受压荷载作用下的层合板结构：材料和结构的屈曲分析

为了提高组合结构设计的可靠性，需要对层合板失效进行更有效的描述。近期的国际组织已经明确肯定，目前的方法过高地估计了压缩荷载下复合材料的强度。为了改进这一点可以采用一种更为完善的方法。首先，提出研究材料的多尺度失效方法，可以预测在较大荷载范围内不同铺层方式的失效。当最后的破坏只取决于材料特性时，此模型能够准确地描述层合板的失效情况。第二，考虑屈曲状态的结构性分析，提高了模型在压缩荷载下的预测精度。提出了一种简单的方法用来预测屈曲应力和屈曲后状态，甚至在很高的非线性材料状态下也能预测。对比模型和试验结果，十分吻合。     

层合板极限强度判据及其最大承载能力的工程设计

在研究层合板在复杂荷载下的极限强度时,提出了基于层合板基本强度和最佳应力比实验强度所确定的层合板张量型强度准则和层合板联合强度理论。通过建立新的层合板铺层刚度退化理论并用实验测定“均衡型刚度退化系数”,实现了LPE包络线预测,进而提出层合板退化张量型强度准则。该准则是一种由单向板基本刚度、强度性能,辅以均衡型刚度退化系数来预测各种铺层序列的层合板在复杂荷载下最大承载能力的强度判据和方法。上述强度准则与[±θ]S层合板的单向拉伸、[±45]S、[0/90]S层合板平板拉剪以及(0/90]S、[0±45/90]S和(0/45]S层合管状件的双向荷载强度实验结果相当吻合。所提出的层和板极限强度判据和最大承裁力的估算方法对玻纤复合材料层合结构的工程强度设计,具有实际的指导意义和实用价值。     

碳纤维复材-铝合金双槽形截面层合板梁承载性能预测研究

为了研究具有双槽形异型截面的碳纤维增强铝合金层合板梁的弯曲承载性能,采用压力模压热固化成形工艺制备了两组碳纤维铺层结构分别为[0°/90°/0°]和[45°/0°/-45°]的双槽形截面层合板梁构件,进行了四点弯曲试验,获得了不同试件的极限弯曲荷载和破坏模式。针对二维Hashin失效准则的局限性,采用FORTRAN语言编写了适用于ABAQUS/Explicit显式分析算法的VUMAT子程序,实现了基于三维Hashin失效准则的CFRP层渐进损伤的数值模拟分析功能,对双槽形层合板梁的承载性能和破坏形式进行了分析。同时,基于经典层合板理论提出了一种预测碳纤维增强铝合金层合板梁安全承载力的理论方法。试验、数值模拟与理论计算结果的比较表明,所提出的安全承载力计算方法可用于预测碳纤维增强铝合金槽形截面层合板梁的安全承载力,可应用于异形截面层合板梁构件的设计。     

带加劲肋的帽形卷边槽钢组合柱的屈曲

研究了带有腹板加劲肋的帽形卷边槽钢截面的薄壁组合柱的屈曲性能。这些柱由具有对称铺设角的层合板构成。采用有限元法对柱的屈曲性能进行分析。通过分叉分析以获得屈曲荷载及柱的振型。采用荷载-挠度曲线分析对柱的后屈曲性能进行研究。结果表明:铺设角和几何参数对柱的屈曲和后屈曲性能影响显著。本文的研究结果有助于研究如何提高组合柱的承载能力。     

含椭圆孔的变角度复合材料层合板的屈曲性能研究

针对变角度复合材料的纤维方向角向着平面位置进行变化,由此得出,使用新铺层方式的优点,并针对椭圆孔的离心率、开孔的方位给层合板屈曲临界荷载带来的影响采取分析,此次研究为日后含椭圆孔的变角度复合材料层合板的结构设计和优化奠定一定的基础。     

微裂纹损伤对纤维复合材料层合板强度的影响

基于连续损伤理论及Hoffman强度准则,采用多标量连续损伤模型和有限元法,对复合材料层合板在横向均布载荷下的损伤破坏过程进行了研究,分析中考虑了几何非线性的影响及单层板失效前由微裂纹损伤所引起的刚度下降。研究表明:微裂纹损伤对破坏区域的演化过程有较大影响;用损伤Hoffman准则得到的层板破坏荷载高于无损Hoffman准则的破坏荷载,提高程度受铺层方式的影响。     

反对称层合板屈曲性态分析

应用屈曲控制方程，导出了反对称层合板在面内双向压缩下的屈曲方程，计算了相应的临界荷载并讨论了层合角对临界应力的影响，分析表明层合角对材料的临界应力有较大的影响。     

四边简支层合板在剪切作用下的稳定分析

采用伽辽金变分法分析了四边简支的FRP复合材料层合板在纯剪作用下的屈曲荷裁,得出了四边简支层合板的剪切屈曲解析解,并使用有限元软件ANSYS对解析解进行了数值验算与对比分析。所得公式适合长宽比≤4的正交异性层合板,与数值分析结果吻合良好,所得理论公式对实际工程有一定的参考价值,并在一定程度上丰富了复合材料层合板屈曲公式的理论研究。     

侧向荷载分布方式对钢筋混凝土框架结构层间耗能分布的影响

本文通过pushover方法研究了侧向荷载分布方式对钢筋混凝土框架结构层间耗能分布的影响。用三种不同的侧向荷载分布方式，对层数分别为四层、七层和十五层的框架结构进行了分析。通过与非线性动力时程分析结果的对比，对侧向荷载的选择提出了合理化建议。     

单向准各向同性碳-环氧复合物抗拉强度的尺寸效应

对单向准各向同性碳-环氧复合物进行一系列足尺试验。研究显示:单向试件样本尺寸增加其抗拉强度降低。通过重复子层合板铺层顺序改变层合板厚度时(从单层到第4层,子层合板厚度增加10%),准各向同性试件强度随尺寸增加而增大。然而,当改变子层合板铺层厚度顺序(子层合板厚度从单层到第8层减少62%)时,准各向同性试件强度随尺寸增加反而降低。层合板不能达到单向材料的强度,所有的试件显示横向裂纹和边缘分层导致了初始破坏。     

Thermal buckling load optimization of laminated composite plates

In this study, the applicability of the Modified Feasible Direction (MFD) method on the thermal buckling optimization of laminated plates subjected to uniformly distributed temperature load is investigated. The objective function is to maximize the critical temperature capacity of laminated plates and the fiber orientation is considered as design variable. The first-order shear deformation theory is used in the mathematical formulation. For this purpose, a program based on FORTRAN is used for the optimization of laminated plates. Finally, the effect of aspect ratio, antisymmetric lay-up, boundary condition, material anisotropy, ratio of coefficients of thermal expansion, and hybrid laminates on the results is investigated and the results are compared.     

Thermal postbuckling of laminated composite skew plates with temperature-dependent properties

Thermal postbuckling and consequently, the role of temperature dependence of material properties on the thermal postbuckling behavior of laminated composite skew plates have not been addressed in literature. Hence, this problem is investigated here. The plate governing equations are based on the first-order shear deformation theory (FSDT) and the geometrical nonlinearity is modeled using Green’s strain tensor in conjunction with the von Karman assumptions. Since the problem is geometrically and physically nonlinear, the differential quadrature method (DQM) as an accurate, simple and computationally efficient numerical tool is adopted to discretize the governing equations and the related boundary conditions. Then, a direct iterative method is employed to obtain the critical temperature (bifurcation point) and consequently the nonlinear equilibrium path (the postbuckling behavior) of symmetrically laminated skew plates. After validating the formulation and the method of solution, the effects of temperature dependence of the material properties on the postbuckling characteristic of laminated skew plates with different skew angle, boundary conditions, length-to-thickness ratio, number of layers and ply layout are investigated.     

Verbundglasplatten – Schubverbund und Membrantragwirkung – Teil II (Fortsetzung aus Heft 1/2005 und Schluß)

Laminated glass plates – shear compound and membrane action. The mechanical behaviour of laminated glass plates is governed by the interlayer shear stiffness and membrane action. The objective of the present work is the analysis of these two parameters and the development of a simple, safe and economic method for determining glass dimensions. In partI a temperature and load‐duration dependant shear modulus is determined for PVB from experimental data. Chapter 3 contains an analytic solution for two side supported laminated plates, based on sandwich theory and describes the creep‐buckling problem of compression elements. The part II investigates the non‐linear behaviour of laminated plates. The load‐stress diagrams show that the curves for plates with a flexible shear interlayer are quite close to, or even exceed, the curve for a layered configuration with no interaction between panes. For this reason an overall boundary curve is developed, which applies conservatively to all the configurations. Owing to the flexibility of shear transfer between the glass panes, non‐linear action is exhibited at an earlier stage than with a monolithic condition. This flexibility significantly influences the actual strength of laminated glass units: when the shear transfer is poor – i.e. at high temperature or long load duration the strength lost in bending action is compensated by gains through membrane action.     

Verbundglasplatten – Schubverbund und Membrantragwirkung – Teil I

Laminated glass plates – shear compound and membrane action – Part I. The mechanical behaviour of laminated glass plates is governed by the interlayer shear stiffness and membrane action. The objective of the present work is the analysis of these two parameters and the development of a simple, safe and economic method for determining glass dimensions. In partI a temperature and load‐duration dependant shear modulus is determined for PVB from experimental data. Chapter 3 contains an analytic solution for two side supported laminated plates, based on sandwich theory and describes the creep‐buckling problem of compression elements. The part II (No. 2/2005) investigates the non‐linear behaviour of laminated plates. The load‐stress diagrams show that the curves for plates with a flexible shear interlayer are quite close to, or even exceed, the curve for a layered configuration with no interaction between panes. For this reason an overall boundary curve is developed, which applies conservatively to all the configurations. Owing to the flexibility of shear transfer between the glass panes, non‐linear action is exhibited at an earlier stage than with a monolithic condition. This flexibility significantly influences the actual strength of laminated glass units: when the shear transfer is poor – i.e. at high temperature or long load duration the strength lost in bending action is compensated by gains through membrane action.     

Optimum design of laminated composite plates to maximize buckling load using MFD method

This paper presents optimal design of simply supported laminated composite plates subject to given in-plane static loads for which the critical failure mode is buckling. The objective function is to maximize the buckling load capacity of laminated plates and the fiber orientation is considered as design variable. The first-order shear deformation theory is used for the finite element analysis. In this paper, the effects of bending–twisting coupling are also included for the buckling optimization. The modified feasible direction method is used as an optimization method. Also, computer programs are coded in MATLAB and Golden Section method is adapted in this program for the optimal design of laminated plates for maximum buckling load. The effect of width-to-thickness ratio, aspect ratio, number of layers, material anisotropy, load ratios (N_y/N_x), uncertainties in material properties and functionally graded materials on the results is investigated and compared.     

运用MFD方法对以屈曲为破坏标准的叠层复合板进行最优化设计

对给定平面内静力荷载作用下,以屈曲为破坏机制的简支叠层复合板进行最优化设计。目标函数是使得叠层板的屈曲荷载达到最大,纤维方向为设计变量。有限元分析中应用了一阶剪切变形理论。优化设计中考虑了弯扭力偶的作用,同时采用了以Matlab和Golden Section法编制的计算机程序进行计算。对宽厚比、纵横比、层数、各向异性材料、荷载比(Ny/Nx)等材料特性中其他一些不确定因素进行了对比和分析。     

Free vibration of composite plates using the finite difference method

The finite difference method was used to solve differential equations of motion of free vibration of composite plates with different boundary conditions. The effects of shear deformation and rotary inertia on the natural frequencies of laminated composite plates are investigated in this paper. Four cases are studied: neglecting both shear deformation and rotary inertia, considering only rotary inertia, considering only shear deformation, and considering both. Solutions were obtained for symmetric and angle-ply laminated plates. The factors that affect natural frequencies of different composite plates, such as span-to-depth ratio, aspect ratio, angle-ply, and lamination sequence were also investigated. Results were found to agree well with exact and approximate solutions reported in literature. Shear deformation showed a considerable effect on the natural frequencies for composite plates, whereas the rotary inertia effect was found to be negligible.     

夹层玻璃板大挠度弯曲分析

文章在夹层玻璃板小挠度理论基础上研究了大挠度情况下的非线性弯曲问题,提出了以5个位移分量表示的夹层玻璃板大挠度控制微分方程。文章同时指出该微分方程的解可由夹层板大挠度的解类比得出,能直接应用于实际工程设计。     

无单元迦辽金法在对称叠层板弯曲问题中的应用

基于Kircihhoff板理论和对挠度函数采用滑动最小二乘近似函数进行插值,研究无单元Galerkin(EFGM)方法在对称叠层板弯曲问题中的应用.分析中,本质边界条件采用罚因子法施加,对称叠层板的无单元法几何刚度矩阵由最小二乘法和变分原理得到.通过单层方板和对称叠层板的数值算例并与其他方法的结果进行比较,表明EFGM法求解对称叠层板弯曲问题具有收敛性好、精度高等优点,从而验证了该法的有效性.     

预应力圆孔板叠合楼板的工程应用

本文以实际工程应用为背景,提出了以新型预应力圆孔板为底板的大跨叠合楼板应用形式。通过9.6m跨度叠合底板及叠合板的加载试验,验证了圆孔板叠合楼板的良好性能,并利用圆孔板叠合楼板成功建造了9.6m×20m跨度的工业厂房。