基于材料选型优化的金属-复合材料组合结构-声辐射优化

基于金属铺层假设,以结构材料属性和材料铺层数量为设计变量,建立了基于金属-复合材料的材料选型结构-声辐射优化设计模型。以钢-纤维增强复合材料组合结构为例,开展了多设计变量、多约束条件的结构-声辐射优化研究。最后,采用遗传算法进行求解,实现了结构材料的转换。数值算例表明,通过金属-复合材料组合结构的材料选型优化,可以有效降低钢-纤维增强复合材料结构的振动和声辐射。文中的研究方法为结构材料的分布优化提供了一种可行有效的思路。     

基于铺层设计特征的碳纤维增强复合材料悬架控制臂结构优化

基于铺层设计特征,提出一种使用碳纤维复合材料对承载结构件进行结构优化设计的方法和流程.该方法综合考虑结构几何特征、材料铺层方式、铺层厚度及铺层角度在设计环节中的序列关系,通过几何设计空间构建、离散变量多目标优化、基于工艺可行性的最优决策等方法实现结构设计.以碳纤维增强复合材料悬架控制臂的轻量化设计为例:首先,以钢质控制臂结构为参考建立复合材料控制臂的几何设计空间;然后,以复合材料铺层便利性为原则对其进行结构设计,采用准各向同性铺层对控制臂的铺层厚度进行设计;进而,以提高控制臂刚度和1阶固有频率为目标,使用优化算法对铺层角度进行多目标优化设计;最后,以工艺可行性为约束对优化结果进行筛选并最终完成结构设计.结果表明,所设计复合材料结构具有更大的刚度和1阶固有频率,并且与钢质结构相比减重47.9%.所提出的方法能够较好地兼顾结构特征和复合材料设计要求之间的关系,为复合材料结构优化设计理论与方法的发展提供有益参考.     

复合材料轴结构力学性能预测及铺层方案设计

针对连续纤维增强金属基复合材料轴结构力学性能预测问题,考虑纤维呈四边形和六角形两种周期性排列方式,基于细观力学有限元方法,建立六种代表体积元(RVE)模型,计算该材料的宏观力学性能参数,并与已有的三种细观力学模型计算结果进行对比分析。在此基础上,以低压涡轮轴为研究对象,将选定的RVE模型预测所得的宏观力学性能参数应用于该纤维增强复合材料轴结构的铺层方案设计中,利用数值模拟方法计算该轴结构在给定弯矩、扭矩作用下的变形量和应力,并分析铺层角度、厚度及铺层顺序对轴结构抗弯、抗扭性能的影响规律。研究发现纤维按某种特定的铺层角度组合铺设,可有效提高轴结构的抗弯、抗扭性能,通过计算分析提出了铺层设计方案。     

碳纤维复合材料控制臂多尺度多目标优化

为实现悬架控制臂轻量化设计,采用碳纤维复合材料(CFRP)对钢制控制臂进行材料替换,并利用多层次优化方法对CFRP控制臂进行铺层优化。基于多尺度分析方法,考虑碳纤维复合材料细观结构参数及铺层角度对控制臂宏观性能的影响,选取细观尺度下纤维束截面高度、宽度、纱线曲折度、单位长度经纬纱数量及四个经典铺层角度作为设计变量,以控制臂的质量最小、一阶模态频率最高为优化目标,以刚度和强度为约束条件,结合响应面近似模型和NSGA-Ⅱ优化算法对碳纤维复合材料控制臂进行多尺度多目标优化,得到Pareto解集。优化结果表明,在刚度满足使用性能要求下,CFRP控制臂的质量较钢制控制臂下降了65%,且强度、振动特性等性能得到大幅提升,轻量化效果显著,可为碳纤维复合材料结构件的轻量化设计提供参考。     

纤维混杂铺层对无伞空投箱抗冲击性的影响

目的 对无伞空投箱所用的碳纤维、玻璃纤维、芳纶纤维/环氧树脂体系纤维混杂铺层的复合材料层合板进行研究,以在低成本下提高实现效果。方法 复合材料层合板分为10层,采用层间混杂结构,通过改变混杂比、铺层角度及铺层顺序,设计148种铺层方案,利用ANSYS–APDL软件分析3种参数变量对层合板拉伸性能及抗弯性能的影响。结果 沿主要受力方向铺设纤维,碳纤维层在外侧、玻璃纤维层集中在中心,且玻璃纤维层体积分数为40%时,材料具有最高的性价比。结论 针对混杂纤维复合材料层合板,通过调整混杂比得出碳/玻璃混杂纤维复合材料性能较好,通过调整铺层角度得出纤维铺设角度越接近受力方向其性能效果越好,通过调整铺层顺序得出不同混杂比、铺层角度下的最佳性能结构。     

玻璃纤维增强铅网/橡胶阻尼复合材料研究

为了改善橡胶的力学性能和阻尼性能,以橡胶、纤维和铅为原料设计了玻璃纤维增强铅网/橡胶阻尼复合材料,研究了不同玻璃纤维增强铅网铺层数量的横向玻璃纤维增强铅网/橡胶复合材料力学性能和阻尼性能,分析了其阻尼机制.结果表明,复合材料具有比橡胶更高的力学性能和阻尼特性,其刚度随铅网铺层数量的增加而提高,而阻尼损耗因子与铺层数呈非线性关系.复合材料中存在材料变形耗能、界面耗能、摩擦耗能等多种阻尼损耗机制.     

基于纤维正交单元层合板面内零膨胀的模型优化分析

基于经典层合板理论,推导出纤维正交单元复合材料层合板面内两个方向热膨胀系数的计算表达式。从理论上分析了不同的纤维体积含量、环氧树脂种类对纤维增强复合材料层合板面内两个方向热膨胀系数的影响。分析结果表明,纤维正交单元层合板面内热膨胀系数与其铺层角度、铺层顺序、层数均无关;采用纤维方向有较大负热膨胀系数的纤维,并调节纤维的体积含量,可以得到面内近零膨胀的复合材料。     

混杂比对碳纤维-玄武岩纤维混杂增强环氧树脂基复合材料弯曲性能的影响

将玄武岩纤维置于混杂铺层的压缩侧,研究了碳纤维-玄武岩纤维混杂增强环氧树脂基复合材料的弯曲性能及混杂比对其弯曲性能的影响。通过对试样进行三点弯曲试验得到了材料的弯曲性能,并通过扫描电子显微镜观察材料的失效模式。与纯碳纤维增强环氧树脂基复合材料相比,当混杂比为16.7%和33.3%时,混杂复合材料的弯曲强度明显提升,弯曲强度分别提高12.4%和15.2%,但是其弯曲模量随着混杂比的提升而降低。混杂后的材料及玄武岩纤维增强环氧树脂基复合材料的失效位移都高于碳纤维增强环氧树脂基复合材料,断裂韧性明显提升。从侧面观察可以发现不同铺层在压缩侧、拉伸侧和中间层有不同的失效形式。      

亚麻/聚丙烯复合材料板材的制备及其冲击性能

以亚麻纱线作为增强体,与聚丙烯（PP）纤维按六种质量比进行混合,制备PP长丝包覆的包覆纱,利用机织工艺织成二维机织布作为复合材料的预制铺层,采用热压法进行层合热压,制备出亚麻增强聚丙烯复合材料板材。通过对板材冲击性能的测试及分析,研究了制备工艺、纱线结构及纤维含量等因素对复合材料冲击性能的影响。结果表明,本试验中当亚麻质量分数为68%时板材的冲击性能最好;＂三明治＂铺层方法制备的板材体现出较好的冲击性能;0°/0°板材在受到冲击时比0°/90°板材吸收的冲击能更多,体现出较好的耐冲击性。     

混杂复合材料非对称铺层结构性能研究EI北大核心

混杂复合材料是两种或两种以上不同基体或增强材料组成的复合材料。混杂复合材料因选用了不同的材料,在性能上常有互补性。通过研究典型基体材料和典型增强材料组成的混杂复合材料,和混杂复合材料的非对称铺层特性,形成混杂复合材料非对称铺层制件。在单一材料性能基础上,主要研究典型混杂复合材料的性能,混杂复合材料非对称铺层结构的性能。     

Design systems for gear elements made of cotton fiber-reinforced plastics

We look on the cotton fiber reinforced plastics as industrial gear materials, and have been developing design systems for industrial gears made of cotton fiber-reinforced plastics. In this report, we deal with a method estimating for tooth root stresses caused by bending movements under running conditions. The gear material used was cotton fiber plain woven cloth reinforced phenolic resin laminates. Paper-reinforced phenolic resin laminates, a commonly used material, was used as a control for comparison. The main dimensions of the gears were module 3–5 mm and tooth width 25 mm. First, accelerations of gears were measured under running conditions to estimate dynamic performance. Second, fracture tests of gear teeth were carried out under bending loads. Different fracture modes at tooth roots for cotton fiber-reinforced plastics and phenolic resin gears were observed. The fractures occurred at a high position from the tooth root in the case of the cotton fiber-reinforced plastics gear because the cotton fiber-reinforced plastics had excellent cleavage and shear strength. This gear also had higher strength for tooth bending loads. Third, the mechanical properties of the gears were researched by tensile, bending, and shearing tests. It was clear that the cotton fiber-reinforced plastics had excellent properties in cleavage fracture between laminates and shear strength. Finally, we proposed a design method for this gear, which considers the cleavage and shear strength.     

Friction and wear behavior of carbon fiber reinforced brake materials

A new composite brake material was fabricated with metallic powders, barium sulphate and modified phenolic resin as the matrix and carbon fiber as the reinforced material. The friction, wear and fade characteristics of this composite were determined using a D-MS friction material testing machine. The surface structure of carbon fiber reinforced friction materials was analyzed by scanning electronic microscopy (SEM). Glass fiberreinforced and asbestos fiber-reinforced composites with the same matrix were also fabricated for comparison. The carbon fiber-reinforced friction materials (CFRFM) shows lower wear rate than those of glass fiber- and asbestos fiber-reinforced composites in the temperature range of 100°C-300°C. It is interesting that the frictional coefficient of the carbon fiber-reinforced friction materials increases as frictional temperature increases from 100°C to 300°C, while the frictional coefficients of the other two composites decrease during the increasing temperatures. Based on the SEM observation, the wear mechanism of CFRFM at low temperatures included fiber thinning and pull-out. At high temperature, the phenolic matrix was degraded and more pull-out enhanced fiber was demonstrated. The properties of carbon fiber may be the main reason that the CFRFM possess excellent tribological performances.     

混合废纸纤维对发泡缓冲包装材料性能的影响

目的 研究废箱板纸和数字印刷废纸混合比例对发泡材料各项性能的影响,确定最佳纤维混合比例。方法 以废箱板纸和数字印刷废纸为主要原料,通过微波发泡法制备了一种废纸纤维发泡材料,通过微距镜头及扫描电镜对发泡材料微观结构进行观察。结果 研究表明,当废箱板纸纤维和数字印刷废纸纤维质量比为12.5∶2.5时,得到的材料综合性能最优,其密度为0.112 g/cm³、发泡倍率为1.728、变形能为6.463×10⁴J/m³、缓冲系数为5.922。结论 将2种废纸纤维混合起来所制备的发泡材料具有低密度、高发泡倍率和较好的缓冲性能。     

瓦楞纸箱包装结构优化设计及计算机辅助设计软件

提出的瓦楞纸箱包装结构优化设计ＣＡＤ，能使瓦楞纸箱包装设计用料成本、运输成本、仓储成本的包装总成本最小，因而最优。     

Characterization of interfacial and mechanical properties of “green” composites with soy protein isolate and ramie fiber

Environment-friendly fiber-reinforced composites were fabricated using ramie fibers and soy protein isolate (SPI) and were characterized for their interfacial and mechanical properties. Ramie fibers were characterized for their tensile properties and the parameters for the Weibull distribution were estimated. Effect of glycerol content on the tensile properties of SPI was studied. Interfacial shear strength (IFSS) was determined using the microbond technique. Based on the IFSS results and fiber strength distribution, three different fiber lengths and fiber weight contents (FWC) were chosen to fabricate short fiber-reinforced composites. The results indicate that the fracture stress increases with increase in fiber length and fiber weight content. Glycerol was found to increase the fracture strain and reduce the resin fracture stress and modulus as a result of plasticization. For 10% (w/w) of 5 mm long fibers, no significant reinforcement effect was observed. In fact the short fibers acted as flaws and led to reduction in the tensile properties. On further increasing the fiber length and FWC, a significant increase in the Young's modulus and fracture stress and decrease in fracture strain was observed as the fibers started to control the tensile properties of the composites. The experimental data were compared to the theoretical predictions made using Zweben's model. The experimental results are lower than the predicted values for a variety of reasons. However, the two values get closer with increasing fiber length and FWC.     

基于非接触激振-测振一体化技术的纤维增强复合材料参数辨识研究

该文综合利用了平面声波激励和激光高精度测振的优势,提出了基于非接触激振-测振一体化技术的纤维增强复合材料参数辨识方法。以该类型复合材料薄板为例,建立了其在平面声波激励下的理论模型,并结合经典层合板理论、复模量法、应变能等方法,通过公式推导,实现了时域振动响应的理论求解。在理论结合实测数据的基础上,通过粒子群迭代求解方式,成功辨识获得了CF140碳纤维/环氧树脂材料的各项材料参数。通过与厂家提供的材料参数进行对比,发现该方法不仅在弹性模量、泊松比获取上具有较高的辨识精度,而且还可辨识出的材料在纤维纵向、横向和剪切方向的损耗因子。     

叠置组合缓冲衬垫设计算例及数值仿真对比分析

目的提出叠置组合缓冲衬垫的设计思路,并对该方法的正确性进行数值仿真验证。方法基于数学思想对叠置组合缓冲衬垫设计方法进行分析,设计线弹性材料模型算例,并获得解析解,最后基于Ansys软件的DTM模块进行数值仿真验证。结果数值仿真结果与解析解的误差为2.1%,验证了叠置组合缓冲设计方法的正确性。结论从数学意义上理解,叠置组合缓冲衬垫设计方法是不确定方程组求解问题,需要通过施加更多的约束条件获得确定的设计结果。Ansys软件的DTM模块可以用于缓冲包装系统的性能评价,是一种简单高效的分析工具。     

Designing the fiber volume ratio in SiC fiber-reinforced SiC ceramic composites under Hertzian stress

Finite element method (FEM) analysis and experimental studies are undertaken on the design of the fiber volume ratio in silicon carbide (SiC) fiber-reinforced SiC composites under indentation contact stresses. Boron nitride (BN)/Pyrocarbon (PyC) are selected as the coating materials for the SiC fiber. Various SiC matrix/coating/fiber/coating/matrix structures are modeled by introducing a woven fiber layer in the SiC matrix. Especially, this study attempts to find the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics under Hertzian stress. The analysis is performed by changing the fiber type, fiber volume ratio, coating material, number of coating layers, and stacking sequence of the coating layers. The variation in the stress for composites in relation to the fiber volume ratio in the contact axial or radial direction is also analyzed. The same structures are fabricated experimentally by a hot process, and the mechanical behaviors regarding the load–displacement are evaluated using the Hertzian indentation method. Various SiC matrix/coating/fiber/coating/matrix structures are fabricated, and mechanical characterization is performed by changing the coating layer, according to the introduction (or omission) of the coating layer, and the number of woven fiber mats. The results show that the damage mode changes from Hertzian stress to flexural stress as the fiber volume ratio increases in composites because of the decreased matrix volume fraction, which intensifies the radial crack damage. The result significantly indicates that the optimum fiber volume ratio in SiC fiber-reinforced SiC ceramics should be designed for inhibiting the flexural stress.     

大型精密仪器运输包装箱设计及试验

目的为了在控制包装箱整体重量的同时,提高包装箱的气密性及承压能力,对大型精密仪器运输包装箱的结构进行设计及优化。方法针对精密仪器运输过程中"气体保护及密封性"的需求,设计钢骨架与玻璃纤维复合的箱体结构,并利用有限元仿真对设计方案进行分析评估,最后进行箱体的承压试验与气密性试验。结果箱体在极端工况下的最大变形量为4.82 mm,在建立的箱内温度和大气压补偿模型基础上,包装箱泄露率仅为520.5 Pa/48 h。结论采用钢骨架与玻璃纤维复合的箱体结构,满足了大型精密仪器运输的承压及密封性要求,为大型密闭箱体设计及试验提供了参考。