can be performed.

Research on vibration characteristics of composite material laminated panel with fiber angle curve variation under different laying numbers

YE Fan, WANG Xianfeng, WANG Dongli, GAO Tiancheng, ZHANG Haotian, FENG Tianyang

2023, 0(1): 44-54. DOI: 10.19936/j.cnki.2096-8000.20230128.005

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Compared with the traditional composite fiber linear laying laminate, the fiber angle curve can change the stress distribution of the laminate and improve the rigidity and load-bearing capacity. For the purpose of damping, fiber curve laminates with different fiber curve angles and different layup quantities were designed and prepared. Modal tests were used to compare and analyze the influence of fiber curve angle and layup quantity on the vibration characteristics of laminates. The results show that when the number of layers is the same, and when the fiber curve angle changes to ±<60|75>,the first three natural frequencies of the laminate have reached the optimal state; when the fiber curve angle changes to ±<45|60>, the damping ratio of the laminate is the largest. When the fiber curve angle changes the same, by comparing the influence of the three sets of three layers of 8, 12 and 16 layers on the natural frequency of the laminate, when the number of laminates is in the range of 8 to 16 layers, when the first two natural frequencies presents a trend of first increasing and then decreasing. The work done can provide a reference for the vibration optimization of the fiber curve laminate.

Experimental study on internal pore structure and energy dissipation of basalt fiber reinforced concrete under stress damage

LI Wei, LI Sen, WANG Hongqiang

2023, 0(1): 55-62. DOI: 10.19936/j.cnki.2096-8000.20230128.006

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The damage degree, pore structure and energy dissipation of basalt fiber reinforced concrete under different stress levels are studied based on experiments. Non-metallic ultrasonic detector is used to measure 0σ_m, 0.15σ_m, 0.3σ_m, 0.45σ_m, 0.6σ_m variation of longitudinal wave velocity and damage factor under five different stress levels. The T₂ spectrum distribution, pore size distribution and porosity of specimens under different stress levels were studied by NMR test. Combined with the universal press machine, the uniaxial compression test of the specimen is carried out, and the variation laws of stress-strain curve, peak stress and energy dissipation are analyzed. The results show that the basalt fiber concrete specimen will be damaged under stress, the specimen height decreases with the increase of the applied stress level, and the longitudinal wave velocity first increases slightly and then decreases. The integrity of the specimen is enhanced under the action of low stress level,and the specimen is damaged under the action of high stress level, and the greater the stress, the higher the damage degree. The peak value of T₂ spectrum of test piece is the lowest under the action of 0.3σ_m stress level and the peak value of T₂ spectrum is the highest under the action of 0.6σ_m stress level. The porosity of the specimen first decreases and then increases with the increase of stress level. The internal pores of the test piece mainly exist in the form of micropores and mesopores. Under the action of low stress level, the original cracks in the test piece are compressed, the mesopores in the test piece are transformed into micropores, and the total porosity decreases. Under the action of high stress level, the test piece is damaged and deformed under the action of stress, the internal crack pore diameter increases and the porosity increases. The addition of basalt fiber increases the plastic deformation capacity of concrete, and the peak stress decreases with the increase of action stress level, and the decrease amplitude increases significantly. The dissipated energy per unit volume of the specimen decreases with the increase of the stress level, and the mechanical damage degree increases slightly with the increase of the stress level. Under the stress damage, the elastic deformation capacity of the specimen decreases and the energy dissipation rate increases.

Three dimensional finite element simulation of curing process and deformation prediction of closed beam with large aspect ratio

WAN Jun, ZHANG Jie, SHEN Yanbin, SHA Huiping, LEI Zuxiang

2023, 0(1): 63-69. DOI: 10.19936/j.cnki.2096-8000.20230128.007

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The curing process of closed beams with large aspect ratio is often difficult to predict due to its variable cross-section characteristics. In this study, a finite element model was established by constructing governing equations of thermal curing, flow-compaction, and stress-deformation coupling and the curing process of a one-piece composite beam with a large aspect ratio closed cross-section was calculated by this model. Design and manufacture of main beam was optimized based on the simulation results. The accuracy of the model was verified by comparing the scaled parts samples with the simulation results. The average error and maximum error between the simulation results of the full-size main beam profile and the actual deformation are 8% and 17%, respectively. This model can provide a basis for the pre-deformation design of the component mold to realize the precise forming of one-piece closed composite beams with large length-to-diameter ratio based on springback deformation compensation technology.

Preparation and natural frequency analysis of CFRP optical system rack for 3D automatic optical inspection machine

LI Lei, CAO Dongfeng, JI Yundong, LIU Pengfei, TAN Yongqing, CHEN Jianping

2023, 0(1): 70-76. DOI: 10.19936/j.cnki.2096-8000.20230128.008

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Automatic optical inspection machine (AOI)is used to detect the welding defects on the surface of printed circuit board (PCB). The vibration of the rack of the optical system affects its accuracy and efficiency. In order to improve the detection accuracy and efficiency of AOI machine, carbon fiber composite material (CFRP) was used instead of aluminum alloy to design and manufacture the rack, and the finite element software ABAQUS was used to model the CFRP rack and aluminum alloy rack for calculating natural frequency and vibration mode. The results of percussion experiments on the CFRP rack and the aluminum alloy rack are basically consistent with the simulation results, and the error is less than 16%. Compared with the aluminum alloy rack, the first-order natural frequency of CFRP rack is increased by 8.51%. Finally, the high-speed imaging test results of the two kinds of rack show that the AOI equipment installed with CFRP rack has higher imaging accuracy, better stability and higher efficiency.

Influence of laminate angle and trigger mechanism to quasi-static axial compression performance of carbon fiber composite hexagon thin-walled tube

CHEN Dongfang, WU Haipeng, LIANG Fan, ZHOU Qi, SONG Xiangang, TIAN Aiqin

2023, 0(1): 77-84. DOI: 10.19936/j.cnki.2096-8000.20230128.009

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Carbon fiber composite thin-walled hexagonal pipe is molded by the combined process of prepreg lay-up and filament winding, and different trigger mechanisms of cavity and hole opening are set at the end of the pipe. The quasi-static axial compression load testing on composite thin-walled tube is carried out, and its deformation mode and energy absorption mechanism, as well as the effects of ply angle and trigger mechanism on the specific energy absorption and total energy absorption of thin-walled tube are analyzed. The testing results show that the specific energy absorption and total energy absorption of hexagonal thin-walled tube specimens with ply angle [±45°] under the same trigger mechanism are 123.7%, 111.5% and 111.5% higher than those with [0°/90°], [±45°₂/0°/0°/90°/0°], [64°₂/0°₂/64°₂/0°₂/64°₂], and the initial peak load with the cavity trigger mechanismunder the same ply angle is higher than that of opening hole.

Experimental study on seismic performance of CFRP-retrofitted earthquake-damaged masonry-infilled RC frame

ZHANG Yongbing, WU Jianxin, DAI Baile, ZHENG Lei

2023, 0(1): 85-93. DOI: 10.19936/j.cnki.2096-8000.20230128.010

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In order to investigate the seismic performance of CFRP-retrofitted earthquake-damaged masonry-infilled reinforced concrete (RC) frames,three earthquake-damaged masonry-infilled RC frame specimens and one RC frame specimen were tested under low-cyclic reversed load after its CFRP reinforcement, the damage characteristics and hysteresis curves of the specimens were obtained, the seismic performance indexes of the specimens, such as bearing capacity, stiffness degradation, energy dissipation and displacement ductility were analyzed, and compared with the earthquake-damaged masonry-infilled RC frame specimens and unreinforced RC frame specimens. The results show that the peak bearing capacity of earthquake-damaged frame specimens retrofitted by CFRP can be effectively improved, the degradation level of structural stiffness is slower than that of the original specimens, and the energy dissipation capacity is also improved. The reinforcement of CFRP can restore the bearing capacity, stiffness and energy dissipation capacity of earthquake-damaged masonry-infilled RC frame with rigid connection to the level before earthquake damage. The specimen with flexible connection filled wall frame retrofitted with CFRP for earthquake damage is delayed due to the presence of rubber, which delays the strong pushing effect between the filled wall and the frame and the destruction of the filled wall, so that the frame and the masonry-infilled wall can still work together and continue to resist horizontal load. CFRP gives full play to the restraint effect under large deformation of the specimen. Its peak bearing capacity and energy dissipation capacity can be significantly improved, and its stiffness degradation is slower than that of the original specimen.

Study on pore structure and permeability of basalt fiber reinforced concrete under confining pressure

HU Xiuyue, PANG Jianyong, LEI Chengxiang

2023, 0(1): 94-99. DOI: 10.19936/j.cnki.2096-8000.20230128.011

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The pore structure, mechanical properties and impermeability of concrete with different basalt fiber contents under confining pressure were studied based on experiments. The uniaxial compression and splitting tests of basalt fiber concrete with 0 %, 0.05 %, 0.1 %, 0.2 % and 0.3 % fiber content were carried out by uniaxial compression machine. The triaxial compression and permeability tests under different confining pressures (4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa and 10 MPa) were carried out by TAW-2000 servo triaxial testing machine. Combined with automatic rapid specific surface area and porosity analyzer and scanning electron microscope (SEM), the internal pore changes and micro-structure of the specimens were obtained. The influence of basalt fiber on the strength, toughness, pore structure and impermeability of concrete specimens was analyzed. The results show that the incorporation of basalt fiber can greatly improve the mechanical properties and ductility of concrete specimens, and the compressive and tensile strengths of specimens are the highest at 0.05% of fiber incorporation, and the toughness of specimens is the best at 0.1% of fiber incorporation, but excessive fiber incorporation will reduce the ability of specimens to resist external load. Besides, the incorporation of fiber can reduce the pore diameter and porosity of the specimen, forming a good bonding effect between fiber and concrete material and eventually form a spatial mesh structure inside the specimen to enhance the integrity and reduce the generation and expansion of cracks. Under different confining pressures, the permeability of basalt fiber concrete is always smaller than that of plain concrete, the incorporation of fibers reduces the porosity of concrete materials and improves the permeability resistance, and the increase of the confining pressure makes the permeability of both kind of concrete specimens decrease continuously until it is in a stable state while the permeability of basalt fiber concrete specimens decreases more gently.

Application of ultra-lightweight and large-scale pultruded GFRP profile for external frame beam in high-rise buildings

QIN Heng, LIU Tianqiao, YU Taofeng, YI Shusheng, XIONG Jinfeng, FAN Yanjun, FENG Peng

2023, 0(1): 100-106. DOI: 10.19936/j.cnki.2096-8000.20230128.012

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A new type of external frame beam for high-rise buildings is proposed based on pultruded glass fiber reinforced polymer (GFRP) composite profiles. Combined the practical engineering problems, the external hanging frame beam of large size pultruded profiles is designed and prepared. In addition, a series of finite element analyses were conducted to evaluate and validate the mechanical performance of proposed GFRP beam. Then, the installation/construction method was introduced in detail. Last but not least, the proposed GFRP frame beam was compared with steel counterpart in terms of the material usage and economic performance. It is observed that the proposed GFRP frame beam is able to reduce the self-weight of the frame structure by 75%, improve the environmental durability of the structure and decrease the construction-related costs.

Research on forming process of CFRP pantograph upper frame with embedded FBG sensor

WANG Yanjuan, DING Guoping, YU Yi

2023, 0(1): 107-111. DOI: 10.19936/j.cnki.2096-8000.20230128.013

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This paper designs a CFRP pantograph upper frame with embedded FBG sensors. Taking the shape and structural dimensions of an aluminum alloy pantograph upper frame as a reference, the CFRP pantograph upper frame is made of carbon fiber composite materials. The structure is optimized under the premise of ensuring that the assembly size remains unchanged. At the same time, combined with the characteristics of the composite material forming process, the ply design and forming process are studied. In order to obtain the interlayer strain information of the upper frame of the CFRP pantograph during service, a certain number of FBG sensors are embedded in the manufacturing process according to its design structure and layering scheme, and the layout of the FBG sensors is determined. The pre-embedded method of the FBG sensor embedded in the upper frame of the CFRP pantograph and the protection method of the optical fiber lead out are studied, and the plastic sleeve is selected to protect the optical fiber drawn from the surface to prevent the optical fiber from being damaged.

Experimental study on ablation characteristics of surface of glass fiber reinforced polymer by femtosecond laser

HE Zongtai, LIU Kexin, LIU Ming, LIU Dun, YANG Qibiao

2023, 0(1): 112-115. DOI: 10.19936/j.cnki.2096-8000.20230128.014

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Glass fiber reinforced polymer is widely used in the manufacture of container or outer skin of radar equipment because of its excellent wave permeability and dielectric properties. In order to etch the surface of glass fiber reinforced polymer precisely, it was etched by femtosecond pulse laser with wavelength of 1 030 nm, and the ablation effect of different laser energy density, scanning speed and etching times were considered. It was found that the ablation state of femtosecond laser can be divided into weak ablation and strong ablation, and the strong ablation state can be formed on the basis of weak ablation. In the weak ablation state, the removal mechanism of laser on the material is mainly vaporization with less thermal effect, and parts of the original structure and chemical properties can be maintained on the processed surface. When the laser energy density, spot overlap rate or scanning times increased, the heat accumulation effect on the surface was enhanced, the ablation rate of the material was intensified, and the ablation state was changed. After ablation, the microstructure and chemical properties of the material surface changed, and the carbonization phenomenon was significant.

Review of high performance organic fibers in ballistic composite fields

DONG Bin, WEI Rubin, WANG Xiaowei, ZHANG Wenting, LI Feng, ZHAI Wen

2023, 0(1): 116-123. DOI: 10.19936/j.cnki.2096-8000.20230128.015

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Fibre reinforced polymer (FRP) composites performed superior potential in bulletproof fields, which could significantly improve the protection capability and lightweight level of protection equipment, and had become the core strategic materials in the competition of various countries. The performance of fibre reinforcements played the crucial role in governing the ballistic performance of FRP composites. In this review, the energy absorption mechanisms of FRP composites during the projectile penetration were briefly discussed. The relationships between the mechanical properties of fibers and the bulletproof ability of FRP composites were also summarized. Nowadays the high performance organic fibers applied in bulletproof fields mainly include para-aramid, heterocyclic aramid, ultra high molecular weight polyethylene, polybenzoxazole and poly diimidazo pyridinylene (dihydroxy) phenylene. The synthetic process, structural characteristics, mechanical properties, advantages, disadvantages and application status in bulletproof fields of high performance organic fibers were discussed and summarized in detail. Finally, the development tendency of high performance bulletproof organic fibres in the future was put forward.

Research progress on tribology of graphene and its composites

ZHU Yanan, LIU Yongye, YU Liang

2023, 0(1): 124-136. DOI: 10.19936/j.cnki.2096-8000.20230128.016

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Graphene is a high-performance two-dimensional nano-lubricating material, which is widely used in the field of tribology. This paper introduced graphene’s unique layer structure and surface morphology, endowing it with excellent intrinsic friction properties, including interlayer slip behavior that accelerates incommensurate transitions,and textured graphene surface wrinkle storage nanoparticles reduce its surface friction coefficient. The problems existing in the composite lubrication performance as the third medium are summarized, including the phenomenon of agglomeration and poor dispersibility. This paper focuses on reviewing the research progress of graphene composite lubrication, including introducing it into the lubrication system to prepare composite additives and play its synergistic effect with each additivephase. It is expounded that graphene nanoparticles have the function of repairing the surface of metal materials in the process of fluid cutting, which can effectively suppress the friction temperature rise and reduce the friction coefficient during the cutting process. Using graphene as a reinforcing phase, the composite materials were prepared by solution blending, lamination and sintering, oxidative modification, in-situ polymerization and other molding processes. The methods to improve the synergy between graphene and the components as well as the bond strength with the matrix material are outlined, and the mechanism of improving the anti-friction and wear resistance of the material is summarized. The future research trends of graphene and its composites are prospected, and further research work is proposed.

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