冲击波和高速破片联合作用下夹芯复合舱壁结构的毁伤特性

为探讨导弹战斗部近炸下舰船夹芯复合舱壁结构设计方法，采用TNT和预制破片近炸实验研究了典型夹芯复合舱壁结构在冲击波与高速破片联合作用下的破坏效应，分析了冲击波和破片联合毁伤载荷，指出了钢质面板和抗弹层的破坏模式，阐述了夹芯复合舱壁结构的防护机理。结果表明:预制破片装药近炸下，破片能远大于冲击波能，是防护结构的主要设计载荷；前面板主要是抵御冲击波，其变形破坏整体为挠曲大变形，局部为集团破片冲塞破口、破片穿孔和撞击凹坑；背板以挠曲大变形吸能为主；陶瓷材料碎裂严重，部分陶瓷碎片反向飞溅撞击前面板；纤维增强复合材料发生了纤维断裂、基体开裂、整体弯曲大变形及分层等破坏，抗弹层应避免产生穿透性破坏。     

垫层对破片冲击起爆带壳炸药影响的数值模拟

将战斗部简化为带钢壳和垫层的炸药组件，用3种不同厚度的材料作垫层，利用非线性有限元软件AUTODYN对高速破片侵彻、引爆带壳炸药的作用过程进行了数值模拟，得到了高速破片冲击起爆带壳带垫层炸药的波后压力剖面。对不同厚度多种材料作为垫层时带壳炸药的冲击到爆轰距离进行了对比分析，结果表明，通过控制垫层的材料和厚度，可以对破片冲击起爆带壳炸药进行有效抑制。研究结果对战斗部破片起爆的防护设计具有指导意义。     

高速破片撞击充液容器时容器壁面的损伤

为研究高速破片（钨球）撞击充液容器（贯穿前后壁面）时容器壁面的毁伤情况，利用ANSYS/LS-DYNA对该过程进行了数值模拟，分析了破片撞击动能对充液容器前后壁面毁伤程度的影响，并进行实验验证。结果表明:高速破片撞击充液容器形成的液压水锤对充液容器前后壁面的破坏程度可分为3个等级，即前后壁面均未出现裂纹、前壁面没有出现裂纹后壁面出现裂纹和前后壁面均出现裂纹且后壁面呈花瓣式开裂；破片撞击充液容器过程中，前后壁面的最大变形量和前后壁面的裂纹总数随破片撞击动能的增加而增大。     

圆弧曲边六边形蜂窝结构吸能特性研究

为提升金属蜂窝结构的冲击吸能特性，提出了圆弧曲边六边形蜂窝结构。建立了显式有限元模型，对面内和面外冲击下的失效模式和吸能特性进行了研究，分析了冲击速度等对冲击吸能特性的影响规律。结果表明在面外冲击情况下，曲边蜂窝具有比传统蜂窝结构更优异的吸能性能；面内冲击情况下，会出现“X”型、“V”型和“一”字型变形带等不同失效形式；冲击速度较大时，变形模式趋近于“一”字型；吸能能力随着冲击速度的增大而增加。     

高速冲击载荷下梯度金属泡沫夹芯梁的动态响应与失效

采用泡沫弹冲击加载实验对梯度金属泡沫夹芯梁结构开展了不同冲击强度下的动态响应和失效研究，分析了由三种不同密度泡沫铝组成的等面密度的五种不同梯度的夹芯结构在夹支边界条件下的抗高速冲击性能，结合三点弯曲实验，研究梯度效应对夹芯结构抗冲击性能的影响。研究表明：密度梯度对结构的失效过程和失效模式有着明显的影响，且夹芯梁结构的初始失效模式对结构整体响应和主要的能量吸收机制起着主导作用；当冲击条件不足以使得均质芯材发生压缩时，均质及负梯度夹芯结构初始失效模式为整体弯曲变形，低强度芯层位于前两层的梯度结构随着冲击强度的变化出现不同程度的局部芯层压缩；当冲击强度较低时，梯度结构通过丰富的局部失效表现出明显优于均质结构的抗冲击变形能力；当冲击强度大于临界值时，均质结构具有更好的抗冲击变形能力。通过合理地设计密度梯度实现逐层压缩吸能，能够有效的提升防护结构的抗冲击性能。     

冲击波与破片对波纹杂交夹层板的联合毁伤数值研究

通过有限元软件LS-DYNA模拟了波纹杂交夹层板在冲击波与破片联合作用下的响应过程，研究了炸药当量、载荷类型和填充方式对波纹杂交夹层板变形与失效模式的影响，并与实体板、间隔板和波纹夹层板的抗联合毁伤性能进行了对比，讨论了波纹杂交夹层板的能量吸收特性。数值计算结果表明:与冲击波单独作用相比，破片群单独作用和冲击波与破片联合作用对结构造成的毁伤更为严重；当药量较小时，波纹夹层板和波纹杂交夹层板的抗联合毁伤性能优于实体板与间隔板，波纹杂交夹层板的抗联合毁伤性能从全填充、迎爆面填充到背爆面填充逐渐降低；当药量较大时，所有结构均产生破口失效；在能量耗散方面，冲击波单独作用时以波纹芯层吸能为主，破片群单独作用和冲击波与破片联合作用时以上面板吸能为主。     

多破片高速冲击下飞机油箱水锤效应数值模拟

作为飞机燃油箱的一种主要损伤模式，水锤效应可能引起油箱结构灾难性的破坏。针对实战环境中多枚破片冲击同一油箱的常见现象，在建立与试验对比一致的单枚破片冲击满水油箱数值模型后，以箱内液体特定单元压力峰值、破片速度衰减、箱内液体吸收的总能量以及油箱壁板变形作为对比参量，分别开展数值模拟，分析其在2枚破片不同间距打击、2枚破片不同时间间隔打击以及多枚破片同时打击时的水锤效应。结果表明:箱内液体的压力峰值来源于破片入水后形成的冲击波，多枚破片入射时液体压力有明显的叠加效应；2枚破片不同时入射将导致先入射破片剩余速度增高；油箱壁板的变形随入射破片数量的增加显著增大。     

复合材料层板的抗贯穿机理与模拟研究

为了研究树脂基纤维增强复合材料层板的抗侵彻贯穿机理和动态力学行为与抗侵彻毁伤的关系, 通过球形破片模拟弹贯穿实验表征了复合材料层板抗高速侵彻的吸能特性;通过高速摄影技术分析了层板 贯穿过程的瞬态变形失效特点;采用CT扫描成像及SEM 电镜分析等手段研究了复合材料层板的抗贯穿破 坏耗能模式。实验结果显示,高速冲击下层板抗贯穿吸能与入射速度成正比;高速侵彻过程是复合材料层板 高应变率变形的动态过程,高应变率动态力学行为对复合层板抗贯穿吸能特性影响显著;冲击波在层板中的 传播特性决定了不同破坏模式阶段的划分以及损伤区域的范围。基于复合层板高速贯穿下的动力学瞬态分 析,建立了复合层板抗高速侵彻吸能的两阶段动态破坏模型,模型计算值与实验值符合良好。研究结果表明, 应变率效应与惯性效应在复合材料层板抗侵彻性能分析中是不可忽视的2个关键因素。     

高硬度聚脲涂层抗侵性能与断裂机制研究

鉴于高硬度聚脲与常规聚脲弹性体的区别，研究了高硬度聚脲涂覆钢板结构的抗侵性能及涂层断裂机制。通过弹道实验加载3.3 g立方体破片撞击无涂层、迎弹面涂层、背弹面涂层与双面涂层4种涂覆类型靶板，获得靶板的弹道极限，分析了不同涂覆方式下结构的抗侵性能、涂层断裂规律与微观断口形貌。结果表明:破片冲击作用下，迎弹面涂层断裂程度高且吸能性好，能够有效提高结构抗侵性能，而背弹面涂层破坏先于钢板层且吸能性差，对结构抗侵性能无提升作用；涂层断裂呈现一定的速度效应、厚度效应与微观特征，其规律反映了不同位置涂层的吸能差异。     

破片高速侵彻中厚背水钢板的剩余特性

为探讨破片高速侵彻中厚背水钢板的剩余特性，通过弹道实验，分析了弹体和靶板的破坏模式，比较了破片侵彻垂直和倾斜背水钢板后的瞬时余速和运动轨迹, 以及由此引起的初始冲击波的压力特性。结果表明，破片在高速侵彻下，头部产生了严重的镦粗变形，钢板背后水介质的动支撑作用不容忽视；背水钢板的破坏模式主要为剪切冲塞破坏，背弹面穿孔存在绝热剪切效应；破片穿透背水钢板初期，会产生空泡和射流，空泡大小和射流强度与破片入水初速有关，而空泡形状和射流方向则受背水钢板的倾斜角度影响；破片穿透背水钢板后，在水中的运动轨迹会发生偏转，偏转方向与破片入水初速有关；由于水介质的动支撑作用和动能耗散效应，破片穿透背水钢板后的动能损失要大于穿透背空钢板的情形；水中初始冲击波的压力特性应考虑稀疏波的影响；相同初速下，破片侵彻垂直背水钢板引起的初始冲击波的峰值压力较侵彻倾斜背水钢板要大。     

复合材料层合板在动集中力作用下的结构声强特性

本文研究了复合材料正交异性层合板在动集中力作用下的结构声强特性。应用MSC/-NASTRAN商业软件计算了复合材料正交异性层合板在动集中力作用下各单元的内力和速度,再应用MATLAB软件得出复合材料层合板的结构声强。算例表明,复合材料正交异性层合板的结构声强流线图与各向同性板存在明显不同的特性。复合材料正交异性层合板的结构声强流线图受边界条件、层合板叠层顺序和层数的影响。从结构声强向量图和流线图可获得关于能量传递路径、源位置和能量汇合点的许多信息。进一步,结构振动产生的噪声可根据上述信息加以控制。     

复合材料层合板壳非线性力学的研究进展

复合材料层合板壳是由多种组分材料组合而成.与单一材料的板壳结构相比,它无明确的材料主方向,各层间材料间断和不连续,具有明显的几何非线性和材料非线性等新的特点.其失效模式也远比单一材料的情况复杂,具有如基体开裂、脱胶、分层、分层裂纹偏转、多分层以及分层传播等多种模式.各国学者基于不同的考虑,提出了多种方法研究复合材料层合板壳的失效.首先,在简要介绍了层合板壳线性力学基本理论的基础上,重点回顾了层合板壳结构非线性力学几种基本理论发展的过程,主要阐述了经典大挠度非线性理论、一阶剪切变形理论、高阶剪切变形理论、锯齿理论、广义分层理论的理论体系及基本公式,并对几种理论之间的联系和差异进行了总结;其次,介绍了当前层合结构非线性领域的研究进展,综述了典型复合材料板壳结构的失效机理及优化设计、复合材料板壳结构在复杂环境下的破坏机理、复合材料板壳结构的物理非线性、含脱层纤维增强复合材料板壳结构的破坏机理等各研究热点的最新研究成果;最后,对该领域未来的研究方向进行了展望.     

Large deflections of heterogeneous anisotropic rectangular plates

An approximate solution is presented for large deflections of clamped, uniformly loaded, unsymmetrically laminated, anisotropic, rectangular plates. Expressing the load and displacements in the form of series, the von Karman-type nonlinear differential equations and immovable boundary conditions are reduced to a series of linear partial differential equations and boundary conditions. The solution obtained by successive approximations can reduce to some existing solutions for large deflections of homogeneous plates. Numerical results based on the first three terms of the truncated series are graphically presented for unsymmetrical cross-ply and angle-ply plates having various values of fiber-reinforced material, number of layers, and aspect ratio. The results in small deflections of coupled laminates are compared with available data.     

Electro-elastic analysis of fiber-reinforced multilayered cylindrical composites with integrated piezoelectric actuators

Based on the electro-mechanical coupling theory and the laminate elasticity theory, an electro-elastic solution is obtained for the fiber-reinforced cylindrical composites with integrated piezoelectric actuators when subjected to mechanical and electrical loadings. The hybrid composite is composed of three parts: internal piezoelectric actuator, fiber-reinforced laminated interlayer, and external piezoelectric actuator. The general solution in each piezoelectric smart layer is obtained by introducing three undetermined constants, and the general solutions in the fiber-reinforced laminated interlayer are obtained by means of the state-space method. The mechanical behaviors of the hybrid fiber-reinforced cylindrical composites are investigated. The illustrative examples show that the fiber’s angle, the stacking sequence as well as the applied electric loading strongly affect the physical fields in the fiber-reinforced multilayered cylindrical composites.     

Effect of initial deformations on wave front propagation in anisotropic plates

The effects of large amplitudes and initial deformations on shock waves and acceleration waves propagating in fiber-reinforced laminated plates are investigated. Three cases are discussed, namely the large amplitude shock under initial in-plane deformations, small amplitude waves under in-plane deformations, and small amplitude waves propagating in a plate with large deflection. It is found that the in-plane force has a substantial effect on the transverse shear mode but little effects on other modes. The large initial deflection, however, is found to have considerable effects on all modes. A general procedure for constructing the wave surfaces is also presented.     

Green’s functions for multi-phase isotropic laminated plates

This work develops a series of Green’s functions for multi-phase Kirchhoff isotropic laminated plates. First, we derive the Green’s functions for a composite laminated plate composed of two bonded dissimilar isotropic laminated semi-infinite plates. Second, the obtained results for bimaterials are judiciously applied to obtain the Green’s function solution for a circular elastic inclusion embedded in an infinite isotropic laminated plate. Third, Green’s functions for a composite space composed of an arbitrary number of wedges of different isotropic laminated plates are derived. Finally, we derive Green’s functions for a laminated plate with an elliptical and a parabolic boundary, respectively.     

An exact analytical approach for in-plane and out-of-plane free vibration analysis of thick laminated transversely isotropic plates

In this article, the governing equations of motion of thick laminated transversely isotropic plates are derived based on Reddy’s third-order shear deformation theory. These equations are exactly converted to four uncoupled equations to study the in-plane and out-of-plane free vibrations of thick laminated plates without any usage of approximate methods. Based on the present analytical approach, exact Levy-type solutions are obtained for thick laminated transversely isotropic plates and, for some boundary conditions, the exact characteristic equations hitherto not reported in the literature are given. Also, the in-plane and out-of-plane deformed mode shapes are plotted for different boundary conditions. The present solutions can accurately predict both the in-plane and out-of-plane natural frequencies and mode shapes of thick laminated transversely isotropic plates.     

A refined finite element method for bending analysis of laminated plates integrated with piezoelectric fiber-reinforced composite actuators

This research presents a finite element formulation based on four-variable refined plate theory for bending analysis of cross-ply and angle-ply laminated composite plates integrated with a piezoelectric fiber-reinforced composite actuator under electromechanical loading. The four-variable refined plate theory is a simple and efficient higher-order shear deformation theory, which predicts parabolic variation of transverse shear stresses across the plate thickness and satisfies zero traction conditions on the plate free surfaces. The weak form of governing equations is derived using the principle of minimum potential energy, and a 4-node non-conforming rectangular plate element with 8 degrees of freedom per node is introduced for discretizing the domain. Several benchmark problems are solved by the developed MATLAB code and the obtained results are compared with those from exact and other numerical solutions, showing good agreement.     

Nonlinear free vibration analysis of piezoelastic laminated plates with interface damage

This paper presents a nonlinear model for piezoelastic laminated plates with damage effect of the intra-layers and inter-laminar interfaces. Discontinuity of displacement and electric potential on the interfaces are depicted by three shape functions. By using the Hamilton variation principle, the three-dimensional nonlinear dynamic equations of piezoelastic laminated plates with damage effect are derived. Then, by using the Galerkin method, a mathematical solution is presented. In the numerical studies, effects of various factors on the natural frequencies and nonlinear amplitude-frequency response of the simply-supported peizoelastic laminated plates with interfacial imperfections are discussed. These factors include different damage models, thickness of the piezoelectric layer, side-to-thickness ratio, and length-to-width ratio.     

具有叉指式电极的1-3型压电复合材料层合板力电耦合行为的三维精确分析

基于三维弹性理论和压电理论,导出了含有1-3型压电复合材料层的有限长矩形层合简支板的静力平衡方程和边界条件,给出了该层合板在叉指式电极和外力共同作用下力电耦合特性的三维精确解.数值算例的计算结果与有限元解进行了对比,取得了很好的一致性.研究了压电矩阵各向异性和刚度矩阵各向异性以及电势等因素对其挠曲面扭率最大值的影响.数值结果表明层合板扭率最大值的绝对值随压电矩阵各向异性系数Rd的增大而增大并随刚度矩阵各向异性系数Rc的减小而增加.