甲虫前翅结构中的优化设计

为了设计开发轻量型仿生复合材料,选择了独角仙和锹形虫两种甲虫前翅为仿生对象,用电子显微镜观察了这两种甲虫前翅结构上的异同,考察了甲虫前翅中的优化设计思路。结果表明: (1) 两种甲虫前翅均采用了以小柱为中空层的夹芯层状结构及框架结构的轻量型设计手法。 (2) 独角仙前翅为一次性式的十分经济的设计方式,而锹形虫则为耐用型设计方式。      

甲虫前翅结构及其仿生研究进展

综述了近年来国内外有关甲虫前翅结构与仿生应用的研究成果及其发展前景。指出前翅是以小柱为中空层的框架式结构, 其左右前翅结合部分是一种巧妙的凹凸啮合结构; 前翅内存在着网状-小柱结构, 这是一种轻量型夹芯层状三合板结构; 小柱中的纤维与上下层中的纤维是连续的, 可有效增加叠层复合材料的抗剥离强度;一些甲虫前翅的表面具有特殊的生物结构, 从而具有一些特殊的功能, 如具有减阻、集水或显色功能。结合生命科学的最新研究成果, 提出了通过基因组技术生产仿生材料的设想。      

“蜂窝-柱子”芯夹层轻量型仿生物复合材料结构

为了设计开发轻量型仿生复合材料, 通过对独角仙前翅内部微细结构及其成因的分析探讨, 提出了一种蜂窝-柱子芯轻量型复合材料的三维结构模型, 并列举了若干可能的设计思路, 同时简述了这种仿生结构的优点及其应用前景。分析结果表明: 独角仙整个前翅内部存在完整的网状-小柱结构, 这种网状结构由气囊构成,呈现出生物界的不规则性、多样化, 但可认为大多为类似于蜂窝状的多边形结构。     

四种甲虫鞘翅的力学参数测定及微结构观测

研究了4种甲虫(白星花金龟、 东方龙虱、 独角仙、 毛黄鳃金龟)鞘翅的材料力学参数及其微结构。鞘翅截面微观结构观察表明, 这4种甲虫鞘翅均由鞘翅背壁、 中空夹芯层和鞘翅腹壁构成, 背、 腹壁之间由桥墩状几丁质纤维空心柱体结构连接, 两鞘翅间以凹凸啮合结构联接。用纳米压痕仪测得这4种甲虫鞘翅背壁致密层的弹性模量均值分别为9.08、 8.21、 4.76、 6.00GPa, 硬度分别为0.44、 0.48、 0.18、 0.18GPa。用多功能材料性能实验机测定白星花金龟、 东方龙虱、 独角仙鞘翅之间的联接强度分别为46.43、 7.38、 11.34mN/mm。该研究为轻质结构的设计提供了仿生学基础。      

独角仙鞘翅微结构及其纳米力学性能

利用SEM对独角仙鞘翅的微结构进行了观测, 并借助纳米压痕仪测试分析了鞘翅的纳米力学性能。SEM试验表明独角仙鞘翅是一种具有拱形空腔的中空轻质生物复合材料, 其断面占空比为26.36%。鞘翅由外表皮和内表皮构成, 而内表皮又通过11~12层纤维层采用45°角正交叠加铺设, 层间辅以许多微纤维丝交叉连接方式编织在一起, 形成层合板结构。试验测得鞘翅外表皮纳米力学性能分别为: 硬度(0.28±0.13) GPa, 弹性模量(5.62±1.21) GPa, 接触刚度 (1.67±0.14)×10⁴ N/m。其纳米力学性能呈现拓扑分布规律, 由头部至尾部区域有增大趋势。试验测试结果为后续研究中设计一种基于独角仙鞘翅的新型轻质仿生结构提供了仿生学模型和理论参考。     

纤维增强Ti/Al3Ti金属-金属间化合物层状复合材料研究进展

连续纤维增强的金属-金属间化合物层状复合材料兼具高强度、高模量和良好的韧性等优异性能, 逐渐成为国内外学者的研究重点.这种复合材料包含庞杂的体系、复杂的结构和性能表现, 因此有必要对其制备技术、结构特征和综合性能开展深入的研究.以纤维增强Ti/Al3 Ti层状复合材料为对象, 系统地综述了其研究现状.首先介绍了Ti/A...     

缠绕图型对纤维缠绕复合材料力学性能影响的有限元模拟

针对纤维缠绕复合材料结构中存在纤维束交叉起伏和铺层走向交替的特点,建立了一种分析缠绕图型对缠绕复合材料结构力学性能影响的有限元方法。采用ABAQUS有限元软件,分析了考虑纤维束交叉起伏和铺层走向交替后缠绕复合材料圆柱壳的应力、应变分布规律,并且研究了缠绕图型对缠绕圆柱壳屈曲临界载荷的影响。结果表明:采用层合板模型计算得到的圆柱壳的应力分布比较均匀;考虑纤维束交叉起伏和铺层走向交替后,缠绕复合材料圆柱壳的应力不再均匀分布,应力云图出现规则分布的菱形图案,在菱形区域中纤维交叉起伏和铺层走向交替处的应力有明显的波动。本实验有限元模型中的菱形特征单元可以反映缠绕复合材料纤维交叉起伏和铺层走向交替的实际情况。     

缠绕图型对纤维缠绕复合材料力学性能影响的有限元模拟

针对纤维缠绕复合材料结构中存在纤维束交叉起伏和铺层走向交替的特点,建立了一种分析缠绕图型对缠绕复合材料结构力学性能影响的有限元方法。采用ABAQUS有限元软件,分析了考虑纤维束交叉起伏和铺层走向交替后缠绕复合材料圆柱壳的应力、应变分布规律,并且研究了缠绕图型对缠绕圆柱壳屈曲临界载荷的影响。结果表明:采用层合板模型计算得到的圆柱壳的应力分布比较均匀;考虑纤维束交叉起伏和铺层走向交替后,缠绕复合材料圆柱壳的应力不再均匀分布,应力云图出现规则分布的菱形图案,在菱形区域中纤维交叉起伏和铺层走向交替处的应力有明显的波动。本实验有限元模型中的菱形特征单元可以反映缠绕复合材料纤维交叉起伏和铺层走向交替的实际情况。     

蝶翅为模板功能材料光吸收特性的研究

阐述了以裳凤蝶前翅(T_FW)和宽带凤蝶前翅(P_FW)为模板,通过化学合成方法制备了具有三维减反射准周期性微纳结构的金属和碳基金属功能材料。通过XRD检测复合材料的组分和晶型;通过SEM和TEM观察了复合材料的表面形貌;通过HRTEM和SAED检测了复合材料的晶体结构。结果表明:复合材料具有优异的加强宽波段红外吸收性能。与性能优异的太阳光吸收材料Blue Tec eta plus_Cu相比,对300~2500 nm波长光,平均光吸收有所增强;对2.5~15μm中红外光,平均光吸收增强几十倍。此外也测试了裳凤蝶前翅和宽带凤蝶前翅的空白实验做对照,说明了性能优异的功能材料与性能优异的功能结构相结合,实现性能的提升、扩展及革新的可行性。     

冷冻铸造技术制备仿贝壳层状结构陶瓷复合材料研究进展

贝壳珍珠层是一种天然的层状结构复合材料,类似"砖和泥"的软硬相交替的层状分级组装结构赋予其优良的力学性能。通过对贝壳的珍珠层进行仿生研究,人们已利用不同技术如冷冻铸造技术等,制备了一系列仿生高强超韧层状复合材料,并且这些材料在航空航天、军事、民用及机械工程等领域表现出广阔的应用前景。首先介绍了贝壳珍珠层的结构性能,并对其断裂机制进行了阐述;然后综合介绍了冷冻铸造技术的发展历程、作用机理、控制因素、装置设计和总体工艺流程。在此基础上,对制备仿贝壳层状结构陶瓷复合材料的表观密度、多孔陶瓷的孔隙率进行介绍,综述了多孔陶瓷的性能、陶瓷/金属层状结构复合材料以及陶瓷/聚合物层状结构复合材料的特点和应用,最后分析和总结了在研究仿贝壳层状结构陶瓷复合材料过程中出现的问题,并对该复合材料的未来发展趋势做了一定的预测。     

In vitro degradation of porous nano-hydroxyapatite/collagen/PLLA scaffold reinforced by chitin fibres

In this paper, a novel porous scaffold for bone tissue engineering was prepared with nano-hydroxyapatite/collagen/Poly-l-lactic acid (PLLA) composite reinforced by chitin fibres. To enhance the strength of the scaffold further, PLLA was linked with chitin fibres by Dicyclohexylcarbodimide (DCC). The structures of the reinforced scaffold with and without linking were characterized by Scanning Electron Microscopy (SEM). The chemical characteristics of the chitin fibres with and without linking were evaluated by Fourier-transformed infrared (FTIR) spectroscopy. The mechanical performance during degradation in vitro was investigated. The results indicated that the nano-hydroxyapatite/collagen/PLLA composite reinforced by chitin fibres with linking kept better mechanical properties than that of the composite without linking. These results denoted that the stronger interfacial bonding strength of the scaffold with linking could decrease the degradation rate in vitro. The reinforced composite with the link-treatment can be severed as a scaffold for bone tissue engineering.     

Fabrication of chitin/graphene oxide composite sponges with higher bilirubin adsorption capacity

Chitin/graphene oxide (Ch/GO) composite sponges had been synthesized in 11?wt% NaOH/4?wt% urea aqueous solution by a simple method. The structure, thermal stability and mechanical properties of the composite sponges were investigated by scanning electron microscopy, Fourier-transform infrared spectroscopy, wide-angle X-ray diffraction, thermogravimetric analysis, and compressive strength measurements. The results revealed that chitin and GO were mixed homogeneously. Interestingly, the composite sponges showed meso-macroporous structure, which played an important role in improving their adsorption properties. Besides, thermal stability and mechanical properties were significantly improved compared with pure chitin sponges. Taking advantages of these fantastic characteristics, the maximum adsorption capacity of composite sponges for bilirubin was up to 422.9?mg/g under the optimized condition, which was not only significantly higher than the adsorption capacities of pure chitin sponges, but also superior to those of many reported adsorbents for removal of bilirubin. Furthermore, blood compatibility evaluations confirmed that this blended sponges had negligible hemolysis and coagulation. Therefore, this work provided a potential possibility to offer Ch/GO composite sponges for removal of bilirubin.     

Three-dimensionally printed designable joint for carbon fibre reinforced plastics

Three-dimensional (3D) printing of carbon fibre reinforced plastic (CFRP) components shows promise for building light-weight strong components for industry. Many structures require multiple components to be joined to form the completed parts. However, tightening of metal bolts used to join CFRP can damage the composite and the bonding strength of adhesive bonding is variable. Here, we propose a new joint system, based on all-3D printed parts. Snap-in joints and Ajax-pins induce a mechanical joining force at the interface between parts, together with a bearing force. This joint system offers comparable strength to that of adhesive and metal bolt joints, while adding negligible weight to the parts. Furthermore, 3D printing of the surface structures, holes and pins enables unprecedented control over the joint design, enabling strength optimization through the thickness and in-place directions as required. The Snap-in joint system shows great potential for the fabrication of strong light-weight 3D printed structures.     

三维夹芯层连织物复合材料真空辅助成型工艺影响因素

三维夹芯层连织物复合材料是由纤维连续织造呈空芯结构的织物作为增强体制备而成的新型轻质复合材料, 本文中以三维夹芯层连织物复合材料为研究对象, 发展了适用于酚醛树脂的真空辅助成型工艺方法, 重点考察了影响复合材料制造质量的关键因素。结果表明, 芯柱高度对织物的抗压缩能力与厚度回复率影响显著, 热处理有利于织物的厚度回复; 注射过程中, 树脂沿织物平面纬向渗透速率大于经向, 使用高渗透率介质层、 降低树脂黏度有助于提高树脂在层连织物中的分布均匀性。      

船体箱形截面梁设计及抗爆性能分析

在船体构件上应用箱形梁设计,能提高结构的纵向强度,具有利于保护重要管道和线缆、提高建造速度、利于质量控制和方便维修等优点。但是,国内外目前都是局部运用箱形梁结构,并未全船性设计使用,在此以某常规船体为基础,针对提高船舶抗爆性能和保持生命力的设计要求,全船性使用箱形梁。这种船体结构使钢制箱形梁承担全部的总强度,而船体型线和必要的使用刚度由轻质高强的复合材料板材来保证,实现局部强度与总体强度的解耦。在ABAQUS软件中基于声固耦合法,对船体水下爆炸响应进行分析,证实箱形梁结构具有较好的抗爆性能。最后对船体箱形梁进行优化设计,进一步提高抗爆能力。     

In situ characterization of the deformation and failure behavior of non-stochastic porous structures processed by selective laser melting

Cellular materials are promising candidates for load adapted light-weight structures. Direct manufacturing (DM) tools are effective methods to produce non-stochastic structures. Many DM studies currently focus on optimization of the geometric nature of the structures obtained. The literature available so far reports on the mechanical properties but local deformation mechanisms are not taken into account. In order to fill this gap, the current study addresses the deformation behavior of a lattice structure produced by selective laser melting (SLM) on the local scale by means of a comprehensive experimental in situ approach, including electron backscatter diffraction, scanning electron microscopy and digital image correlation. SLM-processed as well as heat treated lattice structures made from TiAl6V4 alloy were employed for mechanical testing. It is demonstrated that the current approach provides means to understand the microstructure-mechanical property-local deformation relationship to allow for optimization of load adapted lattice structures.     

轴心受压CFRP—铝合金组合管弹塑性屈曲性能分析

CFRP管具有轻质高强的特点,适合于建造大跨度空间网格结构,但其破坏呈脆性,且以节点连接破坏为主,不能充分发挥CFRP材料的优点,为此建议将CFRP与铝合金组合形成CFRP-铝合金组合管来改善其受力性能和构件连接性能。首先对CFRP-铝合金组合长管进行了轴心受压稳定试验研究,得到其基本受力性能与破坏模式。利用有限元方法对组合管的特征值屈曲进行分析,研究不同CFRP铺层角度、厚度和顺序的影响。根据特征值屈曲的分析结果,引入初始几何缺陷,对组合管进行了弹塑性屈曲分析,并将分析结果与试验结果进行了对比,确定了有限元分析模型的合理性,进一步研究了不同长细比、铺层角度和厚度对组合管弹塑性稳定性能的影响机理。最后基于试验结果与数值分析结果,通过修正Perry稳定计算公式,得到了CFRP-铝合金组合长管屈曲荷载的计算公式。