COMPOSITES SCIENCE AND ENGINEERING

AXIAL COMPRESSIVE PROPERTIES OF GFRP REINFORCED CONCRETE COLUMNS WITH SQUARE SPIRAL STIRRUPS

TU Jian-wei, FU Jin-hai, GAO Kui, XIE Hua

2020, 0(8): 5-11.

Asbtract ( 151 )

PDF (3838KB) ( 201 )

References | Related Articles | Metrics

Through the axial compression test of five GFRP columns (200 mm×200 mm×600 mm) with spiral stirrups and three GFRP columns (200 mm×200 mm×600 mm) with ordinary stirrups, the change rule of ultimate bearing capacity and ductility of GFRP columns with square sections under different stirrups is analyzed, so as to study the influence of spiral stirrups on the axial compression performance of GFRP columns with square sections. The test results indicate that the load-carrying capacity of longitudinal GFRP bars accounted for 3%~7% of the ultimate load-carrying capacity of the columns. The ultimate load-carrying capacity and ductility of GFRP columns with spiral stirrups increased by 0.8%~1.6% and 13%~33%, respectively, compared to GFRP hoops. Reducing the stirrup spacing may prevent the buckling failure of the longitudinal bars and increase the ductility and load-carrying capacity of the GFRP-RC columns. It has been found that setting the GFRP compressive strength to 35% of the GFRP maximum tensile strength yields a reasonable estimation of ultimate load-carrying capacity of GFRP-RC columns.

TENSILE PROPERTIES ANALYSIS OF CFRP-ALUMINUM BONDED-BOLTED HYBRID JOINT

ZHANG Chao-yu, ZHENG Yan-ping, XIONG Yong-jian, WANG Xu

2020, 0(8): 12-17.

Asbtract ( 120 )

PDF (1663KB) ( 222 )

References | Related Articles | Metrics

Based on the three-dimensional progressive damage theory, the tensile strength prediction model of composite laminate-aluminum bonded joint, bolted joint and bonded-bolted hybrid double-lap joints structure were established. The numerical simulation results were in good agreement with the experimental height, which validate the feasibility of the model. On this basis, the influences of parameters such as lap width, lap length, thickness of the adhesive layer, friction coefficient of contact surface and number of bolts on the tensile properties of the bonded-bolted hybrid joint structure were investigated. The results show that with the increase of the lap width and the lap length, the failure load of the joint increases gradually and then stabilizes. The optimum lap width and lap length are 30 mm and 35 mm. The thickness of the adhesive layer has no effect on the tensile failure load of the hybrid joint structure. The greater the coefficient of friction between the bolt joint and the laminate and the bolt and the hole in the rubber-spiral hybrid joint structure, the greater the tensile failure load of the joint structure. In the case where the overlap region is the same, the double-nail hybrid joint structure has a tensile failure load that is 69% higher than that of a single nail.

PROBABILISTIC FREE VIBRATION ANALYSIS OF CARBON FIBER REINFORCED COMPOSITE METRO ROOF PANELS

ZANG Xiao-lei, YIN Qi, LIANG Hai-xiao

2020, 0(8): 18-24.

Asbtract ( 149 )

PDF (2723KB) ( 172 )

References | Related Articles | Metrics

The material properties and physical parameters of composite structures have a quite important variability, which can influence the reliability of structure. In this paper, a stochastic finite element method, the Modal Stability Procedure (MSP), is applied for probabilistic free vibration analysis of carbon fiber reinforced composite metro roof panels. Material properties (elastic properties, densities…) and physical properties (layer thicknesses) are considered as uncertain parameters. The variability of natural frequencies is studied. The MSP is based on an assumption that the mode shapes of the structure are independent of input uncertainty. An explicit expression of natural frequencies, which contains all uncertain parameters, is proposed. Based on the assumption, perturbed modal strains and mode shapes in this expression are replaced by nominal ones. These nominal results are obtained by one nominal finite element analysis with a standard software (Abaqus in this paper). The statistical quantities (mean value, standard deviation, coefficient of variation and distribution) associated to the natural frequencies are evaluated by a Monte Carlo Simulation (MCS) using this expression. For calculating the variability of natural frequencies, the MSP can significantly reduce the computational time, requiring only one nominal finite element analysis and a fast MCS. Using the MSP and Sobol′ method, the influence of uncertain parameters on the first four natural frequencies is studied for sandwich metro roof panels, which are composed of foam cores and carbon fiber reinforced polymer (CFRP) faces. In this paper, the direct MCS is used as a reference. The results obtained by the MSP and the direct MSC are compared. The comparison shows that the MPS can provide accurate results with high computational efficiency. Under the same uncertainty level, the densities and thicknesses, especially the thickness of foam core, have a more important influence on the variability of natural frequencies. By comparison, the variability is not sensitive to uncertain shear moduli of CFRP faces and elastic modulus of foam cores.

OPTIMIZATION OF COMPOSITE CYLINDER BURST PRESSURE BASED ON PROGRESSIVE DAMAGE NUMERICAL SIMULATION

JIA Zi-xuan, LIN Song, JIA Xiao-long, YANG Xiao-ping

2020, 0(8): 25-31.

Asbtract ( 161 )

PDF (4718KB) ( 132 )

References | Related Articles | Metrics

In this paper, the numerical simulation of progressive damage is carried out for the cylinder with metal liner and the optimization is carried out according to the burst results of the cylinder with different layer schemes. The cylinder model was established in ABAQUS software, the Hashin failure criterion and Tan degradation model were selected to put forward the progressive damage theory, and the USDFLD subroutine was written to realize the prediction process of progressive damage of composite model, and the accuracy of the damage theory was verified by NOL ring. The prediction of burst results and progressive damage analysis were carried out for cylinders with different layers modes. The tensile failure results of NOL ring show that the error between the simulated failure stress and the actual value is 1.9%, which proves that the theory of progressive damage is feasible for the circular winding model. The prediction results of cylinder burst show that the predicted pressure and failure position are close to the real test results. The comparison of burst results of cylinders with different layers shows that the angle and number of layers have a great influence on the bursting pressure and position of cylinders. The results of progressive damage analysis show that the damage of composite cylinder is a process from matrix cracking to delamination defect, which consequently leads to fiber fracture and cylinder burst.

PERFORMANCE ANALYSIS OF BLADE ROOT CONNECTION BASED ON PARAMETRIC MODELING

JIANG Chuan-hong, ZHANG Shi-qiang, PANG Xiao-ping, GU Duan

2020, 0(8): 32-37.

Asbtract ( 208 )

PDF (2075KB) ( 205 )

References | Related Articles | Metrics

In view of the existing 2 MW wind turbine blade, the geometry structure and layer condition, were analyzed. The geometry dimension of every metal part connected with the blade root was set, the parameterized geometric model of wind turbine blade root connection was found through MATLAB and ANSYS secondary development, and material properties, grid mesh and contact pairs were set automatically. Based on GL 2010 standard load calculation results, the ultimate load condition of blade root was extracted, the nonlinear solution of the model was carried out according to the load step automatically under the maximum pretension force of bolt, and the load factor of bolt is obtained. The static strength of blade root bolt was validated according to VDI 2230 standard, the stress concentration effect in the drilling area was considered, the static strength of the composite material part of the blade root was validated and analyzed. The results show that the design of blade root connection could meet the ultimate load condition. The research analyzes the static performances of blade root connection every component comprehensively, which lays the foundation for the design of blade root connection to be optimized further.

GEOMETRIC MODELING AND SIMULATION OF 3D WINDING LOOM FABRIC

LI Yong, HU Sheng-long, SHANG Hui-chao, FU Xiao-li

2020, 0(8): 38-43.

Asbtract ( 121 )

PDF (2569KB) ( 272 )

References | Related Articles | Metrics

According to the characteristics of the leno structure, a three-dimensional twist loom fabric is proposed. In order to meet the accuracy and authenticity of the three-dimensional twist loom fabric construction, the parameters of the fabric are characterized by the number of layers, the number of weft rows, the number of warp and weft threads, and the vertical weft distance organization. Then, according to the weaving process and fabric structure parameters, the warp yarn skeining law is studied to propose the law parameters of the warp system. Matlab is used to construct the warp curve to obtain the shape point. The shape point is used to obtain the control point. The cubic B-spline curve control point is used. The warp yarn system model is established, the structural parameter equations of the weft yarn system are proposed, the yarn section shape parameter equations are constructed, and the fabric geometric model is completed. Finally, Solidworks was used to construct a fabric simulation model to obtain a three-dimensional model of the fabric. The volume content of the unit cell fibers was calculated, which can be used for fabric performance analysis to achieve the designable purpose of composite material performance.

THE STUDY OF LAYING PARAMETERS′ INFLUENCES ON COMPOSITE BLADES VIBRATION CHARACTERISTIC

MA Hong-guang, YANG Zheng-xin, GONG Bo, DANG Peng-fei

2020, 0(8): 44-48.

Asbtract ( 133 )

PDF (2589KB) ( 205 )

References | Related Articles | Metrics

Considering the anisotropic characteristics, layup angle, thickness and sequence of composite material, the dynamics model of multilayered composite large fan blade is established. The natural frequency and mode of composite blades are calculated based on the modal analysis method, and the response characteristics of the blades are studied by harmonic response analysis method. The Campbell diagram is used to analyze the natural characteristics of the blades at different speeds. The influence of laying parameters on the vibration characteristics is studied for the composite fan blade. The results show that by adjusting the thickness, angle and sequence of the composite blades, the resonance point and the amplitude can be reduced to achieve the damping effect.

DYNAMIC PROPERTIES OF CO-CURING DAMPING FILM SANDWICH SUTURE COMPOSITES

YANG Gong-xian, LIANG Sen, YAN Sheng-yu

2020, 0(8): 49-57.

Asbtract ( 109 )

PDF (4175KB) ( 189 )

References | Related Articles | Metrics

In order to improve the interlaminar bonding performance of the damping composite material, the Cocuring Damping Film Sandwich Suture Composite Structure (CDFSSCS) was presented. ANSYS software is used to create a finite element model of CDFSSCS plate, and the CDFSSCS dynamics performance of the square plate is investigated with the modal strain energy method revised. The damping films in the CDFSSCS specimens are prepared by brush method, and the simulation method was verified by modal test. The first-order modal frequency and the first-order loss factor of CDFSSCS square plate with different parameters (stitch distance, row distance and damping layer distribution) are obtained by verifying the ANSYS model. The results show that the first order modal frequency and loss factor of the structure can be changed by adjusting the seam parameters and position distribution of the damping sandwich layer. It is of guiding significance to the theoretical design and practical application of CDFSSCS.

EXPERIMENTAL STUDY ON MECHANICAL BEHAVIOR OF GFRP RIBS REINFORCED COMPOSITE SANDWICH BEAMS WITH DIFFERENT SHEAR SPAN-TO-DEPTH RATIOS

ZHAO Xu-dong, CHEN Xun, ZHANG Fu-bin

2020, 0(8): 58-63.

Asbtract ( 103 )

PDF (2994KB) ( 178 )

References | Related Articles | Metrics

The mechanical behavior of GFRP ribs reinforced composite sandwich beams with different shear span-to-depth ratios (a/d) was explored according to four point bending tests. The load-deflection and the typical failure modes and the effect of the a/d ratios and the thickness of the GFRP ribs on the mechanism of GFRP ribs reinforced composite sandwich beams were observed. Test results indicate that specimens with a/d ratio of 1 show the highest load bearing capacity, and it decreases as the a/d ratios increase. And the ductility properties and the strength-to-weight ratio also decrease as the a/d ratios increase. Beams failed in skin indentation failure/core shear failure when the a/d ratio less than is 3, while beams failed in top skin compressive failure as the a/d ratio larger than 3. The GFRP ribs can improve the ultimate bearing capacity and the ductility properties of sandwich beams, the greater the thickness is, the more obvious the effect.

STUDY ON THE INTERFACE OF CARBON FIBER MODIFICATION THROUGH SIZING AGENT CONTAINING CARBON NANOTUBES

CHAI Jin, KONG Hai-juan, ZHANG Xin-yi, YU Mu-huo

2020, 0(8): 64-69.

Asbtract ( 124 )

PDF (5299KB) ( 267 )

References | Related Articles | Metrics

Carbon fiber (CF) is a high-strength, high-modulus, high-performance fiber widely used in composite materials. However, the interfacial bonding property with the substrate is poor due to the low content of reactive functional groups on the surface of the fiber. In this paper, the surface of GQ4922/12K carbon fiber was modified by using sizing agent containing aminated carbon nanotubes (NH₂-CNTs) to improve the interfacial bonding performance between carbon fiber and epoxy resin. The surface functional group and element composition, surface morphology, surface free energy and interfacial shear strength of the modified fiber were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, contact angle measuring instrument, respectively. The results showed that, NH₂-CNTs were successfully grafted onto the surface of carbon fiber, the content of oxygen (nitrogen) element on the surface of the fiber increased, the contact angle with water decreased from 67.1° to 50.5°, and the surface free energy increased from 32.2 mN/m to 41.1 mN/m. The shear strength reached a maximum at an aminated carbon nanotube concentration of 0.6%, which was 23.3% higher than that of the unmodified fiber, from 62.3 MPa to 76.8 MPa. As a result, the surface of carbon fiber can increase the surface activity by introducing the amino carbon nanotubes in the sizing agent, and improve the interfacial bonding property between the carbon fibers and the matrix.

EXPERIMENTAL STUDY OF BOND BETWEEN NEAR-SURFACE MOUNTED BFRP BARS AND CONCRETE UNDER FREEZE-THAWING CYCLES

JIN Liang-liang, YANG Shu-tong

2020, 0(8): 70-75.

Asbtract ( 168 )

PDF (5810KB) ( 169 )

References | Related Articles | Metrics

Alpine areas to explore the effect of freeze-thaw cycles on the embedded FRP reinforcement concrete interface bonding durability, in view of the basalt fiber reinforced composite material (BFRP) tendons embedded reinforcement concrete structure, using epoxy resin (EP) and high toughness of fiber reinforced cement matrix composites (ECC) as the bonding material embedded FRP reinforcement-pull-out tests, from the concrete analysis under the action of freeze-thaw cycle embedded FRP and concrete interface failure mode and the bonding mechanism of degradation, the freezing and thawing cycles, bonding materials, concrete substrate effect on the properties of adhesive performance, the results showed that: Basic performance under the condition of different erosion specimen failure mode for the rubber matrix and shear failure of concrete, rubber matrix fracturing, adjacent to the concrete-concrete thin layer of adhesive interface shear failure, ECC matrix and shear failure of concrete, FRP and ECC interface bond destruction of five kinds of failure modes, the ultimate bond bearing capacity of the specimen increased with the increase of cycling times show varying degrees of decline, within fifty loops on the cohesive force of specimen is small, the influence of ECC specimen compared to epoxy resin adhesive specimen, caking capacity below the epoxy resin specimens, but showed good ductility.

PREPARATION AND PROPERTIES OF HIGH TEMPERATURE RESISTANT RESIN SYSTEM FOR HOT PRESSURE TANK INITIAL PRESSURE PROCESSING PREPREG

ZHANG Qi, WEI Zhen-hai, LIU Qian-li, XU Xiao-kui

2020, 0(8): 76-82.

Asbtract ( 123 )

PDF (6574KB) ( 200 )

References | Related Articles | Metrics

A high temperature resistant toughened epoxy resin (OXEP) was designed and synthesized. A tetrafunctional epoxy resin were modified by chemical rheological agent and OXEP to prepare a hot melt resin system which conformed to hot pressing tank initial pressure forming process. The effect of OXEP content on tensile,toughness and heat resistance of the resin system was studied. Mechanical properties of composites prepared by hot pressing tank initial pressure forming process and traditional process were compared. The results showed that the reaction time of chemical rheological agent should be controlled at 120 min. The addition of OXEP can effectively improve the mechanical properties of the cured resin. When OXEP modified epoxy is added at 32 phr, the tensile strength and impact strength of the modified resin are increased by 29% and 73%, respectively, and the fracture toughness is improved by 3.3 times. Tough fracture surface with deep ravines indicated high fracture energy dissipation, and thus remarkable toughening effect. The mechanical properties of the autoclave-compressed hot-melt composites are better than those of the conventional autoclave. The 0° tensile strength and shear strength of the composites are significantly improved, which are increased by 34.5% and 38.6%, respectively.

STUDY ON INTERFACE PROPERTIES BETWEEN CARBON FIBER LAMINATE AND GLASS FIBER LAMINATE OF LARGE WIND TURBINE BLADES

LUO Sha-sha, RONG Guang, LI Xiao-bo, YUAN Wei

2020, 0(8): 83-88.

Asbtract ( 158 )

PDF (6292KB) ( 232 )

References | Related Articles | Metrics

This paper studies the interface performance of carbon fiber and glass fiber composite materials for large-scale wind turbine blades, which is greatly affected by the test method, the material of the peel ply, and the gram of the peel ply. Comparing with the interlaminar shear test which is commonly used in evaluating interfacial bonding performance, the T-peel test method can better reflect the interfacial bonding performance and change trend of the interfacial bonding performance. Based on the T peel test method, it was obtained that the carbon/glass interface bonding performance treated with nylon peel ply was better than that of polyester peel ply, and the large-gram nylon peel ply was the highest. Finally, according to the mechanism of carbon/glass interface bonding performance influence mechanism, interface failure mode, and microstructure analysis, the conclusions are consistent with the T test results, which provide a basis for evaluating the carbon/glass interface bonding performance and help us to select a suitable test method and peel ply.

STUDY ON SHEAR RESISTANCE OF CONCRETE BEAM STRENGTHENED WITH NSM CFRP STRIPS

ZHANG Zhi-mei, XU Yu-qi

2020, 0(8): 89-96.

Asbtract ( 108 )

PDF (1906KB) ( 186 )

References | Related Articles | Metrics

At present, most of the research methods for the shear strengthening of concrete beams with near-surface mounted FRP strips (NSM-FRP strips) are experimental research, few of which use finite element analysis, and there is no corresponding code to guide the design. In the relevant design formulas put forward by most scholars, most of the effective strain for FRP are obtained through the direct reduction of its ultimate strength, and some scholars have considered the influence factors on the effective strain Ring, but the calculation result is too large. In order to study the shear behavior of concrete beams strengthened by NSM CFRP strips, and derive the expression of shear capacity of reinforced beams. Based on Abaqus, a T-beam model with NSM CFRP strips was constructed to study the effects of concrete strength, stirrups ratio, shear span ratio, embedding angle and interstitial spacing on the shear resistance of reinforced beams. The effective stress expression of CFRP strip considering the related influencing factors is obtained by regression. And the expression of the shear capacity of the beam strengthened with NSM CFRP strips is established. The results show that the strength of concrete, the shear span ratio, the spacing between the battens and the angle of the battens have a great influence on the shear performance of the strengthened beams, and the ratio of stirrups has a certain influence on the strengthening effect. The results calculated using the shear bearing capacity expression are in good agreement with the relevant experimental values.

STRUCTURE DESIGN AND VERIFICATION FOR AN UNDERGROUND FF DOUBLE-WALL OIL TANK

HUANG Qi-zhong, HUANG Yong, ZHANG Xue-mei, PENG Yu-gang

2020, 0(8): 97-101.

Asbtract ( 139 )

PDF (5895KB) ( 197 )

References | Related Articles | Metrics

A double-wall oil tank manufactured by fiber reinforced plastic have been widely applied due to the advantages of light weight and high strength, anti-corrosion and fatigue resistance, convenient fabrication and so on. Based on the service condition of a buried 30 m³ FF double-wall oil tank, the structure of tank manufactured by winding process is designed which is composed by a 4 mm inner wall, a 3.5 mm intermediate wall, a 5 mm outer wall and 13 reinforcement ribs. The response of the oil tank under load cases including external pressure, stability and vehicle running has been analyzed by finite element method, and the results show that the FF double-wall oil tank can fulfill the requirements. A 65 t vehicle running test verifies that the double-wall oil tank is successful. The design method proposed in the paper can be extended to the design for another volume double wall oil tank.

OPTIMIZATION OF EXCITATION LOCATION FOR WIND TURBINE BLADE FATIGUE TEST BASED ON DAMPING EFFECT

ZHU Rui, HUANG Hui-xiu, YU Yong-feng, YUAN Yi-nan

2020, 0(8): 102-106.

Asbtract ( 191 )

PDF (1432KB) ( 193 )

References | Related Articles | Metrics

Composite wind turbine blades are one of the key components of wind power generation system. During the full-size fatigue test period, the structural damping of composite materials and the modal damping factors such as aerodynamic resistance in the test environment have an uncertain impact on the dynamic characteristics of wind turbine blades. Accurately obtaining the vibration characteristics of wind power blades is of great theoretical and practical significance for accurately designing the excitation position of fatigue test. In this paper, based on the theory of transfer function, the fatigue test system of wind power blade is simplified to a dynamic model of damping system with one degree of freedom. The vibration characteristics of composite wind turbine blade in fatigue test were studied by frequency response analysis with finite element simulation model. Then three different excitation position proportional coefficients are discussed to determine the optimal scheme of single excitation position in fatigue test. The correctness of the finite element simulation analysis and the reliability of the optimization scheme were verified by the flap-wise fatigue test of LZ76-3.X.

LENGTH CONTROL OF ULTRA-THIN GLASS FIBER AND THEIR MECHANICAL PROPERTIES OF PTFE BASED COMPOSITE MATERIALS

WANG Jun-shan, JIN Xia, JIA Qian-qian, LIU Zheng

2020, 0(8): 107-112.

Asbtract ( 161 )

PDF (7835KB) ( 131 )

References | Related Articles | Metrics

In order to improve the mechanical properties of PTFE based composites, glass fiber must be added to the dielectric layer as the reinforcing material. In this paper, ultra-fine glass fiber cotton was taken as the research object. A kind of low-speed grinding equipment is adopted. By adjusting the speed and grinding time of the equipment, the length of glass fiber was controlled. The length information of the fiber was characterized by Bauer-Mcnett fiber classifier. Then the fibers were mixed with PTFE and ceramic powders to prepare PTFE based composite as randomly filling reinforcing material. The composite ultra-thin layers were made. The experimental results showed that the length distribution of the short glass fiber prepared under the grinding speed of 70 rpm and grinding time of 10 s was moderate, which met the requirement of PTFE matrix composite material preparation. The mass fraction of trapped glass fibers in 50 mesh, 100 mesh, 200 mesh and 400 mesh screens was 15.3wt%, 20.8wt%, 19.5wt% and 14.6wt%, respectively. The fiber slurry was evenly dispersed without aggregation, and the tensile strength, tensile module and compression module of the prepared PTFE based composite were increased to 15.4 MPa, 762 MPa, and 1232 MPa, respectively.

RESEARCH PROGRESS OF BASALT FIBER REINFORCED POLYMER ANCHORS IN ROCK AND SOIL ANCHORING

WANG Hai-gang, BAI Xiao-yu, ZHANG Ming-yi, YAN Nan

2020, 0(8): 113-122.

Asbtract ( 175 )

PDF (4672KB) ( 223 )

References | Related Articles | Metrics

Basalt fiber reinforced polymer (BFRP) tendons have the advantages of high tensile strength, strong resistance to alkali corrosion, good stability, and environmental protection. They have gradually become the best choice for nonmetal anchors. The field of soil anchoring is emerging. This article mainly introduces the research progress of BFRP anchors in terms of test, theory and numerical calculation, summarizes the types of anchor stress sensors needed to monitor the bolt pull-out test, and analyzes the existing FRP interface bond slip model and BFRP anchor factors affecting the bond strength of rods. In addition, related researches such as durability of BFRP anchors and numerical simulation analysis based on tests are introduced. Finally, the shortcomings of BFRP anchors are analyzed and discussed. Finally, recommendations are made for future developments in the anchoring field.

RROGRESS IN PREPARATION TECHNOLOGY OF CONTINUOUS FIBER REINFORCED THERMOPLASTIC PREPREGS

XU Yun-peng, YAN Chun, LIU Dong, XU Hai-bing

2020, 0(8): 123-128.

Asbtract ( 226 )

PDF (1387KB) ( 533 )

References | Related Articles | Metrics

Continuous fiber reinforced thermoplastic composites have been widely applied in many fileds due to their excellent properties. As an intermediate material for the manufacture of thermoplastic composites, the preparation and quality control technology of continuous fiber reinforced thermoplastic prepregs is very important for the development of thermoplastic composites. In this paper, three preparation methods of continuous fiber reinforced thermoplastic prepregs are introduced in detail, such as melt impregnation, solvent impregnation and powder impregnation. The advantages and disadvantages of these methods are summarized. The development trend of high performance thermoplastic prepregs is prospected.

Table of Content