BA9916-Ⅱ/CCF300复合材料加筋板吸湿特性

为研究BA9916-II/CCF300复合材料加筋板的吸湿特性,在70℃/85%RH湿热环境中开展了吸湿实验,提出了基于厚度划分的Fick吸湿模型M_t=∑ni=1v_i[G_iM_(∞i)+M_(0i)(1-G_i)],并采用质量扩散模块进行了吸湿行为的有限元仿真。结果表明:提出的基于厚度划分的Fick吸湿模型能较好地描述该型结构的吸湿行为,具有较高的分析精度;但由于复合材料加筋板在吸湿后期存在阶段吸湿现象,Fick吸湿模型在该结构吸湿行为后期的描述上存在一定偏差;有限元仿真得到的吸湿动力曲线和水浓度分布结果验证了基于厚度划分吸湿模型的合理性,更好地还原了真实的吸湿过程与水分分布情况。     

复合材料加筋壁板结构件VARI液体成型工艺计算模拟

通过注模模拟软件PAM-RTM可以预测复合材料液体成型工艺中树脂的流动时间和模拟树脂的流动形式.渗透率是成型工艺模拟中重要的参数,面内和面外渗透率通常采用复杂且昂贵的封闭模具来测试,本工作自建了一套结构简单、操作方便且成本低廉的模具,使用真空辅助树脂灌注(VARI)工艺可获得准确的面内和面外渗透率参数.采用一种简单的等效建模方法,通过分层建模方法建立了有限元模型.将渗透率参数输入模拟注模软件PAM-RTM中,将使用等效建模方法所得模拟计算结果与实验液体成型结果进行了比较.计算模拟树脂充模时间为254 s,比实验工艺树脂充模时间(301 s)短.在使用等效建模方法的流道布局基础上,制备了加筋壁板结构件,对所选方案进行了工艺验证.     

平板自由下落的数值模拟

采用动网格技术,通过耦合求解N-S方程和运动方程的方法进行数值模拟,研究二维平板的自由下落运动。选取了不同质量分布的二维平板作为研究对象,研究初始角度、转动惯量和质心位置等因素对其自由下落运动轨迹的影响,以及其中的流体力学和动力学机理。数值模拟结果显示了二维平板的自由下落运动,除了摆动运动、翻滚运动和定常下落等经典运动轨迹外,随着质心位置的偏移还会衍生出非对称摆动、摆翻运动等特殊运动轨迹。研究结果表明:无量纲转动惯量和质心位置是决定二维平板自由下落运动方式的重要参数,但两者对下落运动影响的物理机制存在差异。这些结果对相关物理问题,特别是低雷诺数流体力学和动力学研究,具有一定的指导意义。     

FIBER OPTIC TEMPERATURE MEASURING SYSTEM

提出了一种可用于多种场合的光纤温度检测系统。该系统具有反射式结构,由热双金属片、连杆－活塞机构、光栅及光纤探头组成。温度变化引起热双金属片变形,通过连杆－活塞机构,使得光栅在竖直方向移动。光纤探头用来检测由于温度变化引起光栅移动产生的条纹数。通过光纤光缆可以将检测信号传输１ｋｍ以上,系统的温度测量范围达到１００℃,精度达±０．２℃。     

Integrated design of topology and material for composite morphing trailing edge based compliant mechanism

The morphing trailing edge based compliant mechanism is a developing technology which can increase lift-drag ratio for variable flight modes by bending down the trailing edge. Composite material design is integrated into topology optimization for the morphing trailing edge based compliant mechanism in the paper. A two-step optimization strategy is established to solve the integrated design problem. Initially, lamination parameters are introduced and viewed as a bridge between structure stiffness and fiber angles for composite material. Design variables include the lamination parameters and element density. The least-squares between actual and desired displacements at output points along trailing edge is adopted to evaluate the deformed capability of the trailing edge. An integrated optimization model for the composite morphing trailing edge is established with the volume constraints. The optimal topologic shape and lamination parameters are initially obtained. Subsequently, a least-squares optimization between fiber angles and the optimal lamination parameters is implemented to obtain optimal fiber angles. Finally, morphing capability of composites trailing edge based compliant mechanism is investigated by simulation and experiments. The results indicate the composites trailing edge based compliant mechanism can approximately bend down 8 degrees and satisfies the design requirement.     

基于压缩感知的金属加筋板兰姆波健康监测技术

针对大型复杂板结构安全评价需要，发展了一种基于压缩感知的金属加筋板结构兰姆波健康监测技术。利用压缩感知技术从稀疏阵列得到的少量检测数据中恢复出加筋板结构中兰姆波的频散特性，并提出了一种将余弦相似度和皮尔森相似度相结合的稀疏阵列兰姆波复合成像方法，以实现加筋板结构中大范围缺陷检测和成像。实验结果表明，压缩感知技术可以恢复出金属加筋板中兰姆波的频率-波数关系，提出的兰姆波复合成像方法能够实现金属加筋板中单缺陷和多缺陷的检测及定位。研究工作为复杂板结构损伤检测提供了一种可行的技术方案。     

几何非线性对整体壁板断裂参数的影响分析

基于有限元法和断裂力学理论,借助有限元软件ABAQUS计算了某整体壁板纵向裂纹的J积分。考虑了几何非线性,并与未考虑几何非线性所得结果进行了对比,对于不同的内压下以及不同蒙皮厚度情况下的结果进行了分析,结果表明几何非线性对机身壁板纵向裂纹裂尖J积分有明显的影响。     

Static Analysis of Functionally Graded Sandwich Plates Using an Efficient and Simple Refined Theory

In this paper, a new displacement based high-order shear deformation theory is introduced for the static response of function-ally graded sandwich plate. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory presented is variationally consistent, has strong similarity with classical plate theory in many aspects, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. Two common types of functionally graded sandwich plates, namely, the sandwich with functionally graded facesheet and homogeneous core and the sandwich with homogeneous facesheet and functionally graded core, are considered. Governing equations are derived from the principle of virtual displacements. The closed-form solution of a simply supported rectangular plate subjected to sinu-soidal loading has been obtained by using the Navier method. The validity of the present theory is investigated by comparing some of the present results with those of the classical, the first-order and the other higher-order theories. It can be concluded that the proposed theory is accurate and simple in solving the static bending behavior of functionally graded sandwich plates.     

复合材料加筋板后屈曲设计技术欧盟研究综述

为了保持竞争力,欧洲的飞机工业要求降低开发和使用成本,短期和长期分别降低20%和50%。为了实现这一目标,欧盟在框架计划下支持了一系列复合材料加筋结构后屈曲技术相关的研究项目。飞机复合材料加筋板具有较强的后屈曲承载能力,在飞机设计中可大幅提高结构的承载效率。本文介绍了欧盟在该领域的发展概况,从项目背景、目标、开展的工作、分析方法以及研究成果等方面阐述了欧盟在第五、第六和第七框架及其他项目下支持的复合材料加筋结构后屈曲设计分析技术相关研究项目,并分析了该领域技术的发展趋势及带来的启示。     

民用飞机蒙皮加筋壁板损伤容限分析方法探讨

主要介绍了民用飞机蒙皮加筋壁板损伤容限的分析方法,以中间筋条断裂的两跨纵向裂纹为例,将影响结构损伤容限特性的因素分为三部分进行计算,分别是加筋效应、鼓胀效应以及应力分布效应,最终得到相对应的裂纹尖端的应力强度因子并且进行裂纹扩展分析及剩余强度计算。文中选取实例采用这种方法进行计算,并将计算结果与试验数据对比,两者吻合较好,说明了本方法的可行性及实用性。