FRP透波窗性能设计研究

本研究针对FRP透波窗在使用频段范围实现透波率和结构性能的需求，通过材料选择、透波性能设计、仿真分析和结构设计，采用夹层结构形式，制造了FRP透波窗试验件，进行了结构试验和透波试验。试验结果表明，FRP透波窗的结构设计满足承载和密封性要求，同时在1.0GHz～3.0GHz频段范围内的透波率均大于80%,满足透波性要求。实现了对FRP透波窗的承载、密封和透波的设计要求，可以对内部设备的运行状态实现监测。     

三维中空复合材料天线罩的有限元结构分析

某类型天线罩外形尺寸较大,减重要求高,三维中空复合材料可满足该类型天线罩透波和结构高强的要求。针对上述使用要求和实际工况,选择三维中空织物复合材料为主体结构,玻璃纤维增强环氧树脂复合材料为补强面层,制备三维中空结构天线罩,采用有限元分析软件建立三维中空结构天线罩的有限元模型,对该类型天线罩在使用工况下的刚度、强度和稳定性进行分析,其计算结果满足刚度、强度和稳定性的要求,并通过压力试验验证中空夹层天线罩的变形量与有限元分析结果保持一致,从而指导该天线罩的铺层设计、优化及材料的选用。     

全透波Nomex蜂窝夹层结构的研制及性能研究

研制了蒙皮/Nomex蜂窝/蒙皮的三明治夹层结构。对胶接后固化和整体共固化成型两种成型方式开展了研究，并分别测试了两种方案制备的夹层结构的面外静态压缩性能、侧压性能、对应蒙皮的力学性能（包含拉伸性能、压缩性能、弯曲性能和层间剪切性能），试验测试结果满足设计指标要求，在此基础上进一步开展了夹层结构平板样件的透波试验，试验结果表明，不同厚度夹层样件在2.2～3.0 GHz的频率范围内的透波率均高于95%，满足设计指标要求。     

PMI泡沫夹层复合材料电性能设计与实验研究

聚甲基丙烯酰亚胺(PMI)泡沫夹层复合材料具有优异的宽频透波性能,被广泛用于制备透波雷达天线罩。为了设计满足宽频透波要求的某型天线罩,从复合材料结构原理出发,选择石英纤维增强环氧树脂复合材料为蒙皮,PMI泡沫为芯材的A夹层结构方案,采用三维全波电磁场仿真软件(CST软件)计算比较了不同蒙皮厚度和芯材厚度对A夹层结构透波性能的影响,得到了理论最优结构。进一步的平板试验结果表明,透波率的实际测试值与理论计算结果基本吻合,可见设计的A夹层复合材料结构可满足某型天线罩的宽频透波要求。     

复合材料机载天线罩多学科优化设计

提出一种复合材料机载天线罩多学科优化策略。以满足天线罩透波率为要求,基于等效传输线理论,对天线罩电性能进行分析,找出符合电性能指标的铺层厚度区间,将对透波率的约束转换到设计变量铺层厚度中。在满足透波率要求的前提下,建立了以质量最小为目标,结构刚度强度为约束,罩壁不同方向铺层厚度为设计变量的优化数学模型,以实现天线罩的轻量化设计。以某A-夹层机载天线罩为例进行了优化分析,研究结果表明,优化后的天线罩有显著的轻量化效果和较高的透波率表现,验证了优化方法的可行性。     

泡沫夹芯结构复合材料天线罩静强度分析

机载雷达天线罩减重要求高,泡沫夹芯结构复合材料可满足该类型天线罩透波和轻质高强的要求。本文采用有限元分析方法对某型机载雷达天线罩在使用工况条件下的静强度和刚度进行了分析,结果表明各材料的最大应力值都远小于材料的许用应力,天线罩不会发生由于材料失效引起的结构破坏,并且整体结构刚度合适,变形满足设计要求。     

某Ka波段天线罩的设计

设计制作具有尺寸精度高、透波率高的Ka波段天线罩对于保护天线、减少传输损耗具有极其重要的意义。本文介绍了某Ka波段天线罩的研制过程,通过对该天线罩材料的基本性能进行分析研究,得出应用于该天线罩的初步结构。利用ANSYS软件,对设计的Ka波段天线罩进行了结构分析,并简单介绍了研制的工艺流程。按照设计制作的Ka波段天线罩,其性能完全满足用户的技术指标要求。     

宽频带玻璃钢蜂窝板的试制

玻璃钢由于弹性模量低,限制了它的应用范围,而蜂窝夹层结构是一种提高其刚度的结构形式。玻璃钢蜂窝板就是由二层薄而强的玻璃布蒙皮与起支承联结作用的玻璃布质蜂窝芯子浸胶粘接而成的复合夹层材料。由于它具有质轻、比强度高、刚度高、绝缘性好、电磁波透过率高等优点,所以目前已广泛应用于航     

飞机雷达罩根部约束精细化建模

雷达罩是壁厚由电性能设计出的薄蒙皮夹层电磁透波结构,根部通过密封胶条、铰链、有限的锥销、连接锁与飞机相连,承担飞机的气动载荷。薄蒙皮夹层结构承载能力弱,而根部连接点的刚度大,承载能力强,正确设定连接刚度能够计算出雷达罩中正确的应力应变分布。本文以某型雷达罩为例,围绕NASTRAN软件建模,通过分段线性、非线性单元追踪建模、结果反算和试验验证手段,提出并验证雷达罩静强度计算的精细化建模方法,方法可靠,可以推广应用于其他结构根部约束的精细化建模。     

结构型吸波复合材料的研究进展

结构型吸波复合材料具有吸波性能好、质量轻、可承载等优点,已成为当代吸波材料的主要发展方向,对隐身材料的设计和制造有着重要意义。本文从纤维增强体的截面形状和制备工艺、纤维的铺排结构和夹层复合结构、吸波剂改性等影响吸波复合材料吸波性能的主要因素出发,系统地总结了结构型吸波复合材料的最新研究热点和成果,并指出吸波复合材料的未来发展方向。     

双向格构腹板增强泡沫夹层复合材料梁弯曲性能试验

复合材料夹层结构具有比强度高、比刚度高、可设计性强、耐腐蚀等特点,以聚氨酯泡沫为芯材,以玻璃纤维增强复合材料为面板和格构腹板,采用真空导入成型工艺,制备双向格构腹板增强泡沫夹层复合材料梁。对无格构泡沫夹芯复合材料梁,不同腹板高度、腹板间距双向格构增强泡沫夹层复合材料梁进行三点弯曲试验,研究其破坏模式和机理。基于泡沫填充矩形蜂窝芯材的等效十字模型,预估试件的抗弯刚度和挠度,计算值与试验值吻合较好。     

玻璃钢蜂窝夹层结构板热导率研究

玻璃钢蜂窝夹层结构板除高比强度、比刚度的优点外,还具有低热导率的特点,是一种隔热保温材料,在航天、航空、建筑方面得到广泛应用。本文对蜂窝夹层结构板的热导率进行了理论上的研究,分别对传导、对流、辐射进行分析,最后得到可供设计使用的热导率计算公式及曲线。计算结果与试验值很符合。     

New data for sandwich panels on the correlation between the SBI test method and the room corner reference scenario

Assessment of the fire behaviour of sandwich panels is continuously under discussion. The fire behaviour of these panels is a combination of material characteristics such as the core material and mechanical behaviour of the panels such as joints, dilations etc. The use of small or intermediate scale tests can be questioned for such types of products. Within the proposed European product standard for sandwich panels (prEN 14509) the intermediate scale test method SBI (EN 13823) has been suggested as the fire test method to certify panels. The standard does, however, use quite an artificial mounting procedure, which does not fully reflect the end‐use conditions of the panels. In a previous research project conducted by Nordtest it was shown that the correlation between the SBI test method and both the ISO 9705 and ISO 13784 part 1 was insufficient. The test data produced for the SBI test method, however, did not use the above mentioned mounting technique. In this article new data for a number of products are added to the database using the mounting procedure of the product standard. The data are compared with the previous data and show that the mounting method of the product standard results in slightly more severe conditions but that there are still discrepancies with the full‐scale test results. The data also show an unacceptable level of repeatability due to the fact that small dilations result in a wide variation of classification result. The new data together with the old data show once more that it is dangerous to make a fire safety assessment of a sandwich panel based on small or intermediate scale tests. Copyright © 2004 John Wiley & Sons, Ltd.     

High-velocity impact loading in honeycomb sandwich panels reinforced with polymer foam: a numerical approach study

The employment of lightweight structures is one of the most important goals in various industries. The lightweight sandwich panel is an excellent energy absorber and also a perfect way for decreasing the risk of impact. In this paper, a numerical study of high-velocity impact on honeycomb sandwich panels reinforced with polymer foam was performed. The results of numerical simulation are compared with the experimental findings. The numerical modeling of high-velocity penetration process was carried out using nonlinear explicit finite-element code, LS-DYNA. The aluminum honeycomb structure, unfilled honeycomb sandwich panel, and the sandwich panels filled with three types of polyurethane foam (foam 1: 56.94, foam 2: 108.65, and foam 3: 137.13 kg/m³) were investigated to demonstrate damage modes, ballistic limit velocity, absorbed energy, and specific energy absorption (SEA) capacity. The numerical ballistic limit velocity of sandwich panels, filled with three types of foam, was more than that of a bare honeycomb core and unfilled sandwich panel. In addition, the numerical results showed that the sandwich panel filled with the highest density foam could increase the strength of sandwich panel and the numerical specific energy absorption of this structure was 23% more than that of unfilled. Finally, the numerical results were in good agreement with experimental findings.

     

A comparative study of vacuum‐assisted resin transfer molding (VARTM) for sandwich panels

Vacuum‐assisted resin transfer molding (VARTM) of sandwich panels can be facilitated by using high permeability layers (HPL) over the skins or adding channels in the surfaces of the core (CIC). The present paper investigates the advantages and disadvantages of both methods in terms of manufacturing cost and time through simulations and experimental observations. A cost model is developed, and the resin infusion time for each method was minimized through simulations. The design parameters are the number of high‐permeability layers and the number and size of channels. A penalty function with equal weight on cost and time is used to find the optimum values of the design parameters. Under the conditions studied, the optimal HPL method is found to be better than the optimal CIC method. While the conclusion is limited to the present study, the proposed approach can be used to optimize manufacturing processes for larger sandwich panels under different conditions.     

泡沫夹芯结构板泡沫壁流道内的流动特性

沟槽型真空辅助树脂传递模塑成型工艺（VARTM）是一种新型的泡沫夹芯结构板成型方法,利用实验探明了泡沫夹芯结构板芯材上不可渗泡沫壁流道内的流动行为。实验结果表明,液体在泡沫壁流道的流动能力大幅降低,只有光滑壁流道的60%左右,泡沫壁流道的粗糙内表面是造成这种现象的主要原因。提出了相应的压力驱动流动方程,并采用等效渗透率来表征液体在泡沫壁流道内的流动能力,得到了考虑粗糙表面影响的等效渗透率计算公式,提出了一个正确计算不可渗泡沫壁流道内流动的处理方法。     

格栅增强夹芯板弯曲刚度影响因素及规律研究

基于有限元仿真和实验,对格栅增强夹芯板弯曲刚度的影响因素及规律开展了研究。首先,针对格栅结构对夹芯板抗弯特性的影响进行仿真分析,认为格栅结构能够较为显著地提高夹芯板的抗弯刚度;其次,针对格栅增强夹芯板的蒙皮纤维铺层角度、格栅密度等几个重要参数对其弯曲刚度的影响进行仿真计算并对其规律进行分析;最后,通过实验验证了仿真的准确性。分析结果表明,夹芯板蒙皮纤维±45°铺设时夹芯板具有最优的抗弯刚度,且在格栅总体积即含筋量一定的情况下,一定范围内降低单层格栅的厚度以增加格栅的密度会大幅度提高夹芯板的抗弯刚度。     

Temperature analysis of steel structures protected by intumescent paint with steel claddings in fire

It is of great interest to understand the stabilization effect of steel structures by steel claddings in fire. Structural fire analysis using finite-element method, including temperature analysis and structural analysis, is important to investigate the stabilization effect. However, temperature-dependent thermal material data for the insulation layer of sandwich panels and the intumescent paint for fire protection of steel sections are still scarce. In this paper, the available thermal properties of these materials from the literature are summarized, and 2D and 3D temperature analyses were carried out for steel sections with steel claddings, such as sandwich panels with mineral wool and polyisocyanurate (PIR) cores and trapezoidal sheeting with mineral wool insulation. The analysis results were compared with the fire tests conducted in European research project STABFI (Stabilization of Steel Structures by Steel Claddings in Fire). The study shows reasonable accuracy of modeling using existing thermal material data for temperature-dependent insulation properties and thermal data for intumescent paint, for intumescent coatings (IC) protected steel beam with mineral wool sandwich panel and trapezoidal sheeting claddings. Larger discrepancy between finite element (FE) prediction and test measurement was observed for the case of sandwich cladding with PIR core. Gaps for further research were identified. The study also shows the heat sink effect of the steel section by sandwich panels with a mineral wool core. Therefore, it is recommended that the sandwich panels should be included in the thermal analysis model for steel sections with sandwich claddings.     

Comparison of foam core sandwich panel and through‐thickness polymer pin–reinforced foam core sandwich panel subject to indentation and flatwise compression loadings

Through‐thickness polymer pin–reinforced foam core sandwich (FCS) panels are new type of composite sandwich structure as the foam core of this structure was reinforced with cylindrical polymer pins, which also rigidly connect the face sheets. These sandwich panels are made of glass fiber–reinforced polyester face sheets and closed‐cell polyurethane foam core with cylindrical polymer pins produced during fabrication process. The indentation and compression behavior of these sandwich panels were compared with common traditional sandwich panel, and it has been found that by reinforcing the foam core with cylindrical polymer pins, the indentation strength, energy absorption, and compression strength of the sandwich panels were improved significantly. The effect of diameter of polymer pins on indentation and compression behavior of both sandwich panels was studied and results showed that the diameter of polymer pins had a large influence on the compression and indentation behavior of through‐thickness polymer pin–reinforced FCS panel, and the effect of adding polymer pins to FCS panel on indentation behavior is similar to the effect of increasing the thickness of face sheet. The effect of strain rate on indentation behavior of FCS panel and through‐thickness polymer pin–reinforced FCS panel were studied, and results showed that both types of composite sandwich panels are strain rate dependent structure as by increasing strain rate, the indentation properties and energy absorption properties of these structures are increased. POLYM. COMPOS., 37:612–619, 2016. © 2014 Society of Plastics Engineers     

新型泡沫铝三明治板的弯曲性能

采用复合轧制方法制备界面为冶金结合的泡沫铝三明治. 通过对制备出的泡沫铝三明治进行三点抗弯实验验证界面的结合性和整体的抗弯性. 对载荷-位移曲线进行分析,讨论两种不同孔隙率的三明治板的变形行为,结果表明二者明显不同. 低孔隙率(58.81%)的三明治板的抗弯强度和弯曲弹性模量比高孔隙率(76.21%)的大,而高孔隙率的三明治板的断裂吸收能和断裂挠度比低孔隙率的大. 实验结果对今后泡沫铝三明治板的设计有实际指导意义.