On the Collapse of Cotton/Epoxy Tubes under Axial Static Loading

Experimental quasi-static crushing tests and finite element analysis have been carried out for unidirectional filament wound laminated cotton/epoxy tubes. The work focuses on three main factors, which considerably affect the axial collapse load of unidirectional natural composite tubes. These factors are structural geometry, fibre diameter and fibre orientation. Cotton/epoxy tubes with different diameters (50, 70, 90, 110 and 130 mm) were examined and tested. The fibre orientation angles were 80 and 90°. The initial geometric imperfections are measured using the computerised Mistral coordinate measuring machine. The numerical prediction was obtained using commercially available finite element software. A limited agreement between the experimental and computational results was obtained. For all structures considered classical axial collapse eigenvalues were computed. The initial failure crush load computed from the finite element simulation model has been compared with the experiments.     

引发角对碳纤维/环氧复合材料圆管件轴向压溃性能的影响

研究了碳纤维增强高韧环氧树脂5288复合材料薄壁圆管件的轴向压溃行为和引发角尺寸之间的关系.对15°,45°,60°引发角的相同尺寸试件分别进行轴向压溃试验,记录了试验过程中的结构载荷力-位移曲线,对照各组不同引发角的管形件轴向压溃过程的峰值压溃载荷、最小压溃载荷后发现,当引发角为60°时,结构的峰值压溃载荷最高,最小压溃载荷最低.对试验件失效后组织进行微观分析后发现,对应于不同引发角,由于接触状态不同,圆管件发生了不同方式的压溃失效,导致了结构吸能力-位移曲线的变化.     

Ellipticity Ratio Effects in the Energy Absorption of Axially Crushed Composite Tubes

In this paper, the influence of ellipticity ratio on energy absorption capability and load-carrying capacity of woven roving wrapped composite elliptical tubes has been investigated both experimentally and numerically. A series of experiments was conducted for composite elliptical tubes with ellipticity ratios (a/b) ranging from 1 to 2. Typical failure histories of their failure mechanism are presented and discussed. The experimental data are correlated with predictions from a finite element model. Load-deformation curves and deformation histories of typical specimens are presented and discussed. For all specimens considered, classical axial collapse eigenvalues were computed. The results showed that the ellipticity ratio significantly influenced the energy absorption capabilities as well as the load-carrying capacity. Tubes with ellipticity ratios of a/b 1.25 and 2.0 displayed the highest normalised specific energy absorption capability. A reasonable agreement between the experimental and computational results was obtained for the critical crush load.     

圆弧刻槽薄壁圆管轴向压溃吸能特性数值研究

目的为了提高能量吸收效率,设置出一种合理的诱导结构,对吸能构件产生积极影响。方法薄壁圆管设计一种环向圆弧刻槽诱导结构,在不同长径比、径厚比和刻槽深度的条件下研究薄壁结构吸能特性。结果吸能量与圆管长径比和径厚比成反比,初始压溃载荷随刻槽深度增加而减小。结论在不同的条件下,刻槽结构能够有效降低初始载荷,并获得较为平稳的压溃载荷平台。     

复合材料结构-功能一体化技术与吸能结构的研究

复合材料的结构一体化技术包括结构整体化和结构-功能一体化两个方面.复合材料吸能结构属于典型的结构-功能一体化结构.以复合材料管形件为基础,发现提高管形件轴向性能如增加编织结构的轴向纤维纱数,或调整预浸料复合材料铺层尽可能地平行于轴向,或提高复合材料层间韧性(即高CAI值)等,都有利于提高吸能效果.在整体化制造方面,研制和验证了织物复合材料正弦波梁的液态成型制造技术.     

复合材料圆管端部加强对其轴压性能影响的实验分析

通过实验研究了复合材料圆管端部加缠碳纤维对其轴压性能的影响,并对轴压破坏模式进行了分析.结果表明,复合材料圆管端部加强后,其轴压破坏模式和破坏位置都发生了改变.在轴压载荷作用下,端部加强能减小管的径向变形,并能更好地传递载荷,对提高复合材料圆管的压缩性能有利.     

圆形薄壁构件准静态径向压缩下的吸能特性分析

为探讨薄壁吸能构件径向压缩下的吸能防冲特性,以圆形薄壁构件为例,采用理论分析、数值模拟和实验研究方法,对构件径向压缩下的吸能防冲特性进行研究,得出以下主要结论:构件压缩过程中具有稳定的变形破坏模式和较为恒定的承载力。内径对载荷波动系数、冲程效率和总吸能影响较小,压溃峰值载荷、平均压溃载荷随内径增加而降低。构件压溃峰值载荷、平均压溃载荷和总吸能均随壁厚增加而增大,载荷波动系数和冲程效率随壁厚增加而降低。长度对载荷波动系数和冲程效率影响较小,构件压溃峰值载荷、平均压溃载荷和总吸能均随长度增加而增大。研究结果为圆形构件尺寸选取提供理论依据,为其它类型薄壁构件径向压缩吸能特性分析提供参考。     

加载速率对点阵铝力学行为及吸能特性的影响

目的研究基体材料和加载速率对点阵铝力学性能和吸能特性的影响规律。方法针对工业纯铝、6063铝合金为基体的点阵铝在3种不同的加载速率下进行压缩力学试验。结果加载速率从2mm/min增加到250 mm/min时,点阵纯铝的屈服强度增加了2 MPa,点阵6063铝合金的屈服强度增加了7.6 MPa;加载速率从250 mm/min增加到500 mm/min时,点阵纯铝的屈服强度变化不大,而点阵6063铝合金的屈服强度增加了8.2 MPa;当加载速率一定时,点阵6063铝合金的屈服强度要大于点阵纯铝。结论点阵6063铝合金的力学性能和单位体积吸能随着加载速率的增大而增大,并且点阵6063铝合金的力学性能和吸能特性要大于点阵纯铝。     

静态径向加载速率对樟子松吸能特性的影响

目的研究樟子松在不同静态径向加载速率作用下的能量吸收特性。方法采用横纹径向压缩实验。结果在不同加载速率的作用下,应力-应变曲线都呈现出3个阶段,即弹性阶段,应力平台阶段以及密实化阶段。樟子松存在明显的应变速率敏感性,随着加载速率的增加,应力-应变曲线的应力平台阶段不断上升。当应变为0.06,加载速率为1 mm/min时,应力为4.38 MPa;当加载速率为10和30mm/min时,对应的应力分别为4.71和6.56 MPa。樟子松具有优良的吸能能力,其能量吸收效率可以达到0.7~0.8。其缓冲系数曲线呈"L"型,随着应变的增加缓冲系数不断减小,但受加载速率的影响不大。结论不同加载速率对樟子松的能量吸收特性有一定的影响。     

PP/POE/SGF三元复合泡沫体的压缩吸能特性研究

在准静态单向压缩条件下,测试和分析了聚丙烯(PP)/乙烯-1-辛烯共聚物(POE)/短玻璃纤维(SGF)三元泡沫复合材料的压缩性能,考察了SGF的质量分数对压缩弹性模量、屈服强度和能量吸收特性的影响.结果表明:PP/POE/SGF泡沫复合材料的压缩应力-应变曲线具有典型的弹性变形、屈服平台和致密化三个阶段;适量SGF的引入提高了压缩弹性模量、屈服强度和吸能能力,而在研究的范围内,较高含量(20%以上)的SGF才能提高泡沫复合材料的吸能效率,其增强效果不如吸能能力明显.     

钛酸铅—环氧树脂压电复合材料的极化及压电性能研究

对钛酸铅／环氧树脂复合压电材料的极化性能进行了研究。结果表明,较高的极化电场强度和较高的极化温度均有利于压电复合材料压电性能的提高,但超过一定值时,材料会达到饱和极化状态,压电变常趋于稳定。     

环氧树脂/有机膨润土复合体系的性能研究

以双酚A型环氧树脂(CYD-128)为基体,有机膨润土为增韧改性剂,选用自行合成的固化剂,固化不同质量比的环氧树脂/有机膨润土复合体系的共混物,测定了共混固化复合体系的冲击强度、拉伸强度和热分解温度,并用扫描电镜(SEM)观察了环氧树脂/有机膨润土复合体系的微观结构.结果表明:随着有机膨润土含量的增加,冲击强度逐渐增加,当有机膨润土含量达3%～4%时冲击强度出现了极大值;随着有机膨润土含量的进一步增加,冲击强度减小.当共混复合体系的质量比为(3～4):100时,复合体系增韧的效果非常明显,把冲击强度从20.4kJ/m2提高到25.0kJ/m2;拉伸强度和热分解初始温度均有较大程度的改善;并且随着有机膨润土的加入,复合体系的断裂面逐渐呈韧性断裂.     

浸泡腐蚀对复合材料导电性能和力学性能的影响

对碳纤维/环氧树脂基复合材料进行浸泡腐蚀实验,并对腐蚀前后的试样进行电阻值测量、力学性能检测及试样形貌的显微观察.结果表明:浸泡腐蚀可显著影响试样的电阻值和短梁剪切强度.试样的电阻值随浸泡时间的延长,先增后减;同时浸泡使得试样短梁剪切强度明显降低,并且下降幅度与试样吸湿率相关.     

不锈钢管道在海水中的腐蚀研究

采用失重分析和电偶腐蚀测试等方法研究了气田立管采用的316L／625复合管材料在海水中的腐蚀情况,结果表明,复合管316L不锈钢和625合金在10℃海水中浸泡3个月后,平均腐蚀速率均低于0．01mm／a,而焊接接头处的腐蚀速率较大,为0．015mm／a,电偶腐蚀对316L不锈钢的影响不大,电偶腐蚀系数不超过130％。     

Effect of Temperature on the Tensile Strength and Failure Modes of Angle Ply CFRP Tubes under Hoop Loading

A comprehensive study was undertaken to characterise carbon fibre reinforced plastic (CFRP) tubes at different temperatures. Quasi-static burst tests were performed on tubes of 25°, 55° and 75° winding angle. The tubes were burst under internal radial pressure with minimum end constraints. An experimental rig and two conditioning tanks were designed and built to test the specimens at three temperatures; -46°C (low temperature), +20°C (room temperature) and +70°C (high temperature). For each test the internal pressure and the strains in both circumferential and longitudinal directions were recorded using a digital processing equipment.For a particular batch of tubes, tested at three different temperatures, a decrease in hoop strength and modulus of the 55° tubes with increasing temperature was recorded; the effect was less pronounced on the properties of 25° and 75° tubes. The use of a non-structural liner during the tests led to higher ultimate strength and strain of 55° tubes but had negligible effects on the behaviour of 75° tubes. The use of a liner in 25° tubes altered the mode of failure, resulting in a very large tube deformation with no noticeable increase in burst pressure. Micrographic analysis was also undertaken to study the failure mechanisms during pressurisation of lined and unlined tubes.     

固化工艺对3221环氧树脂体系/玻璃纤维复合材料性能的影响

采用动态热机械分析法(DMA法),研究不同固化工艺下固化的3221环氧树脂体系/高强玻璃纤维复合材料的干态玻璃化温度Tg,相对刚度E′以及分别在50℃和70℃去离子水中浸泡384 h后,材料的湿态Tg、E′、吸水率的变化规律。结果表明:固化温度较高的样品干态Tg较高,但经湿态处理后,Tg下降的幅度较大。固化温度高的样品在水浸泡过程中吸湿较慢。材料吸水后E′下降。     

Micromechanics of Amorphous Metal/Polymer Hybrid Structures with 3D Cellular Architectures: Size Effects,Buckling Behavior,and Energy Absorption Capability

By designing advantageous cellular geometries and combining the material size effects at the nanometer scale, lightweight hybrid microarchitectured materials with tailored structural properties are achieved. Prior studies reported the mechanical properties of high strength cellular ceramic composites, obtained by atomic layer deposition. However, few studies have examined the properties of similar structures with metal coatings. To determine the mechanical performance of polymer cellular structures reinforced with a metal coating, 3D laser lithography and electroless deposition of an amorphous layer of nickel‐boron (NiB) is used for the first time to produce metal/polymer hybrid structures. In this work, the mechanical response of microarchitectured structures is investigated with an emphasis on the effects of the architecture and the amorphous NiB thickness on their deformation mechanisms and energy absorption capability. Microcompression experiments show an enhancement of the mechanical properties with the NiB thickness, suggesting that the deformation mechanism and the buckling behavior are controlled by the brittle‐to‐ductile transition in the NiB layer. In addition, the energy absorption properties demonstrate the possibility of tuning the energy absorption efficiency with adequate designs. These findings suggest that microarchitectured metal/polymer hybrid structures are effective in producing materials with unique property combinations.     

SiC含量对环氧/SiC复合材料冲蚀磨损性能的影响

为了改善工厂、矿山中大型机件的耐冲蚀磨损性,利用SiC颗粒与环氧树脂制备了能够便捷涂覆和快速固化具有优异耐冲蚀磨损性能的环氧/SiC复合材料,着重考察了SiC含量对环氧/SiC复合材料冲蚀磨损性能的影响。用自制的冲蚀磨损试验机对复合材料进行了冲蚀磨损实验,采用SEM等手段对复合材料的冲蚀磨损形貌进行观察分析。结果表明:在复合材料中提高SiC含量可以提高其耐冲蚀磨损性能,当SiC质量分数为复合材料的66.66%时,SiC颗粒与树脂之间"阴影效应"和"粘接效应"相互配合达到最佳,复合材料的冲蚀磨损性能最好;当SiC含量最佳时,复合材料的耐冲蚀磨损性能要好于相同角度下白口铸铁。     

An Assessment of the Double-Notch Shear Test for Interlaminar Shear Characterization of a Unidirectional Graphite/Epoxy under Static and Fatigue Loading

This research explores a modified testing technique for measuring interlaminar shear properties of orthotropic composite materials. An existing test method (double-notched test method) is examined here to characterize the interlaminar shear properties (strength and fatigue life) of a unidirectional ply under both static and fatigue loading conditions. No complicated fixture is required for the testing method which is beneficial for fatigue testing of the materials. The testing method is verified by a finite element technique where an optimized geometry for the specimen is found. AS4/3501-6 graphite/epoxy material is used in this study. The experimental results show that final failure occurs in the gage area for both static and fatigue loading conditions. Moreover, a reasonable amount of scatter for both the static strength and fatigue life is achieved.