夹芯复合材料阻尼性能的研究进展

随着航空航天轻质高速化和精密仪器设备自动化的发展,振动问题日益凸显.夹芯复合材料比强度高、比模量大、减振性能优良,兼具结构和功能一体化的特性,成为航空航天领域研究的热点.从复合材料基体、增强体、界面3个方面阐述了复合材料的减振机理,介绍了目前研究热门的夹芯结构以及芯材、面板、结合界面及其相互作用对阻尼性能的影响规律,概述了夹芯复合材料阻尼改性的研究现状,最后对夹芯复合材料阻尼的研究方向进行了展望.     

碳纤维增强金字塔点阵夹芯结构的抗压缩性能

提出了一种碳纤维增强复合材料点阵夹芯结构的一体化成型工艺方法。该方法克服了传统夹芯结构面板与芯子之间因需要二次粘接或焊接的方法所带来弱界面的缺点。将纤维杆两端埋入面板内,使面板与芯子成为一体而不存在明显的界面。对用该方法制备的碳纤维增强金字塔点阵夹芯板进行平压试验,研究发现随着载荷的增加,纤维杆发生弹性屈曲并在中间部位出现断裂。理论分析了点阵夹芯结构平压载荷下的弹性模量和纤维杆极限屈曲载荷。通过与传统夹芯材料相比较发现,这种新型复合材料点阵夹芯结构具有密度低、比强度和比刚度高等优点。      

缝纫泡沫夹芯复合材料的刚度预测与试验验证

基于材料细观结构,建立了缝纫泡沫夹芯复合材料的刚度预测模型,并进行了刚度性能的相关试验验证。其中,对缝纫复合材料层合面板部分,考虑了缝纫角对单胞尺寸和富脂区大小的影响,以及缝纫前后层合面板厚度的变化对复合材料面板纤维体积含量的影响,采用改进的纤维弯曲模型计算了缝纫复合材料层合面板的刚度;对缝纫增强的泡沫夹芯部分,把缝线树脂柱看作是泡沫基体中的增强相,将其简化为特殊的单向增强复合材料,提出了用串并联组合模型来预测其刚度。试验测试了缝纫泡沫夹芯复合材料板试件的刚度。应用本文模型对缝纫层合面板和缝纫泡沫夹芯复合材料板的刚度进行预测,结果均与试验结果吻合较好。采用理论模型系统研究了缝纫参数和结构参数对缝纫泡沫夹芯复合材料刚度的影响。     

夹芯复合材料阻尼性能的研究进展

随着航空航天轻质高速化和精密仪器设备自动化的发展,振动问题日益凸显。夹芯复合材料比强度高、比模量大、减振性能优良,兼具结构和功能一体化的特性,成为航空航天领域研究的热点。从复合材料基体、增强体、界面3个方面阐述了复合材料的减振机理,介绍了目前研究热门的夹芯结构以及芯材、面板、结合界面及其相互作用对阻尼性能的影响规律,概述了夹芯复合材料阻尼改性的研究现状,最后对夹芯复合材料阻尼的研究方向进行了展望。     

缝合泡沫夹芯复合材料低速冲击的多尺度数值方法

为了发展缝合泡沫夹芯复合材料低速冲击损伤的多尺度分析方法, 建立了缝合泡沫简化力学模型, 将缝合泡沫等效为缝线树脂柱增强的正交各向异性芯材, 其材料参数由各组分性能及所占体积分数根据均一化理论计算得出; 同时, 建立冲击试验有限元模型, 通过界面元模拟面板与芯材之间的层间分层。采用GENOA渐进损伤分析模块对缝合结构冲击动态响应过程进行数值模拟, 并将计算结果与试验记录进行对比分析。结果表明: 缝合可以减小面板破坏面积, 抑制面板与泡沫分层的扩展; 但缝纫会对结构造成初始损伤, 较高的缝合密度使芯材刚度增加, 不利于泡沫结构的缓冲吸能。数值模拟结果与试验记录吻合良好, 验证了多尺度分析方法的正确性。     

柱胞夹芯复合材料设计加工及吸能性能研究现状

柱胞夹芯复合材料因其在吸能减振方面的优异性能以及比强度、比刚度高,被认为是新型吸能材料。为全面了解其在抗冲击吸能方面的优势,本文介绍了柱胞夹芯复合材料的基本概念;阐述了柱胞夹芯复合材料的吸能机理、吸能评估方法以及国内外设计的不同几何构型柱胞单元;分析了填充多孔材料对柱胞单元吸能性能的增强机理;概述了柱胞夹芯复合材料的不同加工工艺,比较各种加工工艺的优缺点及改进方法。文章最后对柱胞夹芯复合材料的发展前景进行了展望。     

热塑性复合材料夹芯结构熔融连接研究进展

面芯界面性能是复合材料夹芯结构发挥其力学/多功能优势的关键,热塑性树脂具有可熔融再造的特点,使热塑性复合材料夹芯结构(TPCSS)可在不引入新材料的前提下,形成连续可靠的面芯界面。对近年来热塑性复合材料夹芯结构熔融连接研究进展进行了梳理,总结了常见构型与所用材料,重点归纳了主要的熔融连接方法,包括热板焊接、模压成型、连续热压、面芯共编和增材制造等。基于国内外研究和应用现状,展望了熔融连接热塑性复合材料夹芯结构的未来发展趋势和应用前景。     

夹芯结构的设计及制备现状

由于夹芯结构具有比强度高、比模量大等众多优点,目前被广泛应用在航空航天等领域.从面板、芯子和面芯界面加强技术等三个方面对夹芯结构的设计和制备现状进行了介绍.重点对蜂窝夹芯结构、泡沫夹芯结构、点阵夹芯结构、格栅夹芯结构和整体夹芯结构等的设计和制备工艺以及为了提高面芯界面结合强度而不断被提出的包括Z-Pin,Stitch和Embedding等在内的面芯界面增强工艺进行了较为系统的介绍.     

弹性阻尼金属螺旋丝网夹芯结构连接工艺及力学特性

针对弹性阻尼螺旋金属丝网夹芯结构界面连接性能不明确的问题,分别采用真空钎焊和胶结两种典型连接工艺,进行了面内压缩和拉伸剪切力学性能试验,结合SEM和EDS等材料微观表征方法,展开夹芯结构界面结合的物理机制和力学特性的研究.研究结果表明:钎焊连接界面相对胶结更均匀连续,钎料中Ni、Si元素与芯材、面板中的Fe、Cr元素扩...     

碳/芳纶混杂纤维增强波纹夹芯结构低速冲击性能

采用碳纤维和芳纶纤维增强复合材料对波纹夹芯结构的面板进行层间混杂铺层设计,通过真空辅助树脂灌注(VARI)成型工艺制备混杂波纹夹芯结构。在60 J、80 J和100 J三种不同冲击能量下,研究了面板混杂铺层方式对波纹夹芯结构低速冲击性能及冲击后压缩强度的影响,并利用超声C扫和工业CT断层成像两种无损检测技术对波纹夹芯结构的冲击损伤机制进行了分析。结果表明：冲击能量较低时,波纹夹芯结构的吸收能量基本不受面板的混杂铺层方式影响,而凹坑深度随表层碳纤维层数增加而减少。冲击能量较高时,面板为分层式混杂(碳/芳纶纤维单层交替铺层)的波纹夹芯结构的抗冲击性能最好,纤维断裂损伤和层间分层主要发生在试样表层,但损伤面积较大;面板为夹层式混杂(以碳纤维为蒙皮、芳纶纤维为芯材)的波纹夹芯结构具有较高的吸收能量,整个上面板的纤维都发生了断裂破坏,但损伤面积较小。碳/芳纶混杂波纹夹芯结构的面板采用分层式和夹层式的混杂铺层设计时,具有较高的冲击后压缩强度。     

Blast impact response of aluminum foam sandwich composites

Military and civilian structures can be exposed to intentional or accidental blasts. Aluminum foam sandwich structures are being considered for energy absorption applications in blast resistant cargo containers, ordnance boxes, transformer box pads, etc. This study examines the modeling of aluminum foam sandwich composites subjected to blast loads using LS-DYNA software. The sandwich composite was designed using laminated face sheets (S2 glass/epoxy and aluminum foam core. The aluminum foam core was modeled using an anisotropic material model. The laminated face sheets were modeled using material models that implement the Tsai-Wu and Hashin failure theories. Ablast load was applied using the CONWEP blast equations (*LOAD_BLAST) in LS-DYNA. This paper discusses the blast response of constituent S2-glass/epoxy face sheets, the closed cell aluminum foam core as well as the sandwich composite plate.     

Non-linear indentation behavior of foam core sandwich composite materials—A 2D approach

Light weight high performance sandwich composite materials have been used more and more frequently in various load bearing applications in recent decades. However, sandwich materials with thin composite face sheets and a low density foam core are notoriously sensitive to failure by localized external loads. These loads induce significant local deflections of the loaded face sheet into the core of the sandwich composite material, thus causing high stress concentrations. As a result, a complex multiaxial stressed and strained state can be obtained in the area of localized load application. Another important consequence of the highly localized external loads is the formation of a residual dent in the face sheet (a geometrical imperfection) that can reduce significantly the post-indentation load bearing capacity of the sandwich structure.This paper addresses the elastic–plastic response of sandwich composite beams with a foam core to local static loading. The study deals with a 2D configuration, where a sandwich beam is indented by a steel cylinder across the whole width of the specimen. The ABAQUS finite element package is used to model the indentation response of the beams. Both physical and geometrical non-linearities are taken into account. The plastic response of the foam core is modeled by the ¹CRUSHABLE FOAM and the ¹CRUSHABLE FOAM HARDENING option of the ABAQUS code. The purpose of the numerical modeling is to develop correct 2D simulations of the non-linear response in order to further understand the failure modes caused by static indentation. In order to verify the finite element model, indentation tests are performed on sandwich composite beams using a cylindrical indentor. The numerical results show good agreement with experimental test data.     

Cellular composites in lightweight sandwich applications

A novel sandwich element without separate joining layers as bonding between core and fibre reinforced face sheets is proposed. The core consists of a syntactic foam on the basis of cellular glass granules. Because of the cellular composite core and the proposed manufacturing process single as well as double curved sandwich elements can be produced. Experimental investigations show the significantly improved properties of such sandwich elements and the novel core material.     

The Use of Sprint Interface Element Delamination Simulation of Sandwich Composite Beam

Sandwich composite beams have been more and more used in various industries because of their excellent mechanical properties. However, the mismatched performance between face sheet and foam core always lead to such as cracks and damages in the core or face/core interface during the processes of manufacturing or service. Delamination damage at the adhesive interface is the most dangerous and could be one main source that the mechanical capability of the structure is serous degenerated. In this paper, a simple and natural model to evaluate the stiffness of the spring interface elements, which is based on the physics and the geometry of the adhesive layers, is proposed. In order to validate the model, cantilever beam bending test were conducted for marine sandwich composite I-beam. A good comparison has been found between predictions and experimental results, and results indicate that the spring interface element can provide an efficient model for the delamination simulation of sandwich composite structures.     

面板材料对泡沫铝夹芯梁抗冲击性能的影响

为考查泡沫铝夹芯梁面板材料对其抗冲击性能的影响,运用数值模拟方法计算了相同重量下面板材料分别为304#不锈钢、工业纯铝和HRB335级钢三种泡沫铝夹芯梁在不同冲量作用下的动力响应;分析了面板材料对泡沫铝夹芯梁跨中变形及芯材压缩应变的影响.结果显示,在冲量相同的情况下,面板材料对泡沫铝夹芯梁的抗冲击性能有一定的影响;爆炸...     

泡沫铝夹层结构复合材料低速冲击性能

以泡沫铝为夹芯材料,玄武岩纤维(BF)和超高分子量聚乙烯纤维(UHMWPE)复合材料为面板,制备夹层结构复合材料。研究纤维类型、铺层结构和芯材厚度对泡沫铝夹层结构复合材料冲击性能和损伤模式的影响规律,并与铝蜂窝夹层结构复合材料性能进行对比分析。结果表明:BF/泡沫铝夹层结构比UHMWPE/泡沫铝夹层结构具有更大的冲击破坏载荷,但冲击位移和吸收能量较小。BF和UHMWPE两种纤维的分层混杂设计比叠加混杂具有更高的冲击破坏载荷和吸收能量。随着泡沫铝厚度的增加,夹层结构复合材料的冲击破坏载荷降低,破坏吸收能量增大。泡沫铝夹层结构比铝蜂窝夹层结构具有更高的冲击破坏载荷,但冲击破坏吸收能量较小;泡沫铝芯材以冲击部位的碎裂为主要失效形式,铝蜂窝芯材整体压缩破坏明显。     

Moisture diffusion in composite sandwich structures

The mechanical properties of polymer core materials in sandwich structures are often degraded by moisture that is absorbed during storage. To date, there is no reliable model to predict the amount of moisture that is present in these sandwich core materials. A multi-layer diffusion model applicable to these sandwich structures is described in this report. Inputs to this model are: (1) diffusivities of core and face sheet materials as functions of temperature, (2) moisture saturation data as a function of relative humidity, and (3) sandwich structure exposure history. The output is a prediction of the amounts of moisture in the core material and face sheets as a function of time.

In order to validate this model, moisture diffusion experiments were performed on a sandwich material consisting of graphite–epoxy face sheets and a core of Rohacell^® polymethacrylimide 200WF foam. Samples of this material were dried, and then hydrated at either 32 °C or 65 °C at either 83% or 100% relative humidity. The face sheets were separated from the core and each component was weighed, dried, and weighed again in order to determine the moisture distribution in the sandwich structure. The results were then compared with the model predictions.     

短切纤维增韧泡沫夹芯复合材料梁界面断裂过程的物质点方法模拟

对短切纤维增韧泡沫夹芯复合材料梁界面韧性试验结果进行了分析讨论并基于物质点方法(material pointmethod, MPM)对试验过程进行了数值模拟。在MPM方法中,通过可视准则引入不连续性来处理裂纹问题,发展了包含裂纹的MPM 算法,模拟了泡沫夹芯复合材料梁界面断裂试验过程,数值分析结果和试验数据取得了良好的一致性。研究结果表明短切纤维增韧工艺能够显著提高泡沫夹芯复合材料结构的界面韧性和承载能力,同时表明该文推导的包含裂纹的MPM方法处理断裂问题的精确性和有效性。