Three-dimensional solution for a hybrid cylindrical shell under axisymmetric thermoelectric load

Summary An exact axisymmetric piezothermoelastic solution is presented for a simply-supported hybrid cylindrical shell made of cross-ply composite laminate and piezoelectric layers. Numerical results for hybrid shells are presented for sinusoidal and central band thermal and electrical loads. The effect of the loading, the radius-to-thickness ratio, the span-to-radius ratio and the number of layers of the substrate on the response is investigated. The interface between the substrate and the actuated piezoelectric layer has been found to be subjected to high shear stress. It has been shown that the maximum values of the deflection and the stresses, due to thermal load, can be appreciably reduced by appropriate application of actuation potential. Accepted for publication 13 October 1996     

Nonlinear finite element analysis of shape memory alloy (SMA) wire reinforced hybrid laminate composite shells

This study introduces a non-linear finite element analysis approach to the procedure of modeling hybrid laminate composite shells with embedded shape memory alloy (SMA) wire subjected to coupled structural and thermal loading. Numerical analyses of SMA wire reinforced composite laminates were carried out by synergizing the non-linear laminate shell element with Brison's model of the SMA constitutive law. To verify the proposed procedure, the present illustrative applications involve rectangular laminated panels clamped along one side. Analysis results were compared with corresponding experimental results from a prior study. Several test cases that depend on the volume fraction of SMA, temperature, and ply angles are presented to illustrate the highly entangled thermo-mechanical behavior of shape memory alloy hybrid composites (SMAHCs). The results of the numerical analysis show the ability of the suggested procedure to compute the thermo-mechanical behavior of a SMAHC in accordance with the SMA's internal phase transformations induced by stress and temperature variation and demonstrate very good agreement with experimental results.     

Multi-objective optimal design of laminated composite skirt using hybrid NSGA

In this paper a new hybridised version of non-dominated sorting genetic algorithm (NSGA) is proposed to solve combinatorial optimisation problems associated with laminated composite structures. The proposed algorithm is used to optimise the design of hybrid laminated fibre composite skirt of solid rocket motor, subjected to a buckling strength constraint and an overstressing strength constraint under aerodynamic torque and axial thrust. The present investigations involve in determining the best laminate configuration to minimise the weight as well as cost of the skirt through multi-objective optimisation. Buckling strength and overstressing strength of the composite cylindrical skirt are analysed using classical laminate theory. Tsai-Wu failure criterion is employed to assess the first ply failure, and failure strength is described by an overstressing load level factor. The superiority of the proposed hybrid algorithm is demonstrated by comparing with the originally proposed NSGA algorithm. The studies presented in this paper clearly indicate that the proposed modification to the NSGA improves the convergence properties quite appreciably.     

竹材层合板弯曲破坏机理的实验研究

竹材层合板是为了满足一定的使用要求，由多层单向板按同一方向整齐排列、胶合、加热固化处理而成的复合结构体。由于竹材层合板的各向异性和非均匀性，它的力学行为十分复杂，特别是弯曲时不仅各个单层产生损伤破坏，而且伴随着层间胶接层的开裂。本文对竹材层合板的弯曲破坏特征进行实验研究；一系列包含变形信息的数字散斑图像被记录；采用数字散斑相关技术(DSCM)提取了三点弯曲变形过程中的面内位移场信息，分析了不同变形阶段的位移场；给出了不同弯曲变形阶段试件的应变场分布和应变集中现象；分析了中性轴在胶层开裂、层内纤维撕裂等复杂应力情况下的演化过程及规律。最终一些宏微观破坏机制被分析，例如基体开裂，界面损伤与撕裂，界面与裂纹作用等。这些研究结果将为竹材层合板的破坏机理等力学行为的研究和工程应用开发提供实验依据。     

空间杆系与叠层板组合结构的非线性稳定分析

本文用非线性有限元法研究一种空间杆系与复合材料叠层板组合结构的非线性稳定问题。将杆系离散成空间梁柱单元，将复合材料叠层板离散成复合材料叠层板单元，并考虑了几何非线性和板的成层正交各向异性性质。为了获得较高的计算效率并顺利通过稳定临界点，求解非线性平衡方程采用了变增量步长和柱面弧长法迭代策略。在考证了程序的正确性之后，具体分析了几个工程模型，得出了于工程设计有益的结论。     

基体开裂的正交复合材料对称层合板的粘弹性力学行为

本文讨论了含有均匀基体裂纹的正交复合材料对称层合板的线性粘弹性力学行为.采用二维剪切滞后模型并对其层间剪应力在厚度方向进行线性假设分布,求得层合板的平均应力应变的线弹性解,利用等效约束模型和经典层合理论可得到层合板因为含有基体裂纹而所引起的刚度退化现象.在弹性-粘弹性对应原理的基础上对其层合板的线粘弹性进行了讨论和研究.结果表明:层合板的松弛模量和蠕变泊松比随着时间的增加而减少,到达稳态后其值基本上是恒值.并跟Zocher的解析解和有限元数值解作了比较,发现结果非常吻合.     

A Note on the Elastic and Geometric Bounds for Composite Laminates

In this paper it is shown that a laminate composed of identical anisotropic layers, like for instance composite plies, cannot reach all the possible elastic states that are allowed by the classical elastic bounds on anisotropic constants. The analysis is carried on and facilitated by the use of particular tensor invariants, the so-called polar parameters.     

Low-energy impact response of composite and sandwich composite plates with piezoelectric sensory layers

An efficient model reduction based methodology is presented for predicting the global (impact force, plate deflection and electric potential) and through-thickness local (interfacial strains and stresses) dynamic response of pristine simply-supported cross-ply composite and sandwich composite plates with piezoelectric sensory layers subjected to low-energy impact. The through-thickness response of the laminate is modelled using coupled higher-order layerwise displacement-based piezoelectric laminate theories. Linearized contact laws are implemented for simulating the impactor–target interaction during impact. The stiffness, mass, piezoelectric and permittivity matrices of the plate are formulated from ply to structural level and reduced by applying a Guyan reduction technique to yield the structural system in state space. This reduction technique enables the formulation of a plate–impactor structural system of minimum size (1 term per vibration mode for composite plates – 2 terms for sandwich plates) and reduces computational cost, thus facilitating applicability for real-time impact and vibration control.     

含孔平面编织混杂铺层层合板压缩破坏仿真

对ANSYS软件平台进行了二次开发,建立了平面编织混杂铺层层合板损伤累积有限元模 型,对含孔平面编织混杂铺层层合板的压缩破坏行为进行了仿真计算. 研究结果表明,所建 模型能够较好地仿真含孔平面编织层合板的损伤破坏过程,并能准确预测层合板的 损伤类型、损伤扩展以及破坏强度;同时提出并验证了适合该类型层合板的损伤判 据和衰减准则. 该模型所给结果形象直观,适合工程应用.     

Non-local theory for cracks in laminated media

Non-local theory for composite is applied to solve the Mode III crack problem under impact loading. The composite is a laminate made up of two different orthotropic layers. Based on the classical boundary conditions, all quantities are expressed in terms of a single unknown function. Integral transform is used to reduce the problem to a system of dual integral equations. The solution is obtained by using the Copson's method [1], which can be generalized to include arbitrary loading applied to the crack.     

复合材料层合板的HOFFMAN塑性区尺寸因子

本文在Hoffman强度准则的基础上,采用复合材料层合板第K层中心穿透裂纹尖端附近的应力分量,得到一个计算复合材料层合板Hoffman塑性区尺寸因子的公式.     

Interaction of thin perforated plates and weak shock waves

The paper presents experimental results on elastic deformation of perforated thin plates made of glass-fiber laminate and subjected to weak shock waves. The characteristics of the dynamic process in the plates are determined __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 11, pp. 126–130, November 2006.     

LCO flutter of cantilevered woven glass/epoxy laminate in subsonic flow

The paper presents a cantilevered composite wing, aeroelastic characteristics of idealized as a composite flat plate laminate. The composite laminate was made from woven glass fibers with epoxy matrix. The elastic and dynamic properties of the laminate were determined experimentally for aeroelastic calculations. Aeroelastic wind tunnel testing of the laminate was performed and the result showed that flutter, a dynamic instability occurred. The cantilevered laminate also displayed limit cycle amplitude, post-flutter oscillation. The experimental flutter velocity and frequency were verified by our computational analysis.     

大开口复合材料层合板强度破坏研究

复合材料层合板的各向异性及非均质,使得复合材料层合板内部的破坏形式非常复杂.在复合材料结构的设计中,为满足制造及使用功能上的需求,在复合材料层合板承力结构件上不可避免地需要设计各种开口.然而,含大开口复合材料层合板的强度破坏问题变得更为复杂,使得现有的强度理论面临新的挑战.针对碳纤维增强复合材料大开口层合板受单向拉伸载荷作用下的强度破坏问题进行了数值分析和实验研究.首先,根据Hashin准则和刚度退化模型,对含不同圆形开口尺寸的[0]_(10)单向铺层、[0/90]_5和[±45]_5正交铺层的层合板,进行了单向拉伸载荷作用下渐进失效的数值模拟分析,获得了对应结构的极限载荷和破坏模式.在此基础上,采用数字图像相关方法,进行复合材料大开口层合板强度破坏的实验研究.研究结果表明,大开口复合材料层合板在单向拉伸加载下主要呈现脆性破坏形式,破坏起始位置处于应力集中区.此外,破坏强度和失效模式与复合材料铺层方式和开口尺寸大小密切相关.其中[±45]_5铺层的开口层合板承载能力最弱,分层破坏最严重.开口尺寸越大,结构的极限载荷值越低.同实验测试结果相比,数值模拟对复合材料层合板的损伤失效分析略显不足,往往很难全面分析复合材料层合板破坏失效过程中的各种因素的影响.     

界面特性对功能梯度智能梁静动态响应的影响研究

采用状态空间法分析了两边简支的含压电夹层的功能梯度梁的静力弯曲和自由振动问题.为了考虑中间压电层与上、下功能梯度层之间的粘结效果,采用线性弹簧模型以模拟界面性能.假设上下功能梯度层的材料参数沿厚度连续变化,而压电层则是均匀材料,并且它们都是正交各向异性的.由于功能梯度梁的不均匀性使得直接求解比较困难,文中用层合模型来进行近似.数值算例中,分别考虑了压电层用于传感器或作动器的情形,分析了粘结界面完美程度对组合梁静力弯曲和自由振动频率的影响.     

A theoretical analysis of piezoelectric/composite anisotropic laminate with larger-amplitude deflection effect,Part I: Fundamental equations

Considering the effects of both the different material properties of composite layers and the poling directions of piezoelectric layers, we utilized the assumption of the simple-higher-order shear deformation theory to model and analyze the laminated composite plate integrated with the random poled piezoelectric layers. Further, the generalized Hamilton’s variation principle for electro-elasticity was employed to deduce the fundamental equations of piezoelectric/composite anisotropic laminate, i.e. the governing equations and boundary conditions. For the special requirement of the larger-amplitude deflection of smart structures, the Von Karman strains were used to account for the geometric nonlinear effect of the practical larger-amplitude deflection on the electro-elastic behavior of smart composite structures. Moreover, the sensor equations were also carried out with considering the large-amplitude deflection effect of smart composite structures.     

Generalized layerwise mechanics for the static and modal response of delaminated composite beams with active piezoelectric sensors

A coupled linear layerwise laminate theory and a beam FE are formulated for analyzing delaminated composite beams with piezoactuators and sensors. The model assumes zig-zag fields for the axial displacements and the electric potential and it treats the discontinuities in the displacement fields due to the delaminations as additional degrees of freedom. The formulation naturally includes the excitation of piezoelectric actuators, their interactions with the composite laminate, and the effect of delamination on the predicted sensory voltage. The quasistatic and modal response of laminated composite Gr/Epoxy beams with active or sensory layers having various delamination sizes is predicted. The numerical results illustrate the strong effect of delamination on the sensor voltage, on through the thickness displacement and on the stress fields. Finally, the effect of delamination on modal frequencies and shapes are predicted and compared with previously obtained experimental results.     

Properties degradation induced by transverse cracks in general symmetric laminates

This paper presents the details of a methodology for predicting the thermoelastic properties degradation in general symmetric laminates with uniform ply cracks in some or all of the 90° layers. First, a stress transfer method is derived by using the concept of state space equation. The laminate can be subjected to any combination of in-plane biaxial and shear loading, and the uniform thermal loading is also taken into account. The method takes into account all independent material constants and guarantees continuous fields of all interlaminar stresses across interfaces between material layers. By this method, a laminate may be composed of an arbitrary number of monoclinic layers and each layer may have different material property and thickness. Second, the concept of the effective thermoelastic properties of a cracked laminate is introduced. Based on the numerical solutions of specially designed loading cases, the effective thermoelastic constants of a cracked laminate can be obtained. Finally, the applications of the methodology are shown by numerical examples and compared with numerical results from other models and experiment data in the literature. It is found that the theory provides good predictions of the thermoelastic properties degradation in general symmetric laminates.     

Nonlinear low-velocity impact on damped and matrix-cracked hybrid laminated beams containing carbon nanotube reinforced composite layers

This paper investigates the low-velocity impact response of a shear deformable laminated beam which contains both carbon nanotube reinforced composite (CNTRC) layers and carbon fiber reinforced composite (CFRC) layers. The effect of matrix cracks is considered, and a refined self-consistent model is selected to describe the degraded stiffness caused by the damage. The beam including damping effects rests on a two-parameter elastic foundation in thermal environments. Based on a higher-order shear deformation theory and von Kármán nonlinear strain–displacement relationships, the motion equations of the beam and impactor are established and solved by means of a two-step perturbation approach. The material properties of both CFRC layers and CNTRC layers are assumed to be temperature-dependent. To assess engineering application of this hybrid structure, two conditions for outer CNTRC layers and outer CFRC layers are compared. Besides, the effects of the crack density, volume fraction of carbon nanotube, temperature variation, the foundation stiffness and damping on the nonlinear low-velocity impact behavior of hybrid laminated beams are also discussed in detail.

     

复合材料加筋板铺层优化设计的等效弯曲刚度法

借助于等效弯曲刚度法和遗传算法,建立了一种复合材料加筋板铺层顺序优化设计算法.等效弯曲刚度法基于层合板的弯曲刚度与其失稳载荷一一对应的关系,将任意铺层顺序的层合板等效成一个只有8层的对称铺层的辅助层合板,通过优化辅助层合板,得到层合板的最优弯曲刚度参数,最后以获得的最优弯曲刚度参数为约束应用遗传算法进行铺层顺序优化,获...