今日更新:Composite Structures 3 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Part B: Engineering 1 篇
Lightweight damping layer with acoustic black hole profile bonded to beam for broadband vibration reduction
Zhiwei Wan, Xiang Zhu, Tianyun Li, Kexin Zhong, Huchuan Wan
doi:10.1016/j.compstruct.2024.118235
带有声学黑洞轮廓的轻型阻尼层与波束结合,用于宽带减振
Inspired by the thickness reduction and wave focusing characteristics of the acoustic black hole (ABH) effect, a so-called ABH-damping layer (ABHD) is proposed for the broadband vibration reduction of a host structure, different from the common-used uniform thickness damping layer (UNID). The ABHD has a lighter weight and shows better vibration suppression ability. It can overcome the defect that ABHs cannot serve as the main load-bearing component due to the stiffness reduction. The primary beam structure and damping layer both follow the Timoshenko beam theory. The null space method handles the continuity between the two-layer structures. Analyses reveal the difference in vibration suppression characteristics between UNID and ABHD, further exhibiting the wave-gathering properties of ABH. The mass reduction ratio of ABHs is presented under different damping material loss factors. Finally, an experiment is conducted to verify the correctness of the proposed method and the feasibility of designing the ABHD. The damping layer’s weight of ABHD is reduced by 30.8% less than that of UNID, when the material loss factor is equal to 1.0. This study provides a new method for lightweight, strong vibration suppression performance and wide-band vibration reduction in engineering with the application of ABH.
根据声黑洞(ABH)效应的减厚和波聚焦特性,提出了一种不同于常用的均匀厚度阻尼层(UNID)的ABH阻尼层(ABHD),用于主机结构的宽带减振。ABHD具有较轻的重量和较好的抑振能力。它克服了ABHs由于刚度降低而不能作为主要承重构件的缺陷。主梁结构和阻尼层均遵循Timoshenko梁理论。零空间方法处理两层结构之间的连续性。通过分析,揭示了UNID和ABHD在振动抑制特性上的差异,进一步揭示了ABHD的集波特性。给出了不同阻尼材料损耗系数下ABHs的减重比。最后,通过实验验证了所提方法的正确性和设计ABHD的可行性。当材料损耗系数为1.0时,ABHD的阻尼层重量比UNID减少30.8%。该研究为ABH在工程上的应用提供了一种轻量化、强抑振性能和宽频带减振的新方法。
Experimental study of the importance of fibre breakage on the strength of thermoplastic matrix composites subjected to compression after impact
F. Naya, J. Pernas-Sánchez, C. Fernández, P. Zumel, M. Droździel-Jurkiewicz, J. Bieniaś
doi:10.1016/j.compstruct.2024.118238
纤维断裂对热塑性基复合材料冲击压缩强度影响的实验研究
Post-impact strength and damage tolerance of composite structures stands as a paramount design consideration in the aeronautical industry. In the event of a low velocity impact, a set of damage manifestations within laminated structures are induced, including matrix cracking, delamination and fiber breakage. Despite the critical importance of discerning the influence of each damage type on post-impact compression strength, only a limited number of studies have endeavored to quantify these effects comprehensively. In response to this research gap, we have developed a novel methodology capable of mimicking damage extension and shape caused by a low-velocity impact, while preserving fiber integrity. This innovation is achieved through the application of induced electrical currents, thereby facilitating controlled damage simulation without compromising fiber structural integrity. Our investigation compares the residual stiffness and strength of AS4/PEEK laminates subjected to low velocity impacts and induction currents, under conditions of equivalent damage. Our findings reveal that fiber breakage significantly influences the loss of stiffness in the laminate, but not its strength. Moreover, our results confirm the role of delamination as the primary determinant of strength degradation in the damaged material.
复合材料结构的冲击后强度和损伤容限是航空工业设计中最重要的考虑因素。在低速撞击的情况下,层合结构内部会产生一系列损伤表现,包括基体开裂、分层和纤维断裂。尽管识别每种损伤类型对冲击后抗压强度的影响至关重要,但只有有限数量的研究试图全面量化这些影响。为了弥补这一研究空白,我们开发了一种新颖的方法,能够模拟低速撞击造成的损伤扩展和形状,同时保持纤维的完整性。这项创新是通过感应电流的应用实现的,从而在不影响纤维结构完整性的情况下促进可控损伤模拟。我们的研究比较了AS4/PEEK层压板在同等损伤条件下低速冲击和感应电流下的剩余刚度和强度。我们的研究结果表明,纤维断裂显著影响层压板的刚度损失,但对其强度没有影响。此外,我们的研究结果证实了分层是损伤材料强度退化的主要决定因素。
Mechanical properties and regulatory strategy of twinned tetrahedral lattice structures
Ning Zhang, Xiaodong Ma, Peng Dai, Xiaogeng Tian
doi:10.1016/j.compstruct.2024.118239
孪晶四面体晶格结构的力学性能及调控策略
Given the outstanding mechanical performance of lattice metamaterials, novel structural forms and performance modulation strategies have garnered considerable attention. Herein, we develop a twined tetrahedral lattice structure (TTL) with a bending defect inside the unit cell. Mechanical properties before and after the introduction of defects in TTLs were studied using experiments and numerical simulations. The developed structure exhibits strictly stretching-dominated properties in the absence of bending defects. Whereas, the bending-dominant component of TTLs is elevated with increasing bending angle that can increase energy absorption efficiency. Moreover, the relative elastic modulus and initial peak stress can be reduced by even more than 70 % and 50 %, respectively, as the bending angle increases. Besides, a theoretical model for the relative elastic modulus of TTL at θ = 0° was established based on the displacement method on the Representative Volume Element (RVE), including both Euler-Bernoulli beam theory and Timoshenko beam theory. However, the two solutions show consistent results for strictly stretching-dominated structures. The accuracy of solutions is verified by experiments and simulations. The plateau stress theoretical model for TTLs was derived from the deformation process of the RVE based on plastic hinge theory. The theoretical solutions under different θ align well with numerical and experimental results. Overall, TTLs have superior relative elastic modulus, relative yield strength, and specific energy absorption compared to common lattice structures. The developed TTLs provide a new perspective on the property regulation of mechanical metamaterials.
由于晶格超材料优异的力学性能,新的结构形式和性能调制策略引起了人们的广泛关注。在此,我们开发了一种具有弯曲缺陷的缠绕四面体晶格结构(TTL)。采用实验和数值模拟的方法研究了引入缺陷前后ttl的力学性能。在没有弯曲缺陷的情况下,发育的结构表现出严格的拉伸主导性能。弯曲主导成分随着弯曲角度的增加而增加,从而提高了能量吸收效率。随着弯曲角的增大,相对弹性模量和初始峰值应力可分别降低70%和50%以上。此外,基于代表性体积单元(RVE)上的位移法,结合Euler-Bernoulli梁理论和Timoshenko梁理论,建立了θ = 0°时TTL相对弹性模量的理论模型。然而,这两种解对严格拉伸主导结构的结果是一致的。通过实验和仿真验证了解的准确性。基于塑性铰理论,从RVE的变形过程中推导出ttl的平台应力理论模型。不同θ下的理论解与数值和实验结果吻合较好。总的来说,与普通晶格结构相比,ttl具有优越的相对弹性模量、相对屈服强度和比能吸收。所开发的ttl为研究机械超材料的性能调控提供了新的视角。
Packaging of ZIF-8 into diatomite sealed by ionic liquid and its application in flame retardant polyurea composites
Xue Bi, Zeqi Zhang, Kunpeng Song, Xiaoyu Zhang, Ye-Tang Pan, Hongqiang Qu, Henri Vahabi, Jiyu He, Rongjie Yang
doi:10.1016/j.compositesa.2024.108283
离子液体密封硅藻土包装ZIF-8及其在阻燃聚脲复合材料中的应用
Diatomaceous earth (DE) has abundant silicon elements and unique pore structure, and has a good application prospect in the field of flame retardants. However, the compatibility between DE and polymers still needs to be improved. In this manuscript, imidazole-based metal organic framework (ZIF-8) was ingeniously filled into the pores of the biomorphic DE as an obstacle, and ternary (Si-P-N) composites (DE@ZIF@ILs) were obtained by introducing phosphorus-containing ionic liquids (ILs) on its surface. It effectively improves the problem of poor mechanical properties of polymer composites caused by large-size DE. The results of the cone test showed that the introduction of DE@ZIF@ILs effectively reduced the fire hazard of polyurea (PUA). The peak heat release rate, total heat release, peak smoke production rate and total smoke production decreased by 49.7%, 45.3%, 53.0% and 41.4%, respectively. This study also explored the specific mechanism of flame retardant and smoke suppression of DE@ZIF@ILs.
硅藻土(DE)具有丰富的硅元素和独特的孔隙结构,在阻燃剂领域具有良好的应用前景。然而,DE与聚合物的相容性仍有待提高。本文巧妙地将咪唑基金属有机骨架(ZIF-8)作为障碍物填充到生物形态DE的孔隙中,通过在其表面引入含磷离子液体(ILs)得到三元(Si-P-N)复合材料(DE@ZIF@ILs)。有效改善了大尺寸DE导致聚合物复合材料力学性能差的问题。锥形试验结果表明,DE@ZIF@ILs的引入有效降低了聚脲(PUA)的火灾危险性。峰值放热率、总放热率、峰值产烟率和总产烟率分别下降了49.7%、45.3%、53.0%和41.4%。本研究还探讨了DE@ZIF@ILs阻燃抑烟的具体机理。
Sustainable assembling of graphite flakes into graphite/carbon composite foams with thermal percolative interfaces for active heat dissipation
L.P. Maiorano, N. Verdú, J.M. Molina
doi:10.1016/j.compositesa.2024.108279
石墨片可持续组装成具有热渗透界面的石墨/碳复合泡沫,用于主动散热
Current methods for producing open-pore graphite foams with heat dissipation potential involve costly graphitization processes, limiting their widespread use. This study presents a sustainable approach to fabricate high-performance graphite/carbon composite foams with porosities in the range of 49–82 %. The method involves the densification and carbonization of solid mixtures comprising natural graphite flakes, sucrose, and NaCl particles. The dissolution of NaCl creates coarse pores, while carbonized sucrose contributes fine porosity and serves as a binder to impart mechanical stability, ensuring the maintenance of thermally conductive percolative contacts between flakes. The composite foams exhibit thermal conductivities of up to 91 Wm−1K−1, permeability values in the range of 10−11–10−10 m2, and excellent mechanical properties. Experimental and computational findings demonstrate that the developed materials surpass the heat dissipation capabilities of conventional heat sinks based on graphite and aluminum foams by about 3 and 1.5 times, respectively, making them excellent candidates for thermal management applications.
目前生产具有散热潜力的开孔石墨泡沫的方法涉及昂贵的石墨化过程,限制了它们的广泛应用。本研究提出了一种可持续的方法来制备孔隙率在49-82 %范围内的高性能石墨/碳复合泡沫材料。该方法涉及到由天然石墨薄片、蔗糖和NaCl颗粒组成的固体混合物的致密化和碳化。NaCl的溶解形成粗孔,而碳化蔗糖形成细孔,并作为粘合剂赋予机械稳定性,确保薄片之间保持导热渗透接触。复合泡沫材料的导热系数高达91 Wm−1K−1,渗透率在10−11-10−10 m2之间,具有优异的力学性能。实验和计算结果表明,所开发的材料的散热能力分别比基于石墨和泡沫铝的传统散热器高出约3倍和1.5倍,使其成为热管理应用的优秀候选人。
High-yield conversion of lab waste to resources for the development of nanocomposite broadband photocatalysts embracing near-infrared plasmonic effects
Jnanraj Borah, Pallab Pathak, Jyotisman Bora, Sritam Biswas, Pabitra Nath, Arup R. Pal, Bimal K. Sarma
doi:10.1016/j.compositesb.2024.111594
采用近红外等离子体效应的纳米复合宽带光催化剂的高产量转化为资源
This work presents novel and environment-friendly nanocomposite photocatalysts capable of utilizing near-UV, visible, and near-infrared light. The primary phase of the nanocomposite is Al-doped ZnO (AZO), which consists of wurtzite nanocrystallites (size: 10–16 nm) and is produced from the discarded sputtering target constituting about two-thirds of the target mass. The AZO/NiO and AZO/CuO nanocomposites are developed by the ball mill method. X-ray diffraction, X-ray photoelectron spectroscopy, and electron microscopy confirm the formation of nanocomposites with phase purity. The plasmonic peak (∼1900 nm) of AZO is strongly noticeable in the reflectance spectra, which is supported by the electromagnetic simulation of the enhancement of the electric field. The AZO/CuO nanocomposite efficiently degrades environmental pollutants, especially, aqueous sulfamethazine and p-nitrophenol which is evident from the liquid-chromatography mass spectrometry measurements. A mechanism of broadband photon collection, carrier generation, charge separation, and redox reactions is proposed and complemented by the scavenger tests, electrochemical impedance spectroscopy, first principles calculations, and photoconductivity measurements.
这项工作提出了一种新型的、环境友好的纳米复合光催化剂,能够利用近紫外光、可见光和近红外光。纳米复合材料的初级相是al掺杂ZnO (AZO),由纤锌矿纳米晶体(尺寸:10-16 nm)组成,由约占目标质量三分之二的废弃溅射靶产生。采用球磨机法制备了AZO/NiO和AZO/CuO纳米复合材料。x射线衍射、x射线光电子能谱和电子显微镜证实形成了相纯度较高的纳米复合材料。AZO的等离子体峰值(~ 1900 nm)在反射光谱中非常明显,这得到了电场增强的电磁模拟的支持。AZO/CuO纳米复合材料可有效降解环境污染物,特别是水磺胺乙烷和对硝基苯酚,这从液相色谱-质谱测量中可见一斑。提出了宽带光子收集、载流子产生、电荷分离和氧化还原反应的机制,并通过清除剂测试、电化学阻抗谱、第一性原理计算和光电导率测量进行了补充。