碳纤维增强聚合物复合材料方形蜂窝夹层结构水下爆炸动态响应数值模拟

基于ABAQUS有限元仿真软件,建立了不同夹芯相对密度的碳纤维增强聚合物（Carbon Fiber Reinforced Polymer,CFRP）复合材料方形蜂窝夹层结构在水中爆炸冲击波载荷作用下的仿真模型,分析了结构的变形过程、夹芯的压缩特性及结构的失效及破坏情况。数值模拟结果表明,CFRP复合材料蜂窝夹芯压缩量在前面板速度降至与后面板相同时达到最大; CFRP复合材料蜂窝夹芯的最大压缩量随着初始压力的增大呈先缓慢增大后快速增大的趋势,其增大趋势在夹芯接近完全压缩时又趋于缓慢; CFRP复合材料夹层结构失效随夹芯相对密度和初始压力的变化呈现不同的模式,且其防护性能优于等重的层合结构。研究结果可以为复合材料夹层结构在水中冲击波载荷防护中的应用提供参考。      

Impact response of fiber metal laminate sandwich composite structure with polypropylene honeycomb core

Fiber metal laminates (FMLs) were used as skin on polypropylene honeycomb core to form a sandwich structure. Impact response was measured by conducting a series of low-velocity impact test. Impact force and the force time history were recorded and analyzed. It was found that the maximum impact load increased up to a threshold value at which it plateaus while the energy absorption in the structure increased with increasing impact energy. Post-impact optical image showed a change in damage area with increasing impact energy. The impact damage threshold energy for the sandwich structure was clearly shown in the range of impact energy between 7.84 J and 11.76 J where damages including delamination of the skins and global bending of the structure were observed.     

嵌锁式碳纤维/树脂基复合材料方形蜂窝夹芯结构的力学性能及损伤失效

设计并采用嵌锁组装工艺制备了碳纤维/树脂基复合材料方形蜂窝夹芯结构,开展了面外平压性能和三点弯曲性能试验研究,获得了夹芯结构在平压载荷作用下的破坏模式,分析了其损伤失效机制及吸能特性,讨论了在三点弯曲载荷作用下面板质量非对称性和槽口方向对夹芯梁的破坏模式及承载能力的影响.研究结果表明嵌锁式碳纤维/树脂基复合材料方形蜂窝...     

Impact tolerant and healable aluminum millitube reinforced shape memory polymer composite sandwich core

In order to improve impact tolerance and energy absorption of sandwich panel under impact loading, a new aluminum hollow tube reinforced shape memory polymer (AHTR-SMP) composite sandwich core is designed and fabricated. Physical/mechanical properties were examined through a variety of tests, including axial compression, three-point bending, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and shape recovery tests. In order to characterize its dynamic performances, low velocity impact test was conducted. According to the tests results, this new AHTR-SMP core demonstrated considerable impact tolerance and damage healing functionality, and may be considered as a promising option for critical structural applications featured by tolerating repeated impacts.     

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.     

The static and impact behaviour of polymer composite sandwich beams

The static and dropped weight impact performance of polymer composite sandwich beams has been investigated in a three-point bend configuration. The skin materials examined included woven fabrics of glass, carbon and aramid fibre, as well as glass chopped strand mat. The core materials were Coremat^™ (resin-impregnated non-woven polyester) and Aeroweb^™ aluminium honeycomb. Polyester and epoxy resin matrices were used. The static failure modes of beams with various core and skin combinations are discussed. The dominant failure modes for both glass/Coremat and glass/Aerolam^™ beams involved upper skin failure in the vicinity of the penetrator. The dropped weight impact performance of the latter two types of beam, at impact speeds of up to 7.5 m s⁻¹, was investigated. The Coremat-cored beams showed marked rate dependence effects, with failure energies reducing to a minimum at a given drop height and then increasing again with increasing drop height. The honeycomb-cored beams showed only slight rate dependence. The dynamics of the beam tests are discussed in terms of mass spring models and times to failure in the upper skins highlighted.     

Mechanical behavior of carbon fiber reinforced polymer composite sandwich panels with 2-D lattice truss cores

Composite sandwich structures with lattice truss cores are attracting more and more attention due to their superior specific strength/stiffness and multi-functional applications. In the present study, the carbon fiber reinforced polymer (CFRP) composite sandwich panels with 2-D lattice truss core are manufactured based on the hot-pressing method using unidirectional carbon/epoxy prepregs. The facesheets are interconnected with lattice truss members by means of that both ends of the lattice truss members are embedded into the facesheets, without the bonding procedure commonly adopted by sandwich panels. The mechanical properties of the 2-D lattice truss sandwich panels are investigated under out-of-plane compression, shear and three-point bending tests. Delamination of the facesheets is observed in shear and bending tests while node failure mode does not occur. The tests demonstrate that delamination of the facesheet is the primary failure mode of this sandwich structure other than the debonding between the facesheets and core for conventional sandwiches.     

Approximate elastic-plastic analysis of the static and impact behaviour of polymer composite sandwich beams

An elastic-plastic beam bending model has been developed to simulate the post-upper skin failure energy absorption behaviour of polymer composite sandwich beams under three-point bending. The beam skins consist of woven and chopped strand glass, while the core is a resin impregnated non-woven polyester material known as Coremat. A polyester resin was used for the construction. The theoretical model consists of a central hinge dominated by a crushing core and tensile elastic strains in the lower skin. Experimental measurements of the non-linear force-deflection characteristics for the beam are compared to the theoretical predictions from the model, and it is shown that the shear crushing of the core has an important effect on the behaviour of the beam. The model shows that the most important material properties are the lower skin tensile failure strain and the core crushing strength. Dynamic effects are included in the model in the form of a strain rate dependence of the core crushing stress and the strain rate dependence of the failure strain in the lower skin. The increase in material strength with strain rate gives rise to an improved energy absorption capacity for the beam under impact loading.     

Geometry effect on the behaviour of single and glue-laminated glass fibre reinforced polymer composite sandwich beams loaded in four-point bending

The research investigated the behaviour of single and glue laminated glass fibre reinforced polymer (GFRP) composite sandwich beams considering different spans and beam cross sections. The composite sandwich beams with different thicknesses (1, 2, 3, 4, and 5 sandwich layers) have been tested in four-point static flexural test with different shear span to depth ratio (a/d). The a/d ratios showed a direct effect on the flexural and shear behaviour. The capacity of the beam decreased with increasing a/d. Various failure modes were observed including core crushing, core shear, and top skin compression failure. The failure mode map developed based on the experimental finding and analytical prediction indicated that the failure mode is affected by the a/d with the number of glue laminated panels.     

Experimental dynamic analysis on naturally curved honeycomb sandwich beams with different damage patterns

In this study, dynamic analysis of naturally curved honeycomb sandwich beam including two surface cracks and an impact region at the facing skin is presented. Laminates of facing skin and backing skin are known as carbon fiber‐plain weave composite laminates with 1.6 mm in thickness. In the first part, in order to determine mechanical properties of both the skin with no‐crack/crack(s) and the honeycomb core of the composite beam, static tensile tests are conducted with respect to straingage measurement technique. In the second part, drop weight impact tests and vibration tests are performed to present the free vibration characteristics of the clamped‐clamped honeycomb sandwich beam including cracks and an impact‐damaged region. Corresponding to damage patterns of the sandwich beam, experimental dynamic analyses consist of six steps: (1) Vibration analysis with no‐crack and no‐impact region, (2) Vibration analysis with no‐crack and an impact region, (3) Vibration analysis with a surface crack and no‐impact region, (4) Vibration analysis with a surface crack and an impact region, (5) Vibration analysis with two surface cracks and no‐impact region, (6) Vibration analysis with two surface cracks and an impact region. For these purposes, an impact hammer with a force transducer is used to excite the undamaged or damaged naturally curved honeycomb sandwich beam through the selected points. After the excitation, the responses are obtained by an accelerometer. Resonant frequencies for the modal responses of the naturally curved honeycomb sandwich beam with different damage patterns are discussed.     

纤维增强复合材料三明治板的破片穿甲实验

研究了钢板-纤维增强复合材料板-钢板构成的三明治结构对破片的防护性能。通过破片模拟弹丸(FSP)高速撞击不同结构三明治板实验, 获得FSP弹丸贯穿16种三明治板的弹道极限, 分析结构特征对纤维增强复合材料三明治板比吸收能的影响。结果表明, 叠层芳纶、玻纤基三明治板较单层结构三明治板比吸收能分别提高了8.31%和16.09%, 8 mm面板+8 mm夹层+6 mm背板芳纶、玻纤基三明治板较4 mm面板+8 mm夹层+10 mm背板的芳纶、玻纤基三明治板比吸收能分别提高了37.72%和25.35%; 芳纶、玻纤基三明治板的比吸收能均随复合材料夹层厚度的增加呈指数递增, 夹层基板的抗拉性能是影响三明治板比吸收能的重要因素; 同面密度下, 厚面板、薄背板及多层叠合夹层结构的三明治板具有更高的比吸收能。     

Armor-piercing experiment on fragment against sandwich plate with fiber reinforced composite cores

研究了钢板一纤维增强复合材料板一钢板构成的三明治结构对破片的防护性能。通过破片模拟弹丸（FSP）高速撞击不同结构三明治板实验,获得FSP弹丸贯穿16种三明治板的弹道极限,分析结构特征对纤维增强复合材料三明治板比吸收能的影响。结果表明,叠层芳纶、玻纤基三明治板较单层结构三明治板比吸收能分别提高了8．31％和16．09％,8mm面板＋8mm夹层＋6mm背板芳纶、玻纤基三明治板较4mm面板＋8mm夹层＋10mm背板的芳纶、玻纤基三明治板比吸收能分别提高了37．72％和25．35％;芳纶、玻纤基三明治板的比吸收能均随复合材料夹层厚度的增加呈指数递增,夹层基板的抗拉性能是影响三明治板比吸收能的重要因素;同面密度下,厚面板、薄背板及多层叠合夹层结构的三明治板具有更高的比吸收能。     

Light-weight honeycomb core sandwich panels containing biofiber-reinforced thermoset polymer composite skins: Fabrication and evaluation

The application of biofiber based paper-reinforced polymer (PRP) composites as skin materials for light-weight sandwich panel constructions was explored. Various sandwich panels with PRP composite skins and a commercial resin-impregnated aramid paper honeycomb core of different cell sizes and core heights were fabricated in the laboratory. The effects of honeycomb core height and cell size on the flexural properties of the lab-made sandwich panels were evaluated. The flexural moduli and strengths of the lab-made panels were compared to the reported values for three existing commercial products used for automotive load floor applications. The lab-made PRP composite/honeycomb core sandwich panels had comparable bending rigidity and flexural load bearing capability but lower areal weights when compared to the commercial products suggesting that PRP composites have the potential to be used as an alternative to glass fiber-reinforced polymer composites as skin materials in sandwich panel fabrication.     

基于频率识别纤维增强树脂复合材料加筋板的分层损伤

以纤维增强树脂（FRP）复合材料加筋板为研究对象,通过对比分层损伤发生前后FRP复合材料加筋板的振动频率变化,来识别FRP复合材料加筋板中的分层损伤。构建了人工神经网络（ANN）和基于有代理模型的优化算法（SAO）两种逆向检测算法,利用FRP复合材料加筋板在损伤前后发生的一系列频率变化值来逆推出FRP复合材料加筋板中的分层位置和大小。分别采用数值验证和实验验证来双重检验ANN和SAO两种算法的识别精度和效率。数值验证结果表明:ANN和SAO两种逆向检测算法对分层损伤位置和大小的识别最大误差分别是5.04%（ANN）和5.24%（SAO）,证明方法在理论上可行。实验验证结果表明:ANN在使用实测频率数据进行识别时预测精度很差,无法得到有效的分层损伤信息;而采用SAO可以较好地预测试件中的分层损伤,且对分层大小的预测比对分层位置的预测精度更高,其中,对贯穿损伤和底板损伤的大小预测误差分别不超过2.05%和9%,而四个试件中有两个试件预测的分层与实际的损伤部位存在重合（重合率分别为34%和32.65%）。因此,当前提出的ANN和SAO在理论上可行,但实际应用时都会受到不同程度实测数据误差的影响,相比ANN而言,SAO算法有更好的鲁棒性,在采用实测频率时也可以较为准确地预测出试件中的分层损伤。      

玻璃纤维增强树脂基复合材料夹芯板-钢板连接接头的弯曲性能

以PVC泡沫或Balsa轻木为芯材的玻璃纤维增强树脂基复合材料（GRP）夹芯板目前广泛应用于船舶与海洋工程结构中。论文设计不同参数的GRP夹芯板-钢板混合接头模型,进行四点弯曲加载下的静力及疲劳试验研究,同时运用ABAQUS软件结合MSC.fatigue软件对接头的静态及疲劳弯曲失效进行数值模拟,分析了接头的弯曲强度、刚度和失效模式,并研究了接头填充区材料及长度、钢板嵌入填充区长度等参数对接头弯曲性能的影响。结果表明：弯曲载荷作用下接头破坏发生在连接结合部,失效模式则因填充区的不同设计而不同;对提高接头的弯曲性能较为明显的设计参数包括将钢板延伸到接头填充区或者选择Balsa轻木替代PVC泡沫芯材;对于受到疲劳弯曲载荷的接头模型,在较大疲劳载荷水平下,所有试件在未达到10⁶次循环时均发生了疲劳破坏;而在相对较小的疲劳载荷水平下,经过10⁶次循环后所有试件全部完好,并且接头的剩余强度与疲劳试验前的静强度相近,表明小载荷水平下接头的疲劳次数对其承载能力无影响。     

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.     

蜂窝夹层复合材料不确定性参数识别方法

提出蜂窝夹层复合材料不确定性参数识别方法。采用三明治夹芯板理论建立铝蜂窝夹层结构的初始有限元模型,其中芯层等效弹性参数由均匀化方法计算。据芯层结构及相对灵敏度分析选存在不确定性且对动态特性敏感性较大的面外剪切模量及面板厚度为待识别参数。对6块铝蜂窝复合材料板进行自由-自由边界条件下动态试验,获得试验模态参数的均值及标准差。据试验结果采用所提方法识别铝蜂窝夹层板不确定性参数。结果表明,对存在不确定性参数的铝蜂窝夹层复合材料用该方法能准确识别铝蜂窝夹层板不确定参数的均值及标准差。并建立具有准确统计意义的动力学模型。     

纤维增强聚合物基复合材料加固锈蚀钢筋混凝土圆柱轴心受压性能

为了给纤维增强聚合物基复合材料（FRP）加固腐蚀环境下钢筋混凝土圆柱的设计和施工提供参考,促进FRP加固钢筋混凝土圆柱的应用,本文通过加速腐蚀得到类似实际环境中已锈损钢筋混凝土圆柱,采用碳纤维增强聚合物基复合材料（CFRP）条带和玻璃纤维增强聚合物基复合材料（GFRP）条带分别对锈蚀钢筋混凝土圆柱进行加固,最后对加固后圆柱进行轴心受压试验,重点研究钢筋锈蚀率、FRP层数和种类对钢筋混凝土圆柱受压承载力的影响;基于对FRP条带间隔约束效应、钢筋锈蚀对混凝土截面及钢筋力学性能影响的研究与分析,提出FRP条带间隔约束锈蚀钢筋混凝土圆柱轴心受压承载力计算模型。试验实测值与模型计算值之比的平均值为1.020,变异系数为0.063,二者符合较好。     

玻璃纤维增强聚合物复合材料筋与工程水泥基复合材料黏结性能

为了研究玻璃纤维增强聚合物（GFRP）复合材料筋和工程水泥基复合材料（ECC）黏结性能的影响因素,对42个GFRP/ECC试件进行了拉拔试验,分析了GFRP复合材料筋表面形式、直径、ECC基体强度及保护层厚度等因素对GFRP复合材料筋与ECC基体黏结性能的影响。结果表明:GFRP/ECC试件的破坏形式主要有拔出破坏、筋剥离剪切破坏、劈裂破坏三种形式。表面带肋GFRP复合材料筋黏结强度比光滑GFRP复合材料筋高约66%;当ECC保护层厚度由1.5D（D为GFRP筋直径）增大至4D时,GFRP/ECC黏结强度提高了约58%;当GFRP复合材料筋直径为12~18 mm时,GFRP/ECC黏结强度随着GFRP复合材料筋直径的增大而降低;ECC强度由33.7 MPa增大至73.3 MPa时,GFRP/ECC黏结强度增大约3倍。增加GFRP复合材料筋表面形式复杂程度,或一定程度上提高ECC基体保护层厚度、提高ECC强度等级,有助于提高GFRP复合材料筋与ECC的黏结强度。