今日更新:Composite Structures 1 篇,Composites Science and Technology 1 篇
Improving energy absorption and failure characteristic of additively manufactured lattice structures using hollow and curving techniques
Disaya Disayanan, Pattarapong Buntornvorapan, Thammayuth Sukprasertchai, Vitoon Uthaisangsuk
doi:10.1016/j.compstruct.2024.118067
利用空心和弯曲技术改善快速成型晶格结构的能量吸收和失效特性
Strut-based lattice structures of various types exhibited a common critical issue, namely, high tensile stress concentration occurred at node-to-strut sites, which often led to lowered energy absorbability as compared to triply periodic minimal surfaces structures. Therefore, this work aimed for improving the Octet-truss structure by a combined technique using hollow core and varying cross-section ratio. Firstly, test specimens were fabricated using a stereo-lithography based additive manufacturing of photopolymer hard resin. Elastic-plastic properties and damage criterion of the used polymer were experimentally determined and applied for finite element models. Validation by compressive tests of lattice samples showed deviations of stress–strain responses less than 12%, in which local deformation and subsequent damages were fairly predicted. Afterwards, finite element simulations of designed lattice structures subjected to compressive, combined shear, shear and tensile loads were performed and obtained stress–strain characteristics including total absorbed energies and deformation behaviors were studied. Under uniaxial compression and combined shear loads, modified Octet-truss structures exhibited considerable increases of energy absorptions up to 173% and 116%, respectively, and stress–strain responses were more stable. On the other hand, by tension mode peak stresses and elongations could be enhanced about 41% and 11%, accordingly. The improved performances of proposed strut-based structures were comparable to those of triply periodic minimal surfaces diamond structure. This was due to that local stress distributions in the structure became more uniform and previously dominated tensile stresses were switched to compressive stresses. Therefore, occurrences of shear bands and plastic hinges could be effectively inhibited.
与三周期最小表面结构相比,基于支柱的各种类型的晶格结构表现出一个共同的关键问题,即在节点到支柱的位置出现高拉伸应力集中,这往往会降低能量吸收能力。因此,这项工作旨在通过使用空心芯材和不同截面比的组合技术来改进 Octet 桁架结构。首先,使用基于立体光刻技术的光聚合物硬树脂增材制造技术制作了测试试样。通过实验确定了所用聚合物的弹塑性能和损伤准则,并将其应用于有限元模型。通过对晶格样品进行压缩试验验证,结果表明应力-应变响应的偏差小于 12%,其中局部变形和随后的损伤得到了很好的预测。随后,对受到压缩、联合剪切、剪切和拉伸载荷的设计晶格结构进行了有限元模拟,并研究了所获得的应力应变特性,包括总吸收能量和变形行为。在单轴压缩荷载和组合剪切荷载作用下,改进型八叉桁架结构的能量吸收率显著提高,分别达到 173% 和 116%,应力-应变响应也更加稳定。另一方面,在拉伸模式下,峰值应力和伸长率分别提高了约 41% 和 11%。所提出的支柱型结构的性能改善程度与三周期最小表面金刚石结构相当。这是因为结构中的局部应力分布变得更加均匀,以前占主导地位的拉应力转变为压应力。因此,剪切带和塑性铰的出现可以得到有效抑制。
Sm2O3 micro-plates/B4C/HDPE composite containing high specific surface area fillers for neutron and gamma-ray complex radiation shielding
Zhipeng Huo, Yidong Lu, Hong Zhang, Guoqiang Zhong
doi:10.1016/j.compscitech.2024.110567
含有高比表面积填料的 Sm2O3 微板/B4C/高密度聚乙烯复合材料,用于中子和伽马射线复合辐射屏蔽
In this study, a series of Sm2O3 micro-plates/B4C/HDPE composites composed of synthesized Sm2O3 fillers (Sm2O3 micro-plates) are prepared for shielding neutron and gamma radiation. The influence of micromorphology of Sm2O3 fillers on neutron and gamma radiation shielding properties of composites is investigated in detail. The XRD pattern reveals that the phase of synthetic Sm2O3 is cubic crystal systems, body-centered cubic lattices, and its space group is Ia3¯(206). SEM images and BET analyses reveal that the micromorphology of synthesized Sm2O3 is micro-plates. The BET-specific surface area of the Sm2O3 fillers is increased with addition of urea content. The differential scanning calorimetry (DSC) curves reveal that Sm2O3 fillers increase the melting temperature of the composites, which is up to 138.6 °C. The thermogravimetric analysis (TGA) results reveal that the initial thermal degradation temperatures of the composites are all above 440 °C. The neutron and gamma radiation shielding tests show that Sm2O3 fillers with high BET-specific surface area (8.20 m2/g) and uniform size improve the neutron and gamma shielding rate of composites. A superior composite containing 10 wt% Sm2O3 (R = 1:25, R value represents the molar ratio of rare earth elements to urea)/20 wt% B4C/70 wt% HDPE has a neutron radiation shielding rate of 98.7% with a thickness of 15 cm under the 252Cf neutron source and a gamma radiation shielding rate of 72.1% with a thickness of 15 cm under 137Cs gamma source. And these lead-free and environment-friendly composites can be widely used in the neutron and gamma complex radiation fields.
本研究制备了一系列由合成 Sm2O3 填料组成的 Sm2O3 微板/B4C/HDPE 复合材料(Sm2O3 微板),用于屏蔽中子和伽马辐射。详细研究了 Sm2O3 填料的微观形貌对复合材料中子和伽马辐射屏蔽性能的影响。XRD 图谱显示,合成的 Sm2O3 为立方晶系,体心立方晶格,空间群为 Ia3¯(206)。扫描电镜图像和 BET 分析表明,合成 Sm2O3 的微观形态为微板状。Sm2O3 填料的 BET 比表面积随着尿素含量的增加而增大。差示扫描量热曲线(DSC)显示,Sm2O3 填料提高了复合材料的熔化温度,最高可达 138.6 ℃。热重分析(TGA)结果表明,复合材料的初始热降解温度均高于 440 ℃。中子和伽马辐射屏蔽试验表明,具有高 BET 比表面积(8.20 m2/g)和均匀尺寸的 Sm2O3 填料可提高复合材料的中子和伽马屏蔽率。含有 10 wt% Sm2O3(R = 1:25,R 值代表稀土元素与尿素的摩尔比)/20 wt% B4C/70 wt% HDPE 的优质复合材料在 252Cf 中子源下,厚度为 15 cm 的中子辐射屏蔽率为 98.7%;在 137Cs 伽马源下,厚度为 15 cm 的伽马辐射屏蔽率为 72.1%。这些无铅环保型复合材料可广泛应用于中子和伽马复合辐射领域。