碳纤维复合材料引擎盖的轻量化设计

以汽车碳纤维复合材料引擎盖为研究对象，采用碳纤维复合材料为研究材料，以层合板理论为力学数值模拟CAE设计基础，利用ABAQUS软件对单层级试样准静态拉伸试验和典型U形梁结构准静态三点弯试验进行仿真，然后进行了台架模态和抗凹刚度测试。采用概念设计、材料性能试验和工艺设计多阶段联合优化设计的方法，最终在满足各种力学性能和制造工艺要求的前提下，实现碳纤维复合材料引擎盖的轻量化设计。     

基于光纤布拉格光栅的复合材料振动性能研究与损伤监测

采用光纤布拉格光栅(FBG)对碳纤维增强复合材料(CFRP)的振动性能和损伤类型进行研究。采用落球击打碳纤维增强复合材料悬臂梁自由端,使复合材料悬臂梁产生谐振。通过测量复合材料悬臂梁的谐振频率,计算其阻尼损耗因子,得到无损伤碳纤维复合材料的振动性能。在此基础上,对碳纤维增强复合材料人为引入损伤,利用FBG测量其损伤状态下的谐振频率,依据谐振频率分析判断损伤类型。研究结果可对碳纤维增强复合材料的振动性能研究和损伤监测提供参考。     

船舶复合材料轴系振动性能的仿真分析研究

碳纤维复合材料传动轴系(简称复合材料轴系)的振动性能是船舶动力传动系统复合材料轻量化技术的重点内容之一,对优化轴系设计,提高轴系可靠性及综合性能具有十分重要的意义。本文介绍了船舶复合材料轴系振动特性的仿真分析过程,对轴系的扭转、纵向及回旋振动开展了模态分析,并研究了轴承刚度、轴系布置方案对复合材料轴系振动特性的影响。结果表明,通过模态分析可以判断复合材料轴系的共振情况,轴承刚度对复合材料轴系的固有频率影响较小。经过减重优化后的复合材料轴系由于轴的弯曲刚度变大,对应前三阶纵向振动频率下降,回旋振动频率提高。本文为船舶复合材料轴系振动性能分析及轴系方案优化提供了一定的理论基础。     

碳纤维复合材料机械臂结构设计与性能优势研究

对碳纤维复合材料机械臂的结构设计与铺层优化情况进行分析,总结出高分子复合材料在传统机械臂金属材料替代领域的性能优势与价值,认为在满足同等机械臂力学强度和刚度条件下,碳纤维复合材料能够有效降低超过90%的机械臂自重,且变臂厚铺层方案能够获得最为理想的机械臂结构。碳纤维复合材料的应用,对现代机械臂的轻量化设计大有裨益。     

石墨烯增强碳纤维复合材料抗冲击性能分析

目前碳纤维复合材料存在脆性大、横向耐冲力差等问题。为了提高碳纤维复合材料的抗冲击性能，文章基于显示动力学下冲击载荷模拟的方法，以单层石墨烯和碳纤维复合材料层合板为研究对象建立冲击模型，对比分析不同石墨烯含量碳纤维板受冲击时表面应力、位移与吸能、损伤与破坏情况。结果表明：添加石墨烯提高了材料的填充率，使材料面密度增大；相同冲击载荷下，加入0.3%石墨烯的碳纤维增强复合材料（CFRP）层合板较传统CFRP位移减小10.2%，最大应力减少18.5%。且加入单层石墨烯含量越高，复合材料界面作用力越强，能够有效减小损伤破坏。     

玻/碳纤维混杂复合材料层合板的振动特性研究

为了获取玻/碳纤维混杂复合材料层合板的振动特性,以玻/碳纤维混杂复合材料层合板为研究对象,基于有限元分析软件ANSYS Workbench分析了夹芯混杂、层间混杂两种混杂方式下的复合材料层合板的振动特性,得到了层合板的混杂类型、铺设厚度、长宽比、铺设角度对玻/碳纤维混杂复合材料层合板固有频率的影响规律.结果表明:夹芯混...     

编织复合材料的横向冲击力学行为研究

本文利用冲击加载实验装置对碳纤维编织复合材料梁的横向冲击损伤与断裂行为进行了实验研究,确定了不同冲击速度下冲击载荷响应、梁的动态位移变化以及梁的动态应变演化历史等动态力学行为,给出复合材料梁的冲击吸收能量及其Mises有效应力。同时,利用扫描电镜对编织复合材料的损伤断裂机理进行微观分析。     

轻质碳纤维复合材料帆船桅杆的设计与制备

碳纤维复合材料与金属相比,具有重量轻、可设计性强等优点.本文目的是设计并制备轻质碳纤维复合材料桅杆.基于等刚度准则,对具有等壁厚、异型截面的中空碳纤维复合材料桅杆进行设计,并运用数值模拟技术对结构铺层进行优化.采用纤维铺放和缠绕工艺制备出长度为16m的大尺寸碳纤维复合材料帆船桅杆,与铝合金桅杆相比减重43.4%.在设计工况下,桅杆变形试验值与数值模拟结果相近.     

NACA构型泡沫夹层复合材料空气风门的结构强度分析

泡沫夹层复合材料具有比强度、比刚度大,保温隔热性能优异等优点,广泛应用于航空航天等诸多领域,在飞机上则应用于一些载荷不大而厚度较小的部件或结构。研究的NACA构型泡沫夹层复合材料空气风门以其材料的特殊性,在组合工况下受力情况复杂,目前对其在多工况下进行强度分析的相关研究较少。以NACA构型的泡沫夹层碳纤维复合材料空气风门为研究对象,建立了有限元模型。通过重点对多工况下风门壳体的等效应力分布情况进行对比和分析,并对夹层结构各层的应力危险区域进行强度校核,得到了各工况下复合材料面板层和泡沫芯材层的应力敏感区域和失效情况,以及载荷对模型应力影响的规律。     

含电流变体智能复合材料梁的振动响应分析

电流变体材料是智能材料系统中重要的作动器材料之一。电流变体材料在外加电场作用下,其流变性能会发生较大变化。本文实验测定了电流变体的剪切模量,建立了含有电流变体材料的智能复合材料梁结构的振动模型,并对不同电场作用下梁的振动响应进行了分析,结果表明,随着外加电场强度的增加,梁的固有频率和损耗系数均显著增加,振动响应明显减少。     

焦炭塔结构的固有频率和振型研究

在传统的直立塔设备固有频率和振型的计算中,将塔设备简化为悬臂梁计算模型,但实际塔的薄壁圆筒结构与梁模型不符,为此对焦炭塔建立有限元分析模型进行模态分析,得到焦炭塔的固有频率和振型,计算分析表明,由于焦碳塔特殊的结构特点使得焦炭塔的振动特性与传统大型直立设备简化为悬臂梁计算模型所得振动特性相比有所不同,因此焦炭塔结构计算中在计及高阶振型与固有频率时,不宜简化为悬臂梁计算模型。     

中高速多级离心泵转子的动平衡试验与研究

通过对中高速多级离心式高压液氨泵转子动平衡试验过程的分析与研究,阐述了该泵转子动平衡按实际的振动波形进行模态平衡的方法。根据转子高速动平衡运转试验及泵实际运行表明,该动平衡方法取得了良好效果。通过对液氨泵转子碰到的振动波形与模态平衡法试验的说明,为今后进一步探索同类机械转子模态平衡法动平衡试验提供了一些应用经验。     

Dynamic mechanical properties of sandwich‐structured epoxy beam composites containing poly(ethyleneterephthalate)/poly(ethyleneglycol) copolymer with shape memory effect

To make smart vibration‐controlling composite laminate, a few poly(ethylene terephthalate) (PET) and poly(ethylene glycol) (PEG) copolymers with shape memory ability were prepared. After selecting the best composition of PET–PEG copolymer in mechanical properties, a crosslinking agent such as glycerine, sorbitol, or maleic anhydride (MA) was included for crosslinked copolymer, followed by analysis of its effect on mechanical, shape memory, and damping properties. The highest shape recovery was observed for copolymer with 2.5 mol % of glycerine, and the best damping effect indicating vibration control ability was from copolymer with 2.5 mol % of sorbitol. With the optimum copolymers in hand, sandwich‐structured epoxy beam composites fabricated from an epoxy beam laminate and crosslinked PET–PEG copolymer showed that impact strength increased from 1.9 to 3.7 times depending on the type of copolymer, and damping effect also increased as much as 23 times for the best case compared to epoxy laminate beam alone. The resultant sandwich‐structured epoxy beam composite can be utilized as structural composite material with vibration control ability, and its glass transition temperature can be controlled by adjustment of PET, PEG, or crosslinking agent composition. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3141–3149, 2003     

复合材料夹层结构翼形件的模态有限元分析

采用Ansys软件对复合材料夹层结构翼形件进行了有限元模态分析和研究,给出了翼形件的前5阶固有频率和振型.根据计算结果,对翼形件泡沫密度进行了调整,使得翼形件的固有频率和振动幅度有较大的下降,满足了设计要求.通过模压工艺制作了8片翼形件并进行了模态测试,结果表明,理论计算结果与试验结果具有较好的一致性.     

Effect of vibration fatigue on modal properties of single lap adhesive joints

As most existing studies focus on developing models and theories describing the static strength of adhesive joints as a function of the fatigue loading, there is a lack of understanding on how the fatigue of the adhesive joint affects dynamic modal properties of the bonded structure. In applications such as automobile components, modal properties are critical in determining their dynamic performances. To investigate the relationship between modal properties of single lap joints (SLJs) and the cyclic-vibration-peel loading, this study first carries out vibration fatigue tests and subsequent modal response measurements using steel–aluminum SLJ specimens. It is experimentally demonstrated that modal frequencies of the SLJ structure tend to decrease with increasing vibration fatigue cycles. Furthermore, it is also shown that this trend is related to the fatigue characteristics of the adhesive layer. The fatigue degradation effects of Young's modulus and contact area between the adhesive and the adherends on modal frequencies are then investigated using a finite element model. Simulation results reveal that dramatic reductions in modulus and contact area values are required to result in the modal frequency shifting observed in experiments, which may not be always realistic. Although the findings in this study are informative, more research effort is needed to further identify the critical reason(s) for the experimental trend of decreasing modal frequencies with increasing vibration fatigue cycles.     

Experimental investigation of the damping enhancement in fiber-reinforced composites with carbon nanotubes

This study experimentally investigates the damping effects of carbon nanotubes (CNTs) embedded in the matrix of fiber-reinforced composite materials. Several different aspect ratios, types, and weight fractions of CNTs are considered, and an analysis of the CNT dispersion in the composite matrix is presented. The composite materials are analyzed using dynamic mechanical analysis and various modal analysis techniques to determine the damping characteristics of the composite as a function of strain, fiber volume fraction, and nanotube type and weight percentage loading. Experiments are conducted using cantilevered beams in both a stationary and rotating frame in order to explore the effects of rotation on the damping behavior of the composite material. The results show that the addition of two weight percent of CNTs to the matrix of carbon fiber reinforced composites can increase the damping in a stationary composite beam by more than 130% and by more than 150% in a composite beam rotating at 500 RPM.     

废旧纤维制备蜂窝夹层复合材料的导热性研究

利用半经验公式,对废旧纤维再生纺织品制备的蜂窝夹层复合材料的蜂窝高度、蜂格边长及蜂窝芯厚度分别与蜂窝结构导热性之间的关系进行理论预测。预测值与实验测定值进行比较,结果表明,预测值与实验测定值基本一致,所以可以通过数值计算的方法为废旧纤维再生纺织品蜂窝夹层复合材料的蜂窝芯子几何尺寸的设计提供参考。     

Measurement of concrete E-modulus evolution since casting: A novel method based on ambient vibration

The use of ambient vibration tests to characterize the evolution of E-modulus of concrete right after casting is investigated in this paper. A new methodology is proposed, which starts by casting a concrete cylindrical beam inside a hollow acrylic formwork. This beam is then placed horizontally, simply supported at both extremities, and vertical accelerations resulting from ambient vibration are measured at mid-span. Processing these mid-span acceleration time series using power spectral density functions allows a continuous identification of the first flexural frequency of vibration of the composite beam, which in turn is correlated with the evolutive E-modulus of concrete since casting. Together with experiments conducted with the proposed methodology, a complementary validation campaign for concrete E-modulus determination was undertaken by static loading tests performed on the composite beam, as well as by standard compressive tests of concrete cylinders of the same batch loaded at different ages.     

硫化机全焊接横梁振动时效数值分析

采用ANSYS有限元分析软件,通过模态分析和谐响应分析,对1665型双模定型硫化机全焊接横梁的振动时效工艺关键参数（激振力、激振频率及激振点等）进行预测.由模态分析可知,横梁前10阶振动4个优选固有频率中318 Hz的波浪振型较为合理,并据此确定其激振点.通过谐响应分析获得一定激振频率、不同激振力时横梁所受最大动应力分布,并根据国家标准确定激振力取值范围为[300,690] kN.     

复合材料身管强迫响应分析复合材料身管强迫响应分析

 为了评价复合材料身管动态特性,在模态分析和阻尼分析的基础上,采用模态叠加动力学有限元计算方法, 对复合材料身管的强迫响应特性进行分析,计算获得复合材料身管的炮口振动情况,并与相同口径的金属身管炮口 响应情况进行比较。结果表明,复合材料身管炮口响应小于金属身管炮口响应,复合材料身管具有更好的动态特性 。