Experimental and Numerical Analysis of Composite Folded Sandwich Core Structures Under Compression

The characterisation of the mechanical behaviour of folded core structures for advanced sandwich composites under flatwise compression load using a virtual testing approach is presented. In this context dynamic compression test simulations with the explicit solvers PAM-CRASH and LS-DYNA are compared to experimental data of two different folded core structures made of aramid paper and carbon fibre-reinforced plastic (CFRP). The focus of the investigations is the constitutive modelling of the cell wall material, the consideration of imperfections and the representation of cell wall buckling, folding or crushing phenomena. The consistency of the numerical results shows that this can be a promising and efficient approach for the determination of the effective mechanical properties and a cell geometry optimisation of folded core structures.     

结构参数对树脂基纤维编织复合材料折叠夹芯结构力学性能的影响

折叠夹芯结构是一种新型的复合材料夹芯结构,其结构参数对力学性能有重要的影响。文中以碳纤维和Kevlar平纹编织预浸料为芯材原料,采用热压工艺,制备了复合材料折叠夹芯结构试样。通过压缩试验得到不同条件下折叠夹芯结构在静态压缩载荷作用下的力-位移变化曲线。构建了复合材料折叠夹芯结构有限元模型,对不同结构参数复合材料折叠夹芯的力学性能进行了数值模拟分析,并将模拟结果与实验结果进行对比验证了模型的可靠性。实验及数值模拟的分析结果表明,随着芯材厚度的增加,折叠夹芯层的压缩强度呈线性增加,其破坏形式由假塑性变形逐渐向脆性破坏转化;面板对夹芯层的约束作用能够极大地提高压缩模量和强度,而且上下面板对压缩性能曲线有着不同的影响;折叠夹芯单元的高度、长度、折叠夹角等参数对其力学性能具有不同程度的影响。     

复合材料褶皱夹芯结构的制备及压缩性能研究

目的 探究复合材料褶皱芯子的一次性成型工艺,并研究浸胶量对褶皱夹芯结构压缩性能的影响。方法 以V型褶皱夹芯结构为研究对象,首先采用真空吸附成型工艺制备V型复合材料褶皱芯子,然后通过黏接工艺将碳纤维复合材料层合板与褶皱芯子进行复合,得到复合材料褶皱夹芯结构,最后通过实验测试,研究该结构在压缩载荷作用下的力学性能和失效模式,以及不同浸胶量对其压缩性能的影响。结果 采用真空吸附成型工艺能够一次性制备出褶皱芯子,其成型精度有待提高;由压缩实验可知,褶皱夹芯结构先从壁面开始失效,后逐步扩散至棱线处,最终导致芯子的整体失效;由压缩实验测试结果可知,浸胶量(质量分数)为11%、17%、22%的褶皱夹芯结构的破坏载荷分别为362.853、420.521、471.389 N。结论 采用真空吸附成型工艺可一次性成型出褶皱芯子,其制备效率较高,但存在成型尺寸精度不高问题,后续需要进一步改进;在一定范围内,复合材料褶皱夹芯结构的压缩破坏载荷与芯子的浸胶量近似成正比例线性关系。     

Fabrication and mechanical testing of glass fiber entangled sandwich beams: A comparison with honeycomb and foam sandwich beams

The aim of this paper is the fabrication and mechanical testing of entangled sandwich beam specimens and the comparison of their results with standard sandwich specimens with honeycomb and foam as core materials. The entangled sandwich specimens have glass fiber cores and glass woven fabric as skin materials. The tested glass fiber entangled sandwich beams possess low compressive and shear modulus as compared to honeycomb and foam sandwich beams of the same specifications. Although the entangled sandwich beams are heavier than the honeycomb and foam sandwich beams, the vibration tests show that the entangled sandwich beams possess higher damping ratios and low vibratory levels as compared to honeycomb and foam sandwich beams, making them suitable for vibro-acoustic applications where structural strength is of secondary importance, e.g., internal paneling of a helicopter.     

Fabrication of Open-cell Al Foam Core Sandwich by Vibration Aided Liquid Phase Bonding Method and Its Mechanical Properties

The open-cell Al foam core sandwiches(AFCSs) were successfully fabricated by using a specially designed Zn-Al-Cu based filler alloy via vibration aided liquid phase bonding method.The effects of the vibration on the bonding seam were investigated and the bonding strength between Al foam core and solid Al alloy face sheet was tested by shearing tests.The results show that vibration can significantly improve the quality of the bonding and the shearing strength of the bonding seam,which implies that this joini...     

瓦楞夹层结构动态力学性能评估

以典型的瓦楞夹层结构--瓦楞纸板为例,本文研究了不同应变率下的A、B、C、E型多层瓦楞纸板的力学性能。结果表明由于变形机制的不同造成动态平台应力值比静态平台应力值有明显的增加。本文采用中等应变率下评估动态应力的Cowper-Symonds方程与试验数据相结合,构建了一个综合考虑结构参数和应变率效应的多层瓦楞纸板的动态平台应力的预测方程。结果表明：随着应变率的增加,多层瓦楞纸板的平台应力明显增加;经过标准化后的方程能够较全面的用于多层瓦楞纸板的动态平台应力的预测,同时,该方程对于其他材质的瓦楞夹层结构的力学性能的研究有重要的参考价值。     

Fabrication,Microstructure and Shear Properties of Al Foam Sandwich

Aluminum foam sandwich (AFS) structure materials have drawn much attention due to their unique structural and functional properties. However, the use of AFS materials as an attractive candidate for some applications was limited. In this work, AFS was fabricated by the brazing method, using Al-Si-based alloy, aluminum foam and steel plates as filler, matrix and panels, respectively. The microstructures of the soldered interfacial region, elemental distributions and phase identification were determined by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The diffusion behavior of Si, Al, Fe and Cr was investigated. The effect of brazing time on the shear strengths of soldered joints was also analyzed. The results showed that the microstructures of joints were changed on increasing the brazing time. When the brazing time was 5 min, the solder started melting, which led to low shear strength. When increasing the brazing time to 10 min, the shear strength reached the peak value of 6.26 MPa due to the formation of a layer plate structure in the joints. When further increasing the brazing time, a number of Al/Fe intermetallic compound were formed in the joints, leading to a decrease of the shear strength due to the formation of brittle phase.     

X-cor夹层结构的力学性能试验研究

X-cor夹层结构比强度高,比刚度大,有望取代传统蜂窝夹层结构作为航空航天器的主承力结构材料。采用真空固化成型工艺,通过改变Z-pin的植入参数制备了X-cor夹层结构,研究了Z-pin植入角度、植入间距和直径对其平压、剪切和拉伸性能的影响。研究结果表明,Z-pin的植入参数对X-cor夹层结构的力学性能影响显著。随Z-pin植入角度的增加X-cor夹层结构的平压性能降低,剪切性能增强,拉伸模量减小,拉伸强度先增加后减小。随Z-pin植入间距和直径增加,X-cor夹层结构力学性能均增加。与泡沫夹层结构相比,X-cor夹层结构压缩、剪切和拉伸模量的测试值分别提高了1.26～5.15倍、2.50～13.56倍和1.90～2.71倍,压缩、剪切和拉伸测试值分别提高了1.63～9.20倍、1.28～2.03倍和1.01～2.30倍。     

纤维缝合结构对夹芯结构复合材料力学性能的影响

通过RTM工艺成型了点阵增强夹芯结构复合材料,研究了纤维缝合结构对复合材料平压及侧压力学性能的影响,并探索了侧向压缩载荷下夹芯结构复合材料的破坏模式。结果表明,采用纤维缝合的方式可显著提高夹芯结构复合材料的力学性能。双向增强夹芯复合材料在长度和厚度方向上的侧压强度和模量相同,单向增强的侧压强度和模量表现出方向性,且长度方向上的模量明显高于宽度方向的。     

蜂窝夹层共形承载天线结构的力电性能

本文对玻璃钢蜂窝夹层共形承载天线结构进行常温四点弯曲试验,并对比了含有真实天线的实验件在实验前后的电磁性能。采用三明治夹芯板理论和分离式实体建模方法,利用ABAQUS建立其有限元模型,并基于各向异性材料最大应力准则,使用USDFLD定义蜂窝芯失效准则。实验和模拟结果表明:此方法能准确地模拟结构的刚度和强度。性能检测显示实验件能够承受预定载荷,从而验证了此类结构在弯曲载荷下的可靠性以及模拟方法的准确性。     

Fabrication and Testing of Carbon Fiber Reinforced Truss Core Sandwich Panels

Truss core sandwich panels reinforced by carbon fibers were assembled with bonded laminate facesheets and carbon fiber reinforced truss cores.The top and bottom facesheets were interconnected with truss cores.Both ends of the truss cores were embedded into four layers of top and bottom facesheets.The mechanical properties of truss core sandwich panels were then investigated under out-of-plane and in-plane compression loadings to reveal the failure mechanisms of sandwich panels.Experimental results indicated...     

ASTM力学性能试验总则标准与分项试验方法标准的技术比较

对美标钢制品力学性能试验总则标准（ASTMA370—2010）与分项试验方法标准（ASTMES／E8M-2009,ASTME10—2010,ASTME18—2008b,ASTME23—2007a^ε1和ASTME384—2010^ε2等）分别从标准的适用范围、环境温度的定义、采用的单位制、对试样和试验设备的要求、尺寸测量精确度、拉伸试验的速率、不同硬度标尺间的相互转换以及试验结果的处理与修约等方面进行了系统的对比分析。结果表明：ASTM力学性能试验总则标准和与其相对应的ASTM分项试验方法标准之间存在着一定的技术差异,其中尤以拉伸试验和冲击试验方法标准与总则标准之间的差异居多,实际使用中应注意区分和选择。     

蜂窝夹层复合材料压缩损伤声发射特征研究

应用声发射技术对蜂窝夹层复合材料压缩损伤过程进行了实验研究。分析载荷与声发射信号经历图,依据其损伤过程和声发射特征,发现随着加载载荷的增加,复合材料的损伤逐步增大。在加载初始阶段,仅有少量声发射信号,各种表征信号量小幅度增加;在加载中期,声发射信号增多,各种表征信号量不断增大;在加载后期,声发射信号明显突增,各种表征信号量急剧增加。复合材料压缩损伤破坏与声发射的幅值、能量、撞击、上升时间、持续时间和计数等参量相关。蜂窝夹层复合材料试件的应力-应变曲线近似为直线,应变速率与声发射信号特征相互对应。     

纳米材料(NSM)的制作方法及其应用

介绍了ＮＳＭ的主要制作方法，包括气相凝固法、机械合金化法和喷雾转化法等。并概述了ＮＳＭ在工业和尖端科学技术领域里的应用状况和前景。     

折叠波导几何尺寸自动测量方法及误差分析

根据W波段行波管的设计要求, 考虑加工设备的固有精度, 编写测量程序, 实现了折叠波导多周期微结构的自动精密测量。实际应用时, 利用视频影像测量显微镜、工具显微镜、激光共聚焦显微镜和高度计完成了W波段行波管折叠波导慢波结构关键几何尺寸的全自动和半自动测量, 分析了测量误差的来源, 提出了最大限度减小误差的方法, 各个尺寸的测量精度全部控制在1.5μm以内, 测量时间从原来的3 h缩短到了1 h以内, 显著提高了工作效率, 为折叠波导行波管的批量生产节约了时间和人力成本。     

Mechanical Response of All-composite Pyramidal Lattice Truss Core Sandwich Structures

The mechanical performance of an all-composite pyramidal lattice truss core sandwich structure was investigated both theoretically and experimentally.Sandwich structures were fabricated with a hot compression molding method using carbon fiber reinforced composite T700/3234.The out-of-plane compression and shear tests were conducted.Experimental results showed that the all-composite pyramidal lattice truss core sandwich structures were more weight efficient than other metallic lattice truss core sandwich structures.Failure modes revealed that node rupture dominated the mechanical behavior of sandwich structures.     

FRP夹强化泡沫芯复合材料的力学性能

本文研究一种新型强化泡沫芯夹层复合材料的力学性能。选择在低成本的PU泡沫中置入圆管状结构增强体,使泡沫芯的等效Z向性能大幅提高。对以FRP面板夹这种强化泡沫芯制成的三明治复合材料结构,进行了平压试验、三点弯曲试验和剪切试验,基于其结构破坏模式,分析其破坏机理,并应用三维层板理论和细观力学方法进行了理论模拟。结果表明,这种强化泡沫芯能显著提高三明治板材的Z向力学性能,具有良好的应用前景。     

泡沫夹芯复合材料力学性能与水声性能综合设计初探

采用Matlab编程,利用经典梁理论和夹层板理论构建了弹性模量、压缩强度等材料参数与泡沫夹芯复合材料弯曲刚度和压缩强度的关系,利用传递矩阵法构建了纵波声速、衰减系数、损耗因子等材料参数与泡沫夹芯复合材料水中插入损失的关系。在此基础上,利用NSGA-II多目标优化算法开展了力学与水声综合设计,初步获得了实用的泡沫夹芯复合材料力学与水声性能综合设计方法。     

泡沫铝夹芯板的制备技术

泡沫金属是一类具有低密度以及新奇的物理、力学、电学、声学等特殊性能的新型材料.而泡沫铝的潜在用途之一是作为泡沫铝夹芯板的芯材使用.详细介绍了制备泡沫铝夹芯板的不同方法,如胶粘法、超声焊接法、激光协助发泡法、扩散焊接法、面板与预制材料轧制-包覆法和粉末复合轧制法等.通过比较,在国内粉末复合轧制法工艺简单,是最有希望适合高温作业和大批量生产的方法.