COMPOSITES SCIENCE AND ENGINEERING

Reliability and sensitivity analysis of compressive strength after low-speed impact for composite honeycomb sandwich structure

LI Hongnian, SHI Qiangbin, WANG Xuan, ZOU Runwen, ZHANG Feng

2024, 0(2): 5-12. DOI: 10.19936/j.cnki.2096-8000.20240228.001

Asbtract ( 84 )

PDF (5900KB) ( 148 )

References | Related Articles | Metrics

A reliability and sensitivity analysis method of compressive strength of composite honeycomb sandwich structure after low-speed impact is established. The progressive damage failure analysis model of composite honeycomb sandwich structure is established by using ABAQUS finite element analysis software and VUMAT subroutine, and the effectiveness of the model is verified by experiments. On this basis, the material mechanical properties, panel thickness and honeycomb core thickness in the model are parameterized by Python language. The radial basis function neural network agent model is used to replace the progressive damage failure analysis model. The reliability analysis of compressive strength after impact is carried out based on Monte Carlo method. The methods based on variance and failure probability are respectively used to analyze the sensitivity of parameters, and the influence of variation coefficient of parameters on structural reliability is studied. The results show that when the external load is less than 10 000 N, the probability of structural failure is less than 0.000 17, and when the external load reaches 12 700 N, the probability of structural failure reaches 0.9. The mechanical properties of the panel, the thickness of the panel and the thickness of the honeycomb core have a great influence on the compressive strength after impact. The coefficient of variation of compressive strength after impact increases with the increase of the coefficient of variation of parameter.

Numerical study of high-energy low-velocity impact damage on stiffened composite panel

FENG Zhenyu, LI Lingling, ZOU Jun, XIE Jiang, WANG Jizhen, GUO Yazhou

2024, 0(2): 13-19. DOI: 10.19936/j.cnki.2096-8000.20240228.002

Asbtract ( 80 )

PDF (7416KB) ( 84 )

References | Related Articles | Metrics

The high-energy wide-area blunt impact problem is a major threat for the operation safety of composite aircrafts. The Hashin criterion and the bilinear progressive damage model were adopted to simulate the in-plane ply failure, and the cohesive interface elements have been implemented to simulate the delamination. The Ogden hyperelastic material model was used to define the rubber's constitutive behavior. Numerical simulations were carried out to validate the effectiveness of the analysis methods, and then the damage characteristics of stiffened composite panel under high-energy low-velocity rigid and soft impacts were investigated. The impact response and damage process of high-energy low-velocity impact on different locations of the skin by rigid and rubber impactors were analyzed, respectively. The deformation and damage modes of stiffened composite panel during the impact process were compared and studied. The results show that the contact pressure for rigid impacts were larger, which leads to more severe local deformation and damages. The rubber impactor could blunt the impact and reduce the contact pressure, while the peak contact forces were about 23% higher than that of rigid impacts. Damages were most serious under the rigid impact at the stiffeners, in which the damages mainly located at the skin, stiffener webs and flanges, while the damages mainly located at the back of skin and stiffener webs for rubber impact. Compared with the rigid impacts, the impact damages under rubber impacts were less serious and external barely visible.

Synthesis and rheological properties of high heat resistant linear epoxy resin

ZHANG Xiangchang, WANG Jun, CHEN Xi

2024, 0(2): 20-26. DOI: 10.19936/j.cnki.2096-8000.20240228.003

Asbtract ( 111 )

PDF (4344KB) ( 69 )

References | Related Articles | Metrics

A modified binary amine (PDP) was synthesized by the Michael addition reaction of N-phenylmaleimide (N-PMI) with 4,4′-diaminodiphenyl methane (DDM), and the linear epoxy resin was prepared by the reaction with bisphenol A epoxy resin. The chemical structure and properties of PDP were studied by hydrogen magnetic resonance spectroscopy (HNMR), infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The thermal resistance (T_g) and rheological properties of linear epoxy resin were studied by DSC, FTIR and gel permeation chromatography (GPC). The results showed that the viscosity of EP/PDP(1∶1 molar ratio) resin system increased from 0.55 Pa·s to 57 Pa·s with the extension of reaction time, while T_g increased from 55 ℃ to 120 ℃, ant the average molecular weight increased from 4 651 to 25 096. With the decrease of temperature, the viscosity of the system increases from 0.55 Pa·s at 200 ℃ to 60 Pa·s at 140 ℃. The T_g of EP/PDP resin system with different proportions increased with the increase of PDP excess ratio. When EP∶PDP was 0.8∶1, T_g was 121 ℃. At the same reaction time, the viscosity of the system increased with the increase of PDP excess ratio.

Residual strength evaluation of laminates with open hole or crack under tensile load

WANG Houbing, DENG Fanchen, WEI Hongyan, LI Xinxiang, YANG Shengchun

2024, 0(2): 27-34. DOI: 10.19936/j.cnki.2096-8000.20240228.004

Asbtract ( 81 )

PDF (4414KB) ( 60 )

References | Related Articles | Metrics

Experiments on about 200 composite laminates with four typical lay-ups, two kinds of damage, and four damage sizes were conducted to investigate the residual strength of composite laminates with open hole or crack. The research indicates that the residual strength of two composite laminates with open hole and crack are equal with same lay-ups and same widths of laminates when the opening diameter is equal to the crack width. Little cracks and delamination appear earlier at the root of crack during the loading process, the stress is redistributed near the root of crack, the stress concentration reduces. The method based on fiber breakage in damage zone criterion, classical laminate theory and complex variable function theory can be used to predict the residual strength of two composite laminates with open hole, the method can also be used for laminate with crack when the crack is equivalent to an open hole, the calculated results are in good agreement with the experimental results.

Fiber stress distribution analysis based on shear lag theory

SHEN Zhiqiang, WANG Huabi, ZHANG Wenyan

2024, 0(2): 35-39. DOI: 10.19936/j.cnki.2096-8000.20240228.005

Asbtract ( 112 )

PDF (1863KB) ( 47 )

References | Related Articles | Metrics

In exploring the stress between the fiber and the matrix during tensioning and compression, the theoretical mathematical equations for axial and shear forces are derived based on the Cox shear lag model. In the derivation process, the radial force is considered, while the stress-transferring process between the fiber and the matrix needs to be realized through shear stress. Finally, the axial force is solved, and the distribution of the axial force and shear force is plotted and analyzed in detail. It was eventually found that the maximum shear stress was reduced by 5.25% in the presence of radial forces, and the maximum axial force was increased by 3.76%. Also, during the stretching process, the maximum shear stress was found to occur at the ends of the fiber, while the maximum axial force appeared at the center of the fiber.

Preparation of high energy storage density composite dielectrics by BNNS intercalation of PVDF/BaTiO₃

SHAO Dandan, WANG Yao, LEI Bingyu

2024, 0(2): 40-44. DOI: 10.19936/j.cnki.2096-8000.20240228.006

Asbtract ( 70 )

PDF (5725KB) ( 49 )

References | Related Articles | Metrics

Electrostatic capacitors with fast storage and release of electrical energy have been playing an important role in energy field industries such as shipboard inverters, naval aircraft ejection devices, and photovoltaic/wind power generation, enhancing the energy storage density (U_e) of capacitor dielectrics can significantly accelerate the development of this industry. Here, polyvinylidene fluoride (PVDF) was used as the matrix and barium titanate (BaTiO₃) ceramics were introduced to enhance the dielectric constant (ε_r) of the matrix. To mitigate the decrease in breakdown strength (E_b) of the composites due to the introduction of high-ε_r ceramics, boron nitride nanosheets (BNNS) were intercalated with PVDF/BaTiO₃ to prepare ternary composites. Experiments and simulations reveal that the highly insulating BNNS can achieve the simultaneous enhancement of E_b and ε_r of the composites and obtain a U_e of 9.7 J/cm³ at 396 MV/m electric field, which provides a basis for alleviating the contradiction between E_b and ε_r and preparing high energy storage density dielectrics.

Study on size effect of resistance welded joint strength of thermosetting composites based on the progressive damage model

ZHAO Yi, ZHAO Gang, FAN Xinyu, YAN Zhongwei, GE Yaqiong, XU Jian

2024, 0(2): 45-51. DOI: 10.19936/j.cnki.2096-8000.20240228.007

Asbtract ( 58 )

PDF (8434KB) ( 64 )

References | Related Articles | Metrics

This paper investigates the size effect of resistance welded heads of thermoset composites on the strength of joints under tensile shear loading, revealing the influence of different lap sizes on the weld strength and the progressive damage behavior of the weld interface. In order to study the progressive damage behavior of the weld interface, a bilinear cohesion unit is introduced, which in turn establishes a finite element model of the welded joint, and then the accuracy of the model is verified by resistance welding in tensile shear tests. On this basis, numerical models with different lap sizes were established and studied. The results showed that increasing the lap length or width can improve the load carrying capacity of the joint structure, but when the lap length is long, warpage failure tends to occur at the edge of the lap area, reducing the single lap shear strength of the joint, while the width has little effect on the shear strength of the joint.

Design and mechanical property analysis of double-side patch repair for CFRP laminates

ZHANG Hongqiang, CHEN Dong, LI Cheng

2024, 0(2): 52-58. DOI: 10.19936/j.cnki.2096-8000.20240228.008

Asbtract ( 71 )

PDF (6910KB) ( 168 )

References | Related Articles | Metrics

Based on the three-dimensional Hashin criterion and with the help of finite element method (FEM), a two-sided patching repair model of composite laminates was established. A patching model with damaged part removed but without the adhesive layer is introduced. Residual strength of the mother plate with and without patch are compared, and the damage process and the best patching angle of double-sided patching repair are also obtained. The results show that the recovery rate of tensile strength with double-side patch is between 50% and 80%, which can achieve the same repair effect as that of single-sided patching through a smaller patching area, which means less damage to the main plate and more applicable scenarios. The repair effect of double-sided patching first increases and then decreases with the increase of patching angle. When the patching angle is 6°, the repair effect is the best, and the strength recovery rate reaches 78%. The main plate and patch material for experimental verification are prepared from T300/7901 material. The failure load of the test specimen shows good agreement with the FEM results, and the relative error is less than 15%, which can prove the correctness of the modeling.

Analysis of the influence of force characteristics of buried sand trap arch structure

YANG Jigang, ZHANG Fangfang, LIANG Yingshuo, ZHANG Zhaoyang, WANG Qingzhou

2024, 0(2): 59-66. DOI: 10.19936/j.cnki.2096-8000.20240228.009

Asbtract ( 68 )

PDF (14282KB) ( 59 )

References | Related Articles | Metrics

In order to study the influence law of the mechanical characteristics of the buried semi-elliptical sand-filled arch structure. The self-made model box is used to carry out the loading test of the buried characteristics of the arch structure, and the hoop strain and vertical displacement are tested, and the ABAQUS numerical calculation model of the buried semi-elliptical sand-incorporated arch structure was established and the accuracy is verified. The finite element method is used to study the influence of different rise-span ratios, soil cover heights and arch foot restraint states on the stress and deformation of the arch structure. The results show that when the four rise-span ratios change between 0.30 and 0.45, the positions of the vault and the vault are the key positions for the stress and deformation of the arch structure. When the height of the covering soil changes from 60 cm, 90 cm and 120 cm, increasing the height of the covering soil can play a better role in reducing the load of the arch structure. When the arch foot is converted from unconstrained to semi-constrained and fully-constrained state, the most unfavorable position of the arch structure is shifted from the top of the arch to the foot of the arch, which is beneficial to the overall force of the structure. In the design and construction of sand-filled arch structure, the most unfavorable position of the force can be used as the safety control point, and attention should be paid to the stress concentration of the arch structure, while taking means such as load reduction to avoid damage to the structure.

High temperature resistance of Al₂O₃-SiO₂ composite nano aerogel materials

WU Jiazhen, XU Changwei, ZHANG Zhonglun, WANG Mingming

2024, 0(2): 67-74. DOI: 10.19936/j.cnki.2096-8000.20240228.010

Asbtract ( 87 )

PDF (12771KB) ( 70 )

References | Related Articles | Metrics

Using tetraethyl orthosilicate (TEOS) and aluminum chloride hexahydrate (AlCl₃·6H₂O) as the mixed precursor and propylene oxide as the network trapping agent, the aerogel with different molar ratios of Al₂O₃-SiO₂ was prepared by sol-gel process and carbon dioxide supercritical drying method without adding chelating agent. The samples were heat-treated at 600 ℃, 800 ℃, 1 000 ℃ and 1 200 ℃ respectively, and the micro-morphology, structure and thermal stability of the Al₂O₃-SiO₂ composite aerogel were characterized by Fourier infrared spectroscopy, scanning electron microscopy, X-ray diffractometer, specific surface area analyzer, thermogravimetric differential thermal analyzer and other instruments. The results show that when AlCl₃·6H₂O∶TEOS=8∶1, the thermal conductivity of Al₂O₃-SiO₂ aerogel samples after heat treatment at 1 000 ℃ and 1 200 ℃ is 0.062 1 W/m·K and 0.080 3 W/m·K, respectively. The pore size is more uniform and the mesoporous structure is preserved above 1 000 ℃. At normal temperature and 1 200 ℃, the specific surface area is 617.14 m²/g and 102.9 m²/g, with uniform mesoporous structure (pore diameter is 8~32 nm), and the pore size is lower than the average free path of air at normal temperature. After heat treatment at 1 200 ℃, the total weight loss rate of the sample is 16.3%, which proves the sample has good high temperature thermal stability.

Ply angle optimization of wind turbine blade considering continuity and symmetry constraints

LI Tianze, LI Hongyu, SUN Pengwen, WANG Zirui

2024, 0(2): 75-80. DOI: 10.19936/j.cnki.2096-8000.20240228.011

Asbtract ( 85 )

PDF (8424KB) ( 62 )

References | Related Articles | Metrics

In the design process of composite structure, necessary manufacturing constraints that satisfies the requirements of structure performance and production process shall be considered to make it conform to the engineering practice. Based on the theory of composite laminates and the discrete material optimization method, the optimization problem of ply parameters of composite laminates is transformed into the optimization of fiber angle distribution of discrete multiphase materials. The patch optimization mathematical model of micro fiber ply angle for composite laminates is established in this paper, which takes the element ply angle as design variable, the minimum compliance as the objective function, the continuity and sum of design variables as the constraint. The optimization results of composite laminate with continuity constraints and a wind turbine blade with continuity and symmetry constraints indicated that the optimized ply scheme considering continuity and symmetry constraints can effectively improve the structure performance, avoid warping deformation, reduce the probability of matrix cracking, which is more suitable for manufacturing requirement.

Experimental research on energy dissipation of damaged concrete restrained by carbon fiber cloth under axial load

ZHANG Zhengya, WANG Zhibo, SUN Mingming

2024, 0(2): 81-88. DOI: 10.19936/j.cnki.2096-8000.20240228.012

Asbtract ( 61 )

PDF (5657KB) ( 66 )

References | Related Articles | Metrics

This paper conducts an experimental study on the mechanical properties of carbon fiber fabric-confined damaged concrete under axial loading. Three variables of concrete damage degree, the number of carbon fiber cloth layers and carbon fiber cloth winding angle were designed, and the influence laws of the three variables on the stress-strain curve, peak stress, energy dissipation effect and mechanical damage degree of carbon fiber cloth confined concrete were analyzed by the test results. The test results show that compared to undamaged specimens, the mean values of damage to plain concrete under 0.4σ_m(σ_m is the uniaxial compressive strength of undamaged concrete specimens), 0.5σ_m, 0.6σ_m, and 0.7σ_m stress amplitude damage are 7.24%, 14.86%, 25.31%, and 36.66%, respectively. There is a good exponential function positive correlation between the damage degree and the damage stress amplitude. The confining effect of carbon fiber cloth enhances the peak stress and ductility of the specimen. After 0.4σ_m damage stress, compared with the specimens without carbon fiber cloth, the increase of peak stress in the specimens with 1, 2 and 3 layers was 34.99%, 55.16% and 64.42%. There is a negative correlation between the number of layers of carbon fiber cloth and the peak stress as a function of exponential, and the excessive amount of fiber cloth makes the stress increase in the specimen no longer obvious. The increase of the winding angle of carbon fiber cloth reduces the dissipation energy per unit volume of the specimen linearly, and the increase of the winding angle reduces the bearing effect of the fiber cloth in the specimen under the load. The increase of the stress damage amplitude reduces the mechanical damage of the specimen, the increase of the number of layers of carbon fiber cloth increases the mechanical damage of the specimen, and the restraint and protection effect of the fiber cloth greatly enhances the energy dissipation effect of the specimen.

Effect of BFRP strengthening on bearing capacity of freeze-thaw damaged concrete short columns

LI Zhiqiang, ZHANG Hongjia, SUN Yujie

2024, 0(2): 89-95. DOI: 10.19936/j.cnki.2096-8000.20240228.013

Asbtract ( 75 )

PDF (5179KB) ( 79 )

References | Related Articles | Metrics

This paper aimed to reduce the effect of freeze-thaw cycles on the mechanical properties of concrete and to extend the service life of freeze-thaw damaged concrete structures in severe cold regions economically and efficiently. In this study, the effect of BFRP cloth reinforcement layers on the bearing capacity of concrete columns with different freeze-thaw damage was systematically investigated through three BFRP cloth wrapping layers (0, 2 and 3 layers) constrained to experience four freeze-thaw cycles (0, 25, 50 and 75 times) for vegetated concrete short columns. The results show that after freeze-thaw cycles, the ultimate bearing capacity of concrete column is significantly reduced and the ultimate displacement is slightly increased. 3 layers of reinforcement increase the ultimate bearing capacity of concrete column by 20%, 16%, 22% and 37% for 0, 25, 50 and 75 freeze-thaw cycles, and also increase the ultimate displacement significantly. From the analysis of the experimental phenomena and data, it was found that additional reinforcement should be applied to the column ends to obtain better reinforcement results. The simulation results of 12 finite element models were established by using ABAQUS and selecting suitable material intrinsic model with reference to the test, and the results were in good agreement with the test results. After considering the effective restrained area division of the FRP-constrained prismatic column, the ultimate stress formula of the BFRP-constrained concrete column and the uniaxial compressive stress principal structure relationship of the freeze-thaw damaged concrete are brought in, and the applicable BFRP-constrained freeze-thaw damaged concrete short column ultimate bearing capacity formula is established.

Design and analysis of surface treatment device for filament wound plastic liner

TIAN Huifang, LIU Jiao, WU Yingfeng

2024, 0(2): 96-101. DOI: 10.19936/j.cnki.2096-8000.20240228.014

Asbtract ( 78 )

PDF (5853KB) ( 107 )

References | Related Articles | Metrics

In order to improve the surface treatment quality and time of plastic liner, save time and labor costs, this paper designs an automatic treatment device for the surface treatment of filament wound plastic liner. It can realize automatic clamping and positioning of plastic liner, surface treatment of plastic liner and other functions. This paper mainly introduces the designed clamping transmission device and plasma surface treatment device and other related structures, and carries out the overall design and assembly of this device in SolidWorks software, checks the strength of some parts in the Workbench, and analyzes the relevant results in the Workbench. The device meets the relevant mechanical requirements and can drive smoothly, meeting the design requirements.

Multi-objective optimization design of energy absorption characteristics of composite origami tubes

ZHOU Zhengyan, LI Xiang, ZHU Lu, SUN Yepei

2024, 0(2): 102-108. DOI: 10.19936/j.cnki.2096-8000.20240228.015

Asbtract ( 93 )

PDF (7586KB) ( 86 )

References | Related Articles | Metrics

Thin-walled structures are widely used in energy-absorbing devices. Traditional straight-tube carbon fiber resin-reinforced composite (CFRP) thin-walled structures always exhibit problems of high peak force and large fluctuations in force-displacement curves when they are crushed. However, the energy-absorbing device must ensure gradual and controlled energy absorption and avoid possible excessive peak forces. Therefore, the CFRP thin-walled tube structure needs to be further improved as an energy-absorbing device. Compared with the traditional straight tube structure, the CFRP origami tube has better energy absorption characteristics due to its unique structural form. The energy absorption characteristics of origami tubes under axial load were studied through numerical simulation, and the nonlinear mapping relationship between the energy absorption characteristics indexes of the tubes and their geometric parameters was obtained. A multi-objective structural optimization design model considering maximization of total energy absorption and minimization of peak force was established, and the NSGA-Ⅱ genetic algorithm was used to solve the problem and the results were analyzed. The optimized design of the origami tube increases the total energy absorption by 144.9% and reduces the peak force by 46.5% while maintaining the same mass, which is significantly improved compared with the original structure.

Comparison and numerical simulation of single/double diaphragm forming of thermosetting carbon fiber prepreg

ZHAO Yueqing, LIN Dezhi, CHEN Ping, TANG Jiali

2024, 0(2): 109-118. DOI: 10.19936/j.cnki.2096-8000.20240228.016

Asbtract ( 115 )

PDF (15912KB) ( 119 )

References | Related Articles | Metrics

Hot diaphragm forming process is a method for rapid forming of preforms combining the advantages of automatic laying technology. In order to compare the difference of the preform formed by single and double diaphragm forming process, a hot diaphragm forming process device was used to form the C-type preform. The influence of temperature, layup sequence, number of layers, size of preforms and forming type on the quality of prepregs was evaluated by observing the size and position of the wrinkle. Moreover, the simulation model of hot diaphragm forming is established and compared with the experimental results. The results show that reducing the overlay combination of [45°/0°] can effectively reduce the wrinkle generation. 0° ply is easy to induce the generation of wrinkle when pressed. The thicker the preform is, the more likely it is to cause defects. For the C-shaped preform, the double diaphragm forming has better forming quality than the single diaphragm forming, especially in inhibiting the generation of wrinkle at the cap. Moreover, the thermal diaphragm forming simulation model based on ABAQUS can predict the wrinkle accurately.

Application progress of CFRP in automotive lightweight and safety

HAN Shanling, WANG Tao, GUANG Xinjie, LI Zhiyong, LI Yong

2024, 0(2): 119-128. DOI: 10.19936/j.cnki.2096-8000.20240228.017

Asbtract ( 214 )

PDF (10158KB) ( 385 )

References | Related Articles | Metrics

Carbon fiber reinforced polymer (CFRP) has excellent properties such as high specific strength and good energy absorption, etc., which makes it a perfect choice for applications in lightweight and structural safety for automobiles. In this paper, the research progress of CFRP in automotive lightweight and safety is summarized, and the application of CFRP in the field of automotive lightweight is illustrated from the aspects of auto body, chassis and accessories parts. The advantages of CFRP in automotive components are analyzed from the perspective of safety. It is pointed out that the challenges posed by structural design theory and heterogeneous connection process that restrict the application of CFRP, and the future prospects of CFRP application in the automotive field are prospected. The goal of this paper is to broaden the application scope of CFRP in automotive lightweight and safety, as well as to provide a reference for its widespread use in automotive development and lightweight.

Table of Content