基于复合材料层板稳定性的铺层参数优化设计方法

提出一种基于复合材料层板稳定性的铺层参数优化设计方法,首先利用最大应变能准则优化分层厚度,利用库塔条件推导出层合板单元厚度迭代公式优化单元厚度,两步交替进行,完成层板厚度与铺层比例优化;在此基础上采用遗传算法优化层合板铺层顺序,最终设计出满足稳定性要求的最佳层合板铺层.通过算例分析表明,文中方法与传统方法相比收敛速度明显提高.同时,最佳的厚度分布也为层合板加筋设计提供理论参考.     

泡沫夹层复合材料与复合材料层合板低速冲击性能的比较

采用[0°]8,[0°,90°]2s方式铺成的碳纤维增强环氧树脂预浸料作为泡沫夹层复合材料的面板,PMI(聚甲基丙烯酰亚胺)泡沫作为芯材,制得泡沫夹层复合材料(12mm厚);采用相同预浸料和[0°]16,[0°,90°]4s的铺层方式制备了复合材料层合板(2mm厚),对比研究了两种复合材料的低速冲击性能。结果表明:无论是泡沫夹层复合材料还是复合材料层合板,正交铺层结构比单向铺层结构的冲击载荷峰值高,冲击损伤程度小,抗冲击能力好;在两种铺层方式下,泡沫夹层复合材料的抗冲击能力明显优于复合材料层合板的。     

不同铺层方式的复合材料层合板弯曲性能的研究

以碳纤维缠绕电动节能车车架为研究对象,采用有限元分析和力学试验对比的方式研究碳纤维铺层角及铺层层数对碳纤维复合材料层合板弯曲性能的影响。以层合板铺层角度、铺层层数为变量设置试验对比组,在ANSYS Composite Prep/Post复合材料分析模块中创建层合板的有限元模型研究层合板在承受弯曲载荷时的抗弯表现。结合弯曲试验结果,分析不同铺层方式对碳纤维复合材料层合板弯曲性能的影响。结果表明:在铺设一定数量的±45°铺层的基础上,增加0°/90°正交铺层可提高层合板的静承载强度;增加铺层层数,可提高层合板的弯曲强度。     

基于自适应遗传算法的层合板铺层优化设计

针对复合材料层合板结构设计中因铺层角度多变、难以确定最优铺层方案的问题,提出一种基于自适应遗传算法的铺层优化设计方案。该方案以层合板铺层角度为变量,以层合板最大形变量为优化目标,采用整数编码策略,运用MATLAB平台进行遗传算法设计。在寻优过程中调用ABAQUS对层合板进行有限元分析并将分析结果返回至MATLAB进行优化计算。通过对比经典遗传算法表明,该算法收敛快,更易达到优化设计的目的。     

基于HyperWorks 的不同铺层方式复合材料剪切强度有限元分析

剪切强度和剪切韧性是反映复合材料构件在复合受力状态下承载能力及耗能能力的重要指标,不同铺层方式的单向玻璃纤维与短切玻璃纤维混杂增强复合材料层合板的层间剪切性能有明显差异。文中基于HyperWorks 商用有限元软件建立了精确的复合材料层合板模型,通过数值模拟分析不同铺层方式复合材料层合板的层间剪切性能。研究结果表明,铺层材料对复合材料层合板的层间剪切性能影响较大,而铺层顺序对复合材料层合板的层间剪切性能影响较小。     

含圆孔复合材料层合板在拉伸载荷下的破坏机理

综合考虑了基体开裂、基纤剪切、分层及纤维断裂等四种复合材料层合板的主要破坏模式,同时在通用有限元分析软件ANSYS基础上进行二次开发,编制了参数化的分析模拟程序,应用此三维逐渐累积损伤理论和有限元模拟方法,对两种不同铺层参数的含圆孔复合材料层合板在拉伸载荷作用下的逐渐破坏过程进行了分析。结果表明:该程序可以预测任意材料体系和任意铺层参数的层合板在拉伸载荷作用下的逐渐损伤破坏过程及最终失效载荷;与参考文献中的试验结果比较发现,该方法的预测精度较高,验证了其正确性。     

基于改进模拟退火算法的复合材料层合板屈曲优化

针对复合材料层合板的屈曲优化问题,提出一种改进的直接搜索模拟退火算法来求解最大化临界屈曲载荷系数的铺层顺序设计问题。改进算法引入搜索范围动态调整的新点产生方式实现全局搜索和局部搜索的协调,提高了算法的计算稳定性和计算效率。以离散铺层角为设计变量,采用里兹法进行屈曲响应分析以考虑弯扭耦合影响,通过典型多极值屈曲优化问题分析比较了算法改进措施的有效性。不同角度增量、铺层数、长宽比和载荷比的层合板屈曲优化结果表明,改进算法能有效地进行层合板铺层顺序优化。     

飞机复合材料雷击损伤热电耦合仿真

参照国外已有的雷击实验结果,建立了复合材料层合板的三维有限元模型,通过施加电边界和热边界以及引入材料性能参数之间的相互依赖关系,运用ABAQUS仿真软件真实地模拟出复合材料在雷击过程中雷电流的传导以及损伤过程.通过仿真研究复合材料层合板在遭遇雷击时热、电之间的耦合作用,得到雷电流注入后层合板中的温度分布场,对比分析后得出了不同层的烧蚀形貌和尺寸均有所不同的结论.通过对比不同铺层层合板的雷击损伤结果发现,当顶层为0°铺层(即与结构长度方向一致)时层合板的损伤面积较大.     

应用扰动广义微分求积法的复合材料层合板剪切屈曲分析与优化

广义微分求积(GDQ)法求解复合材料层合板剪切屈曲时存在计算精度差、计算振荡不收敛问题,研究发现该现象源于载荷矩阵存在奇异,为此,提出扰动GDQ法,通过扰动主对角线权重系数以改善载荷矩阵的奇异性来消除计算振荡。数值算例验证了扰动策略的有效性,实现复合材料层合板剪切屈曲问题的高效稳定求解。在此基础上,结合直接搜索模拟退火算法,开展了含剪切载荷的复合材料层合板铺层顺序优化。结果表明：剪切工况时对称复合材料层合板的优化铺层不受铺层数和铺设形式影响,优化铺层角随长宽比增大而趋于60°;而剪切与轴压组合工况下较小的剪切力能改善层合板屈曲性能,随着剪切力的增大,优化屈曲性能逐渐降低,优化铺层趋同于剪切工况。研究结果为复合材料层合板的剪切屈曲性能设计提供了参考。     

复合材料工字梁铺层结构设计及强度研究

根据复合材料层合工字梁的结构特点,基于经典层合板理论和最大应力强度准则,用MATLAB软件编程设计了复合材料工字梁缘条和腹板的铺层结构。建立了基于工艺的3种工字梁铺层结构有限元模型,分析了静载荷作用下3种铺层结构的应力状态。给出了典型铺层的应力云图。计算了复合材料层合结构材料主方向应力,使用最大应力强度准则,给出了线性状态下3种不同铺层结构工字梁的极限载荷。有限元分析结果与经典层合板理论计算结果进行了对比。分析表明:1)工字梁铺层采用内C形连接和L形连接时极限载荷高于理论设计载荷,外C形连接的极限载荷低于理论值,3种铺层方式极限载荷误差都在9%以内,与理论值基本吻合;2)有限元分析结果显示初始损伤均发生在工字梁下缘条45°铺层中,损伤模式为基体断裂;3)工字梁结构极限载荷主要取决于基体强度;4)工字梁发生破坏的截面位于其固支端;5)所建立的基于经典层合板理论的工字梁设计方法和工字梁有限元分析模型是正确可靠的。     

复合材料率相关本构模型的研究

在不同温度环境下,利用ＭＴＳ材料试验机,在中等应变速率（１／ｓ）下,对玻璃布－环氧层板的动态力学性能进行了实验研究,获得了杨氏模量、拉伸强度和泊松比等力学参数;对该层板材料在不同温度、不同应变速率下的应力应变曲线和破坏过程进行了分析讨论。根据实验数据,拟合了玻璃布－环氧层板材料的本构关系     

Evaluation of material properties and internal damage within CFRP and CFRP/Al sandwich panels due to impact loading

In the present paper, damage development within Carbon fiber reinforced plastic (CFRP) laminates and CFRP/Aluminum (Al) honeycomb core sandwich panels by impact loading was evaluated, and change in material properties due to the damage development was investigated. Falling weight impact tests, 3-point bending tests and cross-sectional observation were carried out. As results, it is found that falling rate of bending elastic modulus due to internal damage in the laminate only is lower than that in the upper face-sheet of the sandwich panel, and that difference in the falling rate between them becomes maximum at the impact energy of 5.1 J. As a result of investigating the relationship between reduction in bending elastic modulus and internal damage development, the reduction is caused by delamination within CFRP laminates mainly. Since total length of cracks in CFRP/Al honeycomb core sandwich panels is smaller than that in the laminates only, the sandwich panels have high impact tolerance because of absorption of impact energy by damaging Al honeycomb core.     

Experimental studies on mechanical behavior of carbon fiber laminates under static and cyclic loading

An experimental investigation of the mechanical behavior of carbon fiber-reinforced plastic laminates under quasistatic and cyclic loading is performed. A uniform nonlinear elastic deformation of carbon fiber reinforced plastic laminates with uniform increment of the tangent modulus is studied. A condition for the initiation of the microscopic damage process was identified. The analysis of discreet continuous stages of the damage process followed by energy release was conducted. A diagram of deformation up to full loss of carrying capacity of the material is plotted. The proposed approach can be useful for diagnostics of elements of composite structures in operation.     

State space solution for thick laminated piezoelectric plates with clamped and electric open-circuited boundary conditions

Based on the theories of 3-D elasticity and piezoelectricity and by assuming appropriate boundary functions, the state equation for laminated piezoelectric plate is established. By using the transfer matrix and recursive solution approach, an analytical solution that satisfies all boundary conditions, including the conditions on the top and bottom surfaces, of the laminates is presented. The solution can take into account all the independent elastic and piezoelectric constants for orthotropic and piezoelectric materials and satisfies the continuity conditions between plies of the laminates. Numerical examples are given at the end of the paper to verify the effectiveness of the present method. The results are compared with those of existing analytical and finite element models.     

纤维金属层板铆接剩余强度影响因素研究

为研究单搭铆接接头中纤维金属层板耦合损伤行为,运用金属硬化Johnson-Cook失效准则、纤维增强复合材料三维Hashin损伤准则、脱层B-K失效理论以及刚度退化失效准则建立了纤维金属层板铆接渐进失效模型,并结合实验验证了模型的合理性。考察了单搭铆接二次弯曲效应、层板铝合金体积分数、预紧力、层板孔边距对纤维金属层板铆接强度和失效模式的影响,为提高纤维金属层板铆接剩余强度提供可靠建议。分析结果表明：二次弯曲效应加速损伤发生,从而降低层板铆接强度,其中偏心加载可以削弱二次弯曲效应,更好地提高铆接强度;层板铝合金体积分数的增大能够提高层板铆接强度,但当体积分数大于50%时层板铆接比刚度和比强度反而下降;预紧力的增加能够提高层板铆接强度和增强层板损伤抗力;随着孔边距的递增,铆接剩余强度有所提高,破坏模式由灾难性拉断失效模式逐渐转化为理想的挤压失效模式,但当孔边距达到一定数值时,铆接强度不再明显提高,而失效模式也维持为挤压破坏。     

Ultrasonic characterization on sequences of CFRP composites based on modeling and motorized system

Composites are a material class for which nondestructive material property characterization is as important as flaw detection. Laminates of fiber reinforced composites often possess strong in-plane elastic anisotropy attributable to the specific fiber orientation and layup sequence when waves are propagating in the thickness direction of composite laminates. So the layup orientation greatly influences its properties in a composite laminate. It could result in the part being rejected and discarded if the layup orientation of a ply is misaligned. A nondestructive technique would be very beneficial, which could be used to test the part after curing and requires less time than the optical test. Therefore a ply-by-ply vector decomposition model has been developed, simplified, and implemented for composite laminates fabricated from unidirectional plies. This model decomposes the transmission of a linearly polarized ultrasound wave into orthogonal components through each ply of a laminate. Also in order to develop these methods into practical inspection tools, motorized system have been developed for different measurement modalities for acquiring ultrasonic signals as a function of in-plane angle. It is found that high probability shows between the model and tests developed in characterizing cured layups of the laminates.     

Impact damage and hygrothermal effects on fatigue bending strength of orthotropy composite laminates

This paper focuses on fracture mechanisms experimentally based on the scanning acoustic microscope (SAM) when subjected to impact damages, i. e., foreign object damages (FOD), and also on the influence of impact damages and hygrothermals on residual fatigue bending strength of CFRP laminates. Composite laminates used in the experiments are CF/Epoxy orthotropy laminated plates, [0₄/90₄]_s. A steel ball launched by an air gun impacts on CFRP laminates to generate impact damages. Bending fatigue tests are periodically interrupted for a nondestructive evaluation (NDE) measurement of the progressive damages to build the fracture mechanism based on impact damages, and three-point fatigue bending tests are carried out to investigate the influence of hygrothermals on the effect of the residual bending fatigue strength of CFRP laminates.     

铺层结构三维等效弹性常数研究

从铺层结构的三维宏观弹性特性出发,利用三维层压结构理论,获得了复合层板的三维弹性常数的等效公式。以MATLAB为平台,编写模块化程序,将层压结构理论运用于某大型回转机械平行铺层和环状铺层结构的三维弹性常数等效中,输入每个单层结构的弹性参数,该程序可自动生成部件等效刚度矩阵、柔度矩阵和等效弹性常数;结合APDL参数化语言建立有限元模型,对等效前后的结构进行模态分析比较。结果表明,等效前后部件前三阶固有频率的变化率都小于5%,说明该方法对此类复合铺层结构的三维弹性常数等效是可行的。     

Buckling of unsymmetrical, cross-ply laminates with matrix cracks

The effect of matrix cracks on the buckling of unsymmetrical, cross-ply laminates is investigated. The cracks are modelled as aligned slit cracks across the ply thickness and transverse to the laminate plane. The distribution of cracks is assumed to be statistically homogeneous corresponding to an average crack density. The results are given for antisymmetrically- and unsymmetrically-laminated plates with a given density of matrix cracks. The effect of reduction in the laminate stiffness is studied by plotting the ratio of the buckling loads of cracked and uncracked laminates against the aspect ratio, crack density and relative layer thicknesses. It is observed that the amount of reduction in the buckling load depends on the stacking sequence as well as on the relative thicknesses of layers. This reduction is found to be substantially less than the reduction in the affected elastic moduli of the material.     

单振子双腔体无阀压电泵结构设计与机理分析

提出了一种单振子双腔体无阀压电泵,应用小挠度弹性弯曲理论导出了圆形复合压电振子的弹性曲面微分方程,分析了采用一个压电振子形成两个工作腔体压电泵的结构和工作机理,并与单振子单腔体压电泵对比分析了该结构与输出流量的关系。设计研制了结构独特、输出性能更高的单振子双腔体无阀压电泵,通过试验表明:单振子双腔体无阀压电泵比单振子单腔体无阀压电泵输出流量有明显提高。