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Effect of gap and overlap on mode Ⅱ interlaminar fracture toughness of automated fiber placement prepreg laminates

Chinese Journal of Aeronautics 2023年第6期36卷 390-401页

作者： Fan ZHANG Xin LIU Yaoyao YE Qisen CHEN Qiang XU Yunbo BI China State Key Laboratory of Fluid Power and Mechatronic System School of Mechanical EngineeringZhejiang UniversityHangzhou 310027China Key Laboratory of Advanced Manufacturing Technology of Zhejiang Province School of Mechanical EngineeringZhejiang UniversityHangzhou 310027China

Automated Fiber Placement(AFP)technology facilitates the manufacturing process of composite structures with complex geometry owing to its high efficiency and accuracy.However.the unavoidable imperfections induced by the automated layup method bring challenges to the stability of the final mechanical properties of composites.The influence of AFP-induced gaps and overlaps on the modeⅡinterlaminar fracture process of oven-cured laminates is experimentally investigated and explicitly revealed.End-Notched Flexure(ENF)tests were performed to measure the interlaminar fracture toughness of unidirectional laminates under three different defect configurations,namely"Gap""Overlap"and"Gap&Overlap".A marginal decline(about-1.2%in non-precracked tests,-5.1%in precracked tests)and an obvious increase(about 15.2%in nonprecracked tests,5.2%in precracked tests)in fracture toughness were observed for the"Gap"group and the"Overlap"group,respectively.Fractographic studies which involve the metallographic observation and Scanning Electron Microscopy(SEM)observation revealed that the increases in fracture area and crack length helped improve the fracture toughness of the Overlap"group.However,the resin-rich area with high porosity induced by gaps was detrimental to the delamination resistance.To capture the interlaminar stress distribution local to imperfections,a three-dimensional numerical model was established.Gap defects facilitate the local delamination process,and the overlap defect postpones the damage onset and the propagation.

关键词： Automated Fiber Placement(AFP) Defects Delamination Fracture toughness laminates

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Design of pure aluminum laminates with heterostructures for extraordinary strength-ductility synergy

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Journal of Materials Science & Technology 2022年第5期100卷 193-205页

作者： Xiang Chen Baoxuan Zhang Qin Zou Guangsheng Huang Shuaishuai Liu Junlei Zhang Aitao Tang Bin Jiang Fusheng Pan State Key Laboratory of Mechanical Transmission College of Materials Science and EngineeringChongqing UniversityChongqing 400044China National Engineering Research Center for Magnesium Alloys Chongqing UniversityChongqing 400044China

Heterogeneous metals and alloys are a new class of materials with superior mechanical properties.In this paper,we engineered sandwich-structured pure aluminum laminates composed of middle coarse-grained layer and outer fine-grained layer via extrusion,rolling and annealing.By controlling the post-annealing regimes,a larger degree of microstructure heterogeneities such as boundary spacing,misorientation and texture across the hetero-interface were obtained,which resulted in obvious mechanical differences.Tensile tests indicated that the 300℃/30 min annealed laminates enabled a relatively high tensile ductility while simultaneously retaining a high strength,which was better than prediction by the rule-of-mixture.To explain the reasons behind it,the evolution of geometrically necessary dislocations and strain gradient at the hetero-interface zone were detected using in-situ tension and microscopic digital image correlation technique.It was found that with the increasing applied strain,a significant strain gradient was developed near the interface,which was accommodated by geometrically necessary dislocations,thereby contributing to higher hetero-deformation induced(HDI)strengthening and hardening.

关键词： Pure aluminum laminates Annealing Heterostructures HDI strengthening and hardening

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Evaluation of stiffness in a cellulose fiber reinforced epoxy laminates for structural applications:Experimental and finite element analysis

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Defence Technology（防务技术） 2018年第4期14卷 278-286页

作者： Furkan Ahmad Pramendra Kumar Bajpai MPAE Division Netaji Subhas Institute of TechnologyUniversity of Delhi

Natural fiber composites have been proved to have the ability to replace the synthetic fiber composites in many structural applications. Unprecedented growth in the field of computational techniques has opened the doors of analysis and simulation of composite materials under various environment.Modelling and simulation using various available softwares saves a lot of time and resources. In the present work, an attempt has been made to analyze the tensile behavior of jute fiber reinforced epoxy based polymer composite materials using the student version of commercially available finite element code Siemens PLM NX 10.0. In most of the structural applications, materials are required to have enough stiffness to resist the shape deformation under normal loading conditions. Therefore, emphasis is given to the load-deformation behavior of the developed composites. A 3-dimensional model of the test specimen was developed using ply-stacking method and the strain-stress values were verified by the available literature. The model showed a good agreement between the experimental and software results. Effect of ply angle, fiber percentage, fiber type, number of layers and weft fiber angle on the stiffness of laminate have been studied.

关键词： Finite element analysis Jute fiber Polymer composite Ply-stacking Weft fiber angle laminates analysis

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Study on Compressive Properties of Z-pinned laminates in RTD and Hygrothermal Environment

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Chinese Journal of Aeronautics 2012年第1期25卷 64-70页

作者： LI Chenghu YAN Ying WANG Ping QI Desheng WEN Yonghai School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China China Electric Power Research Institute Beijing 100192China AVIC Harbin Aircraft Industry Group Co.Ltd. Harbin 150066China

Compressive tests of [0]t2 and [90]t2 unidirectional laminates and [45/0/-45/90] 2s quasi-isotropic laminates are accomplished in both room-temperature and dry （RTD） and hygrothermal environment. And simulation studies on the compressive strength of Z-pinned laminates of [0112 and [45/0/-45/90] 2s are conducted by using finite element analysis （FEA）. A microstructural unit cell for FEA is created to simulate a representative laminates unit with one pin. Within the unit cell, the first directions of the elements＇ material coordinate systems are changed to simulate the fibres＇ deflecting around the pin. The hygrothermal effect is simulated by the material properties＇ adjustments which are determined by the compressive tests of non-pined laminates. The experimental results indicate that the percentage of reduction in the compressive modulus of Z-pinned laminates caused by Z-pin becomes smaller with the percentage of 0° fibres decreasing in the laminates; the compressive strength of quasi-isotropic laminates reduces and the percentage of the reduction in the compressive strength declines with Z-pin volume content increasing, and the moisture absorption ratio of the Z-pinned specimens is greater than that of the non-pinned specimens, because the cracks around Z-pin increase the moisture absorption. In addition, the simulations show that the deflection of fibres around Z-pin is the main factor for the reduction in the compressive strength of Z-pinned unidirectional laminates, the dilution of fibre volume content caused by resin-rich pocket is the principal factor for the decline in the compressive strength of Z-pinned quasi-istropic laminates, and the compressive strength of Z-pinned specimens in hygrothermal environment reduces as the result of superimposition of some factors, including the changes in material properties caused by hygrothermal environment, the deflection of fibres and the resin-rich pocket caused by Z-pin.

关键词： Z-pin laminates hygrothermal environment simulation study strength

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Low velocity impact studies of E-glass/epoxy composite laminates at different thicknesses and temperatures

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Defence Technology（防务技术） 2019年第6期15卷 897-904页

作者： T.Sreekantha Reddy P.Rama Subba Reddy Vemuri Madhu Defence Metallurgical Research Laboratory

Low velocity impact experiments were carried out on E-glass/epoxy composite laminates having varying thicknesses at sub zero and elevated temperatures using hemi spherical steel impactor of 16 mm diameter with impact energies in the rage of 50-150 J.The performance of the laminates was assessed in terms of energy absorption,maximum displacement,peak force and failure behaviour.Results indicated that the effect of temperature on energy absorption of the laminate is negligible although the laminates are embrittling at sub zero temperatures.However it has influence on failure behaviour and displacement.Peak force has increased linearly with increase in laminate thickness from 5 to 10 mm.However it got reduced by 25% when temperature was increased from-20℃ to 100℃,Based on experimental results,laminate perforation energies were predicted using curve fitting equations.Statistical analysis was carried out using Taguchi method to identify the global effects of various parameters on laminate performance and confirmed that the laminate thickness has significant influence as compared to temperature,for the studied range.

关键词： laminates Glass fibres Impact behaviour Delamination

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Constitutive modelling of composite laminates under uniaxial compression

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Chinese Journal of Aeronautics 2019年第4期32卷 938-947页

作者： Hsuan-Teh HU Lung-Shen KE Department of Civil Engineering ‘‘National" Cheng Kung University

A nonlinear constitutive model for a single lamina is proposed for the failure analysis of composite laminates. In the material model, both fiber and matrix are assumed to behave elasticplastically and the in-plane shear is assumed to behave nonlinearly with a variable shear parameter.The damage onset for individual lamina is detected by a mixed failure criterion, composed of the Tsai-Wu criterion and the maximum stress criterion. After damage takes place within the lamina,the fiber and in-plane shear are assumed to exhibit brittle behavior, and the matrix is assumed to exhibit degrading behavior. The proposed nonlinear material model is tested against experimental data of composite laminates subjected to uniaxial compressive loads, and good agreement is obtained.

关键词： Composite laminates Constitutive model Finite element analysis Nonlinearity Uniaxial compression

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ANALYSIS OF ENERGY RELEASE RATE FOR CRACKED laminates

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Applied Mathematics and Mechanics(English Edition) 1995年第6期16卷 565-581页

作者：胡互让吴承平 Department of Mechanical Aerospace and Manufacturing Engineering Syracuse University Syracuse U.S.A. Chongqing Jiaotong Institute Chongqing P. R. China

An interface crack analysis is presented for further understanding the characteristics of the crack-tip field. The conditions under which the energy release rate components would exist are emphasized and the relations between energy release rate components and the stress intensity factors are given. Combining with the results of chasical plate theory analysis. a closed-form solution for stress intensity factors in terms of external loading as well as some geometric and material parameters for fairly general composite laminates is derived Then. an analytical solution for energy release rate components is deduced. In order to get energy release rate components under general loading condition. a mode mix parameter, Ω, must be determined separately. A methodology for determining Ω is discussed. Finally. several different kinds of laminates are examined and the results obtained could be used in engineering applications.

关键词： composite materials laminates crack-tip field energy release rate stress intensity factor interface crack

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CONSTITUTIVE MODEL AND DYNAMIC MECHANICAL PROPERTIES OF GLASS-CLOTH/EPOXY laminates AT DIFFERENT TEMPERATURES

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Chinese Journal of Aeronautics 1998年第2期11卷 9-12页

作者：韩小平韩省亮李华殷民郑长卿 Dept. of Mechanics Northwestern Polytechnic University Xi'an 710072 China Dept. of Mechanics Xi'an Jiaotong University Xi'an 710049 China

Using a servo hydraulic material test machine system (MTS880 10) , tensile experiments of glass cloth/epoxy laminates at moderate strain rates (1/s) were carried out under different temperatures. The curves of stres... 详细信息

关键词： glass cloth/epoxy laminates strain rate temperature effects constitutive equations

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FACTORS AFFECTING FATIGUE CRACK GROWTH RATES OF FIBER REINFORCED METAL laminates

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Chinese Journal of Aeronautics 1998年第2期11卷 73-77页

作者：郭亚军吴学仁 Beijing Inst. of Aero. Materials Beijing 100095 China

Based upon an analytical model for predicting the crack growth in fiber reinforced metal laminates (FRMLs), some factors affecting the fatigue crack growth rates of FRMLs were analyzed, including the lay up of FRMLs,... 详细信息

关键词： fiber reinforced metal laminates (FRMLs) fatigue crack growth rate

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Strain Energy Release Rate Analyse of Matrix Micro Cracking in Composite Cross-Ply laminates

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Materials Sciences and Applications 2011年第6期2卷 537-545页

作者： Jean-Luc Rebière Denys Gamby 不详

The stress field distribution in composite cross ply laminates damaged by matrix cracking is analysed through an approach which uses several hypotheses to simplify the damage state. The proposed cracking criterion involves the partial components of the strain energy release rate associated with transverse and longitudinal cracking. The respective contributions of the 0° and 90° layers to the damage process are also investigated. The initiation of transverse and longitudinal cracking mechanisms is predicted. We also give an assessment of the influence of each individual component of the stress tensor on the strain energy release rate of the damaged laminate.

关键词： Composite laminates Matrix Cracking Damage Mechanics Failure Criterion

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