水下冲击载荷下波纹夹层结构动态响应特性分析

为了探讨波纹芯层夹层结构在水下爆炸冲击波作用下的动态响应特性和抗冲击防护能力,首先基于非药式水下冲击波加载试验,结合显示动力学软件对水下结构抗冲击解耦算法的有效性进行了验证。进而利用该算法对波纹夹层板在水下冲击作用下的动态响应进行了研究,得到了波纹夹层结构气背面板塑性变形与冲击波强度间的关系,同时比较分析了波纹夹层板与格栅夹层板及单层板的抗冲击性能。研究结果表明:具有相同面密度的夹层板抗冲击能力高于单层板,其中波纹型夹层板的抗冲击防护能力优于格栅夹层板,抗冲击性能相对于单层板提高了82.45%。     

水下冲击波作用的铝合金蜂窝夹层板动力学响应研究

为研究铝合金蜂窝夹层板水下爆炸冲击波载荷作用的动态响应及抗冲击性能,利用非药式水下爆炸冲击波加载装置对气背固支5A06铝合金夹层板及具有相同面密度的单层板进行水下冲击波加载试验。利用高速相机结合三维数字散斑技术(DIC)对夹层板后面板动态响应进行实时测量,获得夹层板气背面受水下冲击波作用的动态响应历程及变形毁伤模式,比较分析铝合金蜂窝夹层板抗冲击防护性能。结果表明,较相同面密度的单层板,蜂窝夹层板受水下冲击波载荷作用的芯层压缩能有效减少气背面板的塑性变形,提高夹层结构整体抗冲击性能。     

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。     

方孔蜂窝夹层板在爆炸载荷下的吸能特性

通过有限元数值模拟方法,对方孔蜂窝夹层板在爆炸冲击载荷下的变形机理和吸能特性进行了分析。在单位面积质量以及夹层板芯层薄壁间距、高度给定的情况下,通过对不同夹芯层相对密度下夹层板的吸能率以及上、下面板最大变形的比较,得出了最优的夹芯层相对密度。在此相对密度下,夹芯层吸能率最高,下面板变形最小,夹层板的抗冲击性能最优。同时还讨论了夹层板芯层薄壁间距、厚度、高度以及面板厚度对其各部分吸能率的影响,以得到最优化的夹层板结构。     

铝蜂窝夹层板低速冲击响应及损伤模式的参数化影响

以铝蜂窝夹层板为对象，通过低速落锤试验及包含面板、胶层及蜂窝的细节仿真模型，探究了蜂窝胞元直径、蜂窝壁厚、面板厚度及冲头半径参数影响下低速冲击响应曲线及损伤模式的变化情况，确定在试验工况下的3种损伤模式：芯层屈曲、芯层剪切及夹层板穿透，其中芯层剪切模式具有更好的吸能分布。结果表明：蜂窝胞元直径与蜂窝壁厚对冲击响应与损伤模式具有类似的影响，面板厚度增加可以较大程度地提升抗冲击性能，冲头半径的大小会显著影响损伤模式。在此基础上建立与上述参数相关的损伤模式极限载荷公式，绘制相应的损伤模式图，为铝蜂窝夹层板的抗冲击设计提供参考。     

新型矩形蜂窝夹芯夹层加筋圆柱壳抗水下爆炸冲击载荷分析

提出了一种新型矩形蜂窝夹芯夹层加筋圆柱壳结构形式。分析了其在水下爆炸冲击载荷下的动力响应特征及     

缝合泡沫夹层复合材料低速冲击数值模拟及实验

在ABAQUS分析平台中建立了缝合泡沫夹层复合材料在低速冲击下的动力学有限元模型,采用杆单元模拟缝线树脂柱的作用,基于Hashin破坏准则模拟层板面内损伤,通过各向同性硬化本构模型利用等效塑性变形模拟泡沫夹芯损伤演化。针对相同铺层的缝合和未缝合泡沫夹层结构,模拟了相同冲击能量下的低速冲击响应过程及面板、泡沫的损伤情况,数值结果与实验结果吻合较好,证明了该方法的有效性和准确性。研究结果表明,在低速冲击下,泡沫夹层结构引入缝线后虽然降低了泡沫缓冲吸能的作用,使得面板表面受到较大的冲击破坏,但增强了整体刚度,增大了面板抵抗弯曲变形的能力,减小了内部面板的损伤,使其在改善复合材料面板易分层缺陷的同时还依然拥有优良的面内性能。     

夹层结构复合材料低速冲击试验与分析

设计了聚甲基丙烯酰亚胺(PMI)泡沫、 交联聚氯乙烯(X-PVC)泡沫、 NOMEX蜂窝、 缝合PMI以及开槽PMI泡沫等形式的玻璃布面板夹层结构复合材料, 研究了芯材种类和厚度、 面板玻璃布层数以及缝合和开槽等因素对夹层结构低速冲击性能的影响。结果表明, PMI泡沫芯较X-PVC泡沫芯和NOMEX蜂窝芯具有更高的冲击破坏载荷和吸收能量。随着泡沫密度及面板厚度的增加, 夹层结构复合材料的冲击破坏载荷和破坏吸收能量增大。合理的缝合和开槽, 能够增加PMI泡沫夹层结构的强度、 刚度及界面性能, 提高冲击承载能力。     

芳纶纸蜂窝芯材的制备技术及其应用研究进展

夹层结构作为复合材料领域的重要结构形式之一,它由上下2层较薄的面板和较厚的轻质芯材组成,芯材连接上下面板使之成为一种整体结构,让面板在承担较高的拉压应力时不发生屈曲,同时将剪切应力从面板层传递到芯材内层,因此,夹层结构具有质量轻、弯曲刚度和强度大、抗失稳能力强等优点[1,2]。该结构形式首先在航空航天领域得到应用,如英国的“蚊式”轰炸机上就采用了全木质的夹层结构[3]。     

泡沫金属子弹撞击载荷下多孔金属夹芯板的动态响应

应用泡沫金属子弹撞击加载的方式研究了固支多孔金属夹芯板的塑性动力响应。讨论了多孔金属夹芯板在冲击载荷作用下的破坏模式。结果表明夹芯板的破坏主要表现在前面板的压痕与侵彻失效,芯层压缩和芯层剪切破坏。基于实验研究,应用LS-DYNA 3D非线性动力学有限元分析软件对夹芯板动力响应进行了有限元分析。数值研究结果与实验结果吻合较好。考察了加载冲量、面板厚度、芯层厚度及相对密度对多孔金属夹芯板抗撞击性能的影响。夹芯板的结构响应对其结构配置比较敏感,增加面板厚度或芯层厚度能够明显地减小后面板的挠度,提高夹芯板的抗撞击能力。研究结果对多孔金属夹芯板的优化设计具有一定得参考价值。     

Experiments on curved sandwich panels under blast loading

In this paper curved sandwich panels with two aluminium face sheets and an aluminium foam core under air blast loadings were investigated experimentally. Specimens with two values of radius of curvature and different core/face sheet configurations were tested for three blast intensities. All the four edges of the panels were fully clamped. The experiments were carried out by a four-cable ballistic pendulum with corresponding sensors. Impulse acting on the front face of the assembly, deflection history at the centre of back face sheet, and strain history at some characteristic points on the back face were obtained. Then the deformation/failure modes of specimens were classified and analysed systematically. The experimental data show that the initial curvature of a curved sandwich panel may change the deformation/collapse mode with an extended range for bending dominated deformation, which suggests that the performance of the sandwich shell structures may exceed that of both their equivalent solid counterpart and a flat sandwich plate.     

梯度铝泡沫夹层结构抗爆性能仿真与优化

采用动力显式有限元方法,以面比吸能和背板最大变形量为评价指标,研究了铝合金面板—梯度铝泡沫芯体—装甲钢背板夹层结构的抗爆性能。分析了芯体密度梯度排布对结构抗爆性能的影响,并与均匀密度铝泡沫夹层板进行了对比。同时,基于径向基函数建立了夹层结构抗爆性能预测响应面模型,在此基础上对夹层结构进行了多目标优化设计。结果表明,铝泡沫芯体相对密度排布顺序对夹层结构抗爆性影响明显;具有最佳芯体密度梯度排布的铝泡沫夹层结构的抗爆性能明显优于等质量的均匀密度铝泡沫夹层结构;多目标优化可进一步提高梯度铝泡沫夹层结构的综合抗爆性能。     

Experimental determination of torsion and shear properties of sandwich panels and laminated composites by the plate twist test

A recently developed sandwich plate twist test is employed here for determination of the transverse shear modulus of the core and twist stiffness (D₆₆) of a sandwich panel consisting of a soft (H45 PVC foam) core and glass/vinylester face sheets. The shear modulus of the H45 PVC foam core extracted from the twist test was in good agreement with shear modulus obtained from ASTM plate shear testing of the foam core. D₆₆ values obtained from the sandwich twist test were in good agreement with predictions from classical laminated plate theory. In addition, the twist test was used to determine the in-plane shear modulus of glass/vinylester laminates isolated and as face sheets in sandwich panels with a stiff (plywood) core. The in-plane shear modulus of the face sheets, isolated and as part of a sandwich panel, was in good agreement with shear modulus determined using the Iosipescu shear test. The results point to the potential of the twist test to determine both in-plane and out-of-plane shear moduli of the constituents of a sandwich structure, as well as D₆₆.     

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。     

Effective properties for sandwich plates with aluminium foil honeycomb core and polymer foam filling – Static and dynamic response

The estimation of static and eigenvibration properties of honeycomb sandwich reinforced by polymeric foam were investigated in the paper. A new “real microstructure” numerical 3D FEM model was proposed for the analysis in which the face materials and the honeycomb were modelled by shell elements, whereas filling foam was modelled by solid elements. Two variants of the honeycomb sandwich panel were considered: with and without polymer foam filling. Static and modal analyses have been performed in both, filled and hollow cases, to observe the effect of core stabilization with foam, particularly for higher natural frequencies. The effective properties of the honeycomb sandwich panels were estimated for both considered cases. Similar calculations have been made for the core materials without top and bottom faces and for the sandwich plate without honeycomb core structure (only polymer foam). One can observe: (1) the substantial increase of the effective elastic properties of the plate; (2) that the eigenvibration properties depend strongly on: the face material, honeycomb core and filling materials properties. The above conclusions are important for design process of structural parts.     

Mechanical response of metallic honeycomb sandwich panel structures to high-intensity dynamic loading

Explosive tests were performed in air to study the dynamic mechanical response of square honeycomb core sandwich panels made from a super-austenitic stainless steel alloy. Tests were conducted at three levels of impulse load on the sandwich panels and solid plates with the same areal density. Impulse was varied by changing the charge weight of the explosive at a constant standoff distance. At the lowest intensity load, significant front face bending and progressive cell wall buckling were observed at the center of the panel closest to the explosion source. Cell wall buckling and core densification increased as the impulse increased. An air blast simulation code was used to determine the blast loads at the front surfaces of the test panels, and these were used as inputs to finite element calculations of the dynamic response of the sandwich structure. Very good agreement was observed between the finite element model predictions of the sandwich panel front and back face displacements and the experimental observations. The model also captured many of the phenomenological details of the core deformation behavior. The honeycomb sandwich panels suffered significantly smaller back face deflections than solid plates of identical mass even though their design was far from optimal for such an application.     

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.     

钢板夹泡沫铝组合板抗爆性能研究

鉴于泡沫铝材料优异的吸能特性和夹层结构在强度、刚度上的优势,提出了分层结构为钢板-泡沫铝芯层-钢板的抗爆组合板。对厚度为10 cm、7 cm和5 cm的组合板进行了5组不同装药量的爆炸试验,考察了各板在不同装药量爆炸条件下的变形及破坏情况,并对变形破坏过程进行了理论分析。研究表明:组合板承受爆炸冲击荷载时,通过局部压缩变形和整体弯曲变形吸收能量。钢板相同时,适当增大泡沫铝芯层厚度,增强面板与芯层间连接,可提高该组合板的抗爆性能,防止组合板发生剥离,减小其承受爆炸冲击荷载时产生的变形。     

Dynamic response of clamped sandwich beam with aluminium alloy foam core subjected to impact loading

The dynamic response of clamped sandwich beam with aluminium alloy open-cell foam core subjected to impact loading is investigated in the paper. The face sheet and the core of the sandwich beam have the different thickness. And the sandwich beam is impacted by a steel projectile in the mid-span. The impact force is recorded by using accelerometer. The results show that tensile crack and core shear are the dominant failure modes. And the impact velocity and the thickness of the face sheet and the foam core have a significant influence on the failure modes and the impact forces. Combining with the inertia effect and experimental results, the failure mechanisms of the sandwich beams are discussed. The thickness of the foam core plays an important role in the failure mechanism of the sandwich beam. In present paper, the failure of the sandwich beam with a thin core is dominated by the bending moment, while the sandwich beam with a thick core fails by bending deformation in the front face sheet and the bottom face sheet in opposite direction due to the plastic hinges in the front face sheet.     

Underwater blast response of free-standing sandwich plates with metallic lattice cores

The underwater blast response of free-standing sandwich plates with a square honeycomb core and a corrugated core has been measured. The total momentum imparted to the sandwich plate and the degree of core compaction are measured as a function of (i) core strength, (ii) mass of the front face sheet (that is, the wet face) and (iii) time constant of the blast pulse. Finite element calculations are performed in order to analyse the phases of fluid–structure interaction. The choice of core topology has a strong influence upon the dynamic compressive strength and upon the degree of core compression, but has only a minor effect upon the total momentum imparted to the sandwich. For both topologies, a reduction in the mass of the front (wet) face reduces the imparted momentum, but at the expense of increased core compression. Conversely, an increase in the time constant of the blast pulse results in lower core compression, but the performance advantage over a monolithic plate in terms of imparted momentum is reduced. The sandwich panel results are compared with analytical results for monolithic plates of mass equal to that of (i) the sandwich panel and (ii) the front face alone. (Case (i) represents a rigid core while (ii) represents a core of negligible strength.) For most conditions considered, the sandwich results lie between these limits reflecting the coupled nature of core deformation and fluid–structure interaction.