COMPOSITES SCIENCE AND ENGINEERING

Nonlinear Lamb wave detection of damage propagation of composites under different tensile loads

SONG Zheng-shuo, TIE Ying, ZHANG Cheng

2022, 0(4): 5-10. DOI: 10.19936/j.cnki.2096-8000.20220428.001

Asbtract ( 166 )

PDF (8906KB) ( 120 )

References | Related Articles | Metrics

In order to study the non-linear ultrasonic detection and evaluation method of tensile damage extension of composite materials, based on the numerical value and experimental method of nonlinear Lamb wave, the tensile damage extension of orthotropic carbon fiber reinforced epoxy resin composite material was tested. For anisotropic composite laminates, a nonlinear numerical multi-load step model considering the damage evolution of the material under tensile load and the propagation of Lamb waves is established. The Hashin criterion is used to predict the damage evolution of the laminated plate under tension. The propagation of Lamb in the plate is simulated by de-oscillation damping and displacement loads. The time displacement signal is received and the relative nonlinear coefficient is extracted and calculated to evaluate the damage expansion degree of the material. The tensile mechanical properties of the composite material specimens were tested by the tensile testing machine, and the damaged specimens were detected by the RAM-5000 SNAP nonlinear detection system, and the high-order harmonic signals were extracted, and the numerical calculation results were verified. The results show that the propagation of Lamb waves in the plate will produce obvious nonlinear response after the material is tensile damaged. Before macroscopic fracture occurs, the tensile displacement and damage degree are positively correlated with the nonlinear coefficient. The results of experiment and simulation is in good consistency. Therefore, the nonlinear coefficient can be used as an evaluation index for tensile damage detection.

Natural frequency of FGM circular plate based on physical neutral surface and Levinson′s third order theory

CHEN Yu, LI Qing-lu, ZHANG Jing-hua

2022, 0(4): 11-17. DOI: 10.19936/j.cnki.2096-8000.20220428.002

Asbtract ( 116 )

PDF (1165KB) ( 174 )

References | Related Articles | Metrics

Based on Levinson′s third-order shear theory, the free vibration of functionally graded material (FGM) circular plates was studied by differential quadrature method. Assuming that the properties of FGM were only along the thickness direction of the plate, the governing differential equation of the problem was derived. Then, by using the concept of physical midplane, the tension bending coupling effect in the constitutive equation caused by the transverse non-uniformity of the material was eliminated, simplifying the original complex governing equation. The dimensionless frequency of transverse vibration of FGM circular plate was obtained by DQM, and compared with the natural frequency of FGM circular plate under the first-order shear theory. The effectiveness of DQM method in solving FGM circular plates based on third-order shear theory was illustrated by an example, which enriches the research results of Levinson′s third-order shear theory. The numerical results show that the solution of the first-order shear theory is slightly higher than that of Levinson′s third-order shear theory for clamped FGM circular plates, but the opposite is true for simply supported FGM circular plates. On this basis, the effects of various factors such as material gradient index on the natural frequencies of FGM composite circular plates are discussed in detail.

Prediction of the mechanical properties of graphene/epoxy resin nanocomposites based on flexible node beam element and layered method

PENG Chang-wei, HUANG Jun, WU Yu, YE Tai-zhi, HUANG Li-xin

2022, 0(4): 18-26. DOI: 10.19936/j.cnki.2096-8000.20220428.003

Asbtract ( 122 )

PDF (2607KB) ( 135 )

References | Related Articles | Metrics

The mechanical properties of graphene/epoxy resin nanocomposites were analyzed and predicted by establishing the finite element model of sandwich representative volume element. In the finite element modeling, the flexible node beam element was used to simulate the graphene structure, the layered method was used to deal with the interfacial layer with gradient material properties, and the 8-node hexahedral solid element was used to discretize the epoxy resin matrix. According to the Young′s modulus of graphene, the flexibility coefficient of flexible node beam element was determined by comparing with the experimental value and simulation value given in the literature, and then the Young′s modulus E_cx of graphene/epoxy resin nanocomposites was predicted without considering the interfacial layer. The prediction results are in good agreement with the calculation results of the role of mixture (ROM) formula, which verifies the correctness and reliability of the proposed method. The convergence of the layered method was discussed by numerical examples of Young′s modulus E_cx and shear modulus G_xy. The results show that when the interfacial layer is divided into 8 layers, a good convergence result has been obtained. When considering the interfacial layer, the predicted Young′s modulus E_cx is larger than that of ROM, and the calculated value is closer to the experimental value than that of ROM in the case of exponential function distribution of material properties of interfacial layer, which verifies the necessity of considering interfacial layer.

Fatigue finite element analysis method research of wind turbine extending bladed structural adhesive

YUAN Wei-hua, ZHANG Ju-fang, CHEN Wen-guang, LI Jun-xiang

2022, 0(4): 27-31. DOI: 10.19936/j.cnki.2096-8000.20220428.004

Asbtract ( 167 )

PDF (6165KB) ( 117 )

References | Related Articles | Metrics

The extending blades of wind turbine is the most effective way to improve the annual power generation in low speed wind. At present, the connection of the blades and extension is generally achieved by structural adhesive. The fatigue performance determines the stability of extending blades, and an efficient and accurate analysis method is especially important for engineering application. To this end, the shell element, the solid element, the shell & solid element model are built by the finite element method. The results show that the strain equivalent shear stress method is conservative, and the shell & solid element model is a relatively efficient and exact method for analyzing wind turbine blades extension structural adhesive fatigue strength. Based on this method, the fatigue strength of wind turbine blades extension structural adhesive is satisfied with GL 2010.

Structural design and analysis of composite solar powered unmanned aerial vehicle

LIU Feng, YAN Qing-yun, WANG Zhuo-yu

2022, 0(4): 32-39. DOI: 10.19936/j.cnki.2096-8000.20220428.005

Asbtract ( 294 )

PDF (24155KB) ( 288 )

References | Related Articles | Metrics

A composite solar powered UAV with a conventional aerodynamic layout of three fuselage structures and a maximum take-off weight of 40 kg was designed. Based on the structure design and aerodynamic performance analysis, the finite element structure model of the UAV is established. The strength, stiffness and stability of the wing, the horizontal stabilizer, the vertical stabilizer and the solar cell module of the UAV are checked based on the finite element analysis. The maximum stress criterion is applied for strength check. It is shown that the strength margin of the outer wing section, inner wing section, horizontal stabilizer, central vertical stabilizer and the outer vertical stabilizer of the UAV are 2.4, 0.48, 2.13, 1.84 and 1.94, respectively, with the load factor of 2.5 and the safety factor of 2.0. In order to improve the stability of the upper skin of the wing, the structure weight of the optimal lay-up scheme is about 12.3% heavier than that of the initial lay-up design scheme. Flexible solar cell panel is bonded on the upper skin of the wing, and its strength check is carried out.

Study on properties of rosin based epoxy resin carbon fiber reinforced composites cured at high temperature

LIU Yan-feng, LIU Qing-man, CHEN Xu

2022, 0(4): 40-44. DOI: 10.19936/j.cnki.2096-8000.20220428.006

Asbtract ( 171 )

PDF (1847KB) ( 140 )

References | Related Articles | Metrics

In response to the environmental goal of carbon peaking and carbon neutralization in China, biomass glycidyl esters maleopimaric acid epoxy resin, petroleum based bisphenol A epoxy resin E-54 and curing agent DDS were compounded to study the thermal and mechanical properties of high temperature cured rosin based epoxy resin and its composites. The results show that the cured epoxy resin has high mechanical properties and thermogravimetric temperature. The glass transition temperature of the cured DGE resin is 207 ℃, the tensile strength is 87.3 MPa, the tensile modulus is 3.52 GPa, the elongation at break is 4.38%, and the 5% thermal decomposition temperature is about 297 ℃. The dry glass transition temperature of composite laminates prepared with DGE/CCF300 prepreg is 207 ℃, and the wet glass transition temperature is 170 ℃. The dry and wet mechanical properties are equivalent to those of 5222/HT3 composites which have been applied to aircraft structures.

Study on the properties and process of fiber reinforced alumina ceramic composites

WANG De-pan, LIANG Sen, ZHOU Yue-song, LIU Long

2022, 0(4): 45-49. DOI: 10.19936/j.cnki.2096-8000.20220428.007

Asbtract ( 307 )

PDF (4258KB) ( 199 )

References | Related Articles | Metrics

In this paper, short cut alumina fibers were dispersed uniformly in alumina ceramic slurry by ball milling, and then sprayed and granulated by dry spray molding. The influence of the amount of alumina fiber on the properties and microstructure of alumina fiber/alumina ceramic composite was investigated, and the influence of the particle size of granulating powder, the pressure in the dry pressing process and the holding time on the properties of the composite was investigated. The results show that when the fiber content is 10%, the bending strength and hardness of the material reach the maximum. Compared with the fiber content of 0%, the bending strength increases by 17.15%, the fracture toughness increases by 30.33%, but the density of the material reaches the maximum when the fiber content is 5%. In the process of dry pressing, the greater the molding pressure is, the greater the bending strength of the material is. When the holding time is 8 min, the material performance is the best. Extending the holding time does not improve the material performance.

Direct calculation of structural strength of GRP catamaran

ZHEN Chun-bo, ZHOU Qing-wan, WANG Xiao-peng, YU Peng-yao, ZHANG Xiu-yan

2022, 0(4): 50-55. DOI: 10.19936/j.cnki.2096-8000.20220428.008

Asbtract ( 212 )

PDF (6051KB) ( 193 )

References | Related Articles | Metrics

Glass-fiber Reinforced Composite(GRC) has the excellent quality of light weight and high strength, which is especially suitable for the construction of small ships with high speed such as high-speed yachts. However, the research on the ship strength analysis of GRC is relatively less, and the relevant specifications are not enough. Firstly, the modeling method of GRC with sandwich structure is presented. Then, taking a GRP catamaran as an example, based on the direct strength calculation theory of finite element method and referring to the relevant requirements of CCS, the direct strength calculation method of GRP catamaran is given. The results show that the GRC simulation method can effectively simulate the structural form of the catamaran, and the structural strength meets the requirements of the code, and the transverse bending condition is prone to structural failure. The conclusions drawn in this paper have reference significance for the development and design of GRP ship with sandwich structure.

Study of tensile damage characteristics of carbon fiber composite laminates containing holes under low temperature conditions

GUO Feng, WANG Zhe-feng, WANG Gong-dong, FENG Lu, LI Hua, MA Jia-he, LIU Xi-liang

2022, 0(4): 56-61. DOI: 10.19936/j.cnki.2096-8000.20220428.009

Asbtract ( 155 )

PDF (10087KB) ( 112 )

References | Related Articles | Metrics

Based on the damage mechanism study of carbon fiber composites, this article established a numerical simulation model and predicted the initial occurrence of damage and ultimate loads. Under dry state at room temperature (23±3) ℃ and dry state at low temperature (-60±3) ℃ , tensile damage experiments were conducted on three carbon fiber composite (CFRP) laminates with different hole shapes and diameters, and their tensile properties and damage mechanisms were analyzed. The result shows that the tensile strength of the laminate with circular holes is the highest in both environments, the tensile strength of the laminate with holes in low temperature environment is stronger than that in room temperature environment. Measurements of strains at different locations in the laminate showed that the maximum strain in the tensile test occurred near the tangent point of the hole tangent line parallel to the load, and the minimum strain occurred near the tangent point of the hole tangent line perpendicular to the load.

Influence of nano-SiO₂ on mechanical properties of basalt fiber/concrete after heating at high temperatures

ZHANG Zhen-lei

2022, 0(4): 62-67. DOI: 10.19936/j.cnki.2096-8000.20220428.010

Asbtract ( 132 )

PDF (2268KB) ( 84 )

References | Related Articles | Metrics

The high temperature mechanical properties of the normal concrete(NC), the basalt fiber reinforced concrete(BFRC)and nano-SiO₂ basalt fiber reinforced concrete(NBFRC)were investigated, such as the compressive strength, splitting tensile strength, flexural strength, and so on. The results show that the compressive strength, splitting tensile strength and flexural strength of NBFRC are higher than those of BFRC and NC at each temperature. At 400 ℃, the compressive strength of the three kinds of concrete reaches the maximum, and then decreases gradually, and the splitting tensile strength and flexural strength decrease with the increase of temperature. Compared with NC, the compressive strength, splitting tensile strength, flexural strength of NBFRC increase by 13.2%, 22.9%, 13.2%, respectively, at room temperature, and by 12.4%, 23.3%, 21.9%, respectively, at 400 ℃. At 800 ℃, the strength of three kinds of concrete reaches the lowest, and the compressive strength, splitting tensile strength and flexural strength of the NBFRC are only 47.8%, 29.1% and 35.5% at room temperature. NC, BFRC and NBFRC relative strength prediction model is accurate.

Experimental study on low damage hole making of SiCp/Al composites

WANG Zi-chao, LIU Chang, WANG Kai, GAO Lei

2022, 0(4): 68-72. DOI: 10.19936/j.cnki.2096-8000.20220428.011

Asbtract ( 145 )

PDF (8073KB) ( 70 )

References | Related Articles | Metrics

SiC particle reinforced aluminum matrix (SiCp/Al) composites are important lightweight metal matrix composites widely used in aerospace and precision instrument fields. However, the existence of SiC hard particles can easily lead to the severe wear of the bit in the process of drilling, and then deteriorate the surface quality of machining. In this paper, the machining characteristics of traditional and ultrasonic vibration assisted drilling of SiCp/Al composites under dry and wet cutting conditions, including burr damage at hole outlet, surface roughness of hole wall and tool wear, are studied, and a set of low damage drilling technology is established. The experimental results show that ultrasonic vibration assisted drilling can effectively reduce the drilling force in the cutting process. Compared with traditional drilling, the average cutting force is reduced by 8.32%. The outlet burr height can be reduced simply and effectively by installing the bottom plate of the workpiece. Both the introduction of cutting fluid and ultrasonic vibration assisted machining can improve the accuracy of hole machining. Compared with traditional dry cutting, the hole wall roughness under ultrasonic vibration assisted drilling is reduced by 27.3%, and the hole wall surface roughness can be reduced by 12.3% with the introduction of cutting fluid. For the drilling of the SiCp/Al composites, the tool wear mechanism can be divided into two-body particle wear, three-body rolling wear and adhesive wear. Ultrasonic vibration assisted machining can effectively reduce the tool wear and improve the tool life. The research in this paper can provide theoretical guidance for low damage hole making of SiCp/Al composites.

The investigation of damage evolution behaviour on adhesive interface of composites using nano-adhesive

JI Xiao-long, ZHOU Wei, DU Yong-gang, LIU Jia, MA Lian-hua

2022, 0(4): 73-80. DOI: 10.19936/j.cnki.2096-8000.20220428.012

Asbtract ( 111 )

PDF (11652KB) ( 79 )

References | Related Articles | Metrics

Adhesive plays an important role on the repair efficiency and durability in the field of composites patch repair. Thus, it is important to carry out the optimization studies of adhesive. In this study, aiming to improve the mechanical strength and flexibility of epoxy resin adhesive, 0.1wt% cellulose nanofibers were added into epoxy resin to make nano-adhesive, so as to increase its repair efficiency and durability. Mechanical behaviors and deformation damages of different repair configurations under three-point bending loads were investigated by a combination of acoustic emission and digital image correlation technologies. Failure mechanisms were deeply discussed through the analysis of characteristic signals, cluster results as well as the measurement of global and local strain/displacement fields. According to the cluster analysis results and acoustic emission response of interior damage, the repair performance could be assessed and the main damage modes could be obtained. The deformation fields on the adhesive interface of different repaired specimens obtained from digital image correlation method could help to monitor the damage initiation and extension within adhesive layer. The experiment results showed that nano-adhesive had better bonding effect and showed higher energy absorption and load transfer capacity. The failure load and maximum displacement of repaired specimens were increased by 3.1% and 6.1%, respectively, compared with epoxy resin adhesive. The amplitude, frequency, relative energy and cumulative hits of acoustic emission signals of different repaired composites could successfully reflect the damage changes from micro-scale to macro-scale. The real-time displacement fields and strain fields obtained from digital image correlation technology provided the information of damage accumulation on the adhesive interface. The experimental results of mechanics were in agreement with the analysis results of acoustic emission and digital image correlation technologies. The damage evolution behaviors on the adhesive interface were realized through establishing the correspondence of acoustic emission characteristic response and internal deformation damage.

Study on laser treatment of quartz fiber/cyanate ester resin composite bonding surfaces

XIONG Hua-kun, YUAN Guo-qing, YANG Jia-yong, QIU Xue-shi

2022, 0(4): 81-86. DOI: 10.19936/j.cnki.2096-8000.20220428.013

Asbtract ( 124 )

PDF (10473KB) ( 85 )

References | Related Articles | Metrics

Adhesive bonding is one of the main methods of connecting composite structures, and the surface treatment has a significant impact on the bonding performance. In this paper, ultraviolet laser is used to treat the bonding surface of cyanate ester resin-based composites, and the influence of laser parameters on surface morphology and bonding performance is studied. The numerical simulation results show that the laser heat-affected zone is small, and according to the temperature of fiber and resin and their respective vaporization temperatures, it can be seen that laser treatment is mainly surface resin ablation. Through the observation of the surface state after the treatment, it is found that when laser ablates the cyanate ester resin, carbon black is formed due to the incomplete decomposition of the resin. The results of the single lap tensile shear test show that laser treatment with appropriate laser parameters can increase the bonding strength, and the dispersion is relatively small. But laser treatment with inappropriate laser parameters will reduce the bonding strength. The maximum shear strength after laser treatment is 22.575 MPa, which is 27.1% higher than that of the untreated group. And the dispersion coefficient is 2.7%.

Application of PMI foam on microstrip antenna array

LIU Xiu-li

2022, 0(4): 87-91. DOI: 10.19936/j.cnki.2096-8000.20220428.014

Asbtract ( 167 )

PDF (4851KB) ( 355 )

References | Related Articles | Metrics

In order to meet the requirement of a millimeter wave microstrip antenna with low-loss transmission, the fabrication of microstrip arry with PMI foam sandwich structure was investigated. PMI foam with rigid sealing structure is selected as the interlayer between the two layers of microstrip on the antenna array, thermoset conductive semi-solidified sheet was used as the cementing materia, and the PMI foam sandwich structure was cemented by vacuum hot-pressing process of PCB. The technology of PMI foam material selection, PMI foam fabrication and bonding of sandwich structure are discussed. According to the proposed technological approach, the sample is trial-produced, and the index test and tensile test are carried out. The test results show that the PMI sandwich structure has excellent performance and good bonding strength,which can satisfy the design of microstrip antenna array.

Research on advanced pultrusion technology for composite payload supported cabin stringer

JU Bo-wen, ZHANG Qi, ZHUANG Chun, WAN Li, HOU Jin-sen, HAO Xu-feng, WANG Xiao-lei, TIAN Jie

2022, 0(4): 92-97. DOI: 10.19936/j.cnki.2096-8000.20220428.015

Asbtract ( 136 )

PDF (5705KB) ( 142 )

References | Related Articles | Metrics

In order to improve the forming efficiency and reduce the manufacturing cost of the payload supported cabin stringer product, advanced pultrusion was adopted. Based on the structure characteristics of stringer product, the forming device was designed, the process plan was formulated, the process tests were performed and the product samples were tested. The result show that compared with traditional process, the forming efficiency of the payload supported cabin stringer product was improved significantly by using advanced pultrusion. The product can meet the index requirements, and the pretreatment process can significantly improve the appearance quality.

Automatic creation method of parting line for abnormity part

GE Jia-rong, WANG Zhan-yu, CAI Wan-long, GUAN Guo-ying

2022, 0(4): 98-103. DOI: 10.19936/j.cnki.2096-8000.20220428.016

Asbtract ( 137 )

PDF (9337KB) ( 68 )

References | Related Articles | Metrics

In order to solve the difficult problem of creating parting line for abnormity part, a new method of automatic creating parting line for this kind of part was presented, which is based on maximum profile principle and finite approach. Firstly, some parallel grid curves are created on the surface of this part. Then equal points are created automatically on each grid curve by using VB language programs, and the points on the maximum profile are searched by bubble sort algorithm. Afterward the parting line was created by connecting these points into curves. Finally, mold has been designed according to these curves and the part has been manufactured successfully. The results show that the proposed method is effective and efficient.

Study on impact resistance and toughening modification of phenolic resin and its curing kinetics

XU Guo-juan, JIA Chen-hui, CHEN Jing-ju, TIAN Mou-feng

2022, 0(4): 104-110. DOI: 10.19936/j.cnki.2096-8000.20220428.017

Asbtract ( 262 )

PDF (4274KB) ( 372 )

References | Related Articles | Metrics

Phenolic resin was toughened by polyvinyl butyral (PVB), core-shell rubber, nithile rubber and epoxy resin in this paper. The influence of different toughening agent systems and addition amounts of toughening agents on the toughening effect of phenolic resin was studied by evaluating the impact resistance performance of composite test panels. The curing kinetics of the toughened modified phenolic resin was studied by rheology, DSC testing combined with non-isothermal kinetics. The cross-section morphology of the test plate after impact was observed by SEM, and the toughening mechanism was explained. The results show that the toughness effect of modified phenolic resin modified with PVB as a toughening agent is the most significant, and the addition of PVB will not affect the curing kinetics of the phenolic resin system. When the amount of PVB added is 15%, the impact resistance of the modified phenolic resin composite test board reaches the maximum value of 23.72 J. According to SEM analysis, the PVB added in the toughened modified phenolic resin makes the resin matrix exhibit better ductile fracture when impacted by an external force.

Long-term behavior of FRP prestressed concrete beams-a review

YU Wen, HUANG Yue, HUANG Qian, LIU Xiao-yang, FENG Wei, GUO Rui-peng

2022, 0(4): 111-119. DOI: 10.19936/j.cnki.2096-8000.20220428.018

Asbtract ( 254 )

PDF (1503KB) ( 173 )

References | Related Articles | Metrics

FRP bar composites have been widely used in civil engineering structures because of their light weight, high strength and excellent durability. However, low elastic modulus may lead to applicability problems such as excessive deflection of FRP reinforced concrete beams (RC). Therefore, FRP prestressed structures have received more and more attention in recent years. In this paper, the long-term performance of prestressed concrete beams with FRP bars is reviewed from the material and structure levels, the creep and relaxation properties of FRP bars and their influencing factors are systematically described, and the long-term load-holding test and finite element analysis results of FRP bars are summarized. The time-varying analysis method of beam section based on age adjusted effective modulus method and the calculation formula of long term deflection of prestressed FRP beams are introduced. The results show that the stress relaxation of FRP bars is more serious than that of steel strand wires. Among different FRP bars, CFRP bars have the best anti-relaxation performance. At the same time, the long-term deflection of CFRP prestressed concrete beam is lower than that of steel strand prestressed concrete beam. At the end of this paper, some research suggestions on the shortcomings of the existing FRP bars prestressed concrete beams are put forward.

Organic/inorganic composite materials: mineralization and applications of cellulose and its derivatives

BAI Xue-meng, WANG Lu-yao, ZHENG Ya-hui, XIAO Ying-hong, CHE Jian-fei

2022, 0(4): 120-128. DOI: 10.19936/j.cnki.2096-8000.20220428.019

Asbtract ( 163 )

PDF (3030KB) ( 217 )

References | Related Articles | Metrics

Cellulose and its derivatives composited with hydroxypatite (HA) can create synergistic effects, which can combine the structure, functionality and flexibility of cellulose and the heat resistance, stability and biocompatibility of HA. The commonly used methods for preparing cellulose/HA composite mainly are the biomimetic mineralization and in-situ mineralization, of which the HA synthesized by biomimetic mineralization generally has nanoscale size and morphology, higher surface area and surface roughness, exhibiting more significant biological activity and absorbability. Cellulose can also adjust the crystal orientation and morphology of HA by different crosslinking strategies and chemical modification methods. This review article covers the current knowledge about the cellulose/HA composite materials and summarizes the properties of cellulose and HA as well as the regulation of HA mineralization by cellulose. The research status of cellulose/HA composite materials are highlighted in water treatment adsorbents, drug delivery systems and bone tissue engineering. Finally, the missing of interfacial theory is analyzed and the future research directions are prospected.

Table of Content