听Including Debonding in a Contact Analysis
XFEM中两个命令DAMAGE+STABILIZATION和CONTROLS解释
XFEM(自己写的可能错误指出谢谢O(∩_∩)O~)*DAMAGE STABILIZATIONSpecify viscosity coefficients for the damage model for fiber-reinforced materials, surface-based cohesive behavior or cohesive behavior in enriched elements.*损伤稳定指定纤维增强材料、基于表面的粘结特性或增强单元的粘结特性的损伤模型粘度系数。
This option is used to specify viscosity coefficients used in the viscous regularization scheme for the damage model for fiber-reinforced materials, surface-based traction-separation behavior in contact or cohesive behavior in enriched elements. For fiber-reinforced materials, you can use this option in conjunction with the *DAMAGE INITIATION, CRITERION=HASHIN and *DAMAGE EVOLUTION options; for surface-based traction-separation behavior, you can use this option in conjunction with the *DAMAGE INITIATION, CRITERION=MAXS, MAXE, QUADS, or QUADE and *DAMAGE EVOLUTION options.这个选项是用来指定损伤模型的粘度系数用于粘性正规化，损伤模型包括纤维增强材料，基于表面的粘结特性或增强单元的粘结特性。
CI Tom Pitts 简-Damon系统
矫 bonding plan 矫 来
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molar bracket 稳当 3. 备 bonding 两 bonding 时 认没 两 对 边 brackets 递给 净 认 随时 还 备 树 个 边 两 时 协
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第9讲_接触问题分析
接触面
目标面 接触面 目标面 接触面
接触面
目标面
目标面 硬面
接触面
目标面
15
Lzh_CAE
主讲：练章华 教授
4．定义刚性目标面
单元类型
二维刚性目标面用TARGE169单元 三维刚性目标面用TARGE170单元
在三维情况下，任意形状的目 标面应该使用三角面来建模。
实常数
对TARGE169和TARGE170 仅需设置实常数R1和R2
②划分刚性目标单元 2D目标单元 GUI：Main Menu＞Preprocessor一Meshing一Mesh＞Lines 3 目 标 单 元
Command：AMFSH GUI:Main Menu＞Preprocessor＞Meshing mesh＞Ares一Target Sarf Command，LMESH
4
主讲：练章华 教授
位移等值线图
等效应力等值线图
Lzh_CAE
5
主讲：练章华 教授
实例2: 圆柱壳非线性屈曲分析实例(ANSYS)
问题描述：一个对边简支的圆柱壳，在其中心作用一个垂直的集中载荷。我们的 目的是分析当载荷大小为1000N 时，A、B 两点的垂直位移（UY）。 问题详细说明： 材料特性： EX=3.10275 KN /mm2 （杨氏模量）NUXY = 0.3 （泊松比） 几何特性： R = 2540m L = 254m 铰约束 H = 6.35m ＝0.1 rad 载荷： 2L p = 1000N
(6, 1.5)
(0, 0)
5 12
Lzh_CAE
3
主讲：练章华 教授
/solu nsel , s , loc , x , 0 dsym , symm , x nsel , s , loc , y , 0 dsym , symm , y nsel , all d , all , uz nsel , y , 1.5 d , all , ux nsel , all /solution nlgeom , on pred , on d , 14 , uy , -0.3 time , 0.3
Non-destructive evaluation for FRP-bonded concrete structure (结构无损测试)
Principle: Acoustic emission has been studied and used over the last six decades. The method is based on recording and describing the radiation of acoustic waves generated by a rapid release of stress energy within a tested object which is under external mechanical forces. Proper analysis of these signals can provide information concerning the location of discontinuities and the structural integrity. Advantage: Damage processes in materials being tested can be observed during the entire load history, without any disturbance to the specimen. Disadvantage: Requires the contact between the AE sensor and the concrete structure through the use of appropriate sound coupling. This is inconvenient to detect the areas where it is inaccessible.
External loading conditions Perfunctory manufacturing
第五讲_分析步、接触和载荷
第五讲
ABAQUS/CAE中的分析步、接触和载荷
ABAQUS/CAE_分析步、接触和载荷
概述
• 分析步 • 接触 • 载荷、边界条件和初始条件
L5.2
ABAQUS/CAE_分析步、接触和载荷
分析步
ABAQUS/CAE_分析步、接触和载荷
分析步
• 分析步模块有下面四个用途： 1. 定义分析步。 2. 指定输出需求。 3. 指定分析诊断。 4. 指定分析控制。
Step 3: 为加载的系统提取固有频率。
Step 4: 放开弓弦 (动态响应)。
L5.6
ABAQUS/CAE_分析步、接触和载荷
分析步
• 输出 – ABAQUS/Viewer将使用输出数据库。 • 对于Python和C++保留了API接口，可以用于外部的后处理（比如，在 ABAQUS/Viewer中添加显示数据）。 – 两种类型的输出数据：场和历程数据。 • 场数据用于绘制模型的变形、云图和X–Y绘图。 • 历程数据用于X–Y 绘图。
– 初始条件更一般的标题为“场”。 – 在初始分析步中定义的场是通过定 义初始条件定义的。
在跌落试验中，初始平动速度可以模拟 自由落体的效果。
L5.32
ABAQUS/CAE_分析步、接触和载荷
载荷、边界条件和初始条件
• ABAQUS/CAE中定义载荷和边界 条件
1. 创建载荷（或边界条件），并 选择该载荷激活的分析步。
L5.22
ABAQUS/CAE_分析步、接触和载荷
接触
2. 从几何体的表面、单元表面、 表面集或节点集选择应用接触 的表面。 （可以通过选择一个单元和特 征角度的办法在孤立网格中选 择表面。单个编辑的办法可以 很容易清除不规则的单元。）
碳纤维复合材料英文文献
TEM study of carbon®bre reinforced aluminium matrix composites: in¯uence of brittle phases and interface on mechanical propertiesncin*,C.MarhicPhysique Cristalline,Institut des MateÂriaux Jean Rouxel,BP32229Nantes cedex3,FranceReceived13May1999;received in revised form4November1999;accepted8November2000AbstractThe microstructure of A357aluminium alloy(7wt%Si+0.6wt%Mg)reinforced by1D-M40J carbon®bres is characterised using di erent techniques of transmission electron microscopy(di raction,HRTEM,EDX,EELS).The microstructure of the high modulus PAN based®bre and of the pyrolytic carbon coating(Cp)is fully characterised.Silicon and Mg2Si grains which determine matrix-reinforcement adhesion are investigated.On the basis of the microstructural features,the mechanical properties of the composites are discussed.The mechanical behaviour of composites prepared with and without Cp interphases corresponds to a brittle matrix reinforced by brittle®bres.In the case of the composite without Cp interphase,the most in¯uent parameter is the high resistance to sliding at the interface between silicon and®bres which leads to a strong®bre-matrix``bonding''and thus,to a weak and brittle material.The interfacial resistance to decohesion and to sliding is lower in the composite with Cp interphase resulting in higher strength and limited pull out.This lower interfacial resistance is due to the successive microporous and layered micro-structures of the pyrolytic carbon coating.#2000Elsevier Science Ltd.All rights reserved.Keywords:Al alloy;Al4C3;Carbon®bre;Composites;Electron microscopy;Interphase;Mechanical properties1.IntroductionCarbon®bres are used to increase strength and sti -ness of aluminium alloys while keeping low weight and good thermal and electrical conductivity.However, brittle phases which form or precipitate during the pro-cessing may have a deleterious in¯uence on the mechanical properties of the composites.1À11Studies are being performed to improve the processing and to obtain the required properties.C/Al composites pre-pared at ONERA-Chatillon for aerospace applications contain a high volume fraction of®bres(70%).12,13In one of these,an A357aluminium alloy is reinforced with high modulus M40J carbon®bres,sometimes coated with a pyrolytic carbon interphase(Cp).The M40J/A357composite without the Cp interphase is brittle and weak(%700MPa).13The M40J/Cp/A357 composite with the Cp interphase is stronger(%1360 MPa)but less so than expected from the law of mixtures and,moreover,it is rather brittle(limited pseudo-plastic deformation,low work of fracture),despite some®bre debonding.14Scanning electron microscopy(SEM)did not reveal any reaction layer in either type of composite.13 A transmission electron microscopy(TEM)study was thus performed to reach a full knowledge of the microstructural features of the materials and a better understanding of their mechanical behaviour.The mechanical tests and properties are fully described in a paper previously published.14In this paper,the microstucture of the high modulus carbon®bre and of the carbon coating is characterised. The amounts and locations of the brittle phases,alumi-nium carbides and silicon,are determined.Interdi u-sion,which is known to in¯uence the failure resistance at the interfaces,is also studied.The discussion of the microstructural features reveals important parameters and shows that the mechanical behaviour of the compo-sites does not depend on the metal matrix.Models devel-oped for ceramic±ceramic composites are successfully used to analyse the mechanical properties.2.Materials and experimental procedure1D-composites were fabricated with A357alloy (alloying elements:Si=7wt%,Mg=0.6wt%)and M40J®bres('r=4400MPa,E=377GPa)-by liquid metal in®ltration(LMI),under moderate pressure0955-2219/00/$-see front matter#2000Elsevier Science Ltd.All rights reserved. P I I:S0955-2219(00)00021-2Journal of the European Ceramic Society20(2000)1493±1503*Corresponding author now at:TECSEN Laboratory,case231, 13397Marseille Cedex20,France.E-mail address:lancin@matop.u-3mrs.fr(ncin).(15MPa),during 1min,at 918K.13Two composites were obtained using respectively bare ®bres or ®bres coated by pyrolytic carbon (Cp),both containing a high volume fraction of ®bres (%70%).Longitudinal and cross sections were prepared by mechanical grinding and ion thinning.During grinding and polishing,the cohesion of the samples was main-tained by using an appropriate glue and a Ti ring (Bal-zers).These necessary precautions and the occurrence of cracks sometimes observed between ®bres and matrix (Fig.1a)reveal the weak adhesion between ®bres and matrix in both composites.Ion thinning is carried out in a Balzers ion thinner using a low beam density and a sample holder cooled with liquid nitrogen.The composite micro-structure is not modi®ed by such ion thinning conditions.Phase identi®cation and localisation were performed by electron di raction patterns (EDP)and nanodi raction,high resolution transmission electron microscopy (HRTEM),energy dispersive X-rays spectroscopy (EDX)and electron energy loss spectroscopy (EELS).Experi-ments were carried out using a ®eld emission gun (FEG)HF2000Hitachi microscope (200KV,Scherzer resolu-tion=2.6A)equipped with a CCD camera (MSC Gatan),a Si-Li detector (Kevex Super Quantek)and a PEELS (Gatan).Analyses were performed using a cooling holder (Gatan),a 4±10nm probe size and a 12 tilt angle for EDX spectroscopy.3.ResultsMany microstructural features are shared by the two composites.We thus describe them and underline the di erences where theyoccur.Fig.1.Microstructure of a cross-section of the M40J/A357composite.Bright ®eld (a)and HRTEM (b)images of the Al/®bre interface.(b)Shows the folded aromatic layers surrounding porosities and the EDP characteristic of equiaxed {0002}carbon planes.ncin,C.Marhic /Journal of the European Ceramic Society 20(2000)1493±15033.1.ReinforcementThe mechanical properties of the composites depend on the microstructure of the reinforcement after the processing.The microstructural features of the ®bre and of the Cp were thus investigated on longitudinal and cross-sections of the M40J/A357and M40J/Cp/A357composites respectively. 3.1.1.Microstructure of M40J carbon ®breThe ®bres are regularly distributed in the composites.Their bean shaped cross-section (Fig.1a)is fringed with roughness ranging from a few nanometers to a few microns in size (Figs.1,4a,5,6,7,8).Their longitudinal section is more regular than their cross-section but the surface is wavy,with an amplitude which reaches 10nanometers or so (Fig.2a).Owing to theirbean-shapedFig.2.Microstructure of a longitudinal section of the M40J/Cp/A357composite.Bright ®eld image of the Al/Cp/®bre interface (a)HRTEM image of the microporous Cp (b),HRTEM images and EDPs of the layered Cp (c)the ®bre (d).ncin,C.Marhic /Journal of the European Ceramic Society 20(2000)1493±15031495cross-section,their¯uted surface and their dense pack-ing,the®bres are always in contact with two or three neighbours and are bridged to the others by an irregular and narrow matrix.As a result,the matrix is cut into microlingots and a residual porosity is observed where ®bres are in contact.The®bre section exhibits a uniform contrast in bright ®eld mode(Figs.4a,6)except in its outermost part where signi®cant porosity is revealed by its light con-trast.This porosity,which is not continuously observed all around the®bre,extends over10±200nm beneath the surface.The pore size ranges from4±20nm. Using M40J/A357cross-sections,the®bre micro-structure was characterised.The same di raction pat-tern is obtained in the®bre core and in the®bre periphery whatever its porosity(Fig.1b).This con-tinuous ring pattern is characteristic of equiaxed{0002} planes.HRTEM images con®rm these results and reveal the grain size(Fig.1b).Fibre nanocrystals consist of a stack of a few aromatic layers,one or two nanometers in length,named BSU(Basic Structural Unit15).BSUs of similar orientation are associated in clusters namedLMO(Local Molecular Orientation15)whose width and length rarely exceed10nanometers.BSUs are joined by disclinations where atoms are linked by twis-ted or stretched bonds or tetrahedral bonds as typical in carbon®bres.16Such an organisation results in many places in a strong curvature of the aromatic layers,in very sharp angles between them and in a residual por-osity.The pore size rarely exceeds a few nanometers in the®bre except near the surface as above mentioned.The folded organisation of the aromatic layers is observed throughout the®bre section even in its outermost part. HRTEM images of longitudinal sections reveal the length of BSUs and LMOs organised in micro®brils17 along the®bre axis(Fig.2d).As in the cross-sections,the BSU length is equal to one or two nanometers and the LMO width perpendicular to the®bre axis is about10nm. Unlike the cross-sections,micro®brils extend over several tens of nanometers along the®bre axis and the relative disorientation of aromatic layers is less substantial.EDPs show,indeed,that aromatic planes are aligned to within 17 of the®bre axis(Fig.2d).The space between micro®brils reveals the length of the pore structures (about50nm).Because of this microstructure,the®bre is categorised into the large family of turbostratic carbons. Interdi usion between aluminium and®bre was stu-died by EDX(Fig.3).Aluminium is revealed beneath the®bre surface over about®ve nanometers but ana-lyses may be in¯uenced by the®bre roughness.Traces of aluminium and silicon are also detected in the®bre just beyong this zone(Fig.3a),particularly in the pores. In aluminium,carbon is not detected without ambiguity either by EDX or by EELS.A layer of5nanometers or so in the matrix next to the Al/C interface contains some oxygen(Fig.3c).3.1.2.Microstructure of pyrolytic carbon coating(Cp) In the M40J/Cp/A357cross-sections,the Cp coating is identi®ed at the®bre/matrix interface by a light con-trast in bright®eld mode(Figs.4a,6b)and by EDPs and HRTEM images(Fig.4b)which distinguish®bre and Cp.Every®bre is continuously surrounded by the Cp coating,15±30nm thick.The Cp,in which aromatic lay-ers are cut into BSUs,exhibits a turbostratic structure. Near the®bres,BSUs tend to form continuous sheets which follow the roughness of the®bre surface and LMOs can hardly be distinguished.The orientation of the aromatic layers varies to within 35 with respect to the®bre axis.When the coating thickness exceeds about 10nanometers,LMOs are more and more distinct and their orientation less and less equiaxed resulting in a microporous microstructure near the matrix. HRTEM images and EDPs of longitudinal sections con®rm the change of the Cp microstructure versus thickness(Fig.2b,c).Along the®bre surface,over 10nm or so,we observe a layered structure.As in the cross-sections,LMOs or micro®brils cannot be dis-tinguished on HRTEM micrographs.In the layered zone,the aromatic layers follow the®bre surface and their disorientation versus the®bre( 25 )is only a lit-tle more evident than in the®bre.In the outermost part of the Cp,the microporous microstructure is in excellent agreement with that revealed by HTREM images on cross sections.In the microporous Cp coating,traces of aluminium, silicon and magnesium are detected by EDX but no other heteroatoms and in particular no oxygen atoms are found(Fig.3b).In the layered Cp coating,hetero-atoms are notdetected.Fig.3.EDX analysis.Spectra characteristic of the®bre at20nm from the interface(a)the microporous Cp(b)Al next to the Al/C interface (c)Al at20nm from the Al/C interface(d)Mg2Si(e)and Si next to the Si/C interface(f).ncin,C.Marhic/Journal of the European Ceramic Society20(2000)1493±15033.2.Brittle phasesAl4C3reaction product and matrix precipitates(Si or Mg2Si)are identi®ed on cross-sections by electron dif-fraction,HRTEM,EDX and by plasmon peak energy. Low loss edges permit a more systematic study of the phases than core edges because they are less sensitive to specimen thickness.Moreover,despite the variation of the plasmon peak energy of carbon as a function of the beam orientation versus the basal plane,it was possible to distinguish between the di erent phases because we found distinct values for the volume plasmonenergyFig.4.Microstructure of a cross-section of the M40J/Cp/A357composite.(a)Bright®eld image of a®bre/Cp/Al interface where the Cp and the ®bre porosities are revealed by a light contrast;(b)HRTEM image showing the layered Cp near the®bre and the microporous Cp near the matrix; EDP of the layered Cp.ncin,C.Marhic/Journal of the European Ceramic Society20(2000)1493±15031497(Fig.6):E Mg2Si =12.7eV,E Al =15eV,E Si =16.7eV,E carbide =18.9eV and for the di erent carbons 23.4eV in microporous Cp,24.3eV in layered Cp,23.7eV in the ®bre and 21eV in large ®bre pores.3.2.1.Si and Mg 2Si precipitatesThe matrix contains Si grains,inhomogeneously dis-tributed in the matrix and located predominantly next to the ®bres,generally in contact with two ®bres or between them (Fig.6).All these grains exhibit typical stacking faults;thus their contrast was most often used to identify them.It is noteworthy that the amount of stacking faults is the highest in the narrowest parts of the Si grains which bridge between ®bres.The Si grain size generally ranges between a hundred nanometers to about one micron but some nanometric grains are also detected.Si grains contain various amount of inclusions (Fig.6b,c)in which aluminium is detected but whose exact composition is under study.The largest inclusions were identi®ed as aluminium.Mg 2Si precipitates a few tens nanometers in size were on occasion identi®ed by EDX in the matrix (Fig.3e).Mg 2Si precipitates were never detected between the®bres probably because of the low concentration of Mg in the alloy as compared to Si.3.2.2.Aluminium carbidesIn both composites,aluminium carbide grains exhibiting a lath like morphology were revealed at interfaces using the techniques previously mentioned.In contact with the carbon,but not extending into the ®bres,the carbide grains are included in the matrix.They are generally located at Al/C interface (Figs.1b and 7a)but some of them are included in silicon grains (Fig.7b).The carbide grain length ranges from 100to 350nm and their aspect ratio (length/width)from 8to 15.The amount of carbide grains is di cult to assess because they are irregularly observed at the interfaces.From a systematic study of longitudinal and cross-sections,it is possible to conclude that carbides are rather rare in both composites but rarer at the Cp/matrix interface than at the ®bre/matrix interface.Moreover,their amount is clearly lower than that of the Si grains.3.2.3.Si±C interfacesHRTEM was performed to study the possible reaction between carbon and silicon resulting in SiCformationFig.5.EELS analysis:volume plasmon peaks.ncin,C.Marhic /Journal of the European Ceramic Society 20(2000)1493±1503which has been reported at low temperature(798K)in Al±Zn alloy.18No grains were detected at the Si/C interfaces in either composite(Fig.8)except for the Al4C3as above mentioned.Thus,the C±Si reaction,if any,is not detectable after liquid metal in®ltration. Interdi usion is also to a very limited extent detected by EDX in a narrow zone on either side of the interface. Carbon is not detected in the silicon beneath the inter-face(Fig.3f)whereas traces of silicon and aluminium are observed in the carbon,the spectrum being similar to that obtained at the Al/C interfaces.4.DiscussionBrittle phases have been identi®ed at interfaces in both composites.Their in¯uence depends on their brit-tleness as compared to that of the reinforcement and on the resistance to debonding and to sliding at the inter-face.Although the Cp coating does not change the strength and the Young modulus of the®bre,14it may modify crack propagation in the reinforcement.The resistance to debonding and to sliding between the rein-forcement and the di erent phases,aluminium,alumi-nium carbide or silicon,will accordingly be analysed using the microstructural features of the interfaces.Finally,we show that the conclusions derived from the micro-structural features are consistent with the mechanical behaviour of the composites4.1.Fibre and Cp microstructure and crack propagationThe turbostratic structure of the M40J®bre is more typical of the high strength PAN-based®bres than of the high modulus ones®rst described by Guigon et al.19 The core porosity for example,is close to that observed in ex-Pan high strength T300®bres by Lamouroux et al.20Moreover,in agreement with Feldho et al.,21weFig.6.Silicon grains.Localisation of Si grains in a cross-section thanks to their stacking faults(a).Bright®eld images of Si grains bridging®bres in M40J/Cp/A357(b)and in M40J/A357(c)composites:images reveal stacking faults and Al inclusions in Si and the continuous ribbon of Cp between Si and®bre in(b).ncin,C.Marhic/Journal of the European Ceramic Society20(2000)1493±15031499do not observe the layered structure of the outermost part of the®bres mentioned by Guigon et al.in high modulus®bres.The lack of layered structure could be due to some dissolution of the®bre during composite fabrication.However,in any case,the thickness of the possible lamellar layer must be limited in the M40J®bre because the short duration of the LMI and the small amount of aluminium carbide formed are not consistent with extensive dissolution.Fibre and Cp have di erent turbostratic structures but both of which could avoid crack propagation through the reinforcement.However,the impact of a possible surface notch is di erent whether it is applied on the®bre or on the Cp.The e ciency of pyrolytic carbon as a mechanical fuse is generally ascribed to a layered structure which promotes crack de¯ection and interface sliding.As for the crack de¯ection,the complex structure of the Cp is particularly e cient.The outermost part of the Cp exhibits indeed a microporous morphology where the LMOs are equiaxed.Such a structure is very suitable to promote crack branching on the disclinations as well as crack de¯ection in LMOs in a direction parallel to the {0002}planes and,thus,it is e cient to release stresses at crack tips.If blunted cracks could nevertheless reach the inner part of the Cp,where aromatic layers follow the®bre surface,they could be de¯ected in a direction parallel to the®bre surface more e ciently than the initial crack.As for the interface sliding,we have to consider the adhesion of the di erent phases and we discuss the in¯uence of this parameter later.When submitted to similar stresses than the Cp,the turbostratic structure of the®bre may also promote crack splitting and crack de¯ection in a direction parallel to its axis because folded aromatic layers are oriented to the®bre axis within 17 .However,during atensileFig.7.Identi®cation of A14C3grains.HRTEM images of A14C3grains at an Al/®bre interface(a)and included in a silicon grain identi®ed by its characteristic stacking faults and Al inclusions(b).In both A14C3grains the contrast of{0003}planes is visible.ncin,C.Marhic/Journal of the European Ceramic Society20(2000)1493±1503test,because the®bres are seldom aligned parallel to the applied stress,the notch tip will usually be submitted to shear stresses(failure in mode III22)which will promote propagation through the®bre and thus®bre failure. 4.2.AdhesionAdhesion of aluminium matrix to®bres(bare or coated)is determined by con¯icting e ects.During LMI,carbon is dissolved in liquid aluminium and alu-minium di uses into the carbon.After quenching,car-bon atoms remain in the matrix,even if they are undetectable by TEM,and Al is still observed in the carbon.Therefore,chemical di usion bonds which are said to be``good''bonds4can be considered to link aluminium to®bres.However,we have seen that the matrix is cut into micro-lingots by®bres in contact. During cooling,the shrinkage is determined by the ®bres.The coe cient of thermal expansion of alumi-nium(2310À6KÀ1)being higher than the axial(9À1 10À6KÀ1)and transverse(%À1010À6KÀ1)coe cients of thermal expansion of a®bre,Al/C interfaces are submitted to radial tension and transverse shear stress which counterbalance the chemical di usion bond.The aluminium matrix is,however,®xed here and there to the®bres by aluminium carbide grains.Aluminium carbide grains that are formed by reaction between liquid aluminium and carbon are linked to the reinforcement by a strong chemical reaction bond. However,carbide grains are also strongly linked to the matrix by mechanical bonds because they are embedded during the solidi®cation in aluminium that has a higher coe cient of thermal expansion than aluminium car-bide.Thus,Al4C3/C interfaces as well as Al/C interfaces are submitted to radial tension in opposition to the carbide±carbon reaction bonds.As for silicon-reinforcement bonding,chemical di u-sion bonds may exist because some silicon has di used into the®bres during LMI.However,we think that such bonds are of little importance compared to the mechanical bonds that link silicon to®bre if considera-tion is given to resistance to debonding and to sliding. The coe cient of thermal expansion of silicon(%2.92 10À6KÀ1)being low compared to the transverse coe -cient of thermal expansion of the®bre,silicon grains are ®rmly®xed on the®bre by the interlocking e ect pro-moted by the roughness.Such e ects are e cient enough to grip together phases as di erent as porous alumina and pivalic acid and to resist shear stresses during sample cutting.23Moreover,silicon grains are submitted to compression stresses when they bridge ®bres.Interlocking e ects and compression stresses limit,even if they do not prevent,sliding at the silicon/®bre interface when silicon grains bridge®bres.In silicon grains the gliding of Shockley partial dis-locations in{111}planes which causes stacking faults more numerous in the narrowest part of the silicon bridges,releases some thermal stresses during quench-ing.Residual thermal stresses may,however,decrease the strength to failure of the®bre near these bridges. The transverse stress to failure of the composites which results from these di erent bonds is weak as shown by the di cult thin®lm preparation(Section2and Fig.1a). Because Al4C3/C or Si/C interfaces are rather rare,this low adhesion is not exclusive of stronger bonding at a few points at the interfaces.4.3.In¯uence of the brittle phases on the mechanical behaviourIt is best®rst to discuss the in¯uence of silicon grains because they are more numerous than aluminiumcarbide Fig.8.Si/C.HRTEM images of the Si/®bre interface which shows that no Si±C reaction occurs during the composite fabrication.ncin,C.Marhic/Journal of the European Ceramic Society20(2000)1493±15031501grains and because they often bridge®bres.When®bres are bridged by a silicon grain,the composite has locally a brittle matrix.Because of the high volume fraction of ®bres and because neighbouring®bres are generally in contact,it is reasonable to suppose that the Young modulus of the composites(Ec)is determined by the volume fraction of®bres(Ec=0.7Ef=263GPa).Silicon has the lowest Young modulus(Esi=163GPa)when compared to®bre and composite.During a tensile test, the composite strain is higher than that of a®bre sub-mitted to the same stress and lower than that of silicon. The®bre/Si interface is thus submitted to shear stresses, the®bre being under greater tension than the silicon.These stresses are in opposite direction to the thermal stresses developed during cooling because of thermal mismatch. It is not clear if silicon grains are more or less brittle than®bres.The tensile strength to failure found by Pearson et al.(2GPa24)results in a strain to failure (12.210À3)higher than that of®bres(11.6710À3). However,the strength to failure of brittle materials depends on¯aw size.According to experimental results,14silicon grains seem to be more brittle than ®bres and,thus,we analyse the impact of a silicon crack on the mechanical behaviour in this light.It is helpful®rst to consider silicon grains linked to coated®bres in the M40J/Cp/A357composite.Silicon grains have the critical size to initiate a fracture in the reinforcement25if no mechanism releases the stresses at the crack tip.When silicon is linked to the Cp,stresses will be released by decohesion either at the silicon/Cp interface or in the Cp(Section4.1)depending on the debonding resistance as compared to the shear resis-tance of{0002}planes.After interface failure,a defor-mation of the outermost part of the coating under interfacial shear stresses can occur,despite radial com-pression stresses and surface roughness,because of its microporous microstructure and because®bres are under tension at the interface(see above).Microcracks and local shearing would release the stresses and may allow some sliding at the interface.These mechanisms delay the®bre and the composite failure.However, because these deformations are certainly limited and because the residual thermal stresses decrease the®bre strength,the composite breaks under a stress sub-stantially lower than the value predicted by the law of mixtures(1300instead of3000MPa)and with some pull out consistent with these model.When a silicon grain bridges bare®bres,even if the resistance to debonding at the Si/®bre interface were low,sliding is restricted if not impossible at the interface without notching the®bre.Therefore,whatever the resistance to decohesion,stresses cannot be released at the crack tip and they will induce®bre failure.The simultaneous failure of silicon grains produces the simultaneous failure of many®bres and thus a brittle failure of the composite under low stress.Owing to its well established deleterious e ect,alumi-nium carbide is certainly more brittle than®bres. Moreover,despite their limited size,previous results2À4 suggest that carbide grains can develop cracks which have the critical size to induce a®bre failure.When a crack notches the reinforcement,because of the turbos-tratic structure of the carbon and because of the axial tension at the Al4C3/C interface,it will be soon de¯ected in a direction parallel to the interface.In the case of coated®bres,the crack is de¯ected in the Cp.Sliding along the interfacial failure is possible despite the®bre roughness because of the limited width of the carbide grains(Section3.2.2)and again because of the axial tension at the Al4C3/C interface.Thus,a carbide failure does not induce a®bre failure and the carbide grains have no in¯uence on the strength of the M40J/Cp/A357 composite.In the case of a bare®bre,the notch will initiate a®bre failure when the tensile stress is high enough(Section4.1).Aluminium carbide grains con-tribute to the weakness and brittleness of the M40J/A357 composite,but,due their low amount as compared to silicon grains,do not provide the main in¯uence on M40J/A357strength.5.ConclusionThe main conclusions are as follows:.the microstructure of the high modulus PAN based M40J carbon®bre is fully characterised;it is in better agreement with the microstructure of a high strength than of a high modulus PAN based carbon®bre,.the pyrolytic carbon coating(Cp)used in the M40J/Cp/A357composite consists of two layers of distinct microstructure,a layered structure near the®bre and a microporous structure near the matrix,.the reaction of aluminium with carbon is limited during fabrication processing,particularly with the Cp;no reaction occurs between silicon and Cp or ®bre,.brittle phases,silicon and to a lesser extent alumi-nium carbide,are in contact with or bridge the ®bres,.the response of the composites to tensile stress parallel to the®bre axis is well described by the model of a brittle matrix reinforced by brittle ®bres:the most important parameter is the high resistance to sliding due to interlocking e ects between silicon grains and®bres and compression stresses in silicon bridges;it leads to a brittle and weak M40J/A357composite but its in¯uence is counterbalanced by the special structure of the Cp interphase in the M40J/Cp/A357composite.ncin,C.Marhic/Journal of the European Ceramic Society20(2000)1493±1503。
Abaqus复合材料
Copyright 2008 SIMILIA, Inc.
嵌入单元
• Rebar加强的膜单元和表面单元可以以任意方式嵌入到实体单元中来模拟 复合材料
嵌入的膜单元
rebar
Copyright 2008 SIMILIA, Inc.
实体单元
6
Abaqus复合材料主要功能
*CONTACT PAIR, INTERACTION=FRACTURE, ADJUST=Nsetbond Slave--Slave surface name Master--Master surface name
*SURFACE INTERACTION, NAME=FRACTURE, UCRACK, DEPVAR=12, PROPERTIES=16 , G_IC,G_IIC,G_IIIC,mixType,m,n,o w,
Copyright 2008 SIMILIA, Inc.
IanIlotnentregfarpfcaleacnEeeleeomfleedmnetlsaemnloticnsaalttoeiodcnated along plane of delamination
11
VCCT-for-Abaqus Usage and Keywords
Copyright 2008 SIMILIA, Inc.
复合材料的后处理功能
Copyright 2008 SIMILIA, Inc.
8
复合材料的后处理功能
• 可以显示复合材料厚度方向上变量 的变化曲线
Copyright 2008 SIMILIA, Inc.
CATIA CPD接口
• Simulayt可以作为Abaqus/CAE的中模块，将CATIA CPD中设计的复合 材料模型以及铺层导入
飞机故障描述示范
目录第一章飞机缺陷术语/AIRCRAFT DEFECT TERMS (2)1.1缺陷分类/ Categories of Defect (2)1.1.1结构缺陷术语/Common Structure Defects Terms (2)1.1.2材料缺陷术语/Common material defect terms (3)1.1.3设备及零部件缺陷术语Common part component defect terms (4)1.1.4一般性缺陷术语/General defect terms (6)1.1.5缺陷术语构成/Defect terms define (7)第二章飞机缺陷描述/AIRCRAFT DEFECT DESCRIPTION (8)2.1缺陷术语描述和修理举例/Defect Terms Description and Repair Examples (8)第三章缺陷位置描述/DEFECT LOCATION DESCRIPTION (42)3.1 A320 (42)3.1.1区域/Zoning (42)3.1.2机身/Fuselage (43)3.1.3门/Door (46)3.1.4机翼/Wings (50)3.1.5吊架和短舱/Pylon and Nacelle (53)3.1.6安定面/Stabilizer (56)3.2 B737NG (58)3.2.1区域/Zoning (58)3.2.2机身/Fuselage (59)3.2.3门/Door (64)3.2.4机翼/Wings (65)3.2.5吊架和短舱/Pylon and Nacelle (67)3.2.6安定面/Stabilizer (67)第一章飞机缺陷术语/AIRCRAFT DEFECT TERMS1.1缺陷分类/ Categories of Defect缺陷的分类一般依照维修实践中的经验来分。
在本手册中，我们将缺陷分为四类结构缺陷、材料缺陷、零部件缺陷和一般性缺陷。
量6-abaqus6
ABAQUS ELEMENT LIBRARYSolid stress/displacement elements CAX#, CPE#, CPS#, C3D# Reduced integration elements C…RHybrid elements C…HIncompatible mode elements C (I)Truss elements T2D#…, T3D#…Generalized plane strain elements CGPE…Axisymmetric elements with asymmetric deformation CAXA…NInfinite elements CIN…Heat transfer elements DC2D#, DCAX#, DC3D# Diffusive heat transfer elements DC…Convective/diffusive heat transfer elements DCC…(D)Solid elements including temperature C…TSolid elements including pore pressure C…（R）P(H) Acoustic elements AC…Elements with electric potential C…EM3D…B2…, B3…, PIPE… Open section beams in space B3#OS （H ）Shell stress/displacement elements STRI#, S#R Finite membrane strain S… Heat transfer elementsDS# Coupled temperature- displacement elements S…TAxisymmetric elements SAX…, SAXA#NDashpots DASHPOT(A, 1, 2)Drag chains DRAG2D, DRAG3D Deforming section pipes and pipebends ELBOW…Gap elements GAPUNI, GAPCYL, GAPSPHER Gasket elements GK…Tube/tube support interaction elements ITSUNI, ITSCYLFlexible joint elements JOINTCLine spring elements LS6, LS3SPoint masses MASSRotary inertia at a point ROTARYIFuel subassembly interaction models SPHEX(2, 2B)Springs SPRING(A, 1, 2)INTER…Coupled temperature-displacementINTER…TPore pressure interface INTER…PHeat transfer interfaceDINTER…Acoustic interface ASI…ISL…Master elements are defined by *SLIDE LINETube to tube contact ITT…ISP…Master elements are defined by *SLIDE PLANEIRSMaster elements are defined by *RIGID SURFACER2D2, R3D#, RAX2, RB…UELMATERIAL MODELS IN ABAQUS*ELASTICelk el ijk ij D εσ=*NO COMPRESSION Small strain; ()T D el ijk : linearεσ-*NO TENSIONHypoelasticity *HYPOELASTIC el k el ijk ij d D dεσ=(),...,T D elijk ε : nonlinear yet small strainHyperelasticity *HYPERELASTIC ),,( ,321I I I U U ijU ij ==∂∂εσ Nonlinear elasticity for large strain U : strain energy density potential321,,I I I : Invariants of principal stretch ratios Foam material*HYPERFOAMVery compressiblePorous Elasticity *POROUS ELASTIC ()kk p p p p el V V p n el t el t σ31 ,00-=⎪⎭⎫ ⎝⎛∝++*POROUS BULK MODULI Compressibility of solid grainsSeepage *PERMEABILITYDepends on void ratio *SORPTIONAbsorption or exsorption*VISCOELASTIC()τφτδτσd t K et G tij ij ij ⎰-+-=0)()(2 must be used with *ELASTIC, *HYPERELASIC, or *HYPERFOAM *PIEZOELECTRIC mmijk ijk ijE e D ϕεσ-=and *DIELECTRIC j ij jk ijk i E D e q ϕϕε+=*PLASTIC()pl k k elijk ij d d D dεεσ-=: isotropic yield at 0σσ=Anisotropic yield *POTENTIAL etc. ),( ,301211012011σττσστ===R R*PLASTIC, HARDENING=KINEMATICViscoplasticity *RATE DEPENDENT ()0for 10σσεσσ≥-=pplDCreep *CREEP m n cr t A σε= Swelling *SWELLING(),...,,21f f f sw θε=With *INITIAL CONDITIONS, TYPE=FIELD and *FIELD Swelling gel *GEL*MOISTURE SWELLING with *RATIOS for anisotropic swellingAnisotropic hardening(cont’d)Foam plasticity *FOAM For energy absorption structures Clay plasticity *CLAY PLASTICITY With *POROUS ELLASTIC (Cambridge) Cycled plasticity *ORNL With *PLASTIC or *CYCLED PLASTIC Oak Ridge National Laboratory for304, 316 stainless steel Granular materials *DRUCKER PRAGER Pressure dependent yield *YIELD Hardening/softening for Drucker-Prager *CAP PLASTICITY Drucker-Prager with cap yield surface *CAP HARDENING Concrete plasticity *CONCRETE Cracking failure, damaged elasticity *FAILURE RAIOS, *TENSION STIFFENING, *SHEAR RETENSION Jointed material *JOINTED MATERIALFor materials with parallel joint surfaces Inelastic dissipation *INELASTIC HEAT FRACTION pl ijij pl r εησ =Deformation *DEFORMATION PLASTICITY k ijk ij D εσ=plasticity [D]: nonlinear elasticity → fully plastic, no unloading, need no *ELASTIC*CONDUCTIVITY*EXPANSION*LATENT HEAT *SPECIFIC HEAT*HEAT GENERATION With user subroutine HETVAL *DIFFUSIVITY*ACOUSTIC MEDIUM Bulk modulus & volumetric drag *DAMPING *DENSITY*ORIENTATION*USER MATERIAL CREEP, UHYPEL, UHYPER, UMAT *BOND SURFACE Defines debonding criterion*FRICTION Defined under *INTERFACE, ELSET=or *SURFACE INTERACTION, NAME= *GAP CONDUCTANCE For *INTERxxT or DINTERxx elements *GAP FLOWPermeability in pore pressure interfaces *GAP HEAT GENERATION Frictional dissipation at the interface*GAP RADIATIONNo view factor calculations*CAVITY RADIATION With view factor calculations。
cohesive单元
Traction-separation-based modelingThe modeling of bonded interfaces in composite materials often involves situations where the Inter mediate glue material is very thin and for all practical purposes may be considered to be of zero thickness (see Figure基于牵引-分离建模粘结界面的建模、经常涉及到的情况中间胶材料非常薄,实际上可能被认为是零厚度。
The behavior of the interface prior to initiation of damage is often described as linearelastic in terms of a penalty stiffness that degrades under tensile and/or shearloading but is unaffected by pure compression.界面启动之前的行为损害通常被认为是线性的弹性的惩罚刚度,降低拉伸或剪切载荷作用下却不受影响由纯压缩。
You may use the cohesive elements in areas of the model where you expect cracks to develop.However, the model need not have any crack to begin with.你可以用粘性元素的区域模型,你期望裂缝发展。
然而,该模型不需要任何裂纹。
In fact, the precise locations (among all areas modeled with cohesive elements) where cracks initiate, as well as the evolution characteristics ofsuch cracks, are determined as part of the solution. The cracks are restricted to propagate along the layer of cohesive elements and will not deflect into the surrounding material事实上,(在所有的精确位置领域建模与凝聚力元素),发起、裂缝以及演化的特点这些裂缝,决心作为解决方案的一部分。
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12.1. Including Debonding in a Contact Analysis Debonding can be defined in any model that includes surface-to-surface (CONTA171 through CONTA174), node-to-surface (CONTA175), line-to-line (CONTA176), or line-to-surface (CONTA177) contact. For a detailed discussion on how to set up a contact analysis, see Surface-to-Surface Contact.
To activate debonding for a contact pair, the following contact options must be defined for the contact element:
Augmented Lagrangian method or pure penalty method (KEYOPT(2) = 0 or 1)
Bonded contact (KEYOPT(12) = 2, 3, 4, 5, or 6) In addition, you must specify a cohesive zone material model with bilinear behavior for the contact elements. Two ways to specify the material data are available:
Bilinear material behavior with tractions and separation distances (TB,CZM command with TBOPT = CBDD)
Bilinear material behavior with tractions and critical fracture energies (TB,CZM command with TBOPT = CBDE)
This material model is discussed in more detail in the following section. Once you have defined the required input parameters, you can solve the analysis the same as you would for any nonlinear analysis (see Solving the Problem). After debonding is completed, the surface interaction is governed by standard contact constraints for normal and tangential directions. Frictional contact is used if friction is specified for contact elements.
12.1.1. Cohesive Zone Materials Used for Debonding A cohesive zone material model is needed to model debonding in a contact analysis. This material is defined using the data table method (TB and TBDATA commands). Temperature dependent data is also allowed (TBTEMP command). On the TB command, use Lab = CZM to denote a cohesive zone material, and use TBOPT = CBDD or CBDE to indicate the specific material data you will provide. The two data definitions are described below. For more information on this material, see Cohesive Zone Material Model in the Theory Reference for the Mechanical APDL and Mechanical Applications. 12.1.1.1. Bilinear Material Behavior with Tractions and Separation Distances (TBOPT = CBDD)
This is a linear elastic material behavior with linear softening characterized by maximum traction and maximum separation. To define this material, use the TB,CZM command with TBOPT = CBDD. Specify the material constants as data items C1 through C6 on the TBDATA command:
Constant Symbol Meaning C1 σmax maximum normal contact stress
C2 cnu contact gap at the completion of debonding C3 τmax maximum equivalent tangential contact stress C4 ctu tangential slip at the completion of debonding C5 η artificial damping coefficient C6 β flag for tangential slip under compressive normal contact stress
Sample command input for this material is shown below. TB,CZM,1,2,,CBDD TBDATA,1,σmax, cnu,τmax, ctu,η,β
12.1.1.2. Bilinear Material Behavior with Tractions and Critical Fracture Energies (TBOPT = CBDE)
This is a linear elastic material behavior with linear softening characterized by maximum traction and critical energy release rate. To define this material, use the TB,CZM command with TBOPT = CBDE. Specify the material constants as data items C1, through C6 on the TBDATA command:
Constant Symbol Meaning C1 σmax maximum normal contact stress C2 Gcn critical fracture energy for normal separation C3 τmax maximum equivalent tangential contact stress C4 Gct critical fracture energy for tangential slip C5 η artificial damping coefficient
C6 β flag for tangential slip under compressive normal contact stress Sample command input for this material is shown below. TB,CZM,1,2,,CBDE TBDATA,1,σmax,Gcn,τmax,Gct,η,β
12.1.2. Debonding Modes Debonding involves separation of surfaces forming an interface. The direction of separation determines the debonding mode. ANSYS detects the debonding mode based on material data that you input for normal and tangential directions:
Mode I debonding involves separation normal to the interface. It is activated by inputting data items C1, C2, and C5 on the TBDATA command.
Mode II debonding involves slip tangent to the interface. It is activated by inputting data items C3, C4, and C5 on the TBDATA command.
Mixed mode debonding involves both normal separation and tangential slip. It is activated by inputting data items C1, C2, C3, C4, and C5, and C6 on the TBDATA command.
Mixed mode debonding involves both normal separation and tangential slip. It is activated by inputting data items C1, C2, C3, C4, and C5, and C6 on the TBDATA command.