复合材料层合板低速冲击损伤阻抗性能影响因素研究

基于复合材料层合板的结构特点及典型损伤和破坏模式,建立了基于ABAQUS有限元软件的复合材料层合板低速冲击模型.与实验数据对比结果表明,该模型可以准确地模拟复合材料层合板低速冲击损伤阻抗特性.采用该有限元模型,研究复合材料层合板的铺层材料面内性能和铺层角度等参数对其在低速冲击作用下损伤阻抗性能的影响规律.分析结果表明,提高铺层纤维方向拉伸模量可明显提升其抗冲击损伤能力,在复合材料层合板中增加±45°铺层数量能明显提升其抗分层能力,而提高其它方向弹性模量对复合材料层合板低速冲击损伤阻抗性能的影响不明显.     

含孔二维机织复合材料层合板强度预测方法研究

将基于单层板理论的逐渐累积损伤强度预测方法推广用于含孔二维机织复合材料层合板的强度预测,建立了含孔二维机织复合材料层合板的逐渐累积损伤强度预测方法.并在ANSYS软件平台上开发了相应的参数化二维机织复合材料含孔层合板逐渐累积损伤强度预测程序,对两种孔径两种铺层的含孔二维机织复合材料层合板的强度进行预测,并对其损伤扩展规律进行了分析.经与试验结果对比表明本文所建立的强度预测方法效果良好.     

铺层次序对于碳／玻璃混杂复合材料破坏过程的影响

本文使用有限元方法模拟了三种碳/玻璃编织状混杂复合材料层合板的破坏过程，三种层合板有相同的碳纤维和玻璃纤维的体积比和重量比。层数比相同铺层次序不同，假设碳纤维层首先破坏，计算了破坏处周围的最大拉伸应力、拉伸应变和层间剪切应力，从应力、应变分析和能量分析的观点探讨了铺层次序对于混杂复合材料破坏过程的影响，结果表明：铺层次序影响着脱层破坏的出现，三种分析方法可以得到一致的结论，并与试样断口分析的结果相吻合。     

无矩层合板在Ⅰ、Ⅲ内力象限的能量优化

本文论证了复合材料无矩层合板在Ⅰ、Ⅱ内力象限的最小应变能优化铺层模式一均衡型层合板及其特性,简述了在圆筒形压力容器中的应用.     

采用流固耦合方法的复合材料层合板鸟撞分析

基于流固耦合的方法,利用ANSYS/LS-DYNA软件构建了复合材料层合板鸟撞损伤模型,通过分析层合板鸟撞后的动响应验证了鸟撞过程的4个阶段,探讨了鸟撞过程中冲击波在层合板中的传递情况;分析了层合板在鸟撞时先后出现的基体压缩、基体开裂以及纤维断裂这一损伤过程;研究了铺层方式对鸟撞后鸟体的剩余能的影响.结果表明:合理的设计铺层方式可以有效提升层合板抗撞能力.     

基于CDM的复合材料层合板插层补强强度分析

文章针对复合材料插层补强层合板损伤破坏问题,基于各向异性材料连续介质损伤力学方法,引入材料损伤状态变量对复合材料损伤情况进行描述,建立了复合材料插层补强三维非线性渐进损伤模型;利用该模型对复合材料插层补强层合板的损伤破坏进行了准确预测.重点对补强设计中插层材料铺层比例和补强半径两个设计参数进行了研究,得到了复合材料开口层合板理想的插层材料铺层比例及补强半径范围.     

复合材料尖削结构同级优化方法研究及ISIGHT实现

现有复合材料优化方法在进行尖削结构优化时,设计变量多而且难以保证纤维的连续性,文章提出了一种基于尖削结构模型的复合材料的同级优化方法。通过引入了铺层组、铺层组厚度、铺层组铺层顺序和铺层组距离变量等参数,在不影响优化结果的同时能有效的减少设计变量个数,并保证纤维的连续性。文章借助商业软件ISIGHT实现了该同级优化方法,采用某层合板优化问题验证了该方法的有效性。     

纤维体积含量对含孔对称复合层板孔边应力集中的影响

纤维体积含量是决定纤维增强复合材料各项力学性能的一个重要参数。针对含孔对称层板在面内载荷作用下应力集中的问题,文章以含圆孔、椭圆孔和正方形孔的无限大复合材料对称层合板受无穷远处面内双向拉伸载荷为例,对纤维体积含量发生改变时,孔边应力集中的变化情况进行了研究,得到了纤维含量对孔边应力集中的影响规律。     

考虑弯扭耦合效应的复合材料叶片铺层优化方法

在复合材料叶片设计中,可利用弯扭耦合效应进行铺层优化设计,通过减小叶片气动弹性外形的改变来提高叶片结构的效率。将复合材料叶片简化为对称非均衡悬臂层合板,基于经典层合板理论提出刚度权值和载荷系数2个分析参数。并采用试验和有限元模拟分析了弯扭耦合效应中分析参数对结构变形的影响。进一步以刚度权值的可行域为约束条件,叶片曲率最小为目标函数,对含有0°,90°和±45°铺层的对称层合板进行分析计算,得到关于载荷系数的刚度权值最优路径。并以16层对称层合板为例进行了验证计算。通过对刚度权值最优路径的逆向计算,能够快速得到满足设计条件的最优铺层顺序。该方法可为复合材料叶片的铺层优化设计提供一定的参考和依据。     

双参数地基上层合板屈曲问题的半解析解法

采用经典层合板理论,分析弹性地基上复合材料层合板在单向或双向受压时的屈曲特性,给出了相应的半解析计算格式.通过实际算例讨论了层合板纤维铺设角、地基参数、边界约束条件、板长宽比、弹性转动刚度等因素对其屈曲特性的影响.     

Thermoelastic properties of sandwich materials with pin-reinforced foam cores

Pin-reinforced foam is a novel type of sandwich core materials formed by inserting pins (trusses) into a foam matrix to create a truss-like network reinforced foam core. Upon loading, the pins deform predominantly by local stretching whilst the deformation of foam is governed by local bending. This paper presents a theoretical study on the thermoelasticity of pin-reinforced foam sandwich cores. To calculate the effective thermoelastic properties of pin-reinforced foam cores, the energy-based homogenization approach is employed to develop a micromechanicsbased model, calibrated by the existing experimental data. It is found that the stiffness of the sandwich core is mainly governed by pin reinforcements: the foam matrix contributes little to sandwich stiffness. Compared with traditional foam cores without pin reinforcements, the changes in in-plane thermal expansion coefficients are not vigorous as a result of pin reinforcements, while the throughthickness thermal expansion coefficient changes significantly. It is also demonstrated that it is possible to design materials with zero or negative thermal expansion coefficients under such a context. Supported by the National Basic Research Program of China (Grant No. 2006CB601202), the National Natural Science Foundation of China (Grant Nos. 10572111, 10632060), the National 111 Project of China (Grant No. B06024), the National High Technology Research Development Program (Grant No. 2006AA03Z519), the NPU Foundation for Fundamental Research, the Open Foundation of State Key Laboratory of Structural Analysis of Industrial Equipment (Grant No. GZ0701), and the NPU Foundation for Scientific Innovation     

光纤位移法进行微小长度测量的相关实验研究

从理论和实验两方面,分析了光纤微位移传感器特性,分别给出了实验结果和理论对比结果,利用该光纤微位移传感器进行微小伸长量的测量,从而给出了一种新的扬氏弹性模量和金属固体线膨胀系数的测量方法。     

Al2-xYxW3O12的合成与热膨胀特性的研究

用共沉淀法合成了Al2-xYxW3O12(x=0～2)系列氧化物材料．实验结果表明，通过调整稀土钇(Y)的含量，可以使氧化物的本征热膨胀系数和宏观热膨胀系数逐渐由正到负变化．但是由于其结构的各向异性，多晶陶瓷内部存在的微裂纹使热膨胀曲线出现较大的滞后环．     

功能原理在纤维封层沥青胶浆配合比中的应用

针对纤维封层配合比的控制主要依靠经验法的问题,根据功能原理从理论上分析纤维封层材料配合比参数设计。通过粘附功、应变能、热能损耗的计算,从4种纤维中选择性能最优的作为封层纤维;同时提出破裂面的概念,得到纤维用量与乳化沥青用量的比例关系;进一步讨论了纤维长度与封层性能的关系。结果表明:复合改性玻璃纤维D最适合用于纤维封层;同时D纤维的破裂半径为0.83mm,理论纤维、乳化沥青用量比例为1∶11.919;计算理论纤维长度为72mm。     

Thermal expansion properties and hygroscopicity of Y2-xSmxW3O12 (x = 0.0-0.4) compounds

A novel class of solid solutions of Y2-xSmxW3O12 (x = 0.0-0.4) were synthesized and studied by means of powder X-ray diffraction. All samples crystallize in an orthorhombic space group Pnca. The lattice parameters a, b and c of Y2-xSmxW3O12 increase with increasing Sm content. Since the compounds of this series hydrate at room temperature, thermogravimetric (TG) analysis was carried out. The result shows that the compound stores less water with increasing Sm content. The thermal expansion properties of Y2-xSmxW3O12 (x = 0.1, 0.3 and 0.4) were investigated with high temperature X-ray diffraction. Negative thermal expansion coefficient -α becomes less negative from -6.644×10-6 to -6.211×10-6℃-1 when x changes from 0.1 to 0.4.     

热膨胀系数时变性对混凝土温度应力仿真影响

已有试验研究表明,混凝土的热膨胀系数具有明显的随龄期发展的特性. 为了研究混凝土热膨胀系数时变特性,以及更好地模拟混凝土早龄期温度应力,分析热膨胀系数时变效应对混凝土温度应力仿真的影响,采用温度应力试验机进行试验,对混凝土热膨胀系数进行测定. 引入等效龄期的概念,将混凝土早期变形分离为温度变形与自生体积变形,建立热膨胀系数与等效龄期之间的数学模型. 通过室内试验试件的有限元数值模拟,验证热膨胀系数时变模型的合理性. 将时变模型应用于大岗山特高拱坝施工期的温度应力仿真,通过对比研究,分析热膨胀系数时变效应对混凝土温度应力的影响. 研究表明,混凝土热膨胀系数在早龄期变化较大,考虑其时变性对仿真防裂意义重大. 尤其对于受通水等影响早期温降速率较快的混凝土,考虑热膨胀系数时变效应进行仿真计算应力水平较传统方法偏高,据此计算结果进行防裂设计更安全.     

Thermotics Study of the Semimetallic Nylon1010 Composite

Thermal expansion characteristics of semimetal nylon composites （nylon 1010 incorporated with metal oxides） were analyzed with thermal expansion instrument. The changes of composite weight after being heated and the heat absorption and release of the composites were analyzed by carrying out TG-DSC experiments. Experimental results show that the average thermal expansion coefficient of the composites rises as the average diameter of the metal oxides decrease from room temperature to 160 ℃. Thermal dynamics and physical properties of the nylon composites change with the addition of the oxides; the crystallization temperature rises from 180 ℃ of pure nylon to 190 ℃ （maximum） and the melting point of the oxide composites also increases continuously with the addition of the oxides. The water content of the oxide/nylon composite is related to the kind and content of the oxide. The water content reaches its maximum when the content of oxide is 10%, and the 10% Al2O3/nylon composite has a water absorption ratio up to 1%.     

含微裂纹三维多向编织复合材料热膨胀系数细观力学分析

将三维编程复合材料的纤维束和微裂纹分别看作圆柱型和圆币型夹杂,考虑了微裂纹的任意取向和增强纤维束的空间取向,采用等效夹杂法对含微裂纹的三维多向编织复合材料的热膨胀胀系数进行了细观力学分析,提出了预报含微裂纹三维多向编织复合材料热膨胀系数的方法,由于直接考虑了微裂纹的任意取向和增强纤维的空间取向,这种方法既可应用于一般含微裂纹的三维编程复合材料,也可应用于单向纤维增强复合材料,结合实例分别预报了单向增强复合材料和四向编程复合材料的热膨胀系数,与实验结果吻合较好。     

Design of a continuous fiber trajectory for 4D printing of thermally stimulated composite structures

Deformation control of 4D printing has always been challenging. Herein, a design method for the fiber trajectory for 4D printing composite structures with embedded continuous fibers is reported, wherein the designed composite structures can be deformed into many types of deployable surfaces. Deformation of the bilayer composite structure was driven by differences in the coefficients of thermal expansion (CTEs) between the resin substrate and embedded fibers. The bending curvature and direction of the composite structure is controlled by adjusting fiber orientations. According to differential geometry theory, the relationship between the angle of intersecting fiber bundles and curvature of the final shape was obtained. Therefore, arbitrary deployable surfaces, including conical, cylindrical, and tangent surfaces, can be deformed. This design and additive manufacturing strategy allow precise control of the deforming process, greatly extending the potential applications of 4D printing.     

B_2O_3对硼硅酸盐玻璃结构和性能的影响

硼硅酸盐玻璃与普通的钠钙硅玻璃相比,性能上有非常明显的优势。主要探讨B2O3对硼硅酸盐玻璃结构和性能的影响。通过红外光谱和拉曼光谱分析了硼硅酸盐玻璃在不同含量B2O3的情况下的结构变化,测试了玻璃的热膨胀系数、转变温度、软化温度和化学稳定性。研究结果表明:随着B2O3含量的增加,玻璃结构中[BO3]增多,[BO4]先增多后相当,玻璃的热膨胀系数也是先减小后增大,转变温度和软化温度都逐渐减小;硼硅酸盐玻璃中加入适量的B2O3后对玻璃的化学稳定性有一定的改善。