COMPOSITES SCIENCE AND ENGINEERING

Research on the axial compression behaviour of GFRP-wound tube-wood-reinforced concrete composite columns

SHEN Yebo, ZHANG Fubin, XU Jing, FANG Hai

2023, 0(10): 5-9. DOI: 10.19936/j.cnki.2096-8000.20231028.001

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The axial compression behavior of wood-reinforced concrete composite columns confined with glass fibre reinforced polymer(GFRP)-wound tube was investigated by experiments, and compared with that of GFRP-wrapped composite columns. The effects of each component on the failure mode, bearing capacity, stiffness and ductility of composite columns are analyzed. The results indicated that the stiffness of GFRP tube-restrained composite column with wood core is 36.2%~49.2% higher than that of GFRP-wrapped composite column with wood core, and different GFRP restraint forms have no significant effect on the bearing capacity and ductility of composite columns. The introduction of wood core increased the ductility of GFRP restrained columns by 23.8%~27.0%. Compared with the unbonded combined column, the bearing capacity of GFRP tube-restrained composite column can be significantly increased by 146.5%~208.6%, and the ductility can be increased by 28.4%~56.4%.

Simulation method for curing deformation of composite part considering tool-part interaction

YUAN Zhenyi, WEI Fangjian, KONG Lingfei, YANG Zhenchao, TONG Xinxing, LI Yan

2023, 0(10): 10-16. DOI: 10.19936/j.cnki.2096-8000.20231028.002

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For the assembly problems caused by the curing deformation of L-shaped composite structure, a simulation model of the curing deformation of composite considering the tool-part interaction was established. Firstly, the shear slip effect of the tool on the composite structure during curing process was characterized using the method of setting the friction coefficient with the maximum shear stress. Secondly, the effects of composite anisotropy, material thermal expansion and contraction, and matrix chemical shrinkage on the curing deformation were considered. Finally, the cure hardening instantaneously linear elastic model was used to realize the curing deformation simulation calculation under the premise of effectively improving the computational efficiency. On this basis, the validity of the simulation model was verified by designing experiments of curing deformation of L-shaped structures with different thicknesses and different lay-up sequences. The experimental and simulation analysis results were compared with a maximum error of -20.8% and an average error of -7.35%. The results show that for L-shaped structural parts prepared by aluminum molds, the tool-part interaction exacerbates the curing deformation situation of the structure, and the structural stiffness plays an important role in this deformation.

Numerical investigation on dynamic response of bio-inspired honeycomb sandwich beams under oblique impact loading

ZHANG Wenping, KONG Xiangqing, ZHANG Huiling, ZHANG Wenjiao, LI Ruonan, FU Ying

2023, 0(10): 17-22. DOI: 10.19936/j.cnki.2096-8000.20231028.003

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In order to investigate the mechanical response of the new bio-inspired honeycomb sandwich beam (BHSB) with double core under low velocity oblique impact, a 3D finite element numerical model of BHSB was established via ABAQUS finite element software. And the numerical results are compared with the experimental results to verify the validity of the model. Based on the validated finite element model, the influence of impact angle on damage mode, contact force peak value, contact time and energy absorption of BHSB was studied. Meanwhile, the mechanical properties of BHSB under different impact energies were discussed, and the failure mode and failure mechanism of BHSB under oblique impact load were analyzed. The results show the peak load and energy absorption decrease by 2%~4% and 23%~52%, respectively, the damage area decreases and the contact time increases with the increase of impact angle. With the increase of impact energy, the damage of BHSB increases, the peak load increases by 20%~42%, and the energy absorption efficiency increases from 59% to 83%. The effects of impact angle and impact energy on the oblique impact performance of bionic honeycomb sandwich structures can provide some guides for the practical application of similar structures.

Research on interlaminar impact resistance of self-healing EMAA fiber bundle suture composites

GE Chaokun, TIE Ying, ZHANG Zhenzhen, YANG Weiya

2023, 0(10): 23-31. DOI: 10.19936/j.cnki.2096-8000.20231028.004

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In order to overcome the disadvantage of insufficient interlaminar fracture toughness of carbon fiber reinforced resin matrix composites, low impact damage tolerance and difficult repair after impact damage, thermoplastic resin fiber EMAA suture composite specimens were prepared by suture and phased co-curing process, and the impact properties before and after self-healing were studied. The layered prepreg was sutured with thermoplastic resin fiber EMAA along the thickness direction, a three-dimensional self-healing network was established internally, and the impact specimens were processed through phased heating and pressure curing. The primary impact test and the impact test after self-healing of the suture EMAA composite laminate were carried out with different energies and the healing test of the suture EMAA composite laminate specimen damaged after impact was carried out. The damage of unrepaired laminates and self-healing composite laminates under different impact energy and the impact resistance of self-healing composite laminates before and after repair were studied. The results show that under the same impact energy, the damage loss energy of sutured EMAA composite laminate is 17.66% lower than that of unsutured EMAA composite laminate, and the damage is smaller and the laminate has better impact resistance. The lowest repair efficiency of laminates after self-healing is 97.96%, which better realizes the self-healing function of materials.

The effects of surface area to volume ratio on the water absorption rate of solid buoyancy materials

LIN Shouqiang, YANG Zhuan, LIU Gang, HUANG Hui, CHEN Miaomou, HUANG Xin, Chen Dajiang, HAO Jing

2023, 0(10): 32-36. DOI: 10.19936/j.cnki.2096-8000.20231028.005

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The water absorption rate of solid buoyancy materials under a certain hydrostatic pressure varies with their sizes and shapes. The surface area to volume ratio is one of the major factors that affect the water absorption rate. In order to study this relationship, solid buoyancy material samples of various area to volume ratios were prepared and tested under hydrostatic pressures of 10 MPa and 20 MPa for up to 30 days. The cumulative water absorption rates of the samples are found to increase with the area to volume ratio. A kinetics formula describing the propagation of water in solid buoyancy materials is developed based on Fick’s Law. A linear relationship between the wa-ter absorption rate and a composite parameter (S/V)t has been derived and verified by comparing with the meas-ured data. The findings indicate that the water absorption rate of solid buoyancy materials is proportional to its area to volume ratio under the same hydrostatic pressure and for the same period of time, which offers a meaningful guidance to the engineering design and analysis of such materials.

Study on the effect of layup method and blending ratio of aramid and UHMWPE fiber fabrics on dynamic response to blast loading

FENG Zhenyu, ZHEN Tingting, GAO Binyuan, XIE Jiang

2023, 0(10): 37-46. DOI: 10.19936/j.cnki.2096-8000.20231028.006

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To investigate the blast resistance characteristics of aramid fiber and ultra-high molecular weight polyethylene (UHMWPE) fiber fabric, LS-DYNA R11 was used to establish a fiber fabric blast impact finite element simulation analysis model, and the validity of the model was verified by comparing the dynamic response, failure modes and measured point overpressure curves of the fabric in the test. Numerical analysis of the blast impact was conducted on fabrics with different lamination methods and laination ratios at the same blast distance and equivalent under equal surface density conditions. The analysis of blast resistance from two aspects: failure mode and overpressure decay capacity, the result show that compared with alternate laminated fabric, sequential laminated fabric can better block the shock wave overpressure. Without considering the impact of the blast fireball, the fabric blast resistance increases with the increase of the proportion of UHMWPE fabric. For 12 stacking layers, the anti explosion structure of the mixed fabric adopts a combination of six layers of aramid fabric on the front explosion surface and six layers of UHMWPE fabric on the back explosion surface, which has the best anti explosion performance.

Manufacturing technology of Z-shaped stiffener for large scale composites

YANG Bo, QUAN Yinzhu, WANG Fei, JIANG Wei

2023, 0(10): 47-51. DOI: 10.19936/j.cnki.2096-8000.20231028.007

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In this paper, the structure characteristics and manufacturing technology development trend of composite frame are introduced, according to the structure feature of large curvature radius and both male and female corner of large scale composites Z-shape stiffener, this paper introduces a manufacturing method without soft cover plate during forming process, the Invar steel material was chosen to manufacture the forming tooling, and the springback angle of Z-shaped stiffener inner flange was compensated during the design process of tooling. The key point during product manufacturing is to control the thickness of corner area, surface quality, curing deformation and the hand lay-up quality of corner area. The developed Z-shaped stiffener by this method can well meet the requirements of various technical indexes, this is a high-quality manufacturing method for large scale composites Z-shape stiffener, and this method is suitable for engineering promotion and application.

Experimental study on flexural behavior of FRP bars recycled concrete beams

JIN Gaoming, SUN Kangcai, LIU Shengwei, BAI Chengyu

2023, 0(10): 52-59. DOI: 10.19936/j.cnki.2096-8000.20231028.008

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In order to study the flexural performance of FRP bars RAC (recycled aggregate concrete) beams, 8 FRP bars RAC beams were experimentally fabricated, of which the number of GFRP bars and BFRP bars RAC beams was 6 and 2, respectively. The effects of RA (recycled aggregate) replacement rate and FRP bars type on the failure mode, deflection and bearing capacity of beams were studied by four-point bending test. The test results show that: ①The cracking load and ultimate bearing capacity of the beam both decreased with the increase of RA replacement rate, and the failure mode gradually changes from the compression failure of normal section concrete to the diagonal tensile failure; ②The increase in the elastic modulus of BFRP bars increases the height of the RAC compression zone of the beam, which improves the bearing capacity of the normal section of the beam, but the bearing capacity of the oblique section increases less, so that the diagonal tensile failure of the RAC beam with BFRP bars occurs; ③The safety reserve of the bearing capacity of FRP reinforced RAC beams calculated by the specification is slightly insufficient. It is suggested that when the actual reinforcement ratio is 1~1.5 times of the equilibrium reinforcement ratio ρ_fb, the design value is 0.8 times of the calculated value of the specification; ④The calculated deflection values of GB and ACI are in good agreement with the experimental values, which can well predict the deflection value of FRP reinforced RAC beams.

Modified Drucker-Prager model for circular concrete columns confined with FRP

ZHANG Luke, ZHANG Feng, ZHAO Guohao

2023, 0(10): 60-68. DOI: 10.19936/j.cnki.2096-8000.20231028.009

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In Drucker-Prager (DP) model, the parameters related to friction angle and cohesion determine the yield and hardening softening criteria, and the parameters related to dilation angle determine the flow rule. Through the statistical analysis of the test sample results, the influencing factors of the friction angle are determined, and the friction angle is defined as a function of plastic strain. Then the cohesive force model is updated by the yield criterion of DP model. By calculating the ratio of lateral plastic strain to axial plastic strain, the dilation angle model considering constraint stiffness ratio is established. Based on the USDFLD subroutine in ABAQUS, the parameters of the modified DP model are customized. The results show that the modified DP model can predict the stress-strain response of FRP confined concrete columns with certain accuracy.

Study on the resistance of mixed fiber recycled aggregate concrete to sulfate attack under dry-wet cycles

LI Weikun, XIANG Musheng, MI Li, WANG Jin

2023, 0(10): 69-77. DOI: 10.19936/j.cnki.2096-8000.20231028.010

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Polyvinyl alcohol fibers (PVAF) and basalt fibers (BF) were selected to be incorporated into concrete in different proportions and volume rates, and mixed fiber recycled aggregate concrete was configured with 30% recycled coarse aggregate as an equal mass replacement of normal coarse aggregate. 90 times dry-wet sulfate cycles tests were conducted to measure the changes in mass loss, dynamic elastic modulus and compressive strength of concrete after different times of dry-wet cycles. The study showed that the mass loss rate of concrete in the PVAF group was 0.22%, which was 42% lower than that of normal concrete, and the mass loss rate of concrete in the BF group was 0.19%, which was 50% lower than that of normal concrete, when PVAF∶BF was 1∶4, 1∶2, 1∶1 and 4∶1, and the fiber volume ratio was 0.2%, the minimum mass loss rate. When PVAF∶BF was 1∶1 and 2∶1 with 0.3% fiber volume ratio, after 90 times of wet-dry cycles of sulfate, the minimum values of relative dynamic elastic modulus reduction of concrete were 102.2% and 99.4%, respectively; however, when PVAF∶BF was 1∶2, 1∶4 and 4∶1 with 0.2% fiber volume ratio, the relative dynamic elastic modulus of concrete was reduced to the lowest values of 99.4%, 94.1% and 99.4%. After 90 times of dry-wet cycles of sulfate, when the fiber volume rate was less than 0.2%, the magnitude of compressive strength loss rate of concrete was in the following order: 1∶1 mix<4∶1 mix=1∶2 mix<1∶4 mix<2∶1 mix; when the fiber volume rate was greater than 0.2%, the magnitude of compressive strength loss rate of concrete was in the following order: 2∶1 mix<1∶2 mix<1∶1 mix<4∶1 mix<1∶4 mix. Mixing PVAF and BF on the concrete resistance to sulfate erosion than single PVAF or BF, showing a better “positive effect”.

Durability study and failure mechanism analysis of carbon fiber reinforced composite connection structures for vehicles

YANG Yang, LIN Yinghao, WANG Yuanwu, FAN Yisa

2023, 0(10): 78-86. DOI: 10.19936/j.cnki.2096-8000.20231028.011

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Bonding joints are easy to connect FRP materials, with uniform stress distribution, good fatigue performance, light weight and other advantages, so they are often used in the lightweight structure of vehicles. The vehicle in the process of service will experience huge challenge such as different coupling temperature, humidity, the adhesive of the durability of the structure, therefore, studying the durability of carbon fiber reinforced composite material connection structures (CFRP-CFRP) for vehicles has important guiding significance for the lightweight of vehicles. The CFRP-CFRP single-lap joints were aged at 60 ℃/95%RH, 60 ℃/100%RH, 60 ℃/3.5%NaCl and 60 ℃/5%NaCl for 240 h, 480 h and 720 h, respectively. Fick’s law was used to simulate the adhesive water absorption process, and compared with the actual water absorption rate. The joint failure load and force-displacement curves were obtained through quasi-static tensile test to explore the mechanical properties of the joint. It was observed that failure load did not increase or decrease uniformly with time increasing, indicating that post-curing (failure load increasing) and environmental erosion (failure load decreasing) were two competing factors with opposite effects. DSC and FTIR test equipment were used to characterize the adhesive before and after aging and its internal failure mechanism was analyzed.

Damage analysis of bolted CARALL structures under quasi-static loading

ZHANG Lintao, YANG Tao, DU Yu, ZHANG Jintong

2023, 0(10): 87-93. DOI: 10.19936/j.cnki.2096-8000.20231028.012

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Carbon fiber reinforced aluminum alloy laminate (CARALL) is a relatively new fiber-metal laminated material. To investigate the bolted joint performance of CARALL laminates, specimens were prepared by the hot press pot method of curing and molding process, and quasi-static tensile tests were conducted on their bolted structures. The failure processes of the joints subjected to quasi-static tensile loads were discussed, and the failure modes covered aluminum plastic deformation, carbon fiber fracture and interface delamination. The failure models were developed separately for different material compositions of each CARALL layer, and the VUMAT subroutine was used to realize the progressive damage analysis of the CFRP layer based on the 3D Hashin failure criterion. The relative error between the experimental and finite element predicted ultimate loads is 8.9%, and the proposed model can predict the location of delamination failure of the specimen more accurately, which proves that the model can effectively predict the mechanical properties of the single-nail bolted structure of the carbon fiber reinforced aluminum alloy laminate.

Application of mass scaling in analysis of tensile bearing capacity of post embedded parts of honeycomb sandwich structure

WANG Yingming, ZHANG Shenglan, MO Jie, WANG Jiyun

2023, 0(10): 94-100. DOI: 10.19936/j.cnki.2096-8000.20231028.013

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For the post embedded parts of honeycomb sandwich structures with complex structures, a lot of time is usually consumed in the finite element calculation. In the simulation analysis of the tensile bearing capacity of the post embedded parts of honeycomb sandwich structure, the mass scaling method is used to improve the calculation efficiency of the model, and the accuracy and time of simulation calculation are compared. First of all, in ABAQUS, the simulation analysis of honeycomb sandwich structure post embedded parts without mass scaling technology is carried out and compared with the test results to verify its accuracy. Then, after the mass of the model is expanded by 10², 10⁴ and 10⁶ times respectively by using the mass scaling method, the simulation analysis of the rear embedded parts of the honeycomb sandwich structure is carried out and compared with the model results without using the mass scaling technology. The simulation accuracy is verified by comparing the pull off failure load displacement curve and the specimen failure form, and the calculation time is compared. The results show that when using mass scaling technology to analyze the tensile bearing capacity of the post embedded parts of honeycomb sandwich structures, the calculation accuracy can be guaranteed, and the calculation time can be greatly saved, which provides an efficient calculation method for the study of the tensile bearing capacity of the post embedded parts of honeycomb sandwich structures.

Study on energy absorption characteristics of thin wall tube of carbon fiber triaxial fabric composite filled with polyurethane foam

TAO Yiqiang, ZHANG Honghua, LI Wei

2023, 0(10): 101-108. DOI: 10.19936/j.cnki.2096-8000.20231028.014

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In this paper, the energy absorption performance of carbon fiber triaxial woven tubes filled with polyurethane foam was studied. The failure mode of triaxial woven tube and the ratio of different weft yarn of laminated on the impact of pipe pressure was studied by the quasi static axial compression experiment method, based on the compression process, the count of yarn stress and failure morphology observation, the role of weft yarn in endergonic process was analyzed, and the weight evaluation analysis was introduced. The results show that the increase of weft yarn can significantly improve the total energy absorption and specific energy absorption, but the load efficiency is obviously decreased. The increase of warp can provide transverse binding and extend the compression stroke of the triaxial fabric tube, but the specific energy absorption decreases to different degrees. Different warp and weft ratios have significant effects on the failure modes at interleaving points, and the interleaving points of C₂C₂ and C₃C₂ almost do not participate in compression failure. C₂C₄ and C₃C₄ are more involved in the failure, and C₃C₄ has a more stable deformation failure process.

Research on the key technology of automated winding molding of heat insulation

ZHANG Weichao, HOU Zengxuan, YAN Wencong, XU Minghao, WANG Haodong, LI Yanliang

2023, 0(10): 109-114. DOI: 10.19936/j.cnki.2096-8000.20231028.015

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This paper introduces the research status of automated winding molding of solid rocket motor heat insulation at home and abroad, proposes the heat insulation winding molding scheme and equipment scheme, and focuses on the key technologies of heat insulation winding molding. According to the characteristics of heat insulation winding molding and the winding pressure control requirements, the winding pressure control method was proposed. By analyzing the causes of winding tape deviation, the tape rectification method was put forward. An elliptical concave roller was designed to ensure the tape edge bonding quality and avoid tape edge warpage. A calculation method of universal tape width for heat insulation winding molding was proposed by analyzing the parameters related to the contact deformation of the rubber tape between the cylindrical roller and the smallest mandrel. According to the requirements and characteristics of tape transport speed and tension control for heat insulation winding molding, the tape transport speed and tension control method was proposed. The dynamic demonstration system of heat insulation winding molding was established to provide support for the development of automated heat insulation winding molding equipment.

Study on application technology of composite pole in distribution network angle pole

HE Changlin, KE Rui, ZHAO Chun, ZHU Xiaodong, MEI Duan, WU Feng

2023, 0(10): 115-120. DOI: 10.19936/j.cnki.2096-8000.20231028.016

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The application technology of composite pole in distribution network angle ploe has been studied from theory calculation and true test. By using finite element software and parameterized programming, considering the P-δ effect, the stress and the top deflection of angle composite pole without guyed under various working conditions have been calculated in detail. The results show that the strength and deflection of the composite pole meet the requirements of the code, but the deflection is much larger than that of the concrete pole. The stress, deflection and structural stability of 12 m single circuit, 15 m single circuit, and 15 m double circuit angle composite poles with guyed under the condition of maximum wind speed have been calculated in detail, and the results meet the requirements of use. In order to verify the stability of the composite pole under the pressure, the mechanical true tests of the above-mentioned three kinds of composite poles have been carried out. In the case of overloading to 140%, there is no abnormal phenomenon on the whole pole, which provides a basis for practical engineering applications.

Research progress on gas barrier properties of graphene/polymer composites

LIU Guanjun, WANG Sai, ZHANG Xin, WANG Lu, YANG Fan, WANG Rongguo

2023, 0(10): 121-128. DOI: 10.19936/j.cnki.2096-8000.20231028.017

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Hydrogen energy is an important measure to improve the domestic energy structure and achieve the goals of carbon emission peak and carbon neutrality. Hydrogen storage tanks are one of the key technologies for the development of hydrogen energy. To improve the gravimetric hydrogen densities of hydrogen storage tanks, lightweight type IV tanks with polymer liners have become the key development direction. However, the gas barrier performance of polymer liners has become the core index limiting the development of hydrogen storage tanks. In this paper, the mechanism of graphene improving the gas barrier performance of polymers is expounded, and the theoretical permeation models for two-phase and three-phase composites are summarized. The gas barrier properties of graphene-reinforced polymer matrix composites are outlined based on the chemical structures, modified dispersion, induced polymer crystallization and orientation of graphene. On this basis, future research directions have been prospected.

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