蜂窝纸板弯曲破坏模式和机理研究

基于蜂窝纸板的结构和受力情况,对蜂窝纸板进行三点弯曲实验,分析纸蜂窝夹层结构的弯曲破坏模式和弯曲破坏过程,探究纸蜂窝夹层结构弯曲变形机理。结果表明：蜂窝纸板的弯曲破坏模式主要有面板屈曲褶皱和局部塌陷两种;蜂窝纸板的弯曲破坏过程分为5个阶段;蜂窝纸板的弯曲破坏模式与面板屈曲、蜂窝胞元壁受压形成塑性铰以及蜂窝胞元壁向中间挤压靠近有关。     

蜂窝夹层修理结构的弯曲性能试验分析

采用四点弯加载方式研究分析了含损伤蜂窝夹层修理结构的弯曲性能,该夹层结构由碳纤维增强的聚合物面板和蜂窝芯子组成。进一步分析了挖补斜度、挖补方式、损伤程度、修理设备和修理材料对修理板弯曲性能的影响。研究表明,修理板的破坏模式可分为补片边缘折断、补片中面折断和胶层破坏三种,相同破坏模式修理板的名义弯曲强度相近,其中前两种破坏模式修理板的名义弯曲强度与完好板相近,而第三种破坏模式修理板的名义弯曲强度相对较低。所有修理板的名义弯曲强度恢复率基本处于95%以上,同时修理后抗弯刚度也满足修理准则。     

埋微带天线蜂窝夹层结构的力电性能分析

设计并制备了一种共形承载一体化的埋微带天线蜂窝夹层结构。利用有限元方法分析了该结构的力学性能, 与三点弯曲实验比较, 获得较好的一致性。研究了蜂窝层厚度等参数对电性能和力学性能的影响。结果表明, 蜂窝层厚度为8~14 mm时, 共形承载天线不仅具有高增益和低损耗, 还具有较好的力学性能。      

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。     

含面芯界面缺陷的蜂窝夹芯板侧向压缩破坏模式

为了对含面芯层间脱胶缺陷的蜂窝夹芯板在侧向压缩载荷作用下的典型破坏模式进行数值预报, 建立了基于蔡-希尔破坏准则和粘结模型的计算模型。该计算模型是建立在对蜂窝夹芯板的双悬臂梁(DCB)和单臂梁(SLB) 试验中所发现的一种新的破坏模式的分析基础之上的。对蜂窝夹芯板的侧向压缩破坏行为的数值预报中, 发现一种新的破坏模式: 位于脱胶区域的面板首先发生局部屈曲失稳, 随后面板内部靠近芯子的45°/0°层间出现分层, 与此同时最靠近芯子的45°铺层发生断裂, 伴随着45°/0°层间分层的扩展, 面板发展成为对称性整体屈曲失稳。与侧向压缩试验测试结果对比发现, 计算模型模拟中所预报的破坏模式在实验测试中也得到了很好的验证。      

Kevlar短纤维增韧碳纤维/铝蜂窝夹芯板三点弯曲与面内压缩性能

介绍了碳纤维/铝蜂窝夹芯结构的Kevlar短纤维界面增韧方法。通过三点弯曲实验和面内压缩实验,对比增韧试件与未增韧试件的载荷位移曲线、破坏模式等特征,发现未增韧试件往往先发生界面分层破坏,继而面板和芯体分别发生局部破坏;而增韧试件通常发生整体破坏。实验数据显示,Kevlar短纤维界面增韧可以使碳纤维/铝蜂窝夹芯板的抗弯强度、压缩强度、能量吸收等力学性能分别至少提高14.06%、55.80%和61.53%。对破坏后界面的SEM观测发现:增韧试件并未发生界面脱粘,而是由于芯体撕裂造成面/芯剥离,揭示了Kevlar短纤维的界面增韧机制。对具有Kevlar短纤维界面增韧的碳纤维/铝蜂窝夹芯结构进行有限元建模,并分别对其在三点弯曲和面内压缩载荷下的力学行为进行数值分析,以指导该类夹芯结构的分析与设计。     

Mechanical behaviors of carbon fiber composite sandwich columns with three dimensional honeycomb cores under in-plane compression

Mechanical properties and failure modes of carbon fiber composite egg and pyramidal honeycombs cores under in plane compression were studied in the present paper. An interlocking method was developed for both kinds of three-dimensional honeycombs. Euler or core shear macro-buckling, face wrinkling, face inter-cell buckling, core member crushing and face sheet crushing were considered and theoretical relationships for predicting the failure load associated with each mode were presented. Failure mechanism maps were constructed to predict the failure of these composite sandwich panels subjected to in-plane compression. The response of the sandwich panels under axial compression was measured up to failure. The measured peak loads obtained in the experiments showed a good agreement with the analytical predictions. The finite element method was used to investigate the Euler buckling of sandwich beams made with two different honeycomb cores and the comparisons between two kinds of honeycomb cores were conducted.     

基于多尺度方法的蜂窝夹层复合材料结构轴向压缩稳定性

为有效预测蜂窝夹层复合材料结构压缩失稳载荷和破坏模式,本文基于层压板宏细观多尺度数值分析模型,研究蜂窝夹层复合材料结构在轴向压缩载荷下的屈曲稳定性。基于改进的通用单胞理论模型,并结合ABAQUS用户自定义子程序接口,建立蜂窝夹层复合材料结构宏细观数值模型,预报蜂窝夹层复合材料结构失效载荷和破坏模式,并与试验结果对照,验证了模型的有效性。结果表明:通过本文建立的数值模型可以有效预测蜂窝夹层复合材料结构在压缩载荷下的失稳载荷和破坏模式,其一阶失稳载荷为128.12 kN,与试验结果误差为4.58%,蜂窝夹层复合材料结构破坏模式为先发生屈曲失稳,然后迅速破坏。      

Failure initiation and propagation characteristics of honeycomb sandwich composites

The energy absorbed during the failure of a variety of structural shapes is influenced by material, geometry and the failure mode. Failure initiation and propagation of the honeycomb sandwich under loading involves not only non-linear behavior of the constituent materials, but also complex interactions between various failure mechanisms. Therefore, there is a need for an improved understanding of the material characteristics and energy absorption modes to facilitate the design of sandwich performance. In the present study, failure initiation and propagation characteristics of sandwich beams and panels subjected to quasi-static and impact loadings were investigated. Experimental studies involved a series of penetration and perforation tests on 2D beam and 3D panel configurations using a truncated cone impactor with impact velocities up to 10 m/s. Preliminary tests were also performed on the sandwich beams subjected to the three-point bending. Load-carrying, energy-absorbing characteristics and failure mechanisms under quasi-static and impact loading were determined. Dominant deformation modes involved upper skin compression failure in the vicinity of the indenter, core crushing and lower skin tensile failure.     

高速冲击载荷作用下钎焊蜂窝夹层板动态响应

目的 以钎焊高温合金蜂窝夹层板为研究对象,分析其在弹丸高速冲击作用下的力学性能。方法 采用轻气炮冲击加载试验结合有限元模拟,对蜂窝夹层板开展不同冲击强度下的动态响应和失效研究。开展含高速冲击损伤的蜂窝夹层板侧压试验,研究损伤模式对剩余强度的影响。结果 冲击强度对夹层板的失效过程和失效模式有着明显的影响,当冲击条件不足以使得迎弹面发生侵彻时,夹层板失效为表面压痕损伤;随着冲击强度的提高,出现不同程度的局部芯层压缩;当冲击强度大于临界值时,迎/背弹面陆续被侵彻,夹层板出现侵入损伤及贯穿损伤。结论 高速冲击损伤使得蜂窝夹层板的侧压失效模式,由理想塑性屈曲转变为局部失稳,侧压极限载荷大幅降低。     

Investigation on the square cell honeycomb structures under axial loading

To investigate into the collapse of a sandwich panel or beam with a square cell honeycomb, the novel plate model and beam model are developed according to the cross-sectional symmetry of the cell. The treble series solution of buckling mode is presented, and the formulas of critical compressive stress on skins are derived. The honeycomb sandwich panels are classified as thin, medium and thick plates based on their failure forms. It is found that the different kinds of cells have different buckling modes and different parameter governing equations. A new iterative optimization design method for a square honeycomb sandwich panel is developed and the curves of critical compressive stresses with geometrical parameters are provided in details. Finally, the 3D finite element numeric simulations have validated the formulas presented by this paper. Our study reveals some mechanical characteristics of the square honeycomb sandwich structures.     

Nomex蜂窝夹层结构弯曲刚度温度相关性的力学建模

胶黏剂粘接性能下降导致的面板与蜂窝芯分离是Nomex蜂窝夹层结构在高温下力学性能发生退化的主要原因。为此定义了胶黏剂的等效脱粘系数为温度升高引起蜂窝夹层结构弯曲刚度下降的损伤变量,并引入面板和蜂窝芯弹性模量的温度保持系数,建立了蜂窝夹层结构弯曲刚度温度相关性的力学模型。经外伸梁三点弯曲法试验校验,所建力学模型计算值与试验值的误差在15%内,可以较好地实现蜂窝夹层结构在高温下的弯曲刚度预报。研究成果可以用于软夹心蜂窝夹层结构在高温下弯曲刚度的估算。      

复合材料夹芯板低速冲击后弯曲及横向静压特性

对低速冲击后的复合材料Nomex 蜂窝夹芯板进行了纯弯曲和准静态横向压缩实验, 用X 光技术、热揭层技术和外观检测等对板内的损伤进行测量, 分析了被冲击面在受压情况下蜂窝夹芯板的弯曲破坏特点, 对比了横向静压与低速冲击所造成的板内损伤, 讨论了不同横向压缩速度时接触力P-压入位移$h 的变化规律和损伤情况。结果表明: 低速冲击可使蜂窝夹芯板的弯曲强度大幅度降低; Nomex 蜂窝夹芯板对低速冲击不敏感。      

Fatigue analysis of honeycomb-composite sandwich beams

The fatigue behaviour of honeycomb sandwich beams is experimentally investigated through four-point bending tests. Two kinds of specimens, initially undamaged and damaged by interface debonding, have been tested. The fatigue tests results are presented in standard SN diagrams with a best curve fit of the experimental data, while the fatigue limit is evaluated through a stair-case procedure. Two different failure mechanisms were found: undamaged specimen failure is due to collapse of the compressed face, while damaged specimen failure occurs due to the collapse of the honeycomb cell walls at the tip of the debonded portion.     

多级三角形格栅夹芯板力学分析

为了提高点阵复合材料结构的轻质高强力学特征,尤其提高其抗屈曲性能,设计了一种新型的多级三角形格栅夹芯板结构。根据等效连续介质力学方法提出了多级三角形格栅夹芯板的等效计算理论,预测了拉伸主导型多级三角形格栅夹芯板结构的等效弹性模量以及等效抗弯刚度。分析了侧压条件下多级三角形格栅夹芯板的弹性屈曲载荷和强度破坏模式。在理论模型的基础上绘制了侧压条件下多级三角形格栅夹芯板结构的失效模式图,指出了结构破坏模式与多级三角形格栅夹芯板尺寸之间的对应关系。研究表明:具有工字型截面的多级三角形格栅夹芯板结构相比于传统矩形截面格栅结构具有更高的抗弯刚度和弹性屈曲载荷,是一种性能更加优越的轻质高强点阵结构。      

木质蜂窝夹芯包装材料抗弯性能研究

根据夹层结构原理,就木质蜂窝夹芯材料抗弯性能进行研究,同时根据三点外伸梁和简支梁原理对夹芯结构的抗弯刚度进行了理论分析.结果表明:木质蜂窝夹芯材料的抗弯性能较原蜂窝纸板大大提高,给出的木质蜂窝夹芯材料抗弯刚度的近似公式可以预测夹芯结构的刚度.木质蜂窝夹芯材料作为一种具有良好性能的绿色包装材料,将会有很好的应用前景.     

The Effect of Load and Geometry on the Failure Modes of Sandwich Beams

Facing compressive failure, facing wrinkling and core shear failure are the most commonly encountered failure modes in sandwich beams with facings made of composite materials. The occurrence and sequence of these failure modes depends on the geometrical dimensions, the form of loading and type of support of the beam. In this paper the above three failure modes in sandwich beams with facings made of carbon/epoxy composites and cores made of aluminum honeycomb and two types of foam have been investigated. Two types of beams, the simply supported and the cantilever have been considered. Loading included concentrated, uniform and triangular. It was found that in beams with foam core facing wrinkling and core shear failure occur, whereas in beams with honeycomb core facing compressive failure and core shear crimping take place. Results were obtained for the dependence of failure mode on the geometry of the beam and the type of loading. The critical beam spans for failure mode transition from core shear to wrinkling failure were established. It was found that initiation of a particular failure mode depends on the properties of the facing and core materials, the geometrical configuration, the type of support and loading of sandwich beams.     

Failure behaviour of honeycomb sandwich corner joints and inserts

In nearly all sandwich constructions certain types of joints have to be used for assembly, but little is known about their failure behaviour. This paper deals with the investigation of the mechanical behaviour of three different corner joints as a right-angled connection of two sandwich panels and of two different potted inserts as a localised load introduction in Nomex^® honeycomb sandwich structures with glass fibre-reinforced composite skins. For this purpose, experimental test series were conducted including shear tests and bending tests of the corner joints and pull-out as well as shear-out tests of the threaded inserts. The failure mechanisms and sequences are described for each load case and the influence of the different designs and of the loading rate is discussed. Based on these characteristics, finite element simulation models were developed in LS-DYNA, which are able to represent the respective failure behaviours.     

Flexural behaviour of structural fibre composite sandwich beams in flatwise and edgewise positions

The flexural behaviour of a new generation composite sandwich beams made up of glass fibre-reinforced polymer skins and modified phenolic core material was investigated. The composite sandwich beams were subjected to 4-point static bending test to determine their strength and failure mechanisms in the flatwise and the edgewise positions. The results of the experimental investigation showed that the composite sandwich beams tested in the edgewise position failed at a higher load with less deflection compared to specimens tested in the flatwise position. Under flexural loading, the composite sandwich beams in the edgewise position failed due to progressive failure of the skin while failure in the flatwise position is in a brittle manner due to either shear failure of the core or compressive failure of the skin followed by debonding between the skin and the core. The results of the analytical predictions and numerical simulations are in good agreement with the experimental results.     

明胶鸟弹撞击复合材料蜂窝夹芯板试验

开展明胶鸟弹撞击复合材料蜂窝夹芯板试验,研究夹芯结构在软体高速冲击下的损伤形式,分析相关因素对结构动态响应结果的影响。通过CT扫描对复合材料蜂窝夹芯板内部进行检测可知,面板出现分层、基体开裂、纤维断裂、凹陷、向胞内屈曲等损伤形式,蜂窝芯出现芯材压溃、与面板脱粘的损伤形式;分析复合材料蜂窝夹芯板后面板的动态变形过程及撞击中心处位移-时间数据可知,复合材料蜂窝夹芯板在撞击过程中出现由全局弯曲变形主导和局部变形主导的两种变形模式;通过对比不同工况下的复合材料蜂窝夹芯板损伤程度可知,复合材料蜂窝夹芯板损伤程度随鸟弹撞击速度的增加而增大;蜂窝芯高度为10 mm的复合材料蜂窝夹芯板较蜂窝芯高度为5 mm的复合材料蜂窝夹芯板的损伤程度大;初始动能较大的球形鸟弹较圆柱形鸟弹对复合材料蜂窝夹芯板造成的冲击损伤程度更大。