EPP泡沫填充对铝蜂窝动态冲击性能的影响研究

采用动态冲击实验方法研究了EPP(聚丙烯塑料发泡材料)泡沫填充对铝蜂窝结构动态冲击性能的影响。研究发现:在相同的冲击速度下,相对空铝蜂窝,EPP泡沫填充铝蜂窝结构的初始峰值应力和平均应力分别提高了32.86%~68.57%和15.00%~72.50%,比吸能下降了33.54%~66.56%;在相同的泡沫密度下,填充结构的初始峰值应力、平均应力和比吸能值均随着冲击速度的增加而增加,2.6 m/s和3.2 m/s时的比吸能比2 m/s时的比吸能3.26 J/g增加了68.10%~152.45%;对比准静态压缩实验,动态冲击中的初始峰值应力提升了1.72%~12.04%,平均应力下降了6.51%~18.84%,比吸能下降了31.50%~65.50%。研究表明,利用EPP泡沫填充铝蜂窝,能改善铝蜂窝结构的轴向动态冲击性能。     

EPP泡沫填充对铝蜂窝压缩性能的影响研究

采用准静态轴向压缩实验和有限元仿真相结合的方法,对EPP泡沫(聚丙烯塑料发泡材料)填充对铝蜂窝结构压缩性能的影响开展了研究。实验发现,相对空铝蜂窝,EPP泡沫填充铝蜂窝结构的峰值力、平均抗压强度和吸收能量分别提高了1.9%~43.33%、46.59%~179.53%和46.26%~179.04%。并且相对空铝蜂窝与单独EPP泡沫之和,泡沫填充结构的平均抗压强度和总吸能分别提高了2%~23.5%和3.9%~23.3%。此外,采用Ls-dyna软件对EPP泡沫填充铝蜂窝的破坏过程进行了仿真,发现EPP泡沫填充可以有效抵抗蜂窝壁变形,并且获得了与实验较吻合的破坏过程和位移曲线。研究表明,利用EPP泡沫填充铝蜂窝,能有效改善铝蜂窝结构的轴向压缩性能。     

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     

Experiments and numerical simulations of low‐velocity impact of sandwich composite panels

This article investigates the response of composite sandwich panel with Nomex honeycomb core subjected to low‐velocity impact and compression after impact (CAI) by using the methods of experiments and numerical simulations. Low‐velocity impact of sandwich panels at five energy levels is carried out to research the damage resistance and tolerance. A failure model based on Hashin failure criterion is implemented to model the intralaminar damage behavior of laminated plies in the numerical simulation. The cohesive zone model is used to simulate the delamination damage between adjacent laminated plies. The honeycomb core behavior is defined as an elastic–plastic material. Good agreements, in terms of contact‐force histories, damage shapes, and indentation depths of the sandwich panels, are observed between the experimental and numerical results. During CAI analysis, the damaged panels present a phenomenon of quick crack propagation from impact indentation location to each unloaded side after the structural strength reached. It is found that the in‐plane compressive strength of damaged sandwich panels is almost 25–35% reduction than that of undamaged panels. POLYM. COMPOS., 38:646–656, 2017. © 2015 Society of Plastics Engineers     

Behavior of sandwich structures and spaced plates subjected to high‐velocity impacts

This work evaluates the behavior of sandwich and spaced plates subjected to high‐velocity impacts. The sandwich structures were made of glass/polyester face‐sheet and a PVC foam core. The spaced plates were made of two plates of the same material of the sandwich face‐sheet at a distance equal to the core thickness. The residual velocity, the ballistic limit, and the damage area were selected to compare the response of both structures. The residual velocity and ballistic limit was very similar in both cases. Nevertheless, the damage area of sandwich structures and spaced plates differed due to the dissimilar properties between the sandwich core and the air inside of the spaced plates. An analytical model, based on energy criteria, was applied to estimate the residual velocity of the projectile, the absorbed energy by each face‐sheet, and the ballistic limit in the spaced plates. POLYM. COMPOS., 2011. © 2010 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.     

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。     

聚合物夹层复合板材性能及成型技术研究进展

夹层复合板是一种高强轻质的复合板材。主要包括蜂窝夹层结构与泡沫夹层结构。夹层复合板材广泛应用于航空航天领域。早期的夹层板材以金属材料为主。随着聚合物工业的加速发展,聚合物材料以及纤维增强聚合物也成为夹层复合板材的主要材料。主要介绍各种以聚合物为原材料制成的蜂窝夹层板材和泡沫夹层板材的性能、成型技术和应用领域。     

Fabrication process and mechanical properties of C/SiC corrugated core sandwich panel

Carbon fiber reinforced SiC composite is a kind of promising high-temperature thermal protection structural material owing to the excellent oxidative resistance and superior mechanical properties at high temperatures. In this work, a novel design and fabrication process of lightweight C/SiC corrugated core sandwich panel will be proposed. The compressive and three-point bending of the C/SiC corrugated sandwich panels are conducted by experiment and numerical simulation. The relative density of as-prepared C/SiC sandwich panel and the density composite material are 1.1 and 2.1 g/cm³, respectively. As the density of the C/SiC sandwich panel is only 52.3% of the bulk C/SiC, suggesting that lightweight characteristic is realized. Moreover, the C/SiC sandwich panel manifests itself as linear-elastic behavior before failure in compression and the strength is as high as 15.1 MPa. The failure mode is governed by the core shear failure and panel interlayer cracking. The load capacity under the three-point bending C/SiC composite sandwich panel is 1947.0 N. The main failure behavior is core shear failure. The stress distribution under the compression and three-point bend was simulated by FE analysis, and the results of numerical simulations are in accordance with the experimental results.     

Evidence of optimal interfaces in bio-inspired ceramic-composite panels for superior ballistic protection

Ceramic-composite panels are acknowledged to provide effective impact protection even against small fragments and armour piercing projectiles. Nature shows similar solutions, coupling an hard face and soft backing layers, in dermal animal armours for protection against predators. Finite element simulations of impact on ceramic-composite panels, to evaluate their energy absorption capability, are presented. The influence of key parameters, like interface strength and friction, on ballistic limit is studied. We find that a proper set of interface parameters is able to maximize the specific energy absorption of the panel: although this optimum is variable case by case depending on projectile penetrability and target configuration, general guidelines are provided. Oblique impact results in a higher ballistic limit also thanks to projectile change in trajectory, providing interesting spots for future developments. Numerical results are compared with experimental data from literature and forecasts of analytical models.     

缝合碳纤维泡沫夹芯复合材料低速冲击及损伤检测

研究了低速冲击对缝合与未缝合碳纤维泡沫夹芯复合材料冲击性能及损伤的影响;采用落锤冲击试验机对缝合和未缝合夹芯复合材料板分别进行了不同冲击能量下的冲击实验,得出冲击力和冲头位移分别随时间变化的曲线;采用水浸超声波扫描成像系统对冲击后的复合材料板进行损伤检测,得出夹芯复合材料板内部损伤情况。结果表明,在相同冲击能量下,缝合碳纤维复合材料板的冲击力较未缝合的要大,但冲头接触时间要短;此外,缝合碳纤维泡沫夹层复合材料板比未缝合的损伤面积要小,这说明缝线能有效的抑制冲击载荷下复合材料板内损伤扩散,减小分层损伤面积,提高复合材料板的抗冲击性能;缝合的抑制损伤效果在表面层和最内部层效果显著,而在中间层缝线的效果一般。     

Investigation of sandwich structures with innovative cellular metallic cores under low velocity impact loading

Abstract

Sandwich panels are widely used for energy absorbing applications in cases of low and high velocity impacts. The core itself is capable of absorbing energy by progressive collapse, while the skins are necessary for uniformly distributing the local vertical load over the impacted area as well as for the introduction of overall panel bending resistance. In the present work, the failure response of sandwich panels with open lattice cellular cores subjected to low velocity impact is investigated. Experimental tests are performed using a mass drop testing machine. Additionally, a three-dimensional finite element model of the sandwich panels–impactor system is developed using commercial Finite Element (FE) codes. The core homogenisation is introduced in order to improve the efficiency of the FE analysis by reducing the computational time. Numerical results correlate well with experimental data, enabling detailed understanding of the parameters affecting the initiation and propagation of impact damage.     

复合材料泡沫夹层结构的缺陷评定方法研究

本文以厚壁碳纤维复合材料为面板,硬质聚氨酯泡沫为芯材制造复合材料泡沫夹层结构,模拟实际生产过程中容易出现的面板与芯材之间界面的脱粘和界面胶层过厚的现象,采用人工制造试块的方法,研究了超声波探伤对夹层复合材料缺陷的评定方法,解决了实际检测过程中的疑问,为夹层复合材料结构产品的质量检验提供依据。得出了粘接良好区胶层过厚不会被判定为脱粘的结论。     

轨道车辆泡沫夹芯中顶板夹层设计与优化

轨道车辆的生产中大量采用平板铝合金或玻璃钢板件,产品质量偏重且材料容易出现下垂,满足不了车体轻量化与美观的需求。通过仿真与试验结合的方式研究酚醛泡沫、聚对苯二甲酸乙二醇酯(PET)泡沫、聚氯乙烯(PVC)泡沫夹芯中的面板厚度、芯材模量对中顶板质量及下垂挠度的影响,测试了不同复合夹芯板的平拉强度、平压强度以及弯曲强度。结果表明:经过芯材选型优化后,平拉强度≥2 MPa、平压强度≥2 MPa、弯曲强度≥25 MPa、面密度≤7.5 kg/m²、下垂挠度≤2 mm的泡沫夹芯为中顶板的最优结构组成。     

熔融沉积成型木塑复合夹层板的弯曲性能

采用熔融沉积成型(FDM)制造方法,以木塑复合线材为原料,利用3D打印软件Ultimaker Cura的“填充结构”功能设计网格、直线、三角形等13种芯层结构(二维6种、立体7种),并将其与纸板粘接得到木塑复合夹层板。利用三点弯曲测试,研究不同夹层板的破坏失效形式与弯曲性能。结果表明:木塑夹层板的失效模式主要有弹性变形、面板起皱、芯子剪切和芯子压溃。在13种芯层结构中,立体的同心3D芯层结构夹层板弯曲性能最佳,弯曲模量和静曲强度分别为159.56 MPa和4.85 MPa,分别是网格芯层结构夹层板的5.4倍和2.3倍,具有较强的抗弯曲变形能力,适合于设计制造轻质高强度制品。     

蜂窝厚度对纸蜂窝/聚乙烯泡沫复合层状结构的动态缓冲吸能特性的影响

针对纸蜂窝与聚乙烯泡沫的2种复合层状结构的缓冲防护作用,研究分析在不同跌落冲击条件下蜂窝厚度对其加速度响应、压缩变形和缓冲吸能特性的影响规律。在静态压缩中一层蜂窝对应一个应力波峰,而跌落冲击动态压缩中较大厚度蜂窝会出现次坍塌行为导致的小应力波峰,蜂窝厚度的增加能够提高聚乙烯泡沫及其复合层状结构的抗冲击能力。对于厚度为10、15、20、25 mm的纸蜂窝与聚乙烯泡沫的复合层状结构,在低冲击能量作用下蜂窝厚度的增加降低了缓冲吸能特性,而在高冲击能量作用下蜂窝厚度的增加能提高能量吸收能力。但是,大厚度70 mm纸蜂窝与聚乙烯泡沫的复合层状结构的缓冲吸能效果相对较差。对于相同的蜂窝厚度情况,在相同的冲击质量或冲击能量作用下,单面复合层状结构的应变能、比吸能和行程利用率相比双面复合层状结构分别提高了11.5 %、39.1 %和16.2 %,缓冲吸能效果更好。     

合成纤维的机械性能与防弹性能的关系

介绍了合成纤维的防弹机理;分析了合成纤维的机械性能与防弹性能之间的关系,表征合成纤维防弹性能的主要指标有断裂能量吸收率、应力波传播速度、弹道极限速度等;并对几种新型防弹纤维的机械性能及其防弹性能进行了比较,纤维的机械性能决定其防弹性能。指出我国应开发具有自主知识产权的高性能防弹纤维。     

暗肋夹芯式轻骨料混凝土外墙板热工性能研究

为解决现有建筑能耗中由墙体引起的热损失问题,本文提出一种暗肋夹芯式复合轻质保温墙板,并围绕该种新型墙板的热工性能开展研究。首先分别测试轻骨料混凝土、聚苯颗粒混凝土的热工参数,研究内外叶及芯层不同厚度组合、内置钢筋网及平面桁架对复合墙板热工性能的影响。然后将试验结果与理论分析结果进行对比,验证理论分析模型的可靠性,为复合保温墙板的热工设计提供基础研究支撑。对比常规预制混凝土外墙板,新型复合墙板表现出良好的热工性能。     

Numerical analysis of adhesively bonded T-joints with structural sandwiches and study of design parameters

Adhesively bonded T-joints are extensively used in assembling sandwich structures. The advantage of adhesive bonded joints over bolted or riveted joints is that the use of fastener holes in mechanical joints inherently results in micro and local damages to the composite laminate during their fabrication. One type of adhesive joint in such structures is the T-joint between sandwich panels. The aim of this research paper is to study, by numerical analysis, the effect of fillet geometry and core material of sandwich panels on the performance of T-joints. The base angle of the core triangle (fillet) is the most important geometry parameter of the triangular T-joint. Nine geometrical models with different base angles of the core triangle are made to investigate the effect of the base angle on the performance of the T-joints. It should be mentioned that the base angle in the triangular foam is changed, so that the final volume of the filler is kept constant in all the cases. Different foams with different stiffness are used to model the core of the panels to study the effect of the core material of sandwich panels. To model the adhesive between joint components, contact elements and cohesive zone material models are used. Therefore, failure of adhesive and separation of joint elements can be modeled. Damage and core shear failure of the base panel are modeled by using a written macro-code in the ANSYS finite element method (FEM) program. The ultimate strength of the joint in each case is calculated by modeling adhesive failure and core shear failure of the sandwich panels. Finally, the results of FEM are validated by experimental results available in the literature. In general, the failure load predicted by the FEM is within 5% of the experimental results. The best angle of the core triangle was found to be 45°. Also, the results showed that by changing the core material of the sandwich panel, the joint failure load is also changed.     

轻钢龙骨-泡沫混凝土复合墙板的抗冲击性能

为了对轻钢龙骨-泡沫混凝土复合墙板的抗冲击性能进行定量表征和破坏形式进行定性描述,评价复合墙板抗冲击性能的优劣,利用质量为2 040 g的钢球分别从1.0 m、1.5 m、2.0 m和2.5 m的高度自由落体冲击复合墙板,同时辅以全幅高达2 000帧/s的超高速相机拍摄试验过程,研究了不同结构的轻钢龙骨-泡沫混凝土复合墙板的抗冲击性能。结果表明,采用钢丝网、纤维、玻璃纤维网格布三种增强方式可以提升轻钢龙骨-泡沫混凝土复合墙板的抗冲击性能,三种复合墙板分别在冲击高度为2.0 m、2.0 m和2.5 m时出现裂缝,吸能比例的最大值分别为97.80%、96.70%和96.57%,玻璃纤维网格布增强方式的轻钢龙骨-泡沫混凝土复合墙板具有更好的抗冲击性能;轻钢龙骨-泡沫混凝土复合墙板表面不同位置处抗冲击性能具有差异性,非龙骨区域的吸能比例和硅酸钙板吸收能量小于龙骨区域,具有更好的抗冲击性能。