正交复合材料面层夹层板非线性理论及应用

针对复合材料面层夹层板的构造和变形特点，考虑横向剪应力在面层和芯层粘结处的连续条件，应用Ｈａｍｉｌｔｏｎ原理建立了基于五个未知函数的正交铺设复合材料面层夹层板的非线性精化理论。对静力学问题，控制方程化简为由四个基本未知函数表述。文中还分析了简支正交铺设复合材料面层夹层板的非线性弯曲，给出了载荷—挠度特征关系和板中应力的分布状况。数值计算表明，夹层板面层和芯层粘结处的层间剪应力在工程设计中是十分重要的。     

缝合复合材料层合板拉伸疲劳损伤及其机理

对有、无缝合复合材料层合板的拉伸疲劳性能进行了试验研究,考察了0^\circ缝合对复合材料光滑板拉伸疲劳损伤扩展规律的影响. 通过有限元素法分析了有、无缝合复合材料层合板的应力状态分布情况,对缝合复合材料层合板的拉伸疲劳损伤及其扩展机理进行了分析. 研究表明,缝合改变了复合材料层合板拉伸疲劳损伤起始与扩展的机理,针脚附近的面内正应力\sigma_{x}与层间剪应力的集中对层合板拉伸疲劳损伤的发生与扩展有着重要的作用,自由边界处的层间集中应力对缝合板的疲劳性能也有影响. 自由边界处的层间集中应力是导致无缝合层合板疲劳损伤及其扩展的主要原因.      

含脱层损伤复合材料层合梁的冲击动力屈曲

针对含初始缺陷和脱层损伤的复合材料层合梁的轴向冲击动力屈曲问题进行了分析。基于Hamilton原理导出了考虑初始缺陷、轴向和横向惯性、横向剪切变形以及转动惯性影响时含脱层损伤复合材料梁的非线性动力屈曲控制方程;基于B-R准则,采用有限差分方法求解了受轴向冲击载荷作用下含脱层损伤复合材料梁的动力屈曲问题;讨论了冲击速度、初始几何缺陷、铺层角度以及脱层长度等因素对复合材料层合梁动力屈曲的影响。     

粘弹层合板的稳态振动和层间应力

应用混合分层理论和Ressiner混合变分原理，在板厚方向取二次位移插值函数和三次、四次横向应力插值函数推导出粘弹层合板的动力学方程，得出简支粘弹层合板稳态振动的解。不仅得出与三层弹性板精确的自振频率吻合良好的解，而且对于粘弹层合板，所计算的自振频率和结构损耗因子也与三维结果吻合较好。计算了自由阻尼层合板对应的低阶法向位移响应幅值和层问横向应力的幅值。结果表明，较高的层间横向正应力是低频稳态振动中引起粘弹层合板分层破坏的主要因素，采用适当模量和厚度的粘弹性材料将有效地降低粘弹层合板的层间横向正应力的幅值。     

微裂纹损伤对复合材料层板分层的影响

本文将双标量损伤模型推广,考虑层内及层间微裂纹损伤相互作用,建立了层合复合材料的多标量损伤本构关系,并将该本构关系应用于含贯穿分层层板的后屈曲分析,采用准三维有限元法研究了分层尖端场与极限损伤区演变的特点,结果表明：损伤导致裂尖区层间应力奇异性消失,引起层间应力重新分布;损伤区的发展方向取决于分层上下表面层的铺设角,能量释放率不能反映损伤和分层扩展特征,因而有必要建立基于损伤演化的分层扩展准则。     

复合材料层合板粘弹性固化残余应力分析

基于Ｓｃｈａｐｅｒｙ积分型粘弹性本构关系，推导了考虑横向剪切效应的复合材料层合板线性热粘弹性有限元分析列式，对层合板的粘弹性响应和加工成型过程中的残余应力进行了分析，给出了一些有意义的结果。     

变形对非饱和土渗透系数影响规律模拟研究

对有、无缝合复合材料层合板的拉伸疲劳性能进行了试验研究,考察了0^\circ 缝合对复合材料光滑板拉伸疲劳损伤扩展规律的影响. 通过有限元素法分析了有、无缝合复 合材料层合板的应力状态分布情况,对缝合复合材料层合板的拉伸疲劳损伤及其扩展机理进 行了分析. 研究表明,缝合改变了复合材料层合板拉伸疲劳损伤起始与扩展的机理,针脚 附近的面内正应力\sigma_{x}与层间剪应力的集中对层合板拉伸疲劳损伤的 发生与扩展有着重要的作用,自由边界处的层间集中应力对缝合板的疲劳性能也有影响. 自 由边界处的层间集中应力是导致无缝合层合板疲劳损伤及其扩展的主要原因.     

复合材料层合板粘弹性固化残余应力分析

基于Ｓｃｈａｐｅｒｙ积分型粘弹性本构关系，推导了考虑横向剪切效应的复合材料层合板线性热粘弹性有限元分析列式，对层合板的粘弹性响应和加工成型过程中的残余应力进行了分析，给出一些有意义的结果     

基于新修正偶应力理论的Mindlin层合板稳定性分析

基于新的各向异性修正偶应力理论提出一个Mindlin复合材料层合板稳定性模型。该理论包含纤维和基体两个不同的材料长度尺度参数。不同于忽略横向剪切应力的修正偶应力Kirchhoff薄板理论,Mindlin层合板考虑横向剪切变形引入两个转角变量。进一步建立了只含一个材料细观参数的偶应力Mindlin层合板工程理论的稳定性模型。计算了正交铺设简支方板Mindlin层合板的临界载荷。计算结果表明该模型可以用于分析细观尺度层合板稳定性的尺寸效应。     

压电智能复合材料层合梁的力电耦合模型及层间应力分析

由于非凡的物理性能,石墨烯纳米片(GPL)被认为是最有吸引力的复合材料增强材料之一.GPL增强材料可以明显提高聚偏氟乙烯(PVDF)压电性能和力学性能.在力电载荷作用下,对含均匀石墨烯薄片增强(GSR)智能压电复合材料层合梁层间应力预测至关重要.若对受到力电耦合作用且层与层之间材料性能突变的压电层合梁层间剪切变形预测有误,则其层间应力过大可能导致层间失效.因此,论文提出一种适于分析此类问题且满足层与层之间相容性条件的有效力电耦合模型,用于含GSR致动器的复合材料层合梁层间应力分析.应用Reissner混合变分原理(RMVT),可以提高考虑力电耦合效应的横向剪应力预测精度.三维(3D)弹性理论和所选模型计算结果将用于评估所提梁模型性能.此外,还从力电载荷、压电层厚度、石墨烯体积分数和长厚比等方面对含GSR致动器复合材料层合梁力学响应特性进行了系统的研究.     

THE ANALYSIS OF INTERLAMINAR STRESSES FOR COMPOSITE LAMINATED SHALLOW SHELLS WITH INTERFACIAL DAMAGE

Based on the general six-degrees-of-freedom plate theory towards the accurate stress analysis and nonlinear theory of shallow shells, considering the damage effect of the interlaminar interface and using the variation principle, the three-dimensional non-linear equilibrium differential equations of the laminated shallow shells with interfacial damage are derived. Then, considering a simply supported laminated shallow shell with damage and under normal load, an analytical solution is presented by using finite difference method to obtain the interlaminar stresses. Numerical results show, the stiffness of the shell is weakened, greater absolute values of displacements as well as smaller interlaminar stresses are obtained by interfacial damage. When the interfacial damage is further increased, delamination occurs obviously under normal pulling load and pure shear slip occurs under normal pressure load. The portion of the load undertaken by the two sides of the interface is more different. Different mechanical behaviors are shown in both sides of the interface, and the discontinuation of stresses and displacements takes place in the interface.     

The distributions of the interlaminar stress in a laminated shell with free end boundary

This paper studies the free edge effect yielded by interlaminar stress in a laminated cylindrical shell made up of fiber reinforced layer [0°], [90°] and the isotropic material layer under axisymmetric thermal load or radial pressure. Both ends of the shell are in free boundary condition. The exact solution of the problem can be obtained by using the three-dimensional theory of elasticity. For illustration, the numerical laminar stresses in a double-layer laminated shell under thermal load or radial pressure are calculated.     

Analysis of interlaminar stress and nonlinear dynamic response for composite laminated plates with interfacial damage

By considering the effect of interfacial damage and using the variation principle, three-dimensional nonlinear dynamic governing equations of the laminated plates with interfacial damage are derived based on the general sixdegrees-of-freedom plate theory towards the accurate stress analysis. The solutions of interlaminar stress and nonlinear dynamic response for a simply supported laminated plate with interfacial damage are obtained by using the finite difference method, and the results are validated by comparison with the solution of nonlinear finite element method. In numerical calculations, the effects of interfacial damage on the stress in the interface and the nonlinear dynamic response of laminated plates are discussed.     

ANALYSIS OF INTER-LAMINAR STRESSES FOR COMPOSITE LAMINATED PLATE WITH INTERFACIAL DAMAGE

A constitutive model for composite laminated plates with the damage effect of the intra-layers and inter-laminar interface is presented. The model is based on the general six-degrees-of-freedom plate theory, the discontinuity of displacement on the interfaces are depicted by three shape functions, which are formulated according to solutions satisfying three equilibrium equations, By using the variation principle, the three-dimensional non-linear equilibrium differential equations of the laminated plates with two different damage models are derived. Then, considering a simply supported laminated plate with damage, an analytical solution is presented using finite difference method to obtain the inter-laminar stresses.     

Shear deformation in thermal bending analysis of laminated plates by the GDQ method

The interlaminar stresses and deflections in a laminated rectangular plate under thermal bending were determined by using the generalized differential quadrature method involving the effect of shear deformation. The approximate stress and deflection solutions are obtained under the bending of sinusoidal temperature of thermal load for layer in cross-ply laminates and angle-ply laminates. Numerical results show that the shear deformation has significant effects on the dominant interlaminar stresses and deflections in the laminated plate of thermal bending analysis.     

Nonlinear dynamic response of piezoelastic laminated plates considering interfacial damage effects

This paper presents a nonlinear model for cross-ply piezoelastic laminated plates containing the damage effect of the intralayer materials and interlaminar interfaces. The model is based on the general six-degrees-of-freedom plate theory, the discontinuity of displacement, and electric potential on the interfaces are depicted by three shape functions, which are formulated according to solutions about three equilibrium equations and conservation of charge. By using the Hamilton variation principle, the three-dimensional nonlinear dynamic equations of piezoelastic laminated plates with damage are presented. Then using the finite difference method and the Newmark scheme, an analytical solution is presented. In numerical examples, the effects of different damage models, damage evolution, amplitude and frequency of electric loads on the nonlinear dynamic response of piezoelectric laminated plate with interfacial imperfections are investigated.     

An advanced higher-order theory for laminated composite plates with general lamination angles

This paper proposes a higher-order shear deformation theory to predict the bending response of the laminated composite and sandwich plates with general lamination configurations.The proposed theory a priori satisfies the continuity conditions of transverse shear stresses at interfaces.Moreover,the number of unknown variables is independent of the number of layers.The first derivatives of transverse displacements have been taken out from the inplane displacement fields,so that the C 0 shape functions are only required during its finite element implementation.Due to C 0 continuity requirements,the proposed model can be conveniently extended for implementation in commercial finite element codes.To verify the proposed theory,the fournode C 0 quadrilateral element is employed for the interpolation of all the displacement parameters defined at each nodal point on the composite plate.Numerical results show that following the proposed theory,simple C 0 finite elements could accurately predict the interlaminar stresses of laminated composite and sandwich plates directly from a constitutive equation,which has caused difficulty for the other global higher order theories.     

Free-edge interlaminar stress analysis of piezo-bonded composite laminates under symmetric electric excitation

A stress function-based approach is proposed to analyze the free-edge interlaminar stresses of piezo-bonded symmetric laminates. The proposed method satisfies the traction free boundary conditions, as well as surface free conditions. The symmetric laminated structure was excited under electric fields that can generate induced strain, resulting in pure extension in the laminated plate. The governing equations were obtained by taking the principle of complementary virtual work. To verify the proposed method, cross-ply, angle-ply and quasi-isotropic laminates were analyzed. The stress concentrations predicted by the present method were compared with those analyzed by the finite element method. The results show that the stress function-based analysis of piezo-bonded laminated composite structures is an efficient and accurate method for the initial design stage of piezo-bonded composite structures.