【作者】 周松；

【导师】 王振清；

【作者基本信息】 哈尔滨工程大学 ， 固体力学， 2013， 博士

【摘要】 复合材料以其优异的材料性能广泛应用于航空航天、船舶制造和土木工程行业，复合材料的广泛使用，使得复合材料结构尺寸日渐增大，而复合材料接头则是决定复合材料结构性能的关键因素。有研究表明，结构失效70%发生在接头处，因此，对于复合材料接头的研究就显得至为重要了。接头形式多种多样，胶接和机械连接为主要连接方式。螺栓连接是机械连接的典型连接方式，应用也较为广泛，本文分别使用实验与数值的方法研究了复合材料螺栓连接接头的渐进损伤失效。相关研究的详细内容如下：1.针对复合材料螺栓连接T型接头中接触对较多的问题，选用ABAQUS处理接触有限元问题。同时，改变不同接触属性：接触面摩擦系数和螺栓预紧力，计算二者对T型接头螺栓孔周边应力的影响规律。使用不同外载条件，分析外载对T型接头应力分布的影响。2.使用扩展有限元预测螺栓连接单搭接接头的失效，由于接头问题是一个三维问题，因此，传统壳单元对于解决接头问题并不太适合。本文使用MATLAB开发了复合材料层合板等效模量的计算程序，为了验证扩展有限元的优点和特性，首先我们将数值结果与实验结果进行了对比，同时，研究了不同网格密度对计算结果和失效模式的影响，并数值模拟了不同铺层角度对接头失效的影响。然后，数值模拟了几何参数下的失效模式和失效载荷，几何参数为W/D和E/D。最后模拟了两个螺栓连接接头的失效过程，并与单螺栓连接接头进行了对比。3.实验研究了几何参数对于复合材料螺栓连接单搭接接头的影响规律，选取的几何参数比为W/D和E/D。在试验中用于测试材料参数和接头失效的部件为VARI工艺制备而成。实验测试了接头中复合材料层合板的工程模量，而后通过实验分析了螺栓扭矩对于复合材料接头失效载荷的影响。最后通过实验研究了参数对接头失效载荷及失效模式的影响规律。4.在数值分析中，选用三维HASHIN准则，利用ABAQUS子程序USDFLD和VUMAT开发复合材料渐进损伤子程序。USDFLD子程序中，一旦应力满足失效准则，则将材料刚度进行衰减，而VUMAT子程序中，一旦应力满足失效准则，材料刚度衰减后，同时在子程序中进行应力计算。两种渐进损伤模型与实验结果吻合良好。对比两种渐进损伤模型可以发现，VUMAT子程序收敛速度快，精度也满足工程需要，因此，在工程计算中，可以选用此种简便快速的计算方法，节省计算成本。最后，使用用户子程序UMAT与内聚力方法，预测接头压缩失效。综上所述，本文对不同复合材料螺栓连接接头进行了较系统的研究，希望能为工程设计提供参考和帮助。更多还原

【Abstract】 Composites are widely used in different branches of engineering and structural systemslike those in aerospace and automobile industries, power plants, etc. The composite jointshave become a very important aspect because the structural properties of the compositestructure are determined by its joints.70%of composite structure damage occurs in joint.Failure load and failure mode of composite joints are critical. Bolted joint is commonmechanical fastened joints used for joining the composite parts. So many researchers areinterested in bolted composite joints. In this paper, failure response of composite bolted jointswas carried out by experimants and numerical methods. The following aspects have beenresearched in detail:Firstly, since there were a lot of contact pairs, ABAQUS was used to analyze the contactfinite element of T joint. Contact surface friction coefficient and bolt clamping load were twoaspects which could influence contact properties. Different friction coefficient and boltclamping load were used to simulate the stress distribution of bolt-hole in T joint. At last,different external loads were used to analyze the stress of T joint.Secondly, XFEM was used to predict the failure of bolted single-lap composite joint. Sincethe joint problem was contact finite element which was a three-dimensional problem, andtraditional composite laminate was treat as shell which can not solve the contact problem well.So MATLAB code written by author was used to calculate three-dimensional equivalentmaterial properties of laminate which can simplify the failure simulation of composite joint.To test and verify the advantages of XFEM on failure analysis of composite joint, Firstly,progressive failure simulation result of bolted single-lap composite joint with one bolt wascompared with the experiments result in literature, and the influences of mesh size on crackpropagation path and failure response were investigated. Failure responses of two kinds ofjoints with different laminate designs are studied, too. Secondly, influences of geometricparameters on failure load and bearing strength of joint were investigated. Two geometricparameters include plate width-to-hole diameter ratio (W/D) and the edge-to-hole diameterratio (E/D). At last failure of joint with two bolts was simulated, too. The simulation results oftwo types of joint were compared with each other. Thirdly, experiments were used to investigate the influence of geometric parameters onfailure response of bolted single-lap composite joint. Geometric parameters were the distancefrom the free edge of plate to the diameter of bolt hole (E/D) ratio and the width of thespecimen to the diameter of bolt holes (W/D) ratios. In the experiments, specimens used fortesting material stiffness, strength and failure of bolted single-lap composite joints were madeby VARI process. In order to simulate failure of joint, engineering constants of compositelaminate in joint were tested, and then influence of bolt torque on failure load of joint wereinvestigated, at last effects of geometrical parameters on failure load and failure modes onjoints were studied.Finally, in numerical analysis,3D Hashin failure criteria was chosen for finite elementanalysis of composite joints. Two kinds of progressive failure models developed inABAQUS/Standard and Explicit were used to simulate failure of joints. User subroutinesUSDFLD and VUMAT were used in these two models, respectively. In subroutine USDFLD,stiffness degradation occurred when failure criteria was satisfied. In subroutine VUMAT, oncefailure criteria was satisfied, stiffness degradation occurred, and the stress was calculated bysubroutine. Two finite element models showed an excellent agreement with experimentalresults. Compared with finite element model developed in ABAQUS/Standard, modeldeveloped in ABAQUS/Explicit with subroutine VUMAT was introduced in this paper.Explicit model was found to could improve the convergence speed and reduce thecomputation time. The results of the numerical analysis were presented with a focus onproviding a more detailed insight into the progressive failure process. User subroutine UMATand cohesive method were used to investigate failure of joints under compressive load.In conclusion, the analysis of different bolted composite joints has been carried outsystematically and it will provide useful references to practical engineering problems.更多还原