COMPOSITES SCIENCE AND ENGINEERING

OPTIMIZATION DESIGN AND ANALYSIS OF COMPOSITE WING STRUCTURE OF A CERTAIN ELECTROMAGNETIC-LAUNCH UNMANNED AERIAL VEHICLE

LIU BO, FENG Kun-cheng, ZHANG En-yang, LU Zhen-yu

2015, 0(12): 5-11.

Asbtract ( 21 )

PDF (3769KB) ( 70 )

References | Related Articles | Metrics

Unmanned Aerial Vehicle has been one of the important members in the aviation industry. For lightening the weight of UAV structures in the preliminary design phase, composite material is used. Composite material has been widely used in UAV structures because of various of excellent performances, such as strength and stiffness ratio, shakeproof property as well as the performances in the process of manufacturing. Meanwhile, composite laminate has excellent designable property in the process of manufacturing, so it is widely used among all the types of composite materials. In this paper, the wing structure of a certain electromagnetic-launch unmanned aerial vehicle is selected as the research objective, and the finite element model of a composite wing structure is created. Then, the mass of the structure is chosen as the objective function, the displacement of wingtip and the failure index are chosen as constraints, and the composite wing structure is optimized by using the engineer software. The results should meet the demand of strength and stiffness during the optimization. The final optimization results show that the ratio and thickness of plies of the composite material has been redesigned. Compared with the previous designing scheme, the weight of wing structure is obviously reduced after the free-sizing optimization, which could achieve the objective of optimization.

STRUCTURE DESIGN AND FINITE ELEMENT ANALYSIS OF FILAMENT WINDING VEHICLE CNG CYLINDER

YUAN Shi-hai,LI Yan-hu,ZU Lei,ZHANG Gui-ming

2015, 0(12): 12-17.

Asbtract ( 24 )

PDF (1942KB) ( 46 )

References | Related Articles | Metrics

In this paper, we analyze the influence of the ellipsoid ratio of the cylinder head on the strength and stability of cylinders according to the film theory. Based on the grid theory, combined with the cylinder volume, the use of space and the actual production process and other constraints, we determine the geometry of the cylinder liner, fiber layer thickness of filament winding and winding angle. Finally, we analyze the strength and stability of the cylinder under various conditions by using the APDL. The results show that the strength and stability of 70L fiber wound vehicle CNG cylinder meet the basic requirements of fully wrapped aluminum lined carbon fiber reinforced composite cylinders.

EXPERIMENTAL RESEARCH ON FATIGUE LIFE OF BONDED COMPOSITE REPAIRS TO DAMAGED METALLIC STRUCTURE UNDER COMPOUND ENVIRONMENT

MU Zhi-tao,NIU Yong,LI Xu-dong,ZHOU Li-jian

2015, 0(12): 18-22.

Asbtract ( 31 )

PDF (1346KB) ( 50 )

References | Related Articles | Metrics

Bonded composite repairs have been successfully applied to damaged aircraft structure. The repaired structure is still influenced by compound environment factors during service life of the aircraft. In order to evaluate the influence of environment factors to repair structure, carbon composite patches are double adhesively bonded to center-cracked LY12-CZ plate. The rationality of this repair method was evaluated by experiment, and the fatigue life under compound environment factors was examined by t-test method.

STUDY ON BIAXIAL TENSION OF CRACKED STEEL PLATES REINFORCED BY CFRP PLATES

WU Jian,ZHANG Tong-tong,LI Hong-yun,WANG Wei-bo

2015, 0(12): 23-27.

Asbtract ( 19 )

PDF (1977KB) ( 42 )

References | Related Articles | Metrics

The failure process of steel plates under biaxial tension is simulated by virtual fracture closure method. The reinforced plan is determined by reducing the stress intensity factor of crack. Load-displacement curves of the reinforced specimen and unreinforced specimen under biaxial tension are compared by FEM. Finally, the reinforced plan and simulation method are verified by experimental results. The results show virtual fracture closure method is very effective to simulate the developing progress of crack under biaxial tension. Bearing capacities of original steel structure can be basically recovered by using CFRP. The biaxial steel plates reinforced by CFRP is obviously increased to an extent. This method can be used to reinforce steel with composite crack.

A TRANSFER FUNCTION METHOD FOR NATURAL FREQUENCIES OF A WIND TURBINE BLADE

LU Bin, HUANG Zheng-ming

2015, 0(12): 28-34.

Asbtract ( 42 )

PDF (1157KB) ( 45 )

References | Related Articles | Metrics

A wind turbine blade is considered as a cantilever beam with variable sections, which can be divided to arbitrary segments. Each satisfies the governing differential equations of biaxial bending coupled with torsional variations. The material properties involved can be anisotropic. Solutions to them are represented as functions of 10 free degrees at both end nodes. Nodal displacements of the same cross-section from two adjacent segments are connected by the continuity conditions, resulting in a transfer function correlating the nodal freedoms at one cross-section with those at any other. Finally, a group of homogeneous equations that contain only ten unknown variables is established by applying the boundary conditions at the fixed and the free tip ends of the blade. A nontrivial solution condition results in the frequency equation to be solved. Compared with finite element and other numerical methods, this transfer function method has several advantages such as fewer variable, easier to implement into a computer program, more quickly to obtain a solution and higher accuracy achievable with the same cost in time and computer sources. The method is then applied to evaluate frequencies of a large blade with optimized laminate structure. The result shows that not only the weight of the blade after optimization can be significantly reduced, but also its stiffness and frequency characteristics can meet the operating requirements.

CONSIDERING THE PRESSURE NUMERICAL SIMULATION ANALYSIS OF THE PROCESS OF TEMPERATURE RISE ON THE SURFACE OF THE CORE

XU Jia-zhong, CUI Yu, GAO Liang-chao, QIAO Ming

2015, 0(12): 35-40.

Asbtract ( 33 )

PDF (2490KB) ( 52 )

References | Related Articles | Metrics

The curing process of mold that heats the composite by the mandrel inside the pipe with steam was studied in this paper. The principle of the process is introduced.The heat transfer model of the mandrel and the kinetic model of the steam flow inside the mandrel are established, Based on the standard k～ε turbulence model and the vapor-liquid two phase transition model, and the heating process under different pressures mandrel, the flow and heat transfer of steam inside the mandrel are simulated by using the software Fluent. According to the simulation results of the mandrel surface temperature distribution and change course, we analyzed the relationship between the vapor pressure of the flow field,temperature and other physical quantities. The research of thermal winding provides efficient method to realize the hot winding process,and provides theoretical foundation for the control parameter of the steam.

EFFECTS OF FIBER WAVINESS ON THE STIFFNESS OF COMPOSITE LAMINATES

WU Wei-qing, ZHU Jun, WANG Ji-hui, SHU Ming-jie

2015, 0(12): 41-47.

Asbtract ( 29 )

PDF (3707KB) ( 46 )

References | Related Articles | Metrics

The effects of uniform waviness on the stiffness of composite laminates have been investigated numerically and experimentally. The VARI process is employed to manufacture the specimens with fiber waviness,and the compression test is conducted to obtain the major Young's modulus and Poisson's ratio. Based on the finite element analysis software ANSYS, the laminates with fiber waviness is simulated and the stiffness is predicted for different fiber volume contents and waviness ratios. The results show that the fiber waviness has significant influence on the stiffness of composite laminates. Especially the E_x has a great decrease. The shear failure is prone to initiate at the position of the maximum fiber off-axis angle for most specimens. Furthermore,with the increase of waviness ratio, the fiber volume content has little influence on the variation trend of stiffness. The predictions agree well with the experimental data.

STUDIES ON DUCTILITY RETROFITTING DESIGN METHOD FOR RC BRIDGE PIERS WITH FIBER REINFORCED POLYMER COMPOSITE MATERIAL

DONG Zhen-hua, WANG Ke-hai, DIAO Bo

2015, 0(12): 48-52.

Asbtract ( 37 )

PDF (1148KB) ( 43 )

References | Related Articles | Metrics

In the present retrofit code for the bridge, the calculation method for FRP jacketing ratio is only presented for RC bridge piers and lack of the complete ductility retrofitting design method. So, the behavior and rational seismic retrofitting plans for FRP-confined RC bridge piers has uncertainty. In order to quickly determine the economical and rational seismic retrofitting plans for reinforced concrete (RC) columns with fiber reinforced polymer (FRP) composite material, a new ductility retrofitting design method was proposed based on the target displacement ductility coefficient. In the proposed ductility retrofitting method, the relationships of macro mechanical properties of FRP strengthened bridge piers, such as displacement and ductility, was built with materials performance parameters of the ultimate compressive strain of FRP-confined concrete, the thickness of FRP jacketing, the effective ultimate tension stress and strain of FRP sheets. The proposed retrofitting design method was further used to estimate the behaviors of FRP confined RC bridge piers with rectangular and circle section, and the finite numerical simulation was applied. Among numerical analysis for the RC bridge piers, two calculation models of the ultimate compressive strain for FRP-confined concrete were selected, in which the Seible's ultimate compressive strain model can consider the complex confinement effect provided by stirrup and FRP jacketing. Based on Mander's tie reinforcements confined concrete model, the behavior of FRP retrofitted specimens was obtained, and it was compared with experimental results. The comparison results show that the proposed ductility retrofitting method can correctly estimate FRP jacketing ratio, FRP sheets thickness and the behaviors of specimens. Furthermore, the Seible's ultimate compressive strain model is verified to be applicable. The proposed ductility retrofitting design method is simple. However, it is only applicable to estimate the performance of FRP confined RC bridge piers with axial compressive ratio less than 0.2 at bending failure mode.

STUDY ON CURING REACTION OF EPOXY RESIN WITH p-TOLYBIGUANIDE

HE Zi-qiang, ZHANG Hui-ling

2015, 0(12): 53-59.

Asbtract ( 24 )

PDF (1166KB) ( 48 )

References | Related Articles | Metrics

The nonisothermal and isothermal curing processes of epoxy resin with p-Tolybiguanide were investigated using isoconversional methods and model-fitting methods based on differential scanning calorimetry (DSC). The kinetic mechanism function and kinetic parameters of curing reaction are determined using the most probability mechanism function method developed by Malek. The result show that the values predicted by advanced autocatalytic model with consideration of diffusion-controlled mechanisms tended to match the isothermal curing experimental values. Moreover, curing procedures and mechanism of different temperature programs and different curing degree were discussed on the base of the activation energies varying with curing degree and the comparison of values calculated by autocatalytic models and experimental values. Furthermore, the kinetic research provides theoretical basis for the optimization of the curing process.

SYNTHESIS AND CURING KINETICS OF BORON AND CARDANOL MODIFIED PHENOLIC RESIN

SHI Xiao-min, XIA Tao, LIU Yang

2015, 0(12): 60-64.

Asbtract ( 40 )

PDF (1190KB) ( 47 )

References | Related Articles | Metrics

Aimed at the defects of phenolic resin(PF), boron and cardanol modified phenolic resin of good heat resistance and toughness were prepared. The influences of boric acid dosage and cardanol dosage on modified phenolic resin were studied. FT-IR results show that the boric acid was reacted with the hydroxyl groups in PF to generate the new cross bond. TG results show that the addition of boron to PF obviously improved its heat resistance. The curing behavior of modified phenolic resin was analyzed at different heating rates by DSC. A curing kinetics model was established for modified phenolic resin by Ozawa equation and Crane equation. The curing process parameters were determined.

FLOW OPTIMIZATION AND EXPERIMENT FOR A TYPICAL STRUCTURE COMPOSITE PARTS DURING VARTM PROCESS

ZOU Ru-rong, LIU He-sheng, LAI Jia-mei, YU Song-biao

2015, 0(12): 65-72.

Asbtract ( 33 )

PDF (5599KB) ( 43 )

References | Related Articles | Metrics

Six kinds of commonly injection molding scheme for a typical structure composite shell parts with VARTM process was simulated by the software of the RTM-Worx at first in this paper. The best suitable linear injection scheme was determined by the simulation results. Then, by means of optimizing the linear injection runner length and the location of double linear injection, we can get the best optimization injection method and compare it with the actual VARTM filling process. The results show that the simulation by RTM-Worx has a good agreement with the experimental result. It shows that the establishment of the model is quite reasonable and reliable. We can also get the following conclusions: although lengthening injection runner can reduce the filling time by increasing instantaneous resin flow volume, too long runner can cause the resin which flow to the edge back flow to center. It can easily form bubbles and dry spot defects which affect the quality of the product. We can choose multiple linear injection for a larger width product and when using n-multiple linear injection, the injection runner is suggested to set up along the length direction of product and be located in its width direction i2n( i=1,3,5,…,2n-1). It has an important guiding significance for choosing a reasonable injection scheme in the actual production.

STUDY ON THE CHANGE OF THE UNIDIRECTIONAL COMPOSITE CURED PLY THICKNESS OF WIND TURBINE BLADES

HOU Bo, JIA Zhi-yuan, ZENG Shuai, LI Wei

2015, 0(12): 73-78.

Asbtract ( 41 )

PDF (3796KB) ( 50 )

References | Related Articles | Metrics

It is normal to use UD warp knitted fabric for the spar cap of the wind turbine blade through the vacuum infusion process. Due to the characteristics of vacuum infusion process and parameters of the fabric, it is hard to control the thickness of the composite panel. To investigate the variation of the thickness of the composite,and to analyze the influence of the parameters of the process and the fabrics on the thickness of the composites, 4 popular types of UD warp knitted fabrics were studied. With different vacuum infusion process, it is found that the parameters of the process don't have distinct effect on the thickness of the composite panel. However, the layers of the fabric affect the thickness a lot. And it has great difference among the parameters of different fabrics. Thus it is concluded that the parameters of the fabrics affect the thickness of the composite. This study provides data support to design the blade and give some useful suggestion to the production of the UD warp knitted fabrics.

GALLOPING AND TORSION DAMAGE PERFORMANCE FOR COMPOSITE CORE OF NOVEL ELECTRIC CONDUCTOR

LAN Feng-tao, CHEN Xin, WANG Ying-nan, YANG Chang-long

2015, 0(12): 79-81.

Asbtract ( 26 )

PDF (2790KB) ( 45 )

References | Related Articles | Metrics

As the main load-bearing parts of composite core conductor, the composite cores have been under long-term galloping and torsion effects during their service life. Considering the low toughness of composite materials, the safety and reliability of these cores under the influences of galloping and torsion become a key problem concerned by power grid operators. In this study, the mechanical properties of composite cores were evaluated after different numbers of galloping, which provided an objective assessment of the safety and applicability of the composite cores. From the results, the carbon fiber wires show complete broken strands after 900,000 times of galloping under 25% RTS tensile load. In comparison, carbon fiber composite cores was able to retain a tensile strength of over 90% RTS after a continuous galloping for 1,000,000 times, without any damage. Their mechanical strength was still higher than 90% RTS after 1,000,000 times of galloping under the tensile load of 25% RTS. All results indicated that the carbon fiber composite core can meet the safety requirement for long-term uses in high voltage wires.

VIMP RESEARCH ON THE ROOT OF THE LARGE SIZE OFFSHORE WIND TURBINE BLADE

ZHAO Li-yan,SUN Yu-quan, YAN Chen, LI Hui

2015, 0(12): 82-86.

Asbtract ( 29 )

PDF (3206KB) ( 49 )

References | Related Articles | Metrics

For the past few years, vacuum infusion molding process is widely used in offshore blade which is thicker and large-size. Aiming at resolving the infusion problems which applying on 6MW-offshore blade, we design the flow medium placement process, set the process parameters, optimize the previous infusion process. Finally, the effect of resin infiltration was improved and the resin content was controlled.

STUDY OF THE TENSILE FAILURE MODES OF UNIDIRECTIONAL CARBON FIBER/GLASS FIBER INNER PLY-INTER PLY HYBRID COMPOSITES

MA Teng, LI Wei

2015, 0(12): 87-93.

Asbtract ( 28 )

PDF (5711KB) ( 44 )

References | Related Articles | Metrics

This article uses carbon fiber/glass fiber inner ply unidirectional fabrics to design specimens of 4 types of various hybrid structures and 5 types of different hybrid ratios. The influence of hybrid structure and mixed ratio on the 0° tensile failure mode of C/G inner ply hybrid composites was investigated. The failure modes are given respectively in the paper. The results show that: ①The tensile failure modes of specimens with the same mixed ratio but different hybrid structures can be summed up in three categories. When we design the specimens with the same mixed ratio but different hybrid structure, the structure like should be avoided; ②The tensile failure stress and strain have the opposite trend. The tensile failure modes of specimens with the same hybrid structure but different mixed ratios can be summed up in two categories. In this case, we can get better tensile property with the mixed ratios of C/G to be around 3:2.

AIR-COUPLED ULTRASONIC TESTING FOR COMPOSITE MATERIALS

ZHANG Bin, HE Mei-hong, YANG Tao

2015, 0(12): 94-98.

Asbtract ( 22 )

PDF (2459KB) ( 44 )

References | Related Articles | Metrics

Air-coupled ultrasonic testing has wide-developing prospects for the characteristics of non-contact, non-invasive, non-damage, which can be better used in ultrasonic testing situations where traditional ultrasonic testing is difficult to adapt. This paper gives the systemic overview on the air-coupling ultrasonic testing technology research status and introduces the current research progess of piezoelectric type transducer and the current successfully applied signal processing technology. We also briefly analyzes and introduces the hot research area and progress of the air-couple ultrasonic testing. Finally, We discuss the development trend of air-coupled ultrasonic testing and application prospect.

RESEARCH AND APPLICATION PROGRESS OF CARBON FIBER COMPOSITE HYDROGEN STORAGE CYLINDER

YANG Wen-gang, LI Wen-bin, LIN Song, JIA Xiao-long

2015, 0(12): 99-104.

Asbtract ( 29 )

PDF (1357KB) ( 49 )

References | Related Articles | Metrics

Hydrogen is the most promising new energy in the 21st century, which shows advantages of high energy density, excellent environmental friendliness and good renewability, etc. However, the slow development of storage technology for hydrogen has severely limited its large-scale application. With the advanced performance of light weight, high obdurability and good fatigue resistance, the carbon fiber filament winding composite cylinder has showed the great potential in hydrogen storage. This paper reviews the current progress of high stress gas storage technology for hydrogen in the world. Based on the ongoing application of domestic carbon fiber composites, the newest progress in preparing technology, standard specification and processing equipment of carbon fiber composite hydrogen cylinder is fully analyzed. The future prospect for the application of carbon fiber composite hydrogen cylinder is expected.

PROGRESS IN NUMERICAL SIMULATION OF MOLD FILLING IN RTM

QI Wen,LIU Dong,ZHAO Jun-li,XU Zi-hang

2015, 0(12): 105-109.

Asbtract ( 21 )

PDF (1048KB) ( 49 )

References | Related Articles | Metrics

This paper introduces flow patterns, flow models and numerical simulation methods of mold filling in RTM. We also discuss necessary hypothesis, boundary conditions and numerical computation methods in different simulation cases. Furthermore, RTM simulation software is presented and further work is pointed out.

Table of Content