纤维缠绕固体火箭发动机壳体的力学数值仿真

针对某种纤维缠绕复合材料固体火箭发动机壳体,依据原壳体在ABAQUS中建立了有限元模型,建模过程中将纤维缠绕层视为层合板来处理,简化了模型,并对发射瞬态进行有限元数值计算,分别求出了环向层6层的应力和缠绕层6层的应力,以便于强度分析,并对于铺层方案进行求解,得出数据结论,数据结果与实际情况符合,研究结果为纤维缠绕固体火箭发动机优化分析提供了理论依据。     

缠绕张力对环缠绕复合材料气瓶应力的影响

提出了一种等效降温法,将缠绕张力产生的预应力等效模拟为复合材料层降温产生的预应力,通过理论推导得到了缠绕预应力与复合材料层降温量之间的计算公式,基于等效降温法并利用通用有限元软件研究了缠绕张力对环缠绕复合材料气瓶应力的影响。结果表明：随着缠绕预应力的增大,环缠绕复合材料气瓶内胆工作应力减小、复合材料层工作应力增大;缠绕张力预应力较大时会抵消自紧工艺效果,气瓶工作应力和纤维应力比主要受缠绕张力影响,在进行有限元应力分析和纤维应力比计算时应考虑缠绕张力作用。     

基于ACIS几何造型系统的纤维缠绕复合材料壳体设计

利用图形内核ACIS丰富的几何造型功能和HOOPS图形显示方面的优势,通过VC++.NET这样一个通用的开发平台进行纤维缠绕复合材料壳体设计研究,本研究解决了复合材料壳体模型化、参数化和设计程序化的技术难题,实现了复合材料壳体一体化设计。设计结果可以获得58个参数。主要包括:缠绕壳体纤维数据、几何数据、质量特性参数、力学特性参数以及壳体战术技术性能数据。设计结果为有限元分析提供直接可调用的图形参数,也可以为CAD软件提供初始模型。该设计系统为三维造型显示,可视化程度高,界面友好,交互性强,为用户对复合材料壳体初始设计提供了方便。     

基于逐渐损伤理论的复合材料飞轮转子渐进失效分析

基于三维逐渐损伤理论,采用刚度衰减模型来预测三维复合材料飞轮转子的渐进失效特性,并与已有参考文献进行比对,验证模型的正确性。模型考虑的失效形式主要包括四种:纤维断裂,基体开裂,分层和基纤剪切失效。采用有限元法中的牛顿-拉普森非线性迭代算法进行三维渐进失效分析,分析不同缠绕预应力下飞轮的失效过程,并进行对比分析。计算结果表明,转子的失效首先发生在飞轮的中部,单元发生基体开裂失效,随着转速的提高,单元发生纤维断裂,导致飞轮在外径处发生爆破失效。缠绕过程中对纤维束施加预应力能提高飞轮的初始失效转速。在整个损伤过程中没有出现单元分层失效和剪切失效。     

纤维缠绕复合材料管道双轴疲劳寿命预测研究

对纤维缠绕复合材料管道的双轴疲劳行为进行了实验与理论研究。根据多轴疲劳试验的要求,设计了一种新的纤维缠绕成型复合材料薄壁管型试样,通过对不同缠绕角度试样在不同双轴载荷比条件下的双轴疲劳实验,得出了玻璃纤维/环氧树脂薄壁管的应力/寿命曲线。参考金属材料的多轴疲劳失效准则,结合复合材料各向异性的特点,提出了复合材料多轴疲劳失效准则,对不同缠绕角复合材料管道在不同载荷条件下的疲劳寿命进行统一。结果表明:本文提出的失效准则可以把不同缠绕角复合材料在多种载荷条件下的多轴疲劳寿命统一起来,从而根据一个给定缠绕角度试样在某种试验条件下疲劳寿命来预测其它缠绕角度条件下的疲劳寿命,具有非常重要的理论研究价值和工程应用前景。     

多层复合材料缠绕的"单元死活"有限元计算方法

为更准确地应用有限元分析方法解决树脂基复合材料纤维缠绕的小型压力容器的强度问题，文中提出利用“单元死活”模拟纤维缠绕过程的简易有限元数值计算方法，并通过使用这种方法对复合材料等强度缠绕的某型号小型压力容器进行计算模拟，证明方法的正确性。这种计算方法的提出将为压力容器的优化设计、分析等研究提供更为充分、可靠的依据。     

复合材料环向缠绕飞轮轮体工艺应力研究

在平面应力微分方程中考虑温度影响,可以得到复合材料轮体在制造和使用过程中更真实的应力应变情况。计算结果表明常规固化降温过程产生的应力足以使厚壁圆筒开裂。为解决复合材料环向缠绕飞轮在固化以及旋转时径向强度不足的难题,文中提出采用纤维加力缠绕施加径向压预应力,配合及时在线电子束固化的新工艺方法。将新方法中的加力缠绕过程等效为薄层过盈配合,统一加力缠绕和过盈配合两种制造方法以及后续升降温和旋转等工况下的计算问题。最后编制Matlab程序,给出算例,结果表明新工艺方法对径向应力改善明显。     

超薄单层复合材料缠绕压力容器承载性能研究

针对压力容器承载性能,基于经典层合板刚度等效理论,提出了一种可以考虑复合材料缠绕层单层厚度的压力容器承载性能分析方法;与实际铺层有限元模型进行对比,验证了分析方法的有效性;对不同单层厚度的复合材料进行了单向拉伸试验,获得材料强度与单层厚度的关系;分析了超薄单层复合材料缠绕压力容器的应力分布、失效系数分布及失效压力。结果表明,超薄单层复合材料缠绕压力容器的应力和损伤分布更为均匀,失效内压较常规单层厚度复合材料可提高54.5%。该研究成果可为超薄单层复合材料缠绕压力容器的结构设计提供可靠的理论参考。     

复合材料缠绕压力容器冲击损伤分析

基于复合材料经典层合板理论和冲击动力学理论,采用Chang -Chang损伤准则对受低速冲击后的复合材料缠绕层进行损伤判定,并进行相应的刚度折减,分析复合材料纤维缠绕压力容器在冲击载荷作用下的动态响应和损伤状况.结合动力松弛法分析冲击能量对不同工作压力下复合材料缠绕压力容器抗冲击性能的影响,并对压力容器不同部位的抗冲击敏感性进行了相应研究,预测出压力容器的缠绕层损伤特征和最不利的冲击位置.     

基于ANSYS纤维缠绕复合材料压力容器的可靠性分析

介绍了纤维缠绕复合材料压力容器的可靠性分析方法,在ANSYS 14.0中利用有限元法对压力容器建模并进行力学分析获得相应的力学响应,然后根据计算结果进行失效分析,确定了纤维复合材料压力容器最薄弱的部分,为压力容器的优化设计提供了充分的理论依据。     

含孔各向异性板的孔边应力场分析

根据非均质各向异性弹性理论对含机翼检修孔复合材料板进行了孔边应力分析，解决了复杂孔形的边界条件问题，得到了精确解析解。对工程应用中常见的几种荷载状况（在不同纤维方向，不同加载形式、加载方向情况下）对孔边应力集中系数的影响进行了探讨。采用有限元法进行了对比计算。     

Ultimate strength prediction of continuous fiber-reinforced brittle matrix composites

A model to predict ultimate strength of continuous fiber-reinforced brittle matirix composites has been developed. A statistical theory for the strength of the uniaxially fiber-reinforced brittle matrix composite is presented. Material of matrix is assumed to be homogeneous and isotropic, so that the strength of material is anywhere constant, whilst that of fiber is considered to show Weibull statistical distribution. The theory may be utilized to optimize the biaxial and multidirectional tensile strength properties of laminated materials. The composite strength is estimated by assuming no interacting matrix cracks. The frictional shear stress caused by bridging fibers is involved in the strength computation. The predicted strength is compared to experimental results with LAS-Glass/Nicalon fiber composite.     

复合材料储能飞轮转子的设计

当转子的最大环向应力和最大径向应力同时达到它们各自方向上的强度时,可以得到最优内外径比.基于该设计理念对影响飞轮储能密度的复合材料轮缘内外径比λ进行设计,并选用各向异性材料碳纤维环氧树脂复合材料、玻璃纤维环氧树脂复合材料及各向同性材料高强铝合金为飞轮转子材料进行最大边缘线速度及最大单位质量储能的比较,结果表明:碳纤维环氧树脂复合材料所设计的飞轮转子单位质量储能最高,体积最小,边缘线速度最大.     

Effects of fiber aspect ratio evaluated by elastic analysis in discontinuous composites

An elastic stress analysis to investigate the effects of fiber aspect ratio in short fiber reinforced discontinuous composite materials has been done for different fiber volume fractions. In order to examine the elastic internal behavior, an evaluation of the load bearing capacity of discontinuous reinforcements is needed in advance. Accordingly, analytical derivation of composite mechanics has been carried out to predict fiber stresses and fiber/matrix interfacial shear stresses in discontinuous composites. The model is based on the theoretical development of conventional shear lag theory developed by Cox. However, the major shortcoming of the Cox model is due to the calculation without normal stress transfer from the end of fibers. In order to overcome the shortcoming, both of the normal and shear stress transfer mechanisms between the fiber and the matrix are accounted for with the stress concentration effects as well as material and geometrical properties. Results of predicted stresses concerning the various fiber aspect ratios are described by using the present model that is the closed form solution and compared with the Cox model and Taya model. It is found that the effect of fiber aspect ratio is significant to composite strengthening through load transfer from the matrix to the fiber, whereas the effect of fiber volume fraction is not so sensitive, relatively. It is also found that the present model has the capability to correctly predict the values of fiber stresses and fiber/matrix interfacial shear stresses.     

混合复合材料飞轮转子成本优化设计

基于平面应力理论,计算多层过盈装配混合纤维增强复合材料飞轮转子的应力分布;指出多层过盈装配复合材料转子多种可能的失效形式;结合增广Lagrange乘子法、粒子群优化(Particle swarm optimization,PSO)算法和经典梯度算法各自的优点,提出可求解非线性约束问题的且具有全局收敛性和较高计算效率的两阶段增广Lagrange粒子群优化算法(Two-stage augmented Lagrange particle swarm optimization,TS-ALPSO);利用TS-ALPSO优化算法,以多层过盈装配混合复合材料转子的分层半径、层间过盈量和转速为设计变量,研究多层混合复合材料转子的成本优化问题;并分析转子材料价格不变时,材料次序、分层数及过盈量对转子储能性能的影响;揭示出转子单位成本储能最大时,转子分层半径、层间过盈量及转速随转子材料价格变化的规律。     

Analytical study on the elastic-plastic transition in short fiber reinforced composites

In discontinuous composites, the fiber end effects can be neglected when the length of fiber is much greater compared to the diameter. Thus, conventional shear lag theory is very useful for predicting composite properties deduced from each constituent. However, in the case of short fiber or whisker reinforced composites, the end effects cannot be neglected, and the composite properties are functions of material and geometrical parameters since the fiber end effects significantly influence the behavior of composites. For a good understanding of the behavior of short fiber or whisker reinforced composites, it is necessary to first understand the mechanism of stress transfer and it has well been modified before. However, the modification was limited to the basic elastic stress calculation of the fiber and matrix in a micromechanical model. Accordingly, the former modification of the shear lag model has been extended to predict the overall elastic composite behavior and elastic-plastic behavior of which result can predict the stress concentration in the matrix as well as the onset of matrix yielding. The extended modification results showed that it gives a good agreement with finite element analysis as well as with experimental data. It was also found that the local matrix yielding is initiated in the vincinity of the fiber ends which produces local plasticity and an elastic-elastic transition before the composite stress reaches matrix yield stress.     

轻质复合材料天线辐射梁单元研究

为解决传统钢制大型天线辐射梁单元重量大、重复安装精度差、易腐蚀等问题,采用钢制球形接头与碳纤维复合材料管材胶接组合的方式,对复合材料管材和胶接接头进行了合理设计,成功制造出某大型天线轻质复合材料辐射梁单元。对此辐射梁单元进行了有限元分析与实测研究,能够很好地满足天线使用要求。结果表明：与传统的钢制辐射梁单元相比,复合材料天线辐射梁单元减重50％左右,辐射梁刚度好、强度大,安装一致性好、精度高,特别适合重复安装的大型天线。     

一种快速制作栅格天线的新型解决方案

文中以一种树脂基碳纤维复合材料栅格天线反射面的制作成型为研究对象,详细阐述了该反射面成型后脱模模具工装的设计及成型方案。该栅格反射面所使用的主要材料为东丽公司的T700,基体为3234树脂体系。通过对复合材料模具的设计制作及使用、复杂复合材料制品二次脱模等方面的研究,提出了用球墨铸铁及碳纤维复合材料制造模具、采用真空袋热压罐成型工艺的新型解决方案。结果表明：与传统金属模具相比,在较大温差下复合材料模具具有尺寸精度更稳定、制作更简便、重量更轻等优势;利用复合材料过渡模具实现栅格反射面二次脱模可以大大提高生产效率。该方法对此类栅格反射面的制作具有指导意义。     

复合材料板应力集中数值模拟分析及光弹性实验验证

荷载作用下复合材料构件应力分布状态的分析是工程实践中的一个重要环节。构件中的应力集中现象将使其产生疲劳裂纹,也能使脆性材料制成的零件发生静载断裂。而对应力集中区域的有限元计算分析是一种数值模拟方法,有一定局限性,但其有效性可以通过相应的光弹性实验加以验证。     

SOLUTION OF DIFFERENT HOLES SHAPE BORDERS OF FIBRE REINFORCED COMPOSITE PLATES BY INTEGRAL EQUATIONS

Accurate boundary conditions of composite material plates with different holes are founded to settle boundary condition problems of complex holes by conformal mapping method upon the nonhomogeneous anisotropic elastic and complex function theory. And then the two stress functions required were founded on Cauchy integral by boundary conditions. The final stress distributions of opening structure and the analytical solution on composite material plate with rectangle hole and wing manholes were achieved. The influences on hole-edge stress concentration factors are discussed under different loads and fiber direction cases, and then contrast calculates are carried through FEM.